Springer Science and Business Media LLC Acta Medica Okayama 2045-2322 16 1 2026 Tribolium castaneum with longer duration of tonic immobility have more variations corresponding to the human Parkinson’s disease genomic region 8840 EN Keisuke Tanaka NODAI Genome Research Center, Tokyo University of Agriculture Ken Sasaki Graduate School of Agriculture, Tamagawa University Shunsuke Yajima NODAI Genome Research Center, Tokyo University of Agriculture Takahisa Miyatake Faculty of Environmental, Life, Natural Science and Technology, Okayama University Parkinson’s disease (PD) is a common neurodegenerative syndrome characterized by the loss of dopaminergic neurons and is also a progressive neurodegenerative disorder that is characterized by dopamine deficiency. We established strains artificially selected for longer and shorter durations of tonic immobility, an antipredator behavior that has received much attention recently, in the red flour beetle, Tribolium castaneum, a model insect species for molecular analyses different from Drosophila melanogaster. Previous studies have shown that the long strains (L-strain) have significantly lower levels of dopamine expression in the brain than the short strains (S-strain) and that they have an abnormal pattern of locomotor activity. Furthermore, previous studies have shown that administering dopamine to L-strain beetles reduces the duration of tonic immobility. Transcriptome analysis of brain and thorax of the L- and S-strains also showed differences in mRNA expression of genes involved in dopamine synthesis and tyrosine metabolism. These results indicate that the phenotype and molecular basis of the L-strain are similar to those of Parkinson’s syndrome symptoms. In order to establish a link between T. castaneum and PD, we compared the DNA sequences of the L- and S-strains to human genes affecting dopaminergic pathways. The DNA comparison revealed many mutated regions in these genes in the L-strain. We discuss the relationship between dopaminergic pathway genes and PD-like phenotypes across humans, Drosophila, and the red flour beetle. No potential conflict of interest relevant to this article was reported.

Wiley Acta Medica Okayama 0013-8703 2025 Artificial Selections for Life-History Traits Affect Effective Cumulative Temperature and Developmental Zero Point in Zeugoducus cucurbitae EN Takahisa Miyatake Graduate School of Environment, Life, Natural Science and Technology, Okayama University Kentarou Matsumura Department of General Systems Studies, Graduate School of Arts and Sciences, the University of Tokyo Effective cumulative temperature and developmental zero point are important indicators for estimating the timing of organism development and the area of distribution. These indicators are generally considered to have unique values for different species of organisms and are also important for predicting the distribution range of animals and plants, especially insect pests. These values generally are species-specific, but there is variation within populations in traits having a genetic component. However, there are no studies on what kind of selection pressure affects these indicator values. To address this issue, it would be worthwhile to compare these values using individuals of strains that have been artificially selected for life-history traits by rearing them at various temperatures and calculating these indicators from developmental days and temperatures. In the present study, eggs were taken from adults of strains with many generations of artificial selection on two life-history traits (age at reproduction and developmental period) of the melon fly, Zeugodacus cucurbitae, under constant temperature conditions. Eggs were reared at five different temperatures, and the effective cumulative temperatures and developmental zero points of the larval and developmental periods were compared. The results demonstrate that artificial selection on life-history traits in Z. cucurbitae induces evolutionary changes in both the effective cumulative temperature and the developmental zero point across successive generations. No potential conflict of interest relevant to this article was reported.

Springer Science and Business Media LLC Acta Medica Okayama 0003-6862 2025 Comparison of flight behaviors among laboratory and field strains in Tribolium castaneum (Coleoptera: Tenebrionidae) using a simple method to measure flight ability EN Sota Sone Faculty of Environment, Life, Natural Science and Technology, Okayama University Takahisa Miyatake Faculty of Environment, Life, Natural Science and Technology, Okayama University Most insects can fly. The acquisition of flight is a factor that allows insects to prosper on Earth. On the other hand, in the same species and population, individual differences in flight ability may occur. Flight ability can vary due to geographical conditions and cumulative rearing. Investigating these changes in flight performance is important for understanding dispersal polymorphism and the evolution of flight performance. Thus, in the present study, the flight behaviors between cumulative rearing and field strains and changes in flight behaviors between strains of the red flour beetle, Tribolium castaneum Herbst (Coleoptera: Tenebrionidae), which is distributed around the world were compared. Tribolium castaneum is a worldwide pest of stored grains. Its body length is about 3–4 mm. Previous studies have investigated the influence of environmental and physiological factors on the flight of this species, but no studies have examined individual differences or polymorphism in flight behaviors within this species. In this study, we developed a simple apparatus that can quantify the flight behavior of this species. The experimental apparatus was set up as a double structure with two different size containers. This apparatus was able to assess the flight activity of insects by counting individuals in a big container because insects transfer to the big container only by flight. Moreover, upward flight ability was possible to be assessed by the apparatus adding the barrier. Then, the flight behavior was compared between strains of this species that have been bred in the laboratory for more than 45 years and several strains of this species collected in the field. The results showed no variation in flight activity between strains, but flying ability was higher in strains originating from warmer regions. Here, we discussed the variations in flight behavior of T. castaneum. No potential conflict of interest relevant to this article was reported.

Springer Science and Business Media LLC Acta Medica Okayama 0289-0771 2025 Leg-biting fights reduce the number of sperm transferred by the loser and in draws in Zophobas atratus EN Teruhisa Matsuura Faculty of Environmental, Life, Natural Science and Technology, Okayama University Takahisa Miyatake Faculty of Environmental, Life, Natural Science and Technology, Okayama University Intra-sexual selection has been observed across a wide range of species. Male-male combat can not only determine the winner and loser but also affect subsequent reproductive success. The effects of combat outcomes on reproduction are thought to depend on the reproductive ecology of the target species. However, to our knowledge, studies examining the impact of combat outcomes on sperm competition and fitness remain limited. In the giant mealworm (Zophobas atratus), male’s combat involves biting each other's hind legs. Females mated to the losers of leg-biting contests had significantly fewer eggs and fewer offspring than females mated to males that were not in a contest. Possible explanations for this fitness reduction include the inability of males to transfer sperm effectively due to the combat outcome or the inability of their sperm to fertilize eggs due to female cryptic sperm choice, and the mechanisms underlying this reduction remain unclear. Previous studies have observed distorted mating postures in losing males, leading us to hypothesize that leg-biting during combat might affect sperm transfer. To test this, we allowed uncontested males, winners, losers, and males with a draw outcome to mate with females and compared the number of sperm within the female’s spermatheca. Additionally, we examined the correlation between combat duration and sperm count. Results showed that losers and males with draw transferred fewer sperm than non-combat males. Moreover, the longer the combat duration, the fewer sperm males were able to transfer. These findings suggest that the reduction in sperm transferred was affected by both losing in combat and prolonged combat duration in leg-biting encounters. No potential conflict of interest relevant to this article was reported.

Oxford University Press Acta Medica Okayama 1536-2442 25 1 2025 Behavior, behavioral syndromes, and metabolism: the effects of artificial selection for death-feigning on metabolic rate 16 EN Kentarou Matsumura Graduate School of Environmental and Life Science, Okayama University David J. Hosken Centre for Ecology and Conservation, Faculty of Environment, Science and Economy, University of Exeter Tomohito Noda Centre for Ecology and Conservation, Faculty of Environment, Science and Economy, University of Exeter Takahisa Miyatake Graduate School of Environmental and Life Science, Okayama University Manmohan D. Sharma Centre for Ecology and Conservation, Faculty of Environment, Science and Economy, University of Exeter Death-feigning, or thanatosis, is an anti-predator behavioral strategy in many animals. Because individuals remain immobile while feigning death, individuals with longer durations of death feigning often show lower locomotor activity. Thus, metabolic rate, which is closely related to locomotor activity, may also be related to the intensity of death feigning. If there is a genetic correlation between death feigning and metabolism, metabolic rate may respond to selection on death-feigning behavior. Here, we tested for a relationship between metabolic rate and death-feigning using replicated populations of the red flour beetle (Tribolium castaneum) subjected to artificial bidirectional selection on the duration of death-feigning behavior. The results indicated that metabolic rate did not differ between populations selected for increased or decreased death feigning, although locomotor activity was significantly different between these treatments; populations selected for reduced death-feigning durations tended to be more active. These results suggest that death-feigning behavior is not genetically correlated with metabolic rate in T. castaneum. No potential conflict of interest relevant to this article was reported.

Springer Science and Business Media LLC Acta Medica Okayama 0003-6862 2025 Effects of caffeine on the longevity and locomotion activity of the common green bottle fly, Lucilia sericata (Diptera: Calliphoridae) EN Shine Shane Naing Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Haruna Fujioka Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Teruhisa Matsuura Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Takahisa Miyatake Graduate School of Environmental, Life, Natural Science and Technology, Okayama University The common green bottle fly, Lucilia sericata (Meigen) (Diptera: Calliphoridae), is a promising and useful managed pollinator for greenhouse agricultural crops. The fly can pollinate at lower and higher temperatures than European honeybee. However, management of the longevity of pollinators is important for growers using greenhouses. Previous studies using other insects showed that caffeine affects insect longevity and behaviors. For instance, European honeybee live longer and have increased memory after caffeine consumption. How caffeine affects the longevity and behavior of pollinators is worth investigating because it can affect pollinator’s behavior, extend longevity, or be an insecticide against pollinators. In the present study, therefore, the longevity and locomotion of L. sericata were investigated when they were given different caffeine concentrations. First, the longevity of L. sericata with five different caffeine concentrations was compared to the control. The results showed that higher concentrations of caffeine (2%, 1%, and 0.5%) significantly decreased the life span compared to lower concentrations (0.05% and 0.01%). Second, the locomotion activities of L. sericata were examined at those two caffeine concentrations with treated and control male and female flies utilizing a Drosophila Activity Monitor (DAM). Treatment with 0.05% caffeine dramatically reduced locomotion, but treatment of 0.01% caffeine did not. We also compared lipid concentrations of flies: flies treated with 0.05% caffeine had a lower lipid concentration compared to flies treated with 0% and 0.01% caffeine. These results indicate that caffeine had negative effects on the longevity and locomotion activities of the pollinator L. sericata in laboratory conditions. No potential conflict of interest relevant to this article was reported.

Springer Science and Business Media LLC Acta Medica Okayama 0892-7553 37 2 2024 Death Feigning in Larvae of Scorpionflies (Mecoptera: Panorpidae): Frequency and Postural Changes Based on Larval Instars 152 158 EN Ryo Ishihara Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Kentarou Matsumura Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Takahisa Miyatake Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Death feigning is thought to have evolved primarily as a predator avoidance behavior, and has been reported in 10 of the 31 orders of insects. However, there have been no reports of death-feigning behavior in Mecoptera species. We found that larvae of two scorpionfly species, Panorpa japonica and P. pryeri, showed death feigning in response to external stimuli by brush poking stimulation. First, we examined the frequencies of death-feigning postures. The two species showed two different postures of death feigning, “straight” and “ball.” Most of the 1st instar larvae of P. japonica and P. pryeri adopted the straight death-feigning posture. Next, we examined duration of death feigning. As the larval instar progressed, the death-feigning posture shifted from straight to ball in both Panorpa species. In P. japonica, the longest durations of death feigning were found in the 2nd to 3rd instars, while the longest duration of death feigning was found in the late 4th instar in P. pryeri larvae. No potential conflict of interest relevant to this article was reported.

Springer Science and Business Media LLC Acta Medica Okayama 0289-0771 42 3 2024 Reduced fitness in losers of leg-biting male combat compared to uncontested males in Zophobas atratus 177 185 EN Teruhisa Matsuura Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Takahisa Miyatake Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Sexual dimorphism and male combat are observed in many species. Often, the outcome of male combat affects the outcome of subsequent combats, mating success, number of sperm, and fitness of the male’s offspring. Also, the quantity and quality of sperm may be regulated by winning or losing, depending on species ecology and mating system. However, very few studies have experimentally examined the influence of fight outcomes on male offspring fitness. We studied male combat in the giant mealworm (Zophobas atratus) in which males bite each other’s hind legs. We hypothesized that subsequent fitness could differ between winners and losers in the escalated male combat of this species. We measured several fitness traits including the number of eggs laid by mated females, and the number of hatches sired by uncontested males, winners, and losers in escalated and non-escalated combat, and compared the fitness of each winner and loser to that of an uncontested male. We also measured mating duration. The numbers of eggs and the percentages of hatched eggs of losers in the escalated combat were significantly reduced compared to that of the uncontested males. This reduction may be due to injuries from escalated leg- biting fights and a result of the sperm amount of the uncontested males being greater than that of the loser males. No potential conflict of interest relevant to this article was reported.

Springer Science and Business Media LLC Acta Medica Okayama 0003-6862 59 3 2024 Body-size-dependent predation by some jumping spider species (Araneae: Salticidae) on Tribolium castaneum (Coletptera: Tenebrionidae) 267 271 EN Toma Hayashi Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Kentarou Matsumura Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Takahisa Miyatake Graduate School of Environmental, Life, Natural Science and Technology, Okayama University We examined the predation of two synanthropic jumping spiders, Hasarius adansoni (Araneae: Salticidae) and Plexippus paykulli (Araneae: Salticidae), on Tribolium castaneum (Herbst) (Coletptera: Tenebrionidae), a grain storage pest, that is sometimes found with these species to determine whether the predatory success of synanthropic and grassland jumping spiders on T. castaneum differs. We examined the predation of two synanthropic and three grassland jumping spiders on T. castaneum adults and larvae. We found that the two synanthropic species preyed on T. castaneum adults and larvae, while the three grassland species never attacked T. castaneum adults. The success or failure of predation on T. castaneum adults also depended on the body size of the jumping spiders. No potential conflict of interest relevant to this article was reported.

Springer Science and Business Media LLC Acta Medica Okayama 0340-5443 77 7 2023 Latitudinal cline in reproductive traits in the red flour beetle Tribolium castaneum 85 EN Kentarou Matsumura Graduate School of Environmental, Life Science and Technology, Okayama University Kyosuke Wakabayashi Graduate School of Environmental, Life Science and Technology, Okayama University Renya Kawakami Faculty of Agriculture, Kagawa University Takahisa Miyatake Graduate School of Environmental, Life Science and Technology, Okayama University Several previous studies have reported geographic variation and/or latitudinal clines of morphological sexual characteristics, but there are few studies that consider reproductive traits that are not morphological. Here, we measured the proportion of females fertilized by males, frequency of reproductive failure in males, and number of female copulations of the red flour beetle Tribolium castaneum collected from fields in Japan to investigate the relationship between reproductive traits and latitude. Our results show substantial differences in the reproductive traits of both sexes among field populations. We identified latitudinal clines for reproductive traits in males, but not females. Moreover, female, but not male, reproductive traits were correlated with body size. Our study suggests that selection for male reproductive traits varies with latitude in T. castaneum. No potential conflict of interest relevant to this article was reported.

Nature Portfolio Acta Medica Okayama 2045-2322 14 1 2024 Transcriptomic comparison between populations selected for higher and lower mobility in the red flour beetle Tribolium castaneum 67 EN Kentarou Matsumura Graduate School of Environment, Life, Natural Science and Technology, Okayama University Takafumi Onuma Graduate School of Agriculture, Tamagawa University Shinji Kondo Center for Genome Informatics, Research Organization of Information and Systems, Joint Support-Center for Data Science Research Hideki Noguchi Center for Genome Informatics, Research Organization of Information and Systems, Joint Support-Center for Data Science Research Hironobu Uchiyama NODAI Genome Research Center, Tokyo University of Agriculture Shunsuke Yajima NODAI Genome Research Center, Tokyo University of Agriculture Ken Sasaki Graduate School of Agriculture, Tamagawa University Takahisa Miyatake Graduate School of Environment, Life, Natural Science and Technology, Okayama University Movement is an important behavior observed in a wide range of taxa. Previous studies have examined genes controlling movement using wing polymorphic insects and genes controlling wing size. However, few studies have investigated genes controlling movement activity rather than morphological traits. In the present study, we conducted RNA sequencing using populations with higher (WL) and lower (WS) mobility established by artificial selection in the red flour beetle Tribolium castaneum and compared gene expression levels between selected populations with two replicate lines. As a result, we found significant differences between the selected populations in 677 genes expressed in one replicate line and 1198 genes expressed in another replicate line, of which 311 genes were common to the two replicate lines. Furthermore, quantitative PCR focusing on 6 of these genes revealed that neuropeptide F receptor gene (NpF) was significantly more highly expressed in the WL population than in the WS population, which was common to the two replicate lines. We discuss differences in genes controlling movement between walking activity and wing polymorphism. No potential conflict of interest relevant to this article was reported.

Springer Science and Business Media LLC Acta Medica Okayama 0340-5443 78 3 2024 Experimental quantification of genetic and ontogenetic effects on fighting behavior in the broad-horned flour beetle 34 EN Toshiki Nishitani Graduate School of Environmental, Life, Natural and Technology, Okayama University Kentarou Matsumura Graduate School of Environmental, Life, Natural and Technology, Okayama University Erik Postma Centre for Ecology & Conservation, University of Exeter, Penryn Campus Manmohan Dev Sharma Centre for Ecology & Conservation, University of Exeter, Penryn Campus David J Hosken Centre for Ecology & Conservation, University of Exeter, Penryn Campus Takahisa Miyatake Graduate School of Environmental, Life, Natural and Technology, Okayama University Most animal behaviors show large within- and among-individual variation, and this includes competitive male behaviors. With male fighting for example, aggressiveness often correlates with dominance, and contest duration varies with age. However, few studies have directly quantified how mean aggressiveness and contest duration, the variation among individuals in both traits, and the relationship among them, vary with age. Here we address these gaps and examine the effect of male age and genotype on two key aspects of male fighting behavior - aggressiveness (here measured as latency to fight) and contest duration - and the relationship between them. We do this using isogenic lines of the broad-horned flour beetle Gnatocerus cornutus. We observed fighting behavior of paired males of similar body size and age. Using uni- and multivariate mixed models, we show that although there was a significant difference between younger and older males in contest duration, mean aggressiveness was not affected by male age. However, the variation in aggression and fight duration varied with age, being greater in younger and older males respectively. Additionally, although there was a positive correlation between aggressiveness and contest duration in younger males, this relationship was not found in older males. Finally, the only significant genetic effect was for aggression in younger males. Our study shows that age differentially shapes key components of male fighting behavior as well as the relationship among them, highlighting the dynamic nature and context-dependence of fighting. No potential conflict of interest relevant to this article was reported.

Springer Science and Business Media LLC Acta Medica Okayama 0003-6862 59 2 2024 Spatio-temporal distribution of adults and eggs of the West Indian sweetpotato weevil Euscepes postfasciatus (Coleoptera: Curculionidae) on sweet potato stems 117 126 EN Kimiko Urasaki Okinawa Prefectural Plant Protection Center Kentarou Matsumura Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Takahisa Miyatake Graduate School of Environmental, Life, Natural Science and Technology, Okayama University The West Indian sweetpotato weevil, Euscepes postfasciatus, a serious pest of sweet potatoes, is being eradicated by sterile insect technique (SIT) in the south-western islands of Japan. Information on the diurnal movement of the target pests on host plants and where mating and egg-laying behavior occurs on the host is important for the application of SIT, which eradicates the target pest through mating of released sterile males and wild females. However, little such information is available on this species. In this study, male and female adults were released on host plants to examine the diurnal distribution on seedlings according to sex, as well as the sites where mounting behavior and egg laying occurs. The results showed that females left the host plant more frequently at night, whereas males were more likely to remain on the host plant at night. Both males and females stayed on the nodes of the host plant during the daytime. Mounting behavior also tended to occur more often at nodes. Furthermore, compared to unmated females, mated females stayed at the vertical top of the seedlings. However, it was found that eggs were often laid close to the roots rather than at the top of the vertical stems, even when the seedlings were placed upside down. The results of previous studies and this study will be discussed from the perspective of the application of SIT against E. postfasciatus. No potential conflict of interest relevant to this article was reported.

Springer Science and Business Media LLC Acta Medica Okayama 0289-0771 42 1 2023 Aggregation pheromone interrupts death feigning in the red flour beetle Tribolium castaneum 71 75 EN Motoya Ishikawa Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Kentarou Matsumura Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Takahisa Miyatake Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Death feigning is a behavior in which a prey is rendered motionless due to stimulation or threat by a predator. This anti-predator defense mechanism has been observed across a wide range of animal taxa and is considered adaptive. However, long durations of death feigning can decrease opportunities for feeding and reproduction, and therefore is a fitness cost as compared to environments without predators. Because death feigning is thought to be affected by the balance between survival and other fitness costs, selection pressure may drive individuals who are capable of plastic changes in the intensity of death feigning. Pheromones, which are important semiochemicals that affect foraging and reproductive success, may be one of the factors influencing the intensity of death-feigning behavior. In this study, we investigated the effect of an aggregation pheromone on the death-feigning behavior of the red flour beetle Tribolium castaneum. We found that beetles exposed to the pheromone showed a significantly shorter duration of death feigning than beetles that were not exposed to the pheromone. Therefore, our results suggest that an aggregation pheromone can plasticly alter the death-feigning behavior in T. castaneum. No potential conflict of interest relevant to this article was reported.

Springer Science and Business Media LLC Acta Medica Okayama 0003-6862 58 3 2023 Sex and strain-specific spectral attraction of Tribolium castaneum (Coleoptera: Tenebrionidae): behavioral studies 257 263 EN Sota Sone Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Takahisa Miyatake Graduate School of Environmental, Life, Natural Science and Technology, Okayama University We examined the attraction of adults to six LEDs in the red flour beetles, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), which is widespread as a stored grain insect. In the experiment, bluish green and green were more attractive than the two UVs, blue, and red LEDs only in females. On the other hand, no difference was found in attraction among the six LEDs in males. Next, we investigated the relationship between light intensity and attractiveness. No sexual difference in attractiveness in different light intensities was found, but the strongest light intensity was more attractive than other light intensities. Finally, we investigated the relationship between light attraction and strains artificially selected for the duration of death feigning. Short-strain beetles were more attracted to UV lights than long-strain beetles. No potential conflict of interest relevant to this article was reported.

Elsevier BV Acta Medica Okayama 1226-8615 25 4 2022 Longevity of Lucilia sericata (Meigen, 1826) used as pollinator 101999 EN Koichi Shimomae Graduate School of Environmental and Life Science, Okayama University Takuya Sato Japan Maggot Company, Co. Ltd. Yuichi Yoshida Graduate School of Environmental and Life Science, Okayama University Shine Shane Naing Graduate School of Environmental and Life Science, Okayama University Takahisa Miyatake Graduate School of Environmental and Life Science, Okayama University Pollinators play an important role in the production of many agricultural products. Honeybees, Apis mellifera L., are leading pollinators, but the number of honeybees in the world is declining. Finding alternatives is beginning to be important. In the present study, we compared the longevity of Lucilia sericata (Meigen, 1826), which is used as a pollinator, in cages in the laboratory and in a vinyl greenhouse under controlled feeding conditions. First, we showed that the longevity of the flies was significantly extended (c.a. 40 days) in the laboratory when water and sugar were supplied compared to the cases without sugar and/or water. Second, we found that the average longevity was 20 days with water and sugar in cages kept in a vinyl greenhouse during the summer. Finally, we released marked flies into a vinyl greenhouse where strawberries were cultivated without feeding water or sugar in the spring. As a result, fewer than 10% of the flies survived 10 days after release. Based on the result, we discuss the use of this species as a pollinator in the context of its survival rate. No potential conflict of interest relevant to this article was reported.

Wiley Acta Medica Okayama 0179-1613 128 2022 Artificial selections for death-feigning behavior in beetles show correlated responses in amplitude of circadian rhythms, but the period of the rhythm does not 453 460 EN Takahisa Miyatake Graduate School of Environmental and Life Science, Okayama University Masato S. Abe Center for Advanced Intelligence Project, RIKEN Kentarou Matsumura Laboratory of entomology, Faculty of Agriculture Taishi Yoshii Graduate School of Natural Science and Technology, Okayama University One of the most important survival strategies of organisms is to avoid predators. Studying one of such strategies, namely, death-feigning behavior, has recently become more common. The success or failure of this antipredator strategy will be affected by the circadian rhythms of both prey and predator because death feigning sometimes has a diurnal rhythm. However, few studies have analyzed the effects of differences in circadian rhythms on predator-avoidance behavior at the genetic level. Recently, the relationship between genes relating to circadian rhythm and death-feigning behavior, an antipredator behavior, has been established at the molecular level. Therefore, in this study, we compared three circadian rhythm-related traits, the free-running period of rhythms, amplitude of circadian rhythms, and total activity of strains of three Tribolium species that were artificially selected for the death-feigning duration: short (S-strains) and long (L-strains) durations. As a result, the amplitude of circadian rhythms and total activity were significantly different between S- and L-strains, but there was no difference in the free-running periods of the rhythm between the strains in T. castaneum, T. confusum, and T. freemani. Although the relationship between death-feigning behavior and activity has been reported for all three species, a genetic relationship between the duration of death feigning and the amplitude of circadian rhythms has been newly found in the present study. It is important to investigate the relationship between antipredator strategies and circadian rhythms at the molecular level in the future. No potential conflict of interest relevant to this article was reported.

WILEY Acta Medica Okayama 2045-7758 12 2 2022 Freezing or death feigning? Beetles selected for long death feigning showed different tactics against different predators e8533 EN Masaya Asakura Graduate School of Environmental and Life Science, Okayama University Kentarou Matsumura Department of Agriculture, Kagawa University Ryo Ishihara Graduate School of Environmental and Life Science, Okayama University Takahisa Miyatake Graduate School of Environmental and Life Science, Okayama University Prey evolve antipredator strategies against multiple enemies in nature. We examined how a prey species adopts different predation avoidance tactics against pursuit or sit-and-wait predators. As prey, we used three strains of Tribolium beetles artificially selected for short (short strain) or long (long strain) duration of death feigning, and a stock culture (base population). Death feigning is known to be effective for evading a jumping spider in the case of the long strains, while the present study showed that the long-strain beetles used freezing against a sit-and-wait type predator, Amphibolus venator, in this study. The short- strain beetles were more easily oriented toward predators. The time to predation was also shorter in the short strains compared to the long strains. The results showed that, as prey, the short strains displayed the same behavior, escaping, against both types of predators. Traditionally, death feigning has been thought to be the last resort in a series of antipredator avoidance behaviors. However, our results showed that freezing and death feigning were not parts of a series of behaviors, but independent strategies against different predators, at least for long-strain beetles. We also examined the relationship between a predator's starvation level and its predatory behavior. In addition, the orientation behavior toward and predation rate on the prey were observed to determine how often the predatory insect attacked the beetles. No potential conflict of interest relevant to this article was reported.

Nature Portfolio Acta Medica Okayama 2045-2322 11 1 2021 Genomic characterization between strains selected for death-feigning duration for avoiding attack of a beetle 21816 EN Keisuke Tanaka NODAI Genome Research Center, Tokyo University of Agriculture Ken Sasaki Graduate School of Agriculture, Tamagawa University Kentarou Matsumura Graduate School of Agriculture, Kagawa University Shunsuke Yajima NODAI Genome Research Center, Tokyo University of Agriculture Takahisa Miyatake Graduate School of Environmental and Life Science, Okayama University Predator avoidance is an important behavior that affects the degree of adaptation of organisms. We compared the DNA variation of one of the predator-avoidance behaviors, the recently extensively studied "death-feigning behavior", between the long strain bred for feigning death for a long time and the short strain bred for feigning death for a short time. To clarify how the difference in DNA sequences between the long and short strains corresponds to the physiological characteristics of the death-feigning duration at the transcriptome level, we performed comprehensive and comparative analyses of gene variants in Tribolium castaneum strains using DNA-resequencing. The duration of death feigning involves many gene pathways, including caffeine metabolism, tyrosine metabolism, tryptophan metabolism, metabolism of xenobiotics by cytochrome P450, longevity regulating pathways, and circadian rhythm. Artificial selection based on the duration of death feigning results in the preservation of variants of genes in these pathways in the long strain. This study suggests that many metabolic pathways and related genes may be involved in the decision-making process of anti-predator animal behavior by forming a network in addition to the tyrosine metabolic system, including dopamine, revealed in previous studies. No potential conflict of interest relevant to this article was reported.

Wiley Acta Medica Okayama 0013-8703 169 2021 Selection for age at reproduction changes pre‐mating period and mating frequency in Zeugodacus cucurbitae : impacts on insect quality control 959 965 EN Takahisa Miyatake Laboratory of Evolutionary Ecology, Graduate School of Environmental and Life Science, Okayama University In the mass-rearing of insects for sterile insect technique (SIT), it is important to maintain the quality of mass-reared males so that they can compete with wild males in mating with wild females. Mass-reared insects sometimes have shorter pre-mating periods and higher mating frequencies than their wild conspecifics. Indeed, this was the case for mass-reared individuals of the melon fly, Zeugodacus cucurbitae (Coquillett) (Diptera: Tephritidae), used in the SIT program to eradicate the melon fly on the Southwest Islands of Japan. Therefore, I hypothesized that divergent artificial selection for age at reproduction altered these traits in the melon fly as well. To examine the effects of eggs produced by younger parents on each generation, six artificially selected lines were established, for which eggs were collected from young (Y lines) and old (O lines) females. Then, the pre-mating periods and mating frequencies in males and females of the selected lines were compared. The results show a decreased pre-mating period and an increased mating frequency in younger lines compared to older lines, which was driven by males rather than females. These traits ensure efficient offspring production in mass-rearing, and are likely advantageous to the success of SIT programs. The impact of artificially selecting for these traits, especially in males, on insect quality and the efficiency of SIT is discussed. No potential conflict of interest relevant to this article was reported.

Elsevier Acta Medica Okayama 12268615 24 1 2021 Swarming and mating behavior in Ephemera orientalis Mclachlan, 1875 (Ephemeroptera: Ephemeridae) with morphological analyses 376 382 EN Takahisa Miyatake Graduate School of Environmental and Life Science, Okayama University Taichi Suge Graduate School of Environmental and Life Science, Okayama University Shunsuke Suzaki Graduate School of Environmental and Life Science, Okayama University Shintaro Tanabe Graduate School of Environmental and Life Science, Okayama University Ryo Ishihara Graduate School of Environmental and Life Science, Okayama University Kentarou Matsumura Graduate School of Environmental and Life Science, Okayama University Swarming and mating behaviors of a mayfly species, Ephemera orientalis Mclachlan, 1875 were observed in 2015, 2016, and 2018 at a river bank of the Asahi River, Japan. Males started to make swarms between late April and middle May in 2016 and 2018. The numbers of mated pairs in a swarm correlated with the numbers of flying males in a swarm in 2016 and 2018. Swarms were formed during a limited period at dusk most probably because that interval is free from natural enemies. Males competed with each other to copulate with females in swarms. We clarified the function of the forelegs of males, which are significantly longer than those of females. Males used their forelegs to hold up a female from below. Besides forelegs, males have longer tails than females. We will discuss why sexual differences are found in these traits. Our results represent the first observation of swarm mating behavior in E. orientalis. No potential conflict of interest relevant to this article was reported.

Brill Acta Medica Okayama 0005-7959 158 2 2021 Age-dependent walking and feeding of the assassin bug Amphibolus venator 123 133 EN Kentarou Matsumura Graduate School of Environmental and Life Science, Okayama University Mana Iwaya Faculty of Agriculture, Okayama University Naohisa Nagaya Kyoto Sangyo University Ryusuke Fujisawa Kyushu Institute of Technology Takahisa Miyatake Graduate School of Environmental and Life Science, Okayama University Animal behaviours often dependent on age. In many insect species, walking shows an age-dependent decline, and food intake may also be dependent on age. However, few studies have investigated the relationship between age and walking or food intake. In the present study, we compared walking traits and food intake among individuals of different ages in the assassin bug Amphibolus venator (Hemiptera, Reduviidae). The present results showed an age-dependent decline in walking, similar to findings in many animal species. On the other hand, food intake showed a positive correlation with age. Therefore, the decline in walking did not lead to a decline in feeding. The positive relationship between food intake and age may be related to the type of predation, sit-and-wait, used by A. venator via alterations in investment in reproductive traits with age. No potential conflict of interest relevant to this article was reported.

Public Library of Science Acta Medica Okayama 1932-6203 16 1 2021 Amplitude of circadian rhythms becomes weaken in the north, but there is no cline in the period of rhythm in a beetle e0245115 EN Masato S. Abe Center for Advanced Intelligence Project, RIKEN Kentarou Matsumura Graduate School of Environmental and Life Science, Okayama University Taishi Yoshii Graduate School of Natural Science and Technology, Okayama University Takahisa Miyatake Graduate School of Environmental and Life Science, Okayama University Many species show rhythmicity in activity, from the timing of flowering in plants to that of foraging behavior in animals. The free-running periods and amplitude (sometimes called strength or power) of circadian rhythms are often used as indicators of biological clocks. Many reports have shown that these traits are highly geographically variable, and interestingly, they often show latitudinal or longitudinal clines. In many cases, the higher the latitude is, the longer the free-running circadian period (i.e., period of rhythm) in insects and plants. However, reports of positive correlations between latitude or longitude and circadian rhythm traits, including free-running periods, the power of the rhythm and locomotor activity, are limited to certain taxonomic groups. Therefore, we collected a cosmopolitan stored-product pest species, the red flour beetle Tribolium castaneum, in various parts of Japan and examined its rhythm traits, including the power and period of the rhythm, which were calculated from locomotor activity. The analysis revealed that the power was significantly lower for beetles collected in northern areas than southern areas in Japan. However, it is worth noting that the period of circadian rhythm did not show any clines; specifically, it did not vary among the sampling sites, despite the very large sample size (n = 1585). We discuss why these cline trends were observed in T. castaneum. No potential conflict of interest relevant to this article was reported.

Wiley Acta Medica Okayama 0179-1613 127 1 2021 Effects of caffeine on mating behavior and sperm precedence in Tribolium castaneum 45 49 EN Yuhao Ji Graduate School of Environmental and Life Science, Okayama University Yuki Ryuji Graduate School of Environmental and Life Science, Okayama University Kentarou Matsumura Faculty of Agriculture, Kagawa University Takahisa Miyatake Graduate School of Environmental and Life Science, Okayama University Biogenic amines such as dopamine are physiologically neuroactive substances that affect behavioral and physiological traits in invertebrates, and it has long been known that these substances affect mating behavior in insects. Caffeine is a dopamine activator and thus enhances dopamine receptor activity. However, the effects of caffeine intake on insect mating behavior have been largely unexplored. Therefore, we examined the effect of caffeine on mating behavior in the red flour beetle Tribolium castaneum. Caffeine, which activates dopamine, affected the mating behavior of T. castaneum males. Males who orally ingested caffeine courted faster than males who did not, resulting in faster mounting of females and less time to a male's external aedeagus protrusion. However, the present results showed no difference in sperm precedence measured as a P2 value between males fed caffeine and males not fed caffeine. We discuss the effects of caffeine on insect mating and the possibility that caffeine consumption may cause males to mate with more females in the laboratory. No potential conflict of interest relevant to this article was reported.

Springer Acta Medica Okayama 0289-0771 39 2020 Arousal from death feigning by vibrational stimuli: comparison of Tribolium species 107 113 EN Ryo Ishihara Department of Evolutionary Ecology, Graduate School of Environmental and Life Science, Okayama University Kentarou Matsumura Department of Evolutionary Ecology, Graduate School of Environmental and Life Science, Okayama University Jordan Elouise Jones Department of Evolution, Ecology and Behaviour, Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool Ji Yuhao Department of Evolutionary Ecology, Graduate School of Environmental and Life Science, Okayama University Ryusuke Fujisawa School of Computer Science and Systems Engineering, Kyushu Institute of Technology Naohisa Nagaya Faculty of Information Science and Engineering, Kyoto Sangyo University Takahisa Miyatake Department of Evolutionary Ecology, Graduate School of Environmental and Life Science, Okayama University Death feigning (or tonic immobility) is an effective antipredator strategy. However, prolonged immobility on the ground increases the risk of being parasitized or eaten by predators, and thus, insects must rouse themselves when appropriate stimulation is provided. Very few studies on the effect of stimulus intensity on arousal from death feigning have been conducted. A previous study using Tribolium castaneum showed an existing threshold for the intensity of the stimulus that causes arousal from death feigning. Whether there are differences between species in the threshold for arousal is an interesting question. In the present study, we, therefore, compared the effect of stimulus strength on arousal from death feigning in two closely related species, namely, T. confusum and T. freemani, which are established strains that have been artificially selected for longer duration of death feigning. Also, part of the study was to determine whether there was a positive association between intensity of stimulus needed to rouse and the duration of death feigning. We discuss why there is a difference in the strength of the stimulus needed for arousal from death feigning among Tribolium species, for which we included the data for T. castaneum from a previous study. No potential conflict of interest relevant to this article was reported.

Oxford University Press Acta Medica Okayama 0024-4066 130 1 2020 Genetic variation and phenotypic plasticity in circadian rhythms in an armed beetle, Gnatocerus cornutus (Tenebrionidae) 34 40 EN Kentarou Matsumura Graduate School of Environmental and Life Science, Okayama University Masato S Abe Center for Advanced Intelligence Project, RIKEN Manmohan D Sharma Centre for Ecology and Conservation, School of Biosciences, University of Exeter David J Hosken Centre for Ecology and Conservation, School of Biosciences, University of Exeter Taishi Yoshii Graduate School of Natural Science and Technology, Okayama University Takahisa Miyatake Graduate School of Environmental and Life Science, Okayama University Circadian rhythms, their free-running periods and the power of the rhythms are often used as indicators of biological clocks, and there is evidence that the free-running periods of circadian rhythms are not affected by environmental factors, such as temperature. However, there are few studies of environmental effects on the power of the rhythms, and it is not clear whether temperature compensation is universal. Additionally, genetic variation and phenotypic plasticity in biological clocks are important for understanding the evolution of biological rhythms, but genetic and plastic effects are rarely investigated. Here, we used 18 isofemale lines (genotypes) of Gnatocerus cornutus to assess rhythms of locomotor activity, while also testing for temperature effects. We found that total activity and the power of the circadian rhythm were affected by interactions between sex and genotype or between sex, genotype and temperature. The males tended to be more active and showed greater increases in activity, but this effect varied across both genotypes and temperatures. The period of activity varied only by genotype and was thus independent of temperature. The complicated genotype–sex–environment interactions we recorded stress the importance of investigating circadian activity in more integrated ways. No potential conflict of interest relevant to this article was reported.

Wiley Acta Medica Okayama 1010061X 33 8 2020 Death feigning as an adaptive anti‐predator behaviour: Further evidence for its evolution from artificial selection and natural populations 1120 1128 EN Kana Konishi Graduate School of Environmental and Life Science, Okayama University Kentarou Matsumura Graduate School of Environmental and Life Science, Okayama University Wataru Sakuno Graduate School of Environmental and Life Science, Okayama University Takahisa Miyatake Graduate School of Environmental and life Science, Okayama University Death feigning is considered to be an adaptive antipredator behaviour. Previous studies on Tribolium castaneum have shown that prey which death feign have a fitness advantage over those that do not when using a jumping spider as the predator. Whether these effects are repeatable across species or whether they can be seen in nature is, however, unknown. Therefore, the present study involved two experiments: (a) divergent artificial selection for the duration of death feigning using a related species T. freemani as prey and a predatory bug as predator, demonstrating that previous results are repeatable across both prey and predator species, and (b) comparison of the death‐feigning duration of T. castaneum populations collected from field sites with and without predatory bugs. In the first experiment, T. freemani adults from established selection regimes with longer durations of death feigning had higher survival rates and longer latency to being preyed on when they were placed with predatory bugs than the adults from regimes selected for shorter durations of death feigning. As a result, the adaptive significance of death‐feigning behaviour was demonstrated in another prey–predator system. In the second experiment, wild T. castaneum beetles from populations with predators feigned death longer than wild beetles from predator‐free populations. Combining the results from these two experiments with those from previous studies provided strong evidence that predators drive the evolution of longer death feigning. No potential conflict of interest relevant to this article was reported.

Springer Acta Medica Okayama 02890771 38 2020 Relationships between mating tactics and male traits such as body size and fluctuating asymmetry in the Japanese scorpionfly 233 239 EN Ryo Ishihara raduate School of Environmental and Life Science, Okayama University Takahisa Miyatake Graduate School of Environmental and life Science, Okayama University Fluctuating asymmetry (FA) is defined as small, random deviations from perfect bilateral symmetry in a morphological trait. It has sometimes been used as an indicator of male quality because it affects male mating success. In the Japanese scorpionfly, Panorpa japonica, males are known to use two mating tactics, donation of nuptial gifts and forced mating. In P. japonica, low FA males are more likely to win a competition with another male, and females prefer low FA male sex pheromones. However, no studies have been conducted on the effect of FA on the mating tactics adopted by males. In the present study, we first observed the mating behaviors of P. japonica and classified these into three patterns: (1) nuptial gifting, (2) forced mating, and (3) feeding mating. Second, we investigated the relationships between mating tactics and male traits, including body size, FA, and weapon size. The results showed a positive correlation between absolute FA and mating duration only in the case of feeding mating. We discuss the reasons why this significant correlation was found in P. japonica. No potential conflict of interest relevant to this article was reported.

Herpetological Society of Japan Acta Medica Okayama 1345-5834 38 1 2019 Individual and Sexual Differences in Time to Habituate to Food-stimuli Presentation of Potential Prey in Hyla japonica 14 22 EN Shintaro Tanabe Graduate School of Environmental and Life Science, Okayama University Eiiti Kasuya Department of Biology, Faculty of Sciences, Kyushu University Takahisa Miyatake Graduate School of Environmental and life Science, Okayama University The traits of many animal species exhibit individual and sexual differences. Individuals repeatedly receiving a stimulus without harm become habituated to it. However, few studies have been conducted on individual and sexual differences in the process of habituation to unfamiliar food stimuli. Therefore, we hypothesized that individual differences or sexual differences would be observed in reaction to an in-lab food-stimuli presentation of potential prey items (after that "food stimuli"). We tested the hypothesis using the Japanese tree frog Hyla japonica, and conducted statistical analyses of these results. A generalized linear model (GLM) showed individual and sexual differences in time to get used to the food stimuli. Females habituated more rapidly to food stimuli than males. The difference between sexes is discussed in view of two ultimate and one proximate reasons. No potential conflict of interest relevant to this article was reported.

Brill Academic Publishers Acta Medica Okayama 0005-7959 157 1 2019 Lines selected for different durations of tonic immobility have different leg lengths in the red flour beetle Tribolium castaneum 17 31 EN Kentarou Matsumura Graduate School of Environmental and life Science, Okayama University Takahisa Miyatake Graduate School of Environmental and life Science, Okayama University Tonic immobility is an adaptive anti-predator behaviour observed in many species. This anti-predator behaviour is often correlated with a species' movement motivation, so a relationship between the duration of tonic immobility and morphological traits supporting movement would be expected. Using the red flour beetle, Tribolium castaneum, we carried out two-way artificial selection for the duration of tonic immobility over more than 43 generations, establishing populations with longer (L) and shorter (S) tonic immobility durations compared to those of a non-selected control (C) population. Here, we investigated differences in walking motivation and leg length between the selected populations. Walking motivation was significantly higher in beetles from the S population than that in those from the L population. Moreover, S-population beetles of both sexes had significantly longer legs than those from L and C populations. The present results suggest the evolution of longer legs in response to selection pressure for a shorter duration of tonic immobility in T. castaneum. No potential conflict of interest relevant to this article was reported.

Springer Acta Medica Okayama 0289-0771 36 2 2018 Responses to relaxed and reverse selection in strains artificially selected for duration of death-feigning behavior in the red flour beetle, Tribolium castaneum 161 168 EN Kentarou Matsumura Graduate School of Environmental and Life Science, Okayama University Takahisa Miyatake Graduate School of Environmental and Life Science, Okayama University Divergent lines selected artificially for many generations make it possible to answer two questions: (1) whether genetic variation still exists within the selected population; and (2) whether the selection itself is costly for the selected strain. In previous studies, the red flour beetle Tribolium castaneum was divergently selected artificially for duration of death-feigning, and strains selected for longer (L-strain) and shorter (S-strain) durations of death-feigning have been established (Miyatake et al. 2004, 2008). Because the selection experiments have been conducted for more than 27 generations, genetic variation may be eroded. Furthermore, because another previous study reported physiological costs to L-strains, the L-strains selected artificially for longer duration of death-feigning may have suffered more costs than the S-strains. In the present study, therefore, we relaxed the selection pressure after the 27th or 30th generation of S- and L-strains. We also carried out reverse selection during the most recent eight generations of S- and L-strains. The results showed that each strain clearly responded to relaxation of selection and reverse selection, suggesting that (1) additive genetic variation still existed in both strains after long-term selection, and (2) selection for shorter and longer duration of death-feigning was costly. These results suggest that anti-predator behavior is controlled by many loci, and longer or shorter duration of death-feigning is costly in a laboratory without predators. No potential conflict of interest relevant to this article was reported.

Oxford University Press Acta Medica Okayama 00018244 30 6 2019 Artificial selection on walking distance suggests a mobility-sperm competitiveness trade-off 1522 1529 EN Kentarou Matsumura Graduate School of Environmental and Life Science, Okayama University C Ruth Archer Centre for Ecology & Conservation, University of Exeter David J Hosken Centre for Ecology & Conservation, University of Exeter Takahisa Miyatake Graduate School of Environmental and Life Science, Okayama University Securing matings is a key determinant of fitness, and in many species, males are the sex that engages in mate searching. Searching for mates is often associated with increased mobility. This elevated investment in movement is predicted to trade-off with sperm competitiveness, but few studies have directly tested whether this trade-off occurs. Here, we assessed whether artificial selection on mobility affected sperm competitiveness and mating behavior, and if increased mobility was due to increased leg length in red flour beetles (Tribolium castaneum). We found that, in general, males selected for decreased mobility copulated for longer, stimulated females more during mating, and tended to be better sperm competitors. Surprisingly, they also had longer legs. However, how well males performed in sperm competition depended on females. Males with reduced mobility always copulated for longer than males with high mobility, but this only translated into greater fertilization success in females from control populations and not the selection populations (i.e. treatment females). These results are consistent with a mate-searching/mating-duration trade-off and broadly support a trade-off between mobility and sperm competitiveness. No potential conflict of interest relevant to this article was reported.

Kluwer Academic/Plenum Acta Medica Okayama 00018244 49 5 2019 Arousal from Tonic Immobility by Vibration Stimulus 478 483 EN Takahisa Miyatake Department of Evolutionary Ecology, Graduate School of Environmental and Life ScienceOkayama University Kentarou Matsumura Department of Evolutionary Ecology, Graduate School of Environmental and Life ScienceOkayama University Ryota Kitayama Department of Evolutionary Ecology, Graduate School of Environmental and Life ScienceOkayama University Keiichi Otsuki Faculty of Computer Science and Engineering Kyoto Sangyo University Yuhao Ji Department of Evolutionary Ecology, Graduate School of Environmental and Life ScienceOkayama University Ryusuke Fujisawa School of Computer Science and Systems EngineeringKyushu Institute of Technology Naohisa Nagaya Faculty of Computer Science and Engineering Kyoto Sangyo University Tonic immobility (TI) is an effective anti-predator strategy. However, long immobility status on the ground increases the risk of being eaten by predators, and thus insects must rouse themselves when appropriate stimulation is provided. Here, the strength of vibration causing arousal from the state of TI was examined in strains artificially selected for longer duration of TI (L-strains: long sleeper) in a beetle. We provided different strengths of vibration stimuli to the long sleepers in Tribolium castaneum. Although immobilized beetles were never awakened by the stimuli from 0.01 to 0.12 mm in amplitude, almost of the beetles were aroused from immobilized status by the stimulus at 0.21 mm. There was a difference in sensitivity of individuals when the stimuli of 0.14 mm and 0.18 mm were provided. F2 individuals were also bred by crossing experiments of the strains selected for shorter and longer duration of TI. The arousal sensitivity to vibration was well separated in the F2 individuals. A positive relationship was observed between the duration of TI and the vibration amplitude, suggesting that immobilized beetles are difficult to arouse from a deep sleep, while light sleepers are easily aroused by even small vibrations. The results indicate a genetic basis for sensitivity to arousal from TI. No potential conflict of interest relevant to this article was reported.

Springer Japan Acta Medica Okayama 00036862 54 2019 Effects of temperature during successive generations on life-history traits in a seed beetle Callosobruchus chinensis (Chrysomelidae: Coleoptera) 459 464 EN Kenji Terada Graduate School of Environmental and Life Science Okayama University Kentarou Matsumura Graduate School of Environmental and Life Science Okayama University Takahisa Miyatake Graduate School of Environmental and Life ScienceOkayama University Temperature is an important environmental factor for life-history traits in poikilothermic animals. Many of experiments on evolution have been conducted using Drosophila species, and effects on life-history traits vary depending on the study. On the other hand, few studies have been conducted on the effects of temperature on life-history traits in the other insect species. In the present study, we reared adzuki bean beetles under two different temperatures, high and low, for 2 years (20 generations), and compared life-history traits including body size of females, fecundity, egg size, rate of egg hatching, emergence rate, development time, and wing length. No differences in responses were found in these traits between selection strains, except the rate of egg hatching. That is, the rates of egg hatching in high-temperature (32 °C) selection strains were significantly higher than those in low-temperature (24 °C) selection strains. We discuss the cause of change in egg hatchability during successive generations under different temperature treatments from the following viewpoints including evolutionary adaptation to high temperature and the experimental protocol. No potential conflict of interest relevant to this article was reported.

Springer Nature Acta Medica Okayama 20452322 9 1 2019 Transcriptomic comparison between beetle strains selected for short and long durations of death feigning 14001 EN Hironobu Uchiyama NODAI Genome Research Center, Tokyo University of Agriculture Ken Sasaki Graduate School of Agriculture, Tamagawa University Shogo Hinosawa Graduate School of Agriculture, Tamagawa University Keisuke Tanaka NODAI Genome Research Center, Tokyo University of Agriculture Kentarou Matsumura Graduate School of Environmental and Life Science, Okayama University Shunsuke Yajima Graduate School of Environmental and Life Science, Okayama University Takahisa Miyatake Graduate School of Environmental and Life Science, Okayama University The molecular basis of death feigning, an antipredator behavior that has received much attention recently, was analyzed. We compared the gene expression profiles of strains with different behaviors, i.e., different durations of death feigning, in the beetle Tribolium castaneum. Beetles artificially selected for short (S) and long (L) durations of death feigning for many generations were compared thoroughly by RNA sequencing. We identified 518 differentially expressed genes (DEGs) between the strains. The strains also showed divergence in unexpected gene expression regions. As expected from previous physiological studies, genes associated with the metabolic pathways of tyrosine, a precursor of dopamine, were differentially expressed between the S and L strains; these enzyme-encoding genes were expressed at higher levels in the L strain than in the S strain. We also found that several genes associated with insulin signaling were expressed at higher levels in the S strain than in the L strain. Quantitative real-time PCR analysis showed that the relative expression levels of Tchpd (encoding 4-hydroxyphenylpyruvate dioxygenase, Hpd) and Tcnat (encoding N-acetyltransferase, Nat) were significantly higher in the L strain than in the S strain, suggesting the influence of these enzymes on the supply of dopamine and duration of death feigning. No potential conflict of interest relevant to this article was reported.

PUBLIC LIBRARY SCIENCE Acta Medica Okayama 1932-6203 8 12 2013 Male Courtship Behavior and Weapon Trait as Indicators of Indirect Benefit in the Bean Bug, Riptortus pedestris e83278 EN Yû Suzaki Masako Katsuki Takahisa Miyatake Yasukazu Okada Females prefer male traits that are associated with direct and/or indirect benefits to themselves. Male–male competition also drives evolution of male traits that represent competitive ability. Because female choice and male–male competition rarely act independently, exploring how these two mechanisms interact is necessary for integrative understanding of the evolution of sexually selected traits. Here, we focused on direct and indirect benefits to females from male attractiveness, courtship, and weapon characters in the armed bug Riptortus pedestris. The males use their hind legs to fight other males over territory and perform courtship displays for successful copulation. Females of R. pedestris receive no direct benefit from mating with attractive males. On the other hand, we found that male attractiveness, courtship rate, and weapon size were significantly heritable and that male attractiveness had positive genetic covariances with both courtship rate and weapon traits. Thus, females obtain indirect benefits from mating with attractive males by producing sons with high courtship success rates and high competitive ability. Moreover, it is evident that courtship rate and hind leg length act as evaluative cues of female choice. Therefore, female mate choice and male–male competition may facilitate each other in R. pedestris. This is consistent with current basic concepts of sexual selection. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 02890771 25 1 2007 Interpopulation variation in female remating is attributable to female and male effects in Callosobruchus chinensis 49 55 EN Tomohiro Harano Okayama University Takahisa Miyatake Graduate School of Environmental and life Science, Okayama University <p>The evolution of female multiple mating is best understood by consideration of male and female reproductive perspectives. Females should usually be selected to remate at their optimum frequencies whereas males should be selected to manipulate female remating to their advantage. Female remating behavior may therefore be changed by variation of male and female traits. In this study, our objective was to separate the effects of female and male strains on female remating for the adzuki bean beetle, Callosobruchus chinensis, for which there is interstrain variation in female remating frequency. We found that interstrain variation in female remating is primarily attributable to female traits, suggesting genetic variation in female receptivity to remating in C. chinensis. Some interstrain variation in female remating propensity was attributable to an interaction between female and male strains, however, with the males of some strains being good at inducing nonreceptivity in females from one high-remating strain whereas others were good at inducing copulation in nonvirgin females from the high-remating strain. There is, therefore, interstrain variation in male ability to deter females from remating and in male ability to mate successfully with nonvirgin females. These results suggest that mating traits have evolved along different trajectories in different strains of C. chinensis.</p> No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 25 3 2007 Ownership-dependent mating tactics of minor males of the beetle Librodor japonicus (Nitidulidae) with intra-sexual dimorphism of mandibles 255 261 EN Kensuke Okada Takahisa Miyatake <p>Intra-sexual dimorphism is found in the weapons of many male beetles. Different behavioral tactics to access females between major and minor males, which adopt fighting and alternative tactics, respectively, are thought to maintain the male dimorphism. In these species major males have enlarged weapons that they use in fights with rival males. Minor males also have small weapons in some of these species, and it is unclear why these males possess weapons. We examined the hypothesis that minor males might adopt a fighting tactic when their status was relatively high in comparison with that of other males (e.g., ownership of a territory). We observed the behavioral tactics of major and minor males of the beetle Librodor japonicus, whose males have a dimorphism of their mandibles. Major males fought for resources, whereas minor males adopted two status-dependent tactics, fighting and sneaking, to access females, depending on their ownership of a sap site. We suggest that ownership status-dependent mating tactics in minor males may maintain the intra-sexual dimorphism in this beetle.</p> No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254 91 1 2002 大量増殖されたウリミバエの遺伝的虫質管理 61 69 EN Takahisa Miyatake Quality control in mass-reared melon files, Bactricera cucurbitae, after eradication is discussed, based on the results of artificial selection experiments. First, a brief history of quality control in mass-rearing of insects is described. In practical mass-rearing of melon fly, many traits habe already been differentiated between mass-reared and wild files. These differing traits are reviewed and the factors which caused these differences are considered. It was considered that the differences between wild and mass-reared melon files depended on the selection pressures from the mass-rearing method. Next, the results of several artificial selection experiments using the melon fly are reviewed. Finally, consideration is given to some correlated responses to artificial selection in mass-rearing. Longevity that is correlated to early fecundity was successfully controlled by artificial selection for reproduction in the mass-rearing system. On the basis of these results, an improved method for quality control in mass-reared melon fly with considerations for quantitative genetics is discussed. No potential conflict of interest relevant to this article was reported.