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ID 32978
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Abstract
Embryos attached to the female crab Sesarma haematocheir hatch synchronously within 1 h. Hatching is also synchronized near the time of the expected nocturnal high tide. These events are governed by a single circatidal clock (or pacemaker) in the female crab. The present study examined the role of the optic peduncle of the eyestalk on hatching and hatching synchrony. Surgery was performed either from the tip of the eyestalk [to remove the region of the optic peduncle from the compound eye–retina complex to the medulla interna (MI)] or from a small triangle 'window' opened on the eyestalk exoskeleton [to create lesions on the medulla terminalis (MT) of the optic peduncle]. Neither hatching nor hatching synchrony was affected by removal of the region of the optic peduncle from the compound eye–retina complex to the MI: the circatidal rhythm also remained. Removal of the MI probably caused damage to the sinus gland and the bundle of axons running from the sinus gland to the X organ. Nevertheless, maintenance of highly synchronized hatching indicates that the X organ–sinus gland system is not related to hatching. Hatching and hatching synchrony were not affected by dorsal-half cuts of the MT: the timing of hatching was not affected either. By contrast, transverse and ventral-half cuts of the MT caused severe damage to most females; hatching of many females was suppressed, while hatching of some females was either periodic, at intervals of approximately 24 h, or arrhythmic for a few days. The bundle of neuronal axons is tangled in the MT, and the axons inducing hatching pass through the ventral half of the MT. Complete incision of these axon bundles may have suppressed hatching. Incomplete incision of the axon bundle or partial damage to the neurons may have caused periodic or arrhythmic patterns of hatching. There are two possible roles for MT in hatching. One possibility is that neurons in the MT only induce hatching under the control of the circatidal pacemaker located in a site somewhere other than the optic peduncle. Another possibility is that the circatidal pacemaker is actually present in the MT. The second possibility seems more plausible. Each embryo has a special 48–49.5 h developmental program for hatching. This program could be initiated by the circatidal pacemaker in the female, and hatching synchrony may also be enhanced by the same pacemaker.
Keywords
circatidal pacemaker
estuarine crab
gentle-release
behavior
hatching synchrony
medulla terminalis
optic peduncle
eyestalk
neuronal pathway
vigorous-release behavior
Sesarma
haematocheir.
Note
Published with permission from the copyright holder. This is the institute's copy, as published in The Journal of Experimental Biology, November 2002, Volume 205, Issue 22, Pages 3487-3504.
Publisher URL:http://jeb.biologists.org/cgi/reprint/205/22/3487
Copyright © 2002 The Company of Biologists Limited. All rights reserved.
Published Date
2002-11
Publication Title
The Journal of Experimental Biology
Volume
volume205
Issue
issue22
Publisher
The Company of Biologists Limited
Start Page
3487
End Page
3504
ISSN
0022-0949
NCID
AA00697490
Content Type
Journal Article
language
英語
Copyright Holders
The Company of Biologists Limited
File Version
publisher
Refereed
True
PubMed ID
Web of Sience KeyUT
Submission Path
biology_general/17