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Published on: December 11, 2014
Patterns of structural change in gonads of the divine dwarfgoby Eviota epiphanes as they sexually transition
Jessica M Maxfield1, Kathleen S Cole1
1Department of Biology, University of Hawai'i, Honolulu, Hawai'i, USA.
Abstract:
This study documents changes in gonadal structure for the serial hermaphrodite (or bidirectional sex changer) divine dwarfgoby Eviota epiphanes (family Gobiidae) as individuals transition in both directions. To evaluate transitional gonad morphology, individuals actively producing the same gamete type (oocytes or sperm) were set up into pairs and euthanised over a period of 14 days to get a time series of morphological changes during gonad transformation. Results from this study show that rapid changes in the gonad take place at a structural level as individuals change their reproductive function and gamete production. Changing from oocyte production (o-phase) to sperm production (s-phase) starts with the breakdown of vitellogenic oocytes (i.e., atresia) followed by the appearance and proliferation of spermatogenic tissue which, in most cases, was not previously visible. Changing from sperm production to oocyte production included the cessation of sperm production, a reduction in size and number of seminiferous lobules and the maturation of previtellogenic oocytes already present in the gonads. Experimental fish changed from oocyte production to sperm production more readily than from sperm production to oocyte production. The hypothesis that shifts in sexual function among serially hermaphroditic fish species have a similar cost in either direction is not supported in E. epiphanes.
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