CHARACTERIZATION OF EARLY LIFE HISTORY AND SEXUAL SYSTEM OF THE YASHA GOBY Stonogobiops yasha

Laüra Gaitan Daza*, Joseph T. Szczebak, Bradford D. Bourque, Andrew L. Rhyne, and Kerri S. Warren.
 
Department of Marine Biology
Roger Williams University
Bristol, RI, 02809
lgaitandaza299@g.rwu.edu

The yasha goby, Stonogobiops yasha, has remained largely unstudied since its first description in 1997, despite its high demand in the marine aquarium trade. In 2016, the Roger Williams University (RWU) Marine Lab successfully bred this species in captivity. Facilitated by this success, our study aimed to (a) characterize the embryonic and larval development of S. yasha from fertilization to juvenile metamorphosis, and (b) determine the sexual system employed by S. yasha (i.e., gonochorism or hermaphroditism). This research will constitute the first examination of the full life history of this genus, providing essential data for commercial-scale production of S. yasha in hatcheries.

Embryology was documented using video and camera lucida sketching, and larval development was documented using microphotography to measure body length and characterize onset of key morphological changes. Embryos and larvae were collected from 4 separate nests of eggs, and approximately 10 embryos or larvae were used for each developmental stage analyzed. Embryonic development lasted 6 days, with larval hatching occurring the morning of day 6. Flexion occurred between day 8-12, settlement morphology was evident at day 15-20, and metamorphosis took place at day 27- 50.

Based on culture trends observed in the RWU Marine Lab and literature on other reef-dwelling gobies, this study tested the hypothesis that S. yasha are protogynous sequential hermaphrodites. An attempt to determine the sexual system of the specie was performed on recently settled juveniles (N=41). The juveniles were collected and separated into 13 pairs and 15 individual arrangements. Half of the pairs and individuals (N=7, N=8, respectively) were provided PVC pipe burrows; the other half were maintained in bare-bottom tanks. Total length (mm) was measured monthly, and juveniles were visually observed daily for the display of secondary sexual traits (i.e., presence/absence of black-tipped pelvic fins). At 70 days post hatch (dph), 50% of the juveniles from each of the four treatments were euthanized and processed histologically to assess gonad development, comparing results to previously processed adult specimens. The remaining juveniles were euthanized and processed at 200 dph.

This research aims to expand the understanding of Gobiid sexual system diversity, and provide essential data for S. yasha  and culture methods. These results are the first characterization of this genus, and reveal broader implications for survival at key developmental stages, as well as the role of culture environment on developing juveniles into highly socially dominated dynamics.