A Dynamic Shift: a Molecular Perspective on Bidirectional Hermaphroditism in Two Reef Fish Species in the Family Goblidae

Jessica Maxfield - UH Manoa Zoology (Dissertation Defense)
Friday, February 22, 2019 - 3:30pm to 4:30pm
Bilger 150

Sex change in fishes is a well-studied phenomenon from a morphological, social,
and hormonal perspective. Very little is known however, about how sex change is
regulated at the genetic level. Here I investigate the changes in gene expression
in two species of bidirectional sex changing gobies, Lythrypnus dalli and Eviota
epiphanes, as they transition from oocyte production to sperm production, using
whole transcriptome sequencing. Unlike many sex changing species that have
been studied, both of these gobies maintain both oogenic and spermatogenic
tissue in their gonads throughout life. This makes them a unique and interesting
subject for comparative analyses. In addition to providing insights into how this
process is regulated, I provide a comparison between the two species, identifying
conserved and novel features, in order to better understand the evolution of
bidirectional sex change in the family Gobiidae. I find that the overall
transcriptome, the genes represented, and pathways and Gene Ontology (GO
terms ) associated with those genes, to be very similar between species.
However, when I look at what genes are differentially expressed during the sex
change process (i.e. being utilized to make the transition) I find very few
conserved elements. Additionally I find several key sex regulatory genes, known
to play a pivotal role in sex determination and differentiation in a wide range of
fishes, to not be differentially expressed between active oocyte producing (o-
phase) and active sperm producing (s-phase) fish or during the transiting
process.