Silverstripe Shiners Are Like Telescope Shiners

This is not a big surprise, since silverstripe shiners (Notropis stilbius) are close relatives of the telescopes (N. telescopus). In particular, the results of our western blots last week with NMDA subunit 1 from 7 silverstripes' brains showed the same pattern as with telescopes: no sexual structuring of NMDA concentration, unlike with the scarlet shiners (Lythrurus fasciolaris). From high to low, the pattern with silverstripes was: M, F, M, M, F, F, M. At the suggestion of Ernie in the Bishop lab I calculated the male average vs. female average, along with standard error, and found that males have a slightly higher average amount of NMDA than females, but not statistically signficantly so. The same is true with telescope shiners. On the other hand, doing the math for scarlet shiners showed that males have a statistically significant higher concentration of NMDA than do females. As a funny thought, I didn't think to do that at first because we have low sample sizes with the western blots, from 7 to 10, and because of my background in ecology I unconsciously thought of these as very small samples (which they are, of course). But in neuroscience these are perfectly robust sample sizes, since running western blots is such a tedious process.

So now I'm convinced that we've demonstrated that there is a phylogenetic basis for NMDA in fish brains, in turn related to breeding strategy: strong sexual dimorphism with high-NMDA males (scarlet shiners), or low sexual dimorphism with no significant NMDA differences between males and females (telescope and silverstripe shiners). The bigger question is what drives this difference -- is it the influence of different levels of steroids like 11-KT, or something further upstream like AVT release by the hypothalamus? This is a much more challenging question to address, but I think we've got to head in that direction.

A silverstripe shiner, from my files (thanks to the Biology Dept. at Samford University):