Telescope Shiner Ooctyes, March vs April

We've started to examine the ovaries of telescope shiners we've collected from March 3 and April 7. What we're doing is to photograph the intact ovaries, and then tease them apart and separate the developing eggs out on to glass slides for microscopic photography at 10X. Below are two such shots, the first from March and the second from April. My working theory was that the fish would be reproductively competent by early April. I think that's basically true, although with the cold snap and drop in water temperature that weekend they probably weren't until temperatures rebounded a week later. Three differences emerge comparing these oocytes: the March ones are smaller, in the range of .5 - .7 mm in diameter compared to .8 - 1 mm for the April fish; the March ovaries contain fewer maturing ooctyes, by a margin of roughly 500 to 250; and the whitish March ooctyes are whitish with little evidence of yolking compared to the April oocytes which are distinctly yellow. We still have to examine the oocytes at higher magnification to better characterize the development of internal membranes. Interestingly, the nucleus can be seen in many of the March oocytes but not the April ones which are loaded with yolk and lipoproteins. The separated oocytes are stored in small glass vials for easy (I hope) later examination.

We go back to Hurricane Creek next Saturday for our next collection.