Variation in neutral and polar lipid compositions of ova in ten reproductively isolated populations of walleye (Sander vitreus)

We examined variation in the mass and composition of egg lipids within and among 10 walleye (Sander vitreus) populations. Larger eggs contained more lipid, but neither absolute lipid content (mg.egg(-1)) nor relative lipid content (percent of egg mass as lipid) were related to maternal age or size. Among populations, the proportion of egg mass as neutral lipid varied significantly, whereas the proportion as polar lipid did not. Egg fatty acid composition did vary with respect to maternal traits. In the Lake Ontario population, larger females appear to produce a qualitatively superior egg; relative abundances of docosahexaenoic acid (22:6(n-3), DHA) and arachidonic acid (20:4(n-6), AA) increased, and the relative abundance of eicosapentaenoic acid (20:5(n-3), EPA) decreased in egg fatty acids with increasing maternal length. We predicted that fatty acid profiles would be less variable in the polar than in the neutral lipid fraction. Relative abundances of DHA, AA, the sum of AA and EPA, and several other fatty acid classes were all significantly less variable in the polar than in the neutral fraction both among females and among populations. Our results indicate a high level of conservatism of egg lipid mass and polar lipid composition in this species.