Lipid Dynamics during Reproduction in Two Livebearing Fishes, Gambusia holbrooki and Poecilia latipinna

In animals, strategies of energy allocation among growth, maintenance and reproduction can be significantly altered by lipid storage. Poeciliid (livebearing) fishes store energy in late summer and fall for overwintering and first reproduction in spring, but details of energy use in reproduction are lacking. We conducted a laboratory experiment on the eastern mosquitofish (Gambusia holbrooki) and the sailfin molly (Poecilia latipinna) to document changes in lipid content in both the ovary and soma during development of a brood. In females of both species, ovarian lipid content was highest early in embryogeny and then declined; adult somatic lipids increased (were replenished) during embryonic development in mosquitofish, but declined in mollies. Larger clutches sequestered a larger share of body lipids in both species, possibly indicating energetic limits to reproduction. Finally, growth rate was positively correlated with somatic lipid content in both species, indicating among-individual differences in metabolic efficiency or feeding efficiency rather than a trade-off between growth and energy storage.