Diet-induced fatty acid variation in critical tissues of a spawning estuarine fish and consequences for larval fitness.

Freshwater and marine fishes exhibit a dichotomy in biosynthesis of long-chain polyunsaturated fatty acids (LC-PUFAs) from shorter-chain precursors. Marine species generally lack this ability due to deficiencies in requisite desaturase or elongase enzymes. Gulf killifish Fundulus grandis is a euryhaline cyprinodont whose fatty acid (FA) dynamics have not been previously examined. We utilized experimental variations in exogenous FAs available to spawning F. grandis in order to construct a multitissue evaluation of FA allocation and quantify effects on reproductive output and offspring fitness. No significant decrease in fecundity occurred in animals consuming low levels of LC-PUFAs, although embryo viability rates were affected. Maternal dietary FA variation did produce differences in starvation tolerance, hypoosmoregulatory ability, and acute thermal stress tolerance for larvae. These variations occurred at elevated salinities and temperatures seldom if ever encountered by F. grandis in culture or natural environments and are unlikely to affect larval survival in these settings. FA composition of eggs and tissues from spawning females suggested potential biosynthesis of LC-PUFAs from shorter-chain precursors in F. grandis. Results of this study suggest that F. grandis possesses physiological mechanisms allowing maintenance of reproductive function when subjected to dietary deficiencies in FAs generally considered essential for marine fishes.