Nutritional ecology of a marine teleost : maternal maturation diets affect egg and larval composition of Southern Flounder (Paralichthys lethostigma)

Date
2021-12-03
Authors
Bailey, Hunter Scott
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Abstract

Maternally derived nutrients in marine fish yolk play important roles in early larval development. A principal subclass of these nutrients is fatty acids (FAs), which are involved in a variety of key physiological processes related to gene regulation, cellular membrane structure, and energy production. FAs residing in yolk are acquired from maternal sources either immediately prior to spawning (income breeders) or through somatic reserves established from dietary intake well-before spawning (capital breeders). The FA composition of eggs has been previously linked to measures of egg quality and subsequent larval quality. A study was conducted to determine how changes in maturation diets fed to Southern Flounder affect egg composition and egg quality. Differences in egg composition were assessed from broodstock populations fed one of four different diets using gas chromatography. It was found that levels of 20 of 27 FAs measured in eggs had direct positive relationships with amounts of the same FA in the maternal diet when the maternal diet changed at least 16 weeks before spawning. Among the egg quality metrics measured, hatching rate and larval hatching length were most sensitive to differences in maternal diet that produced compositional changes in eggs. A second study had two objectives, to: (1) investigate the relationships among egg and larval composition and maternal diet and egg composition for effects of metabolic programming; and (2) determine how FA composition of the larval body affects larval performance in ecologically relevant survival skills (e.g., routine swimming and predator evasion). Eggs and larvae from the first study were reared until two distinct developmental stages (15- and 35-days post-hatching, dph) and larvae were used in performance assays at each stage. Several FAs found to have direct diet-egg relationships in the first study were found to affect larval body composition at 15-dph (16:1ω7, 20:4ω6, 20:1ω9) and 35-dph (18:1ω7, 20:1ω9, 22:5ω3, 22:6ω3:20:4ω6). Since larvae were all fed the same high-quality diet, the presence of differences in body FA composition in 15- and 35-dph larvae suggests that maternal diet alters egg composition which, in turn, affects lipid metabolism in the larvae, a process known as nutritional programming. Further, several significant relationships were observed between these FAs and larval performance metrics. These studies suggest that maternal diet can have important consequences for egg and larval quality in hatchery settings even when larval diet is of high-quality and proposes several candidate FAs for future studies investigating nutritional programming in Southern Flounder

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