The environment, host, and microbial interactions influence fish microbiota structure. Despite many studies describing the microbiota of larval fishes, few have addressed potential parental contributions to these communities. This study fed broodstock red drum populations two diets: shrimp (Shrimp) and shrimp, squid, and sardines in equal proportions (ShSqSa). Larvae (7- and 10-days post-hatch) were collected from eleven spawning events throughout a year for microbiota analysis. Fatty acids were quantified in broodstock diets, eggs, and larvae.
Parental and environmental factors influenced larval bacterial assemblages. Larvae from broodstock fed ShSqSa had different communities than those fed Shrimp (Fig. 1), with discriminatory taxa belonging to the Desulfobacterota and Actinobacteria, respectively. In broodstock fed Shrimp followed by ShSqSa, the larval microbiota corresponded to that of ShSqSa-fed groups. Temporal differences in microbiota structure were apparent, with larval bacterial communities clustering by spawn month within each diet. Predicted microbiota function indicated greater potential for metabolism of α-linolenic acid (ALA) and arachidonic acid (ARA) in larvae from Shrimp and ShSqSa, respectively, corresponding with observed patterns in larval fatty acid composition (Fig. 2).
Arachidonic (ARA) and palmitoleic (POA) acids were significantly higher in eggs from Shrimp-fed broodstock but lower in the corresponding larvae; eicosatrienoic acid (ETA) showed the opposite trend. Operational taxonomic units positively associated with ARA and POA were negatively associated with ETA and vice versa, indicating a possible influence of microbiota on larval fatty acid composition. This study suggests a relationship between parental diet and bacteria associated with fish larvae, with possible effects on larval fatty acid metabolism, highlighting the complex interactions selecting for larval microbiota.