Ontogenetic and sex-based trophic niche divergence in Macrobrachium borellii: evidence from the isotopic composition from different tissues

Abstract

Within the same species, juveniles, males, and females may target different resources to satisfy stage-specific and sex-specific nutritional needs, reduce intraspecific competition, or use an abundant resource. Our objective was to explore whether diet varies according to sex and ontogenetic stage due to nutritional and physiological needs. We predicted that 1) juveniles and females would have a better quality diet and greater specialization than males, 2) female tissues would have higher δ13C during vitellogenesis, and 3) eggs would reflect either “capital storage” (female muscle) or local “input” (female hepatopancreas). Contrary to prediction 1, females and juveniles showed greater trophic diversification than males, with juveniles consuming better quality prey for rapid growth. Females utilized C3 macrophytes and better quality prey (during reproductive stage). In agreement with prediction 2, females had higher δ13C in both tissues during vitellogenesis. Regarding prediction 3, the isotopic area of eggs was more closely related to the hepatopancreas (25% niche overlap) than to muscle (5% overlap). This reproductive strategy, termed income breeding, along with the selective consumption of C3 macrophytes, shows a high coupling to environmental resources and ecosystem productivity.