Stable isotope analyses reveal major nutritional deficiencies in captive vs. field juvenile individuals of Pinna nobilis

Abstract

The pen shell, Pinna nobilis L. is critically endangered by the spread of a haplosporidan parasite. Stable isotopes have been shown an association with dietary assimilation, trophic level, and body condition, and can provide valuable information for ex situ conservation and breeding. In this context, the aim of this study was to investigate the nutritional status of individuals using δ¹³C and δ¹⁵N patterns across pen shell body tissues as tracers of elemental incorporation from treatment diets based on commercial gels and living phytoplankton and/or sediment. Further comparisons were also conducted with field animals and diets to better understand nutritional needs. Captive individuals, were enriched in δ¹³C and δ¹⁵N (~18.9 and 1.3‰, respectively), suggesting severe nutritional stress and utilization of own N and C pools, especially muscle. The mixing model for field individuals evidenced a large contribution from the zooplankton fraction (34.9%), which was further confirmed by experimental feeding with Artemia nauplii.

Keywords: Dietary formulation; Isotopic enrichment; Microalgae gels; Nutritional stress; Pen shell; Zooplankton.