Diet and association of Pontonia pinnophylax occurring in Pinna nobilis: insights from stable isotope analysis

Stable carbon isotope measurements (delta C-13) were used to assess the sou rces of carbon assimilated hy the fan mussel Pinna nobilis, in sea grass Po sidonia oceanica meadows, and an associated shrimp Pontonia pinnophylax whi ch occurs within this bivalve's mantle cavity. The primary carbon sources a vailable to both animals displayed a wide range of delta C-13 values, from -12.3 to -22.3 parts per thousand,. The delta C-13 and delta N-15 of Pinna nobilis and Pontonia Pinnophylax suggest that they assimilate carbon from s imilar sources, occupy comparable trophic levels and that their association is commensal.