Cost and benefits of symbiosis in Port Lincoln ascidians

Frequencies and densities of symbiotic amphipods (Leucothoe commensalis) and mussels (Musculus cf. subpictus) in three ascidians from Port Lincolns, South Australia (Herdmania fimbriae, Styela plicata, and Phallusia obesa). Palatability of the tunic of H. fimbriae, amphipods, and mussels were compared to control food pellets using the fish Scobinichthys granulatus (rough leatherjacket). Three condition indices (gonad, tunic, and viscera) were calculated for H. fimbriae, as proxies for host health and compared against densities of the two symbionts.