Cost and benefits of symbiosis in Port Lincoln ascidians

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