ASCIDIANS (TUNICATA, ASCIDIACEA) OF POTTER COVE, SOUTH SHETLAND ISLANDS, ANTARCTICA

Certain physical factors, substrate type and ice action appear to be i mportant determinants for ascidian distribution. Three different subst rate types were sampled at depths between 0-30 m by SCUBA diving: soft bottoms, hard bottoms and moraine deposits. The species found were Ap lidium radiatum, Synoicum adareanum, Distaplia cylindrica Sycozoa gaim ardi, Sycozoasigillinoides, Tylobranchion speciosum, Corella eumyota, Ascidia challengeri, Cnemidocarpa verrucosa, Styela wandeli, Dicarpa i nsinuosa, Pyura bouvetensis, Pyura discovery, Pyura obesa, Pyura setos a, Molgula enodis and Molgula pedunculata. Highest diversity and patch y distribution was found in less stringent environments, where epibios is is a commmon phenomenon on stolidobranch ascidians. Differences in stalk development were found in the most abundant species Molgula pedu nculata and Cnemidocarpa verrucosa. Ice action may be the main factor that determines the absence of ascidians above 15 m in all the station s sampled.