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

Certain physical factors, substrate type and ice action appear to be important determinants for ascidian distribution. Three different substrate types were sampled at depths between 0-30 m by SCUBA diving: soft bottoms, hard bottoms and moraine deposits. The species found were Aplidium radiutum, Synoicum adureanum, Distapiiacyiindrica, Sycozoagaimardi, Sycozoasigiliinoides, Tylobranchionspeciosum, Corella eumyota, Ascidia chaliengeri, Cnemidocurpa verrucosa, Styela wundeli, Dicarpa insinuosa, Pyuru bouvetensis, Pyura discoveryi, Pyura obesa, Pyura setosu, Molgula enodis and Molgulapedunculata. Highest diversity and patchy distribution was found in less stringent environments, where epibiosis is a commmon phenomenon on stolidobranch ascidians. Differences in stalk development were found in the most abundant species Moiguiapedunculuta and Cnemidocurpa verrucosa. Ice action may be the main factor that determines the absence of ascidians above 15 m in all the stations sampled.