On the ecology and cirral behaviour of a new barnacle from the Red Sea and Indian Ocean

Tetrachthamalus oblitteratus is a small chthamalid found high up in the intertidal zone in the Gulf of Aqaba, Red Sea and at Mauritius, Seychelles and Aldabra Island, Indian Ocean. The general behaviour and rate of cirral activity are described and shown not to differ greatly from those of other chthamalids. The species appears well‐adapted to the life in the tropics, and the present restricted distribution is presumed to be the result of competition with larger chthamalids of Indo‐Pacific distribution. The absence of the larger chthamalids from places where Tetrachthamalus is found may be due to geographical isolation reinforced by the effects of a small tidal range and other extreme environmental conditions. Summary Tetrachthamalus oblitteratus is found high up in the intertidal zone in the Gulf of Aqaba, Red Sea and at Mauritius, the Seychelles and Aldabra Island, Indian Ocean. It is small compared even with other chthamalid barnacles. For this reason, and its apparently restricted distribution and our general lack of knowledge of island faunas, it has escaped notice until recently. The general behaviour and rate of cirral activity are described. The species does not differ significantly from other chthamalids, and seems as well adapted to life at high temperatures as the tropical forms previously investigated. The present restricted distribution of Tetrachthamalus is possibly due to competition with the larger chthamalids found in the Indian Ocean. The absence of these larger chthamalids from places where Tetrachthamalus is found may be due to geographical isolation, probably reinforced by the effects of small tidal range and other extreme environmental conditions in Continental situations.