Hydroids from French Polynesia with notes on distribution and ecology

INTRODUCTION Distribution and ecology of hydroids from coral reefs of high islands and atolls of French Polynesia so far have received little attention. Redier (1967, 1971) published a preliminary list of 14 species from Salvat's collections, sampled during several trips to Tahiti, Tuamoto (Mururoa, Reao and Maturei Vavao Atolls), to the Australes Islands (Rapa) and to Gambier. The present paper results from researches carried out by one of us (P.V.) concerning the benthic bionomy of reef sciophilous communities of hard bottoms. They have been carried out at Tiahura, Moorea, Society Islands (fig. IA) and on Takapoto Atoll, Tuamoto Archipelago (fig. 2A) in 1973 and 1974. They gave us occasion to compile a revised list of about 22 species of hydroids from French Polynesia. Regarding the general environmental conditions, the tides are of a semidiurnal type and the amplitude during spring tides does not exceed 40 to 50 cm. The water temperature varies between 2 5 o C, during the cold season, and 28o C, during the hot season. Moorea island is under the trade winds, blowing from a southwesterly direction and turning to the N . E . Accordingly the Tiahura region (fig. 1B), which is located at the N.W., is sheltered from the trade winds. Nevertheless, those winds induce a water circulation from W. to E. around the fringing reef and the barrier reef. Takapoto Atoll, to the contrary, is submitted to prevailing winds, blowing from N.E. to S.E. with a dominance in the eastern sector.