Bathyal echinoderms of the Galapagos Islands

Several areas of the Galapagos bathyal, in depths from approximately 105 in to 925 in, were investigated in June-July 1998 using the research submersible Johnson-Sea-Link II. The seabed in the study areas usually consisted of extensive bare rock and patchy soft bottoms ranging from black sand to tan mud. The small collection of echinoderms comprised 27 species, and included four new records for the Galapagos islands and eight new species: four (one representing a new genus), holothurians, one echinoid, and three asteroids. The bathyal echinoderm fauna is characterized by low diversity at the species level and high population densities of a few species. The cidaroid echinoid Centrocidaris doederleini (A.Agassiz), formerly believed to be rare, occurs in numerous populations of one million or more individuals, reaching average densities of 185 individuals per square in. Ophiotrichid and ophiacanthid ophiuroids often occur together in aggregations of more than 100 individuals. Possible benthic feeding behavior of the bathypelagic holothurian Pelagothuria natatrix Ludwig was observed and videotaped. Information on ecology and feeding preferences of approximately 25 species was obtained. Conclusions reached by Maluf (1988,1991) concerning composition and affinities of the Galapagos deepwater echinoderm fauna are supported by the present study. A plea is made for more exploration around Pacific island groups in bathyal/abyssal depths.