Anchialine Fauna of the Galápagos Islands

Abstract

From the biogeographic viewpoint, marine caves on oceanic islands represent ‘islands within islands.’ Due to the isolation and environmental stability of this habitat, such caves act as refuges, preserving primitive relict taxa. Investigations of marine caves in the Atlantic have resulted in the discovery of many higher taxa including the new crustacean class Remipedia (Yager, 1981), the new peracarid order Mictacea (Bowman and Iliffe, 1985), the new copepod order Platycopioida (Fosshagen and Iliffe, 1985), the new isopod family Atlantasellidae (Sket, 1979) and the new caridean family Agostocaridae (Hart and Manning, 1986). Unexpectedly however, the troglobitic (i.e., cave-limited) fauna of Atlantic marine caves show highly anomalous biogeographical distributions, as well as close taxonomic affinities to deep sea species. Particularly noteworthy in this regard is the fauna of the Jameos del Agua, a marine lava tube cave in the Canary Islands. Members of six crustacean genera inhabiting this cave, including the remipede Speleonectes, the anthurid isopod Curassanthura, the amphipod Spelaeonicippe, the mysid Heteromysoides, the ostracod Danielopolina, and the thermosbaenacean Halosbaena, also have species inhabiting caves on the western side of the Atlantic. This amphi-Atlantic distribution suggests that these taxa are Tethyan relics having an origin in caves early in the history of the Atlantic and subsequently dispersed by plate tectonics and sea floor spreading (Iliffe et al., 1984; Wilkens et al., 1986). Also from the same cave, the galatheid crab Munidopsis polymorpha and the polynoid polychaete Giesiella jameensis belong to groups known primarily from the deep sea.