Metabolic rates of stygobiontic invertebrates from the Túnel de la Atlántida, Lanzarote

Numerous studies have shown that hypogean organisms have a reduced metabolism when compared with their epigean counterparts. Although the cause of this metabolic cave adaptation is still uncertain, a current theory holds that it results from a reduced oxygen environment. This study examines the metabolism of specimens collected from the Túnel de la Atlántida, Lanzarote, Canary Islands, the completely submerged, seaward-most segment of a 7-km-long lava tube. Unlike many cave systems, the Túnel de la Atlántida is an oxic environment. Invertebrate metabolism was examined directly by measuring oxygen consumed by the organisms. When compared to two suboxic to anoxic anchialine limestone cave systems in the Bahamas, the Lanzarote invertebrate oxygen consumption rates were significantly greater. Amphipods of the genus Spelaeonicippe (family Pardaliscidae) found in the Túnel de la Atlántida and in anchialine caves in the Bahamas were compared based upon mass, with Spelaeonicippe buchi from Lanzarote being significantly larger than S. provo from the Bahamas. The selective pressures of living in a reduced oxygen environment that have forced the Bahamian amphipods to be smaller are released in the oxic environment of the Lanzarote lava tube, allowing for greater body mass and potentially increased clutch sizes.