Stauromedusan populations inhabiting deep-sea hydrothermal vents along the southern East Pacific Rise

Dense populations of "stalked jellyfish" (Stauromedusae) were encountered at two geographically-separated, deep-sea hydrothermal vent fields located at 7°26′S; and 20°02′S along the East Pacific Rise (EPR). DSV Alvin was utilized (on dives 3320 and 3334) at the sites to collect numerous stauromedusans, which were immediately frozen (at -70°C) or preserved in 70% ethanol upon arrival on board the research support vessel (R/V Atlantis). High resolution images were collected of the organisms in situ. A 530-560-bp region of mitochondrial 16S was amplified, and edited 16S sequences were aligned, along with sequences from 7 other stauromedusans. Results suggest that the Stauromedusae encountered at 7°26′S, and 20°02′S are very closely related, if not conspecific. It remains unclear whether or not these Stauromedusae are distinct from Lucernaria janetae (collected from 8°37′N along the EPR), which was recently described by Collins and Daly (2005). To date, dense populations of stauromedusans have been encountered at four separate deep-sea hydrothermal vent fields along the EPR located at the following latitudes: 20°50′N, 8°37′N, 7°26′S and 20°02′S. Many fascinating questions remain concerning the biogeography and mechanisms of dispersal of these cnidarians between discrete deep-sea hydrothermal systems.