Sunday 10 July 2016

Pachycara caribbaeum: A new species of Eelpout from vent fields in the Caribbean.

Eelpout, Zoarcidae., are bottom-dwelling Eel-like marine fish related to Sticklebacks and Scorpionfish. Members of the genus Pachycara are found at bathyal to abyssal depths (between one and six kilometers below the surface of the sea) in all oceans except the Arctic. There are currently twenty seven described species, of which three have been described from hydrothermal vent fields, areas where superheated water laden with minerals that has percolated through hot volcanic rocks reaches the surface, supporting whole ecosystems that get their energy from chemotrophic Bacteria (Bacteria that gain energy by breaking down chemicals from the vents rather than photosynthesis).

In a paper published in the journal Zootaxa on 13 January 2016, Eric Anderson of the South African Institute for Aquatic Biodiversity, Russell Somerville of Ocean and Earth Science at the University ofSouthampton and Jonathan Copely also of Ocean and Earth Science at the University of Southampton and of the Natural History Museum, describe a new species of Pachycara from the Von Damm Vent Field on the Mid-Cayman Spreading Centre and an un-named methane seep (area where methane is escaping from sedimentary rocks on the sea-floor, also often supporting ecosystems based upon chemotrophic Bacteria) close to Tobago.

The new species is named Pachycara caribbaeum, in reference to the area where it was found. The species is described from two male and one female specimens recovered from the Von Damm Vent Field at depths of 2309-2313 m by deep-sea submersibles, none of which are judged to be mature. The males are 117 and 199 mm in length, the female 197 mm.

Pachycara caribbaeum in the Von Damm Vent Field. Anderson et al. (2016).

Pachycara caribbaeum was found close to areas of visible diffuse flow venting in the Von Damm Vent Field, with temperatures ranging from 5-20ºC with several potential prey species in the vicinity. This suggests that the species does not have the tolerance of high temperatures seen in some vent-dwelling organisms and avoids areas of higher temperatures. He species was also observed at a methane seep close to Tobago, though the individuals seen here were not as large or as numerous as those seen in the Von Damm Vent Field, suggesting this was a less optimal environment. The species has not been seen on the roughly 2000 km of seafloor that separates the two sites, nor in the Beebe Vent Field which lies close to the Von Damm Vent Field (about 30 km) away, but much deeper (about 5 km compared to the 2.3 km depth at the Von Damm Vent Field.

Locations (indicated by stars) of Pachycara caribbaeu; West, Von Damm Vent Field (depth ca.2300 m), east, methane seep near Tobago (depth 1049 m). Scale bar is 1000 km. Anderson et al. (2016).

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