Discovering the oceans with Ifremer

This strange decapod was recently discovered by Michel Segonzac during an American diving cruise (the PAR5 cruise, Pacific-Antarctic Ridge, 2005) on which he was invited by Robert Vrijenhoek (Chief scientist, Institut MBARI, California, USA) and funded by NSF, on the Research Vessel Atlantis, carrying the submarine Alvin in March 2005, to explore four sectors of the south-eastern Pacific Ridge and the Pacific-Antarctic Ridge, where the spreading tectonic plates shows highest spreading rate (~150 mm/year).

The principal goals of this cruise were to understand the role of the geographical barriers in the current distribution of the animal species colonizing the hydrothermal sources discovered along the ridge; in particular the role of Easter Microplate and, southern, Juan Fernandez Microplate. It was also necessary to make a first comparison between the faunistic composition of several hydrothermal vents of north and south of the ridge.
 

Michel Segonzac, Ifremer Brest, Laboratoire Environnement Profond
© Ifremer / Jean-Yves Quintin

What about the new crustacean?

The animal, collected on a vent site called Annie’s Anthill (S of Easter Island, 38°S, 2300 m depth) has surprising characters, which most visible are the presence of a dense seta covering the appendices regularly carrying the legs. Observed under the electron microscope, these seta reveal the presence of many filamentous bacteria. The role of these seta and these bacteria is for the moment quite unknown. In addition, the animal is blind. In the place of the eyes, one observes only one vestige of membrane. The species is also characterized by the carapace shape and ornamentation, unknown in other decapods, the insertion of the fifth pereopod not visible and situated below the sternal plastron, and the sternite between the third maxillipeds large and strongly produced anteriorly.

These morphological characteristics, as well as genetic analyzes, made by Joe Jones (MBARI, California), allow to place it in the super-family of Galatheoidea (infraorder Anomura) which includes, pagurids and galatheids (small shellfish which the fishermen sometimes bring back among crawfish), but in any known families of this group (Galatheidae, Chirostylidae, Paguridae, Porcellanidae and Aeglidae).
 

© Ifremer / A. Fifis

This shellfish decapod is now described in the review Zoosystema* of the Muséum National d’Histoire Naturelle of Paris. It belongs to a new family, Kiwaidae (from Kiwa, the goddess of shellfish in the Easter Island Polynesian mytology), and its new Latin name is: Kiwa hirsuta.
The last new family described in the group of Anomura goes up at the end of the XIXe century.

* Macpherson E., Jones W. & M. Segonzac (2005) A new squat lobster family of Galatheoidea (Crustacea, Decapoda, Anomura) from the hydrothermal vents of the Pacific-Antarctic Ridge. Zoosystema 24(4): 709-723.
 

The harvests carried out by the diving cruises on the hydrothermal vents make it possible to carry out an inventory of the fauna of these exceptional ecosystems and few known. This work make possible the publication of numerous papers in many scientific reviews specialized like the publication, with Daniel Desbruyères, Deep-Sea Laboratory (Ifremer, Brest) of the first inventory of the hydrothermal vent fauna. A work whose Daniel Desbruyères and Michel Segonzac currently prepare a new version, to appear in April.