A new species of Ambilimbus nom. nov., a replacement name for Amphicrossus Huys, 1991 (Copepoda, Cyclopoida, Erebonasteridae), from the Mid-Atlantic Ridge at 36°N (hydrothermal vent site Rainbow)

Abstract

A new deep-sea species of Ambilimbus nom. nov. (Copepoda, Cyclopoida, Erebonasteridae) is described from the Mid-Atlantic Ridge (hydrothermal vent site Rainbow, 36°13′N 33°54′W, depth 2285 m). This is the first record for the family Erebonasteridae Humes, 1987 from the Mid-Atlantic Ridge. Ambilimbus nom. nov. is here proposed as a replacement name for Amphicrossus Huys, 1991, as the latter is preoccupied by Amphicrossus Erichson, 1843 (Insecta, Coleoptera). The new species, Ambilimbus arcuscelestis, is similar to A. pacificus (Huys, 1991) comb. nov. and A. tuerkayi (Martínez Arbizu, 1999) comb. nov. in having the third exopodal segments of legs 1 and 2 armed with four and five inner setae, respectively (instead of three and four inner setae as in A. spinulosus (Humes, 1989) comb. nov. and A. altalis (Humes & Huys, 1992) comb. nov.). It differs from its four congeners by the lack of the inner coxal seta on leg 3. This character and the mid-ventral processes located between the intercoxal sclerites of legs 1–4 are presumed to be apomorphies of the new species.

Résumé

Une nouvelle espèce du genre Ambilimbus nom nov. (Copepoda, Cyclopoida, Erebonasteridae) est décrite de la ride médio-Atlantique, à la latitude 36°N (site hydrothermal Rainbow, 36°13′N 33°54′O, profondeur 2285 m). C'est la première découverte de la famille des Erebonasteridae Humes, 1987 dans la ride médio-Atlantique. Ambilimbus nom. nov. est proposé ici comme nom de remplacement pour Amphicrossus Huys, 1991, car ce dernier est préoccupé par Amphicrossus Erichson, 1843 (Insecta, Coleoptera). La nouvelle espèce, Ambilimbus arcuscelestis, ressemble à A. pacificus (Huys, 1991) comb. nov. et A. tuerkayi (Martínez Arbizu, 1999) comb. nov. en ayant le troisième segment de l'exopodite des deuxième et troisième paires de pattes armé de 4 et 5 soies internes, respectivement (au lieu de 3 et 4 soies internes, comme chez A. spinulosus (Humes, 1989) comb. nov. et A. altalis (Humes & Huys, 1992) comb. nov.). Elle diffère de ses quatre congénères par l'absence de la soie coxale interne sur la troisième paire de pattes. Ce caractère, ainsi que les processus médio-ventraux situés entre les sclérites intercoxaux des pattes 1 à 4, sont supposés être des apomorphies de l'espèce nouvelle.

Keywords:

• Copepoda
• deep sea
• hydrothermal vents
• Mid-Atlantic Ridge
• morphology
• systematics

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgments

We thank Daniel Desbruyères, Chief Scientist of the PICO cruise (Ifremer, Brest) for collecting the copepods, in the framework supported by the programme AMORES (MAST3 CT 95-0040). Michel Segonzac (Ifremer) provided his comments on the manuscript. Mark Judson (Muséum National d'Histoire Naturelle) commented on the manuscript. The late Dr Arthur G. Humes suggested the replacement name Ambilimbus to one of us (RH). The research of VNI was supported by the Muséum National d'Histoire Naturelle.

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark