Pourtalesiid sea urchins (Echinodermata: Echinoidea) of the northern Mid-Atlantic Ridge

Abstract

Five species of deep-sea pourtalesiid echinoids were collected by the RV G.O. Sars MAR-ECO expedition to the northern part of the Mid-Atlantic Ridge: Solenocystis imitans new genus, new species, Echinosigra phiale (Thomson, 1872), Echinosigra (Echinogutta) fabrefacta Mironov, 1974, and two unidentified species of Pourtalesia. Three types of plastron plating are distinguished within the family Pourtalesiidae; in Solenocystis new genus the plating is similar to that in Spatagocystis, a genus known only from the deep-sea Antarctic. Each of three groups with distinctive plastron plating shows a continuous morphological gradation from a less elongated test without subanal rostrum to an extraordinarily elongated test with large rostrum and wide subanal fasciole; the ratio width/length of test varies from 0.86 to 0.12. Some morphological characters of the pourtalesiids are regarded as adaptations to burrowing and appear to be correlated with test elongation. The family is represented in the northern Atlantic only by ‘advanced’ genera (Echinosigra, Pourtalesia and Solenocystis) with very elongated tests.

Keywords:

• Echinoids
• morphological adaptations
• northern Atlantic
• Pourtalesiidae

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

Acknowledgements

I thank Jon Anders Kongsrud, Endre Willassen and Andrey Gebruk for the opportunity to examine the MAR-ECO collection; Andrey Gebruk for the opportunity to examine Helgocystis carinata taken by Polarstern (cruise ANT XIX-4); Thomas Soltwedel for the image of Pourtalesia jeffreysi lata in situ; David Pawson for his constructive review of the manuscript; Alan J. Southward for editing of English; David Billett for the data on the morphology of the North Atlantic Pourtalesia; Kirill Minin for identifications of Echinothuriidae and Echinidae. Special thanks are due to the anonymous reviewers whose constructive comments and suggestions helped improve this paper. This study was supported by a grant from the Russian Foundation for Basic Research No. 05-05-65283; also this work was an element of MAR-ECO, a field project under the Census of Marine Life programme.

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