Redescription of the leptothecate hydroid Halecium macrocephalum Allman, 1877 (Cnidaria: Hydrozoa)

Abstract

Hydroids are a species-rich component of the benthic fauna inhabiting deep, cold-water coral habitats. Fertile colonies of the leptothecate species Halecium macrocephalum Allman, 1877 collected from cold-water coral habitats off the southeastern USA exhibited morphologically peculiar male gonophores, distinct from those described and illustrated for the holotype. We redescribe H. macrocephalum based on this new material, and consider the gonophores of the holotype to be either damaged or immature. Following re-examination of non-type material (the holotype being lost), we characterize H. macrocephalum as a strictly subtropical western North Atlantic bathyal species, occurring between North Carolina and Florida, the Straits of Florida inclusive of the Bahamas, and the eastern Gulf of Mexico including the Tortugas. This study also provides a taxonomic distinction between H. macrocephalum and its morphologically similar Southern Ocean congener, Halecium jaederholmi Vervoort, 1972.

Keywords:

• hydroids
• Haleciidae
• cold-water corals

Acknowledgements

The authors wish to thank Adam Baldinger and Ardis Johnston of the Museum of Comparative Zoology at Harvard University, Patricia Sadeghian at the Santa Barbara Museum of Natural History and Geoff Keel at the National Museum of Natural History, Smithsonian Institution for providing us with station data and specimen loans to aid our work, and Steve Ross for providing the recent submersible-based specimens. Mary Arai and Dale Calder kindly helped to locate lost and archived hydroid material. Cheryl Ames provided technical support. The manuscript greatly benefitted from comments by two anonymous reviewers and editorial suggestions from Louise Allcock. Funding for L-A. Henry was provided by a Marie Curie fellowship through the EC FP6 Programme “Structuring the European Research Area” (contract no. MIF1-CT-2004-002469) and the EC FP7 Integrated Project HERMIONE (contract no. 226354). Finally, the last two authors would like to respectfully acknowledge the significant contributions and advances in hydrozoan systematics and taxonomy made by Prof. Willem Vervoort; his highly productive and respected scientific authority will be greatly missed.

Notes

^†Deceased.