Hydroids (Cnidaria: Hydrozoa) recorded from depths exceeding 3000 m in the abyssal western North Atlantic

• Published in: Canadian Journal of Zoology
• Main Author: Calder, Dale R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1996
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Southern Ocean; Pacific; Indian; North Atlantic
• Online Access: http://dx.doi.org/10.1139/z96-190; http://www.nrcresearchpress.com/doi/pdf/10.1139/z96-190

Hydroid diversity and abundance appear to be low in the mid-abyssal zone of the western North Atlantic Ocean. Only two species (Acryptolaria longitheca,?Opercularella sp.) were collected during investigations by submersible (Deep Submergence Vehicle Alvin) at depths between 3011 and 3550 m along the northwest slope of the Bermuda Pedestal in March 1993. Moreover, bottom samples from 59 deep stations (all > 3000 m) between southern New England and Bermuda, collected by the Woods Hole Oceanographic Institution Benthic Ecology Program between 1961 and 1973, contained just two hydroid specimens (both referred here to Halisiphonia megalotheca). Of some 424 species of hydroids currently recognized from the western North Atlantic, only 8 have ever been reported in the region from depths exceeding 3000 m. One of these (Cryptolarella abyssicola) has been recorded from the North and South Atlantic, North and South Pacific, and Southern Ocean, and another (Halisiphonia megalotheca) from the North and South Atlantic, North and South Pacific, and southern Indian Ocean. The other six (Stylactaria ingolfi, Eucuspidella pedunculata, ?Opercularella sp., Halecium dubium, Acryptolaria longitheca, and Aglaophenopsis verrilli) have been reported exclusively from the North Atlantic. The hydroid fauna of the mid-abyssal zone may be sparse compared with that of neritic waters, but it is less frequently sampled and remains poorly known.