Abstract
The Selachinematidae is a globally distributed family of predatory nematodes found from shallow waters to the abyssal plain. Here, three new species of Halichoanolaimus de Man, 1886 (H. ossilagulus sp. nov., H. funestus sp. nov. and H. pumilus sp. nov.) and one known species (H. ovalis Ditlevsen, 1921) are described from the New Zealand continental margin, thus bringing the total number of selachinematid species recorded from the New Zealand region to 14 and the total number of species of Halichoanolaimus to 26. The range of H. ovalis is extended from the Southern Ocean to the Southwest Pacific Ocean (latitude 42° S to 53° S); the depth range of this species, which was originally described from the littoral zone, is also extended to 1061 m depth. Dorsosublateral rows of pore complexes and pseudocoelomocytes, features that have either rarely or not been recorded previously in the genus, were observed in all four species described here. The taxonomic significance of these features remains to be ascertained for the family and will require observations of other species of Halichoanolaimus and selachinematid genera. Pseudocoelomocytes and pore complexes may have an excretory function, thus aiding to process the waste products of digestion in selachinematid taxa with a blind intestine.
Highlights
The Selachinematidae Cobb, 1915 is a globally distributed family of predatory nematodes most commonly reported from shallow water environments (Warwick 1971; Okhlopkov 2002; Tchesunov & Okhlopkov2006), but occuring as deep as the abyssal plain (Miljutin et al 2010)
I describe three new species from continental slope and submarine canyon habitats of New Zealand and provide a new deep-sea record for Halichoanolaimus ovalis Ditlevsen, 1921, which was originally described from the littoral zone of New Zealand’s subantarctic islands
The present study brings the total number of valid species of Halichoanolaimus from 23 to 26, and the total number of selachinematid species recorded from the New Zealand region from 11 to 14
Summary
The Selachinematidae Cobb, 1915 is a globally distributed family of predatory nematodes most commonly reported from shallow water environments (Warwick 1971; Okhlopkov 2002; Tchesunov & Okhlopkov2006), but occuring as deep as the abyssal plain (Miljutin et al 2010). The Selachinematidae Cobb, 1915 is a globally distributed family of predatory nematodes most commonly reported from shallow water environments The family is characterized by a large buccal cavity with cuticularized rhabdions and/or mandibles, and is currently divided into two subfamilies, the Selachinematinae and Choniolaiminae Schuurmans-Stekhoven & Adam, 1931 based on buccal cavity armature (Tchesunov 2014). The monophyly of these two subfamilies, is not supported by molecular phylogenetic analyses (Leduc & Zhao 2016). In the New Zealand Exclusive Economic Zone, three selachinematid species have been reported from coastal waters (Leduc & Gwyther 2008; Leduc & Zhao 2015) and a further eight species have been described from the shelf and continental slope down to a depth of 1240 m
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