Free-living nematodes of the genus Halomonhystera (Monhysteridae) from the Southwest Pacific region and Ross Sea

Abstract

Three Halomonhystera species are described from the Southwest Pacific region and Ross Sea. Halomonhystera tangaroa sp. nov. is described from the byssus threads of hydrothermal vent mussels (Gigantidas gladius) at the summit of Tangaroa Seamount on the southern Kermadec Arc, Southwest Pacific. Halomonhystera tangaroa sp. nov. is characterized by the presence of four relatively long cephalic setae (one-quarter to one-third of the labial diameter), deep and narrow buccal cavity, gubernaculum with dorsal apophyses, males with three pairs of subventral papillae near tail tip, and females with vulva situated at 85–86% of body length from anterior. Halomonhystera spp. A and B (from the New Zealand coast and Ross Sea shelf, respectively) are morphologically distinct from each other, but are both consistent with previous descriptions of Halomonhystera disjuncta (Bastian, 1865). Molecular studies have shown that H. disjuncta is in fact a species complex, and, because the original description of H. disjuncta provides only limited morphological data, and the subsequent re-description of the species encompasses a wide range of morphologies, it is not possible to determine to which lineage(s) these descriptions may be pertaining. Determining the identities of Halomonhystera spp. A and B will require comparisons of morphological and molecular characters with H. disjuncta specimens from the type locality.http://zoobank.org/urn:lsid:zoobank.org:pub:029E6773-5E37-4D69-A85E-D4FB663BC059