Chaetozone Malmgren 1867

Genus Chaetozone Malmgren, 1867

Type species: Chaetozone setosa Malmgren, 1867 by monotypy.

Diagnosis. (after Blake 2018). Prostomium blunt to conical; peristomium elongate to short, usually lacking eyespots, with a pair of small nuchal slits or depressions at posterior edge; with a single pair of grooved dorsal tentacles arising from posterior edge of peristomium, or sometimes more posterior on an asetigerous anterior segment, or rarely on an anterior setiger. First pair of branchiae arising from an asetigerous segment or first setiger, sometimes with first two pairs of branchiae on a single anterior segment. Body usually expanded anteriorly and narrowed posteriorly, rarely with middle or posterior body segments beaded or moniliform; posterior end often expanded. Setae include capillaries on most setigers and sigmoid acicular spines in neuropodia and notopodia, with spines typically concentrated in posterior segments; setae forming weakly developed to distinct cinctures with unidentate spines carried on elevated membranes, cinctures with few to many spines sometimes encircling entire posterior end, accompanied with zero to many alternating capillaries; bidentate spines sometimes accompanying unidentate spines in cinctures in juveniles or occasionally in ventral-most position of far posterior setigers of adults; some species with long, natatory-like capillary notosetae. Pygidium a simple lobe, disk-like, or with long terminal cirrus.

Remarks. Chaetozone is the largest genus of Cirratulidae with 54 species (Blake 2018). According to Dean (2012) only two species, C. atlantica McIntosh, 1885 and C. setosa Malmgren, 1867 have been reported from Caribbean waters. Chaetozone setosa is the type-species of the genus and, although it has been reported globally, is now considered to be limited to the Arctic (Blake 2015). The records of C. setosa from Colombia by Dueñas (1999) and Báez & Ardilla (2003) therefore most certainly represent a different species.

The holotype of C. atlantica, described by McIntosh (1885) from 713–860 m off St. Thomas, Virgin Islands, is in the British Museum of Natural History (BNH ZK 1885 121.277) and was examined by the first author (JAB). The specimen is incomplete and in poor condition. All setae are capillaries and the species cannot be confirmed as Chaetozone and likely belongs to Aphelochaeta.

In the present study, a single species, C. dossena n. sp. from shallow water in the Bahía de Mochima, Venezuela, has been discovered. Damaged specimens of a second species were also found but are not described here due to their poor condition.