Aphelochaeta Blake, 1991

Blake, James A. & Dean, Harlan K., 2019, New Species of Cirratulidae (Annelida, Polychaeta) from the Caribbean Sea, Zootaxa 4671 (3), pp. 301-338 : 303

Genus Aphelochaeta Blake, 1991

Type-species: Tharyx monilaris Hartman, 1960 . Original designation by Blake (1991).

Diagnosis. (after Blake 2018). Prostomium conical to rounded; peristomium elongate with a pair of grooved dorsal tentacles arising either on or anterior to setiger 1. Anterior segments often expanded, crowded or uncrowded; abdominal segments sometimes beaded or moniliform in appearance; setae simple capillaries lacking distinct serrations using light microscopy but distinct fibrils may be visible using SEM; posterior end frequently expanded, tapering to a simple pygidial lobe.

Remarks. The genus Aphelochaeta was established by Blake (1991) as part of a revision of the genus Tharyx . Bitentaculate cirratulids with non-serrated capillary setae were assigned to the new genus. The absence of setae other than simple capillaries results in species of Aphelochaeta being more difficult to identify than those of other bitentaculate genera. In the absence of setal details, systematists are therefore required to use body and segment shape, details of the pre-setiger region, origin of the dorsal tentacles and anterior branchiae, presence or absence of dorsal and ventral grooves and ridges, form of the posterior end, nature of the pygidium, and MG staining patterns to identify individual species. Blake (2018) reviewed a wide range of morphological detail that is available within the genus, but species of Aphelochaeta are the most difficult of the bitentaculate cirratulids to identify.

As part of the present study, most specimens identified as Aphelochaeta are assigned to a new species, A. caribbeanensis n. sp. A few additional specimens of another species were in poor condition and not suitable for further study.