Aphelochaeta Blake 1991

• Main Author: Blake, James A.
• Format: Other/Unknown Material
• Language: unknown
• Published: 2018
• Subjects: Biodiversity; Taxonomy; Animalia; Annelida; Polychaeta; Terebellida; Cirratulidae; Aphelochaeta; Antarc*; Antarctica
• Online Access: https://zenodo.org/record/3798632; https://doi.org/10.5281/zenodo.3798632

Genus Aphelochaeta Blake, 1991 Type species: Tharyx monilaris Hartman, 1960. Original designation by Blake (1991). Diagnosis. (emended, Dean & Blake 2016). Prostomium conical to rounded; peristomium elongate with 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. Blake (1991) assigned bitentaculate cirratulid species having only simple, non-serrated capillary setae to the genus Aphelochaeta. The species belonging to Aphelochaeta are among the most enigmatic and difficult to identify of all cirratulids because of the lack of obvious variability in setal morphology. However, there is considerable variation in body shape, details of the prostomium and peristomium, placement of the dorsal tentacles and anterior branchiae, presence or absence of dorsal and ventral grooves and ridges, form of the posterior end and pygidium, and Methyl Green staining patterns. Sometimes the capillaries do differ in thickness and length among species, but this is difficult to quantify and depict in a manner that enables readers of descriptions to distinguish one species from another. Additionally, the capillaries often exhibit numerous fibrils along the shaft, but these are best seen with SEM and difficult to observe in light microscopy. Despite the specific nature of different combinations of these characters, closely related species are usually difficult to distinguish from one another. Blake (1996) pointed out that it is usually only at the local or regional level that keys to species have any utility. Hartman (1966, 1967) referred all bitentaculate cirratulids having only capillary setae and previously reported from Antarctica to Tharyx according to definitions then in use. Types of ...