Home | Overview | Browse families | Key to families

Identification tips
Natural History
Identification guide



Parergodrilids have a rounded prostomium and the peristomium is a complete annulus. Antennae and palps are absent. A pair of retractable nuchal organs are present on the prostomium in Stygocapitella, but absent in Parergodrilus. Numerous sensory papillae cover the body surface. A muscular gular membrane is absent, but the septum behind the head is better developed than subsequent ones, which are almost lacking. Segments are few (8 to 13), all similar and lack parapodia. Aciculae are absent, but simple chaetae are present in paired ventro-lateral bundles; capillaries and furcate types in Stygocapitella and spines in Parergodrilus. The pygidium lacks anal cirri. The eversible ventral buccal organ leads to an oesophagus, stomach, intestine and hind gut; the intestine is coiled in Stygocapitella. Nephridia, as metanephridia, are present along the body (Stygocapitella) or restricted in distribution (Parergodrilus). The circulatory system of Parergodrilus is closed and a heart body is absent; it is presumably present in Stygocapitella and lies at the level of the oesophagus.

The purported autapomorphy of the group is the unique arrangement of muscle and glandular cells of the ventral pharynx (Rouse & Fauchald 1997); however, the pharynx of the two genera differs slightly in the form of the tongue like organs and the muscle bulb, present in Stygocapitella, is lacking in Parergodrilus.

The description above is taken from Glasby (2000).

Identification tips

Recognising the family
Parergodrilids are very small grub-shaped worms that lack a head, pygidial appendages and parapodial lobes. Some species occur interstitially in intertidal sediments and some have been found in decomposing terrestrial plant debris.

Distinguishing species
Characters used to distinguish species include the types of chaetae present; these include furcate chaetae and spines. The distribution of metanephridia along the body is another useful specific character. Species tend to be habitat specific.


Description | Identification tips | Natural History | Diversity | Checklist | References | Identification guide