Aeolosomatids are minute oligochaete-like worms which
inhabit mostly freshwater. Like the similar potamodrilids they
lack head appendages and parapodial lobes, but may be
distinguished from them by the presence of coloured
epidermal glands all over the body surface.
Aeolosomatids are minute, ciliated worms with
no clear affinity to other polychaetes. The large, lobe-like
prostomium is almost completely ciliated ventrally and has
lateral ciliated grooves that have been
interpreted as nuchal organs by Rouse & Fauchald (1997); the
muscular pharynx lies in the peristomium. Constrictions along
the trunk give the appearance of external segmentation, but
they actually represent a chain of zooids produced by
paratomy (fragmentation). Parapodia are absent. Chaetae are
usually present as four bundles per segment; they are rarely
absent. They comprise usually only capillaries, but in some
species, some sigmoid hooks may be present, or, rarely, only
hooks. The body is often brightly coloured due to the
epidermal gland cells. Each gland cell consists of a vacuole,
filled with red, green, blue-green, yellow, or sometimes
colourless liquid; the function of the gland cells is unknown
(Bunke 1988).
The above description is taken from Paxton (2000), which in turn is based on that of Fauchald & Rouse (1997).
The Aeolosomatidae, together with the Potamodrilidae, had been considered to be members of the Clitellata prior to the analysis of Rouse & Fauchald (1997) which placed them as provisional Polychaeta incertae sedis. However, further work may yet cause the Potamodrilidae and Aeolosomatidae to be removed back to the Clitellata (Rouse 2000).
Identification tips
Recognising the family
The Aeolosomatidae are apparently the only polychaete family which has epidermal glands present as discrete coloured spots. This family will be collected only when interstitial fauna is being sampled. This specialised habitat has been poorly sampled worldwide and especially in Australia.
Distinguishing species
Characters used to separate species of Aelosomatidae include the type of chaetae present (these include capillaries and sigmoid hooks), and the colour of the epidermal gland cells (which range from red, green, blue-green, yellow to colourless).
