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Serpulidae
Description
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Prostomium fused to peristomium; forming a branchial crown anteriorly. Peristomium forming a ring with partial anterior collar. Antennae absent. Branchial crown homologous to palps of other polychaetes; emerging in juveniles from prostomial region. Nuchal organs present. Longitudinal muscles grouped in bundles; segmentation present. First segment similar to next following segments; buth with notopodial chaetae only. Variably developed thoracic membrane present. Thoracic notopodia short, truncate cylinders and thoracic neuropodia tori; in abdomen notopodia tori and neuropodia short cylinders. Dorsal and ventral cirri, gills, epidermal papillae and pygidial cirri absent; gut a straight tube. Segmental organs mixonephridia; first pair excretory, posterior ones gonoducts. Circulatory system closed; heart body absent. Aciculae absent; chaetal inversion present. Chaetae variously ornamented capillaries and uncini.
The above description is taken from Fauchald & Rouse (1997).
Much of the literature recognises the Spirorbidae as a family separate from the Serpulidae. Spirorbids may be a a natural group, but recognising the taxon probably renders the Serpulidae paraphyletic (Rouse 2000) thus all are treated here as a single family.
Identification tips
Recognising the family
Serpulids are most likely to be confused with the Sabellidae which also have a tentacular crown of pinnate feeding tentacles and which also have marked thoracic and abdominal regions characterised by inversion of notochaetae and neurochaeta. The hard calcareous tube constructed by serpulids easily distinguishes them from Sabellidae, which have soft tubes of mucus and sediment particles. [Calcisabella piloseta Perkins 1991 is apparently unique among sabellids in constructing a tube of calcareous matrix with sediment particles incorporated but this species is not known from Australia.] The presence of a thoracic membrane immediately distinguishes serpulids from sabellids. Presence of an operculum (a modified radiole) also enables immediate recognition of Serpulidae, but this structure is absent in some serpulids and in others is fragile and often missing in preserved specimens.
Distinguishing species
The structure of the operculum (if present; it is frequently lost) and its ornamentation is important, as is the structure of the tube, although both may be influenced by environmental conditions.
The presence or absence of collar chaetae and their structure is important as is the extent and development of the thoracic membrane.
Description | Identification
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