Segmented worms: Beachworms, bristleworms

Code LP999999

Key terminates here

Class: Polychaeta

Annelids are segmented worms with a subterminal mouth, a straight gut with or without diverticulae, posterior anus, dorsal pre-oral brain, paired ganglionated ventral nerve cords, a closed blood circulatory system (occasionally reduced or absent), a well-developed coelom divided by septa (corresponding to the external segmentation, except in leeches) and typically with moveable setae in bundles on most body segments.

Polychaeta (beachworms, bristleworms) are mainly marine, and uncommon in freshwater or terrestrial habitats. Five families are known from Australian inland saline waters with sea connections or else from near-fresh upper estuarine reaches. These families are:

1 Neritidae (Code LP019999)

Typical errant polychaetes with tentacles around the head end, the body uniformly segmented and with uniform setation. Predatory. Active worms found in crevices, under rocks or in burrows.

2 Capitellidae (Code LP029999)

Deposit feeders which build mucus-lined burrows in mud, silt or sand. Somewhat thread-like or earthworm-like, without conspicuous parapodia or head tentacles. They may be mistaken for oligochaetes but differ in that they are not obligately hermaphrodite, generally have more sexual segments, and never develop a clitellum. A single species is recorded from Australian inland waters (Williams, 1980). The sole record is from a small lake with sea connections near Beachport, South Australia.

3 Spionidae (Code LP039999)

Surface detritus feeders which live in fixed tubes. Body moderately long and tapering. Side of head bearing two long tentacles used to sweep food into the mouth.

4 Serpulidae (Code LP049999)

Filter feeders living in fixed, calcareous (white) tubes, usually on hard surfaces. The mouth is surrounded by pinnate tentacles in two semicircular or spiral lobes. There may or may not be a specialised, flattened tentacle used as an operculum to close the end of the tube.

5 Histriobdellidae (Code LP059999)

Small (under 2mm) aberrant polychaetes which live in the gill chambers of freshwater crayfish (Crustacea: Decapoda). The head carries one median and two pairs of lateral, short tentacles plus a pair of stouter, lateral palps. The body is 5-segmented, with three pairs of cirri and an additional pair of mid-lateral clasping cirri in males. The parapodia of the terminal segment are developed into a pair of short, limb-like outgrowths each with cirri in two bundles.

Reference:

Williams, W.D. (1980) Australian Freshwater Life: The Invertebrates of Australian Inland Waters. The Macmillan Company of Australia, Melbourne.