Spionids are benthic polychaetes with a pair of grooved feeding palps (which are usually lost from preserved specimens), a prostomium that is posteriorly prolonged, and prominent dorsal parapodial lobes and, usually, gills.
Spionids are common and widespread in soft sediments throughout most marine habitats and are often abundant in benthic samples. One group of genera, the polydorids, includes many species which bore into mollusc shells and other calcareous substrates. The polydorid genera
may be significant pest of abalone, oysters and other fisheries and aquaculture
ventures.
Diversity
There have been a number of recent publications on the relationships of spionid genera. The southern Australian fauna appears to be relatively well-known, especially estuarine and inshore soft sediment habitats. The interactive key provided here recognises 33 genera known globally, and includes some 124 species presently known to occur in Australian waters (some of these are poorly known or may be undescribed).
