Quick guides - polychaetes with lots of "tentacles"

The families in the following table are not all closely related to one another, but are nevertheless sometimes confused, because first impressions of inexperienced sorters are simply of worms "with masses of long tentacles". These are quickly sorted out when it is realised that the "tentacles" are different structures, which are arranged on different parts of the body. The interactive key to polychaete families distinguishes these exhaustively, but the following table may also help:

Ampharetidae	Ampharetidae have retractile oral filaments that arise from within the mouth, and 3 or 4 pairs of simple or pinnate branchiae arising from anterior segments. Distinct division into "thoracic" (10+ segments) and "abdominal" body regions. Chaetae include capillaries and uncini; hooks are absent; spines and anterior palae may be present. Tube membraneous.
Cirratulidae	Unlike the following families in this table, in cirratulids the "tentacles" occur as a pair of long branchial filaments that occur throughout the body, on most segments (though a fair few are often broken). No distinct division into "thoracic" and "abdominal" body regions. There is also a pair or a group of palps, on anterior segments. Chaetae may include smooth and serrate capillaries, and spines; hooks and uncini are absent. Tube absent, or a fragile membraneous or mucus structure. Often brightly coloured yellow, red or green in life.
Sabellidae	Large Sabellidae are recognised from the pinnate non-retractile radioles that form a feather duster-like "crown" at the anterior end, none of which are modified. Palps and branchiae are absent from body segments. Distinct division into "thoracic" (usually 8 segments) and "abdominal" (a few to many) body regions. Thoracic membrane absent. Chaetae include various capillaries, and uncini; hooks absent. Tube parchment-like, or calcareous (in one tropical genus).
Serpulidae	Serpulidae have pinnate non-retractile radioles that form a feather duster-like "crown" at the anterior end, one is modified into an operculum that closes the end of the calcareous tube. Palps and branchiae are absent from body segments. Distinct division into "thoracic" (usually 7 segments) and "abdominal" body regions. Usually with a distinctive thoracic membrane. Chaetae include various capillaries, and uncini; hooks absent. Tube calcareous (sinuous or tightly coiled).
Terebellidae	Terebellidae have numerous non-retractile filaments around the mouth, 2-3 pairs of simple or branched branchiae (branchiae sometimes absent). Distinct division into "thoracic" (usually 15+ segments) and "abdominal" body regions. Chaetae include various capillaries, and uncini; hooks absent. Tube absent, membraneous or parchment-like.
Trichobranchidae	Trichobranchidae have numerous non-retractile filaments around the mouth, branchiae simple filaments or a stalked lamellate structure (branchiae sometimes absent). Prostomium projects ventrally as a distinct bulbous membrane. Distinct division into "thoracic" (usually 15+ segments) and "abdominal" body regions. Chaetae include various capillaries, hooks and uncini. Tube membraneous.