Ryan Photographic - Polynoidae - Scale worms
The familyPolynoidae contains around 900 species in 167 genera. This makes them the second most speciose family of polychaete. Their common name of scale worm is because most of them are covered in flat plates called elytra (okay - why aren't they called elytra worms then? Because elytra is the fancy scientific name for them and laypeople call elytra "scales"). Interestingly, in some species, these scales are bioluminescent. It is believed that if the worm is attacked at night the elytra will glow around the mouth parts of the attacker - thereby making it a potential target for something higher in the food chain.
Polynoids exhibit a variety of forms and are widely distributed in the world's oceans. They are often found as Echinoderm commensals, as evidenced in some of my photos below. The biggest polynoids grow to 20 cm in length and in one species, 10 cm in width.
Asterophilia carlae Sea star scale worm
Asterophilia carlae Sea star scale worm on Linckia laevigata seastar, Fiji. The mollusc is Thyca crystallina, the Crystalline sea star snail
Gastrolepidia clavigera? Sea cucumber scale worm
Gastrolepidia clavigera, Sea cucumber scale worm, on underside of large holothurian, Raja Ampat, West Papua IMG_2188
Gastrolepidia clavigera, Sea cucumber scale worm on underside of large holothurian, Raja Ampat, West Papua IMG_2191
Lepidonotus species, Wellington, New Zealand IMG_0158. The solid white shells are from the polychaete Spirorbis
Paralepidonotus species, Fiji