This sigalionid is one of the most common species of scale worms on soft bottoms and it can reach densities as high as 10,000 specimens per square meter.
Up to 2 cm long, but usually shorter than 1 cm, and with at most 80 segments.
The body is yellow brownish with a red anterior end when alive. The species has two pairs of eyes and in addition to the median antenna, it has a protuberance, called a facial tubercle, situated in the mouth opening. This facial tubercle is similar in size and shape to the median antenna. The scales on the dorsal side do not cover the dorsal side completely, but leaves a median part naked. The scales have papillae that are quite small and furnished with a distinct head.
In addition to P. baltica there are three other species of the genus in Norwegian waters. Pholoe baltica can be separated from P. pallida in that the latter lack eyes, and it can be separated from P. assimilis and P. inornata in that neither of these two species have a fascial tubercle ventral to the median antennae. Furthermore, P. assimilis and P. inornata both have scales that almost completely cover the dorsal side of the animals, and the papillae on their scale are comparably longer with a less distinct head than is found in P. baltica.
Pholoe baltica is a predator that feeds on other small annelids and crustaceans as well as single-celled foraminifera. It becomes mature at the age of three, and reproduction takes place in March to April, and it may reproduce several times during its life. The larvae are free-swimming but does not feed during its larval phase.
Pholoe baltica lives on soft bottoms starting from a couple of meters depth and downwards.
Chambers SJ and Muir AI (1977). Polychaetes: British Chrysopetaloidea, Pisionoidea and Aphroditoidea. Synopsis of the British Fauna (New Series). Edited by RSK Barnes and JH Crothers. No 54.
Nygren A. Pholoe baltica Ørsted, 1843. www.artsdatabanken.no/Pages/313089. Downloaded <year-month-day>.