ИСТИНА

Pseudopotamilla reniformis (Sabellidae) is a very abundant species inhabiting rocks along the upper sublittoral zone (6-25 m) of the White Sea. Morphology of P. reniformis from the White Sea fits the original description of this species that is supposedly widely distributed in the Arctic and Boreal shallow waters. To confirm the species identification, we sequenced a D1 region of 28s rDNA gene and found that sequence of the animals from the White Sea were identical to those of P .reniformis from Iceland (Rousset et al., 2004). To assess inter-colonial variability, we analyzed 16s rDNA sequences of 3 specimens from three locations in the vicinity of the White Sea Biological Station. No 16S sequence variation was found. Colonies of P. reniformis formed by males and females have density of up to 1000 animals per m2. The colonies are associated with sponges (Halichondria panicea, Leucosolenia spp) and ascidians Halocynthia aurantium and Molgula spp. Within colonies the basal parts of P. reniformis tubes are entangled and attached to the hard substrates and to each other; and the proximal parts are free and more or less erect. Total adult tube length can reach up to 20 cm. The middle parts of the tubes are often surrounded by the crust-like sponges. Asexual breeding and regeneration of P. reniformis was studied both in the laboratory experiments and in situ experiments. Growth and reinforcement of dense P. reniformis colonies are achieved by a combination of sexual and asexual reproduction. Asexual reproduction takes place in October – April. Thin juvenile tubes in the upper colony level result from larval settlement, while small inhabited tubes in the colony base appear to be a product of archetomy, the process where posterior parts of abdomens are be fragmented into one to three pieces.