Structure of winter growth interruption lines and mechanism of their formation on Hydrobia ulvae Pennant 1777 (Gastropoda, Prosobranchia) shell in the White Sea.

A.M.Gorbushin, Zoologichesky Zhurnal, 1993, vol.72, N 11, pp. 29-34 [In Russian; English summary].

Abstract: Growth interruption lines were found on mud snail's shells in the White Sea. The presence of them is not connected with snail's position in the intertidal zone, sex or infection with larvae of Trematodes. The lines were observed in mature and immature (excluding recruits of the current season) individuals. This fact denies that connection between their formation and reproductive season exists. The results of shell condition analysis in early spring convincingly testify coincidence of the lines formation moment and the winter diapause. At long and cold winter in the region of investigations the mud snails survive in mud on the depth of 0.5 - 2 cm. Mineral layer on the edge of shell hardly and sometimes even entirely dissolved during winter months. The reconstruction of shell wall normal structure occurs in spring, however, "scar" in form of a line is well observed. Thus discovered changes in the inner structure and on the external shell surface of White Sea mud snails are seasonal and may be used for snail age determination quite successfully. Maximal longevity of H.ulvae in region of investigations was assessed preliminary as 3 years long, H.ventrosa Montagu, 1803 - as 1.5 years.