Двустворчатые моллюски Белого моря - Зоологический институт ...

SUMMARYA natural border should be found for any waterbody to define its fauna. Such a boundary isexpected along the line of maximum gradients of environmental characteristics if the waterbasinsare connected to another one. According to conducted analysis of water structure and water currentpeculiarities (Naumov, Fedyakov, 1991, a), a narrow area in the White Sea fits this condition.It lies in the northern open part of the sea where Barents Sea waters are mixed with WhiteSea waters in equal proportion between the mouths of Ponoy and Shoyna Rivers in the middlepart of Voronka Strait (Fig. 18). It was also found out that a number of Barents Sea species do notspread southward behind this line (Naumov et al., 1987; Naumov, Fedyakov, 1991, a). It allowsdrawing the faunistic border of the White Sea within the area of oceanographic boundary mentionedabove. Thus, Derjugin’s (1928) opinion of the White Sea independency was confirmedonce more. The White Sea is an individual waterbody with its own features ofhydrological regime and its own fauna, different from fauna of other seas.The revision of clam species composition was needed after the introduction of clarityinto the faunistic boundary of the White Sea. Two species: Yoldiella intermedia (M. Sars)and Macoma torelli (Steenstrup) were excluded because they were encountered only in thenorthern part of Voronka Strait northward of the faunistic border. Furthermore, it was discoveredthat no living specimens were found in the White Sea among some species previouslyincluded by different authors in the list of the White Sea bivalve mollusks. This concernsPortlandia aestuariorum (Mossewitsch), Bathyarca glacialis (Gray) and Zirphaeacrispata (Linnaeus). The majority of modern malacologists consider Mya pseudoarenaria(Schlesch) as a synonym of Mya (Mya) truncata (Linnaeus) and Lyonsia schimkewitschiDerjugin, Gurjanova as a synonym of Lyonsia arenosa (Møller), so they also should beexcluded from the White Sea fauna. Some authors include the Pacific mussel Mytilus trossulusGould in the White Sea clam list. They do this because in several specimens of theWhite Sea mussels colouration and shell structure near the ligament edge resemble thosefound in Pacific individuals. Such point of view cannot be accepted, since neither biochemicalnor physiological data confirm it. Lastly, Yoldiella frigida (Torell) was added tothe White Sea fauna due to mistaken perusal of the original label during writing down thedata into the catalogue of the Zoological Institute basic collection. Yet, a new species forthe White Sea bivalve fauna Yoldiella nana (M. Sars) was found during our investigations(Naumov et al., 1987). Besides, it has been ascertained that there are two species of genusHiatella in the White Sea, not one, as it was considered before.Seemingly, species composition of the White Sea bivalve mollusks is studied almostcompletely. At the moment, 39 species belonging to 30 genera, 20 families, 7 orders and 3subclasses represent the White Sea fauna of this taxon. Theoretical calculations using theoriginal method of the total species number in a regional fauna estimation (Naumov et al.,1986, a) show an opportunity to discover two or three extremely rare species in the future.Thus, it should be claimed, that inventory of the White Sea clams is almost finished; furtherinvestigations hardly can enlarge the species list within the framework of methods used.