198 BIOLOGY OF THE SEAS OF THE U.S.S.R. 



By K. Derjugin's reckoning (1928) the majority of the more substantial 

 groups of benthos are half composed of Arctic species ; but for individual groups 

 the proportion of Arctic forms rises to 69 per cent (Decapoda) and even to 86 per 

 cent (Echinodermata). Many of these Arctic forms are highly characteristic 

 of the Kara Sea and the coldest parts of the Barents Sea, and certain ones in the 

 White Sea have already acquired a relict aspect. Arctic-boreal forms compose, 

 on the average, 17 to 25 per cent. On the other hand, the proportion of boreal 

 forms is also large — 11-5 to 23 per cent, of which many represent, in the White 

 Sea, warm-water relicts. That is, they also have broken away from their main 

 habitat. 



Endemic characteristics. Although the fauna of the White Sea is, geologically 

 speaking, young, it nevertheless possesses definite endemic characteristics. 

 Both in the plankton, in the benthos and among the fish we find more or less 

 pronounced endemic forms. The majority of these are sub-species and variants 

 but sometimes they are clearly individual species. Of these we indicate the 

 remarkably mobile lucernaria Lucernosa saint-hilairei, the mollusc Lyonsia 

 schimkevitchi, the fishes Lycodes maris-albi, Gadus callarias maris-albi, Clupea 

 harengus pallasi maris-albi and others. There is also a genus endemic in the 

 White Sea, namely the Porifera Crellomima imparidens. As regards this last 

 Derjugin suggests that either it is a fragment of a more ancient group, or its 

 related forms will be found somewhere in the neighbouring seas. 



Link with Pacific Ocean fauna. There are likewise in the White Sea a series 

 of forms which establish a link between its fauna and the fauna of the seas of 

 the Far East. The White Sea is the extreme western outpost of this fauna. Of 

 this latter group one may point to one of the White Sea herring, Clupea 

 harengus pallasi maris-albi, the lamprey Lampetra japonica septentrionalis, 

 and the polychaete Scalibregma robusta which inhabits the Sea of Okhotsk 

 and the White Sea. 



Link with Baltic Sea fauna. Finally, the last group characteristic of the White 

 Sea, which indicates the existence in the Yoldian stage of a link between the 

 White and Baltic Seas. A series of forms both plant and animal are common 

 to both Seas and are absent from the Barents Sea and even from the waters 

 of the Norwegian coast. Among them are forms of both thermophilic and 

 cold-living character. As indicated in the chapter devoted to the Baltic Sea, 

 some geologists and zoogeographers deny the existence of a bygone link be- 

 tween these Seas in the post-glacial period; but the majority recognize it. 

 The most interesting of the forms that inhabit both Seas is the marine grass 

 Zostera marina, which in the Barents Sea is encountered in the most western 

 part of the Murman Peninsula (beginning at Vayda Guba and farther to the 

 west. The peridinean Pyrophacus horologicum and the diatom Chaetoceros 

 danicum, which are common in the Baltic Sea, are likewise not encountered 

 in the Barents Sea. In 1944 Z. Palenichko (1947) discovered in the Gulf of 

 Onega a boreal polychaete which was new for the White Sea, Nereis virens. 

 This is one of the most numerous representatives of the polychaete worms. 



