372 



kg/m 2 

 90,000 



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



with 92,000 specimens, Pontogammarus maeoticus — 1-38 kg/m 2 with 

 specimens, Hypaniainvalida — 5, 500 and 15-4 g/m 2 , Monodacna color ata 



—9,000 and 1-35 kg/m 2 , Corophium 

 maeoticum — 39,780 and 158-7 g/m 2 , 

 and so on. It is most characteristic 

 that in relation to salinity the 

 autochthonous and Mediterranean 

 forms are distinct from each other; 

 this is clearly seen even in the case 

 of the mysids (Fig. 178). 



Penetration of the relict community 

 into fresh water 



The autochthonous relict community 

 penetrated into fresh water during 

 the phases of greatest loss of salinity 

 and the subsequent increase of salin- 

 ity. The migration into fresh water 

 was easiest for the crustaceans and 

 fishes and for some individual species 

 of coelenterates, molluscs, bryozoans and polychaetes. Like the fresh waters 

 of the Arctic basin those of the basins of our southern seas give shelter to an 

 abundant relict fauna {Table 150). 



C\) Nh tQ °0 C3 C\j xj- CO OO Сэ C\J 0°/ 



Fig. 178. Distribution of Black Sea my- 

 sids according to salinity: / Relicts 

 (endemic forms) ; and II Mediterranean 

 forms (Bacesko). 



Fresh-water immigrants 



The low salinity of the bodies of water situated where the Black and Caspian 

 Seas now lie opened them to immigrants from fresh water. In this case 

 too, fish yield the greatest number of species, mainly the cyprinoid and 

 Percidae families, and, to a lesser extent, next come the lower crustaceans, 

 molluscs, oligochaetes and insect larvae (Chironomidae). 



The Arctic community 



The Arctic relict (or rather pseudo-relict) community which penetrated into 

 the south-Russian bodies of water from the north in the post-glacial period, 

 consisting mainly of crustaceans, is most original. It includes also some 

 fish, seal and, possibly, the polychaete Manayunkia. The Arctic immigrants 

 are very scarce in the Black Sea and are absent from the Aral Sea. 



The Mediterranean community 



The Mediterranean flora and fauna which filled the Black and Azov Seas 

 penetrated as far as the Aral Sea, although the connection between the Black 

 and Caspian Seas through the Kuma-Manych system and farther east through 

 the Uzboi was poor. Some thousands of years ago the mollusc Cardium edule 

 penetrated in this manner into the Aral Sea and Lake Charkhal, the fish 

 Atherina and the sea-weed Zostera nana (the latter also into the Aral Sea) 



