THE BLACK SEA 435 



6. Mediterranean immigrants, which feed and spawn in the summer in the 

 Sea of Azov and come back to the Black Sea in winter ; such as, for instance, 

 the Azov form of anchovy. 



7. Fresh-water forms. 



As regards the wealth of species the following forms are notable: the 

 autochthonous Acipenseridae (6 species), the mixed Clupeidae (9 species), the 

 fresh-water Cyprinidae (23 species), the Mediterranean Mugilidae (5 species), 

 partly the fresh-water Percidae (8 species), the Mediterranean Sparidae (8 

 species), Labridae (8 species), the mixed Gobiidae (22 species), the Medi- 

 terranean Blenniidae (8 species) and Syngnathidae (7 species). 



Moreover, some forms, which penetrated into the Black Sea even earlier 

 but do not multiply there, are growing acclimatized, forming some separate 

 Black Sea colonies. Lobster, mackerel, Sarda, tuna and others can be included 

 among these forms. Finally, there are some forms which used to spawn very 

 rarely in the Black Sea before, but which within recent years have multiplied 

 there annually in large numbers. 



The Black Sea is supplemented also by occasional immigrants from more 

 distant countries. V. Makarov (1941) has lately found in the Bug and Dnieper 

 inlets a mass settlement of the crab Rithropanopeus, carried there on ships from 

 the Zuyder Zee (Holland), which had come even earlier to the European shores 

 from the coast of Northern America. The gastropod mollusc Rapana bezoar 

 which has done incalculable harm to the oyster and Mytilus colonies, mainly 

 off the Caucasian shores, came to the Black Sea from the Sea of Japan in a 

 similar manner. Some Mediterranean forms, settled in the Black Sea, have 

 found here particularly favourable conditions for development, and, although 

 small in size, they form a very dense population. Thus there are the algae 

 Phyllophora and Cystoseira; the molluscs Teredo navalis, Cardium edule 

 and Syndesmya ovata ; the polychaetes Nereis diversicolor, N. cultrifera, N. 

 sue cine a, Nephthys hombergii and Melinna palmata, and a number of others. 



The fauna which penetrated into the Black Sea has not yet had time to 

 change much and to deviate from the original Mediterranean species. This 

 demonstrates the youth of this fauna. Thus E. Slastenenko records (1938, 

 a, b) only nine Black Sea endemic forms among 105 species and sub-species 

 of fish of Mediterranean origin living in the Black Sea.* As early as 1902 

 Sovinsky pointed out that among the 680 Mediterranean immigrants only 

 194 (28 per cent) had evolved taxonomically separate forms. Frequently this 

 evolution of the Black Sea forms into species and sub-species is temporary in 

 character. Thus, for example, until lately anchovy inhabiting the Black Sea 

 were divided into two sub-species : the Azov Engraulis encrasicholus maeoticus 

 (I. Puzanov, 1936) and the Black Sea E. e. ponticus (I. Aleksandrov, 1927); 

 moreover, it was proposed (A. Mayorova, 1934) to divide the latter into two 

 regions — an eastern and a western. Moreover, there was a tendency to consider 

 anchovy as a relict of the Tertiary Period. S. Maljatzky (1939), having recon- 

 sidered the whole of this problem, came to the conclusion that the anchovy 



* A tenth — the pipefish Syngnathus phlegon longicephalus — described by V. Nikitin 

 {Transactions of the Zoological Institute of the Georgian Academy of Sciences, 1946), 

 may be added to them. 



