THE CASPIAN SEA 



563 



rises in salinity. Such were the cyprinids and perch, the most important 

 among fish, all or almost all the gastropods, tubificid worms, some of the 

 Turbellaria, and a considerable number of animal and plant planktons. Two 

 main components of the modern Caspian population, the original marine 

 and fresh-water faunas, having lived together through the phases of its sub- 

 sequent history had become, in a remarkable manner, interlocked with each 

 other, acquiring similar biological characteristics and similar distribution 

 throughout the Sea. Both groups include some typical ' marine ' forms living 

 exclusively in the most saline parts of the Sea, some 'brackish- water' 

 ones, some tolerant to various degrees of salinity, and other forms which 



AMPHIPODA PONTOGAMMARUS 

 ARALENSIS 



2. BIVALVE DIDACNA TRIGONOIDES 



3. WORM NEREIS SUCCINEA 



4. COCKLE CARDIUM EDULE 



5. DREISSENA CASPIA 



6. MYTILASTER LINEATUS 



7. SEAWEED ZOSTERA 



8. AMPHIPODA DIKEROGAMMARUS 



9. BULLHEAD GOBIUS FLUVIATILIS 



10. BENTHPHILUS 



11. MOLLUSC THEODOXUS SCHULTZI 



12. M'ESIDOTHEA ENTOMON 



13. PONTOPORFIA AFFINIS 



14. PSEUDOLIBROTUS 



15. PRAWN LEANDER 



16. MYSIS 



17. MEDUSA MOERISIA r ; 



18. PARAMYSIS 



19. GOLDEN SHINER 



20. HERRING CASPIALOSA 



VOLGENSIS 



21. PIKE PERCH 



22. CASPIAN HERRING 



23. VOBLA 



24. SPRAT 



25. STURGEON;;;;. 



26. STARRED STURGEON ■ 



27. MICROMELANIA I 



28. WORM HYPANIA INVAL 



Fig. 270. General distribution of Caspian Sea fauna (Zenkevitch, 1951). 



have migrated into fresh water. Recent immigrants from the Black and Azov 

 Seas and from the north, from the Arctic basin, have joined these basic 

 groups of the Caspian fauna. However these genetically heterogeneous com- 

 munities retain some of their biological and physiological peculiarities. 



The present-day distribution of an organism throughout a sea often does 

 not provide us with a clue as to its genesis. This should be considered mainly 

 as the result of subsequent changes in sahnity. The time and means of 

 penetration of many groups and individual representatives of the Caspian 

 fauna into the Sea, their migration into fresh waters and their subsequent 

 life in the body of water remain obscure. 



Derzhavin (1951) and Mordukhai-Boltovskoy (1960) revised the list of 

 the present-day fauna of the Caspian Sea. It now comprises 727 animal species 

 (374 genera) — 538 free-living specimens (301 genera) (see Table 235), 170 para- 

 site forms (67 genera) and 23 species (14 genera) which have penetrated into 



