THE ARAL SEA 663 



however, the stock of sturgeon Acipenser was not restored to its former 

 numbers. 



It was discovered in 1945 that the Aral sturgeon Acipenser was infected, in 

 addition to the trematode, by a parasite of the roe of Acipenseridae fish well 

 known in the Caspian Sea — the coelenterate Polypodium hydriforme. The poor 

 multiplication of Acipenser sturgeon when the epizootic epidemic caused by 

 Trematoda was over may have been due to its infection by Polypodium 

 hydriforme. V. Dogjel and B. Bykhovsky noted the general poverty of the 

 parasite-fauna of the Aral fish (two to three times poorer than the parasite- 

 fauna of Neva Inlet in the Gulf of Finland), caused by the properties of the 

 Aral waters and by the absence among the rest of the fauna of vector forms, 

 the intermediate hosts. 



Mass zoobenthos forms. The most common benthos forms are the Oligo- 

 chaeta Paranais simplex and Nais elinguis; among Ostracoda Cyprideis 

 littoralis, widely distributed in the Azov and Caspian Seas ; only one repre- 

 sentative of higher Crustacea, Pontogammarus aralensis; among molluscs 

 Adacna minima, Dreissena polymorpha and, much more rarely, Cardium edule ; 

 and among the insects, the larvae of caddis flies and of chironomids. The 

 highest number of specimens recorded and the weight of these forms per 

 1 m 3 are given in Table 281. 



Table 281 



It is evident from Table 281 that even the highest mass forms, such as for 

 example Dreissena, which in the Caspian Sea frequently produces a few kilo- 

 grammes per 1 m 3 , do not produce more than a few dozen grammes in the Aral 

 Sea. The Dreissena genus is represented in the Aral Sea (according to N. Husai- 

 nova, 1958) by four species — Dr. polymorpha with two variants {obtusecari- 

 nata and aralensis), Dr. caspia, Dr. pallasi and Dr. rostriformis. Cyprideis 

 littoralis, at times found in the Sea of Azov in hundreds of thousands of 

 specimens per m 3 , is in the Aral Sea no higher than 1,000 with a biomass 

 of 0-2 g/m 2 . The same holds true of plants. The highest Zostera biomass 

 recorded is only 90 g/m 2 , Tolypella 9-5 g/m 2 , and Vaucheria 531 g/m 2 . The 

 total weight of all the plants rarely exceeds 0-5 kg/m 2 . 



