

310 



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



10 



65-Ъ 



60- 

 55 ■ 



50 



45 \ 

 40 



35 

 30 

 25- 

 20- 



15- 



10 

 5 1 

 



t~"?*<A 



\ 



■Пса \y. 



Byth Lma tentacutata 

 Theo doius ftuwa h its 



35 30 25 



20 15 10 

 SALINITY 



Fig. 147. Changes in the length of the body 

 of marine bivalves and fresh-water Gastro- 

 poda with change in the salinity of the 

 medium (Remane, 1934). 



Macoma reaches 21 to 24 mm in the areas west of Helsingfors, which are most 

 favourable for its existence (as regards its feeding). For the rest, both Cardium 

 and Mytilus are larger in this area. Unlike Mytilus, Mya and Cardium men- 

 tioned above, the size of Macoma is clearly only slightly affected by changes 

 of salinity. Macoma baltica becomes smaller with the depth of its habitat 

 {Table 127). 



According to H. Luther's data (1908) Macoma baltica from the inner bays 

 of the Gulf of Finland is larger in size than the samples from the Littorina 

 Sea deposits. 



At the same time, marine forms without a calcareous skeleton often do not 

 undergo a decrease in size, as for example the amphipods Gammarus zad- 

 dachi oceanicus and Corophium volutator, and the shrimp Leander adspersus 

 fabricii, which are the same size in Danish waters as in the Gulf of Finland. 



