have very little probability of being infected with the larvae of D. paradoxum. 



Certain observations of the life cycle of Mazocraes alosae 

 Hermann were conducted by us on the Caspian Sea during 1931-32. The 

 hosts of this parasite in the Caspian Sea are numerous types of herrings 

 among which we dealt basically with Alosa brashnikovi (Borodin), A. 

 saposhnikovi (Grimm), and A. caspia (Eichwald) in the region of the Island of 

 Sara. The study of the worms during May and June disclosed a strong 

 cyclical nature in the period of reproduction of this species and conse- 

 quently a quite complex character of the life cycle. According to 

 our observations the herring bears only large mature M. alosae on their 

 gills until the naiddle of May, and the latter do not form or deposit eggs. 

 In our diaries there are notes that even in artificial conditions we were 

 unable to obtain deposition of eggs from the worms. The beginning of the 

 formation and deposition of eggs was first noticed in the beginning of the 

 second half of May, and this process took place in a very turbulent fashion. 

 The eggs are deposited by worms on the gills and attach to them very 

 tightly by the tens and even hundreds on a single fish. From experimental 

 data, we know that the deposition of eggs of M. alosae takes place during 

 4 to 6 days. Taking into consideration that in nature temperature con- 

 ditions are different, we can consider the periods of development of eggs 

 in nature equal to 8 to 10 days. This fully corresponds with our obser- 

 vations. Thus, the first depositing individuals of M_. alosae were noticed p. ii6 

 May 19th and already 8 days later we discovered larvae on the Kislerov Herring 

 which liad just settled. ^ The number of the larvae which settled on 



_ 



In 1955 on the Isle of Sara we observed egg depositing individuals of 

 M. alosae even earlier- -May 13. 



the gills of the fishes is not very great. According to our notes, it fluctu- 

 ates from five to fifty- -mostly around 20, 1. e. , it corresponds to the 

 number of adult worms normally observed in nature m other periods of the 

 year. The period of infection of herrings apparently is not very long-- 

 within limits of a month or less. The further growth of the settled larvae 

 takes place fairly rapidly; thus already a fortnight later (13 June) we found 

 young M. alosae with three pairs of clannps and with the fourth in the process 

 of inception. Thus, the complete formation of the attaching apparatus takes 

 place during 15 to 20 days, on the average. 



In view of what has been said before and also from the obser- 

 vations on the nature of infection of herrings of the genus Alosa from 

 the Caspian and Black Seas, one can visualize the life cycle of M^ alosae 

 more or less exactly (Fig. 123). As is known, our southern herrings 

 approach the shores or enter the rivers for spawning for relatively short 

 periods, mainly in April-June. After that they descend from the rivers 

 into the sea, or depart from the shores and maintain themselves in the 



120 



