depths: according to the data of Svetovidov (1952), in a scattered fashion 

 and, in addition to that, the younger ages keep themselves separate from 

 the old ones. Thus, the basic favorable time for cross -infection of the 

 host is the period of the approach of the herring toward the shores for 

 spawning. The mass deposition of eggs of M. alosae coincides precisely 

 with this period. Undoubtedly the probability of infection of the host would 

 have been exceedingly small if the eggs were deposited directly into the 

 water, for during the migration of the herring their scattering would have 

 been exceedingly great. Thus, it is clear what a great adaptative 



significance the deposition of these eggs on the gills of the host by M. alosae 

 has. From this, certain peculiarities of the infection of the host of different 

 ages emerge. M. alosae is encountered only on adult fishes starting with 

 three-year-olds (let us remember that as a rule the majority of Caspian 

 herring spawn at this age for the first time and that two-year -olds spawn 

 only in rare cases), that is younger ones are not infected with M. alosae, 

 which is easy to understand because the contact betv/een the younger and 

 older ages of the herring is very insignificant, if it isn't practically absent 

 all together. It isn't clear whether the less than one-year-old or the 

 yearling herring are in a position to be infected. In nature they never meet 

 with larval M, alosae capable of infecting them, whereas the two-year-olds 

 have more chances to enter into contact with the older ages there and con- 

 sequently have a greater possibility of being infected. Actually in rare 

 cases we observe this in nature. The question about infection of fishes in 

 fresh water appears unclear in the life cycle of M. alosae. We have no 

 factual observations on this but it seems to us that, taking the biology 

 of the host into account, this possibility is not excluded. Further research 

 will verify the correctness of the supposition. 



Apparently the life cycles of two species of Octostoma which para- 

 sitize the Japanese mackerel- - Pneumatophorus japonicus (Houttuyn) are 

 close to the life cycle of M. alosae. In nature we see that Oct. scombri 

 (Kuhn) and Oct . minor (Goto) (Fig. 124) are encountered only on adult 

 fishes, beginning with two-year-olds. At the same time, the parasites 

 which are encountered are always of one size --fully matured. Hence, p. 117 



one can suppose that the multiplication and deposition of eggs of both species 

 have a periodic nature. 



The Japanese mackerel usually maintains a depth of 20 to 40 

 meters in the open sea and connes to the shores in large schools for 

 spawning in May and June. The spawning extends approximately from the 

 middle of June to the middle of July within 5 to 6 miles of the shore. The 

 young ones which emerge from the roe wander toward the shore where they 

 remain the entire summer, going to the depths in the late fall and returning 

 (to the shore, nobis) early (the next spring, nobis). In such a fashion, contact 

 between the early ages and the mature mackerel is absent. Because of that 

 and also of the fact that, as among M. alosae, the eggs of both types of 

 Octostoma are detained on the gills of the host, one can expect that the 



121 



