Among Dactylogyrus the life cycle of _D. iwanowi Bychowsky, 

 which parasitizes the Far-Eastern Rudd--Leuciscus brandti (Dyb. ), stands apart. 



Ugay,or Rudd as it is more often called in the Far East, is the 

 only marine representative of carp in our fauna. It is a typical anadromous 

 species.During its entire life it is encountered in the sea, sometimes far 

 away from the mouths of the rivers and entering into the latter only for 

 spawning: "In the Suyfun and other rivers entering into Peter the Great Bay 

 it ascends (the rivers, nobis) when the ice begins to melt and sheds roe in 

 the beginning of May-Jvme and during the sunamer up to September, and 

 the individuals which finish spawning during the summer then descend into 

 the sea; the immature ones are encountered all year round at the mouths 

 of the estuaries; the young ones, having hibernated inthe river and having 

 reached 7 to 9 centimeters in length, descend into the sea" (Berg, 1949). 



Although very insignificant and based predominantly on fixed material, our 

 data show that infection by D^ iwanowi takes place in the river period of the life of the Rudd 

 and that mainly the young individuals which are descending into the sea are infected. The 

 worms live on their hosts more than a year, reach maturity during the marine period of 

 their lives, and during the approach of the host to the river begin an increased deposition 

 of eggs. What remains to be explained is whether a deposition of eggs takes place during 

 the marine period of life of D^ iwanowi and what Is the fate of these eggs. Apparently, 

 even if this deposition takes place, the larvae emerging from the eggs practically do not 

 infect Rudd, because conditions exclude the possibility of the encounter of the larva with 

 its host. Likewise, the secondary infection of the adult individuals which takes place in 

 the fresh water is a more rare occurrence than the infection of the young, for the same 

 reasons as were indicated for D^ vastator. Thus, the life cycle of D^ iwanowi (Fig. 120) 

 (Fig. 120) already has a much more complex character and is adapted to the peculiarities 

 of the biology of the host. 



We observed a singular life cycle in the parasite of the Zheltoperaya flounder 

 (Green-flnned Flounder, nobis) , Llmanda aspera (Pallas)- -Protancyrocephalus strelkowl 

 Bychowsky (Fig. 131). This species is encountered almost exclusively on mature flounders 

 at ages ranging from less than a year to three years mainly along the coast or the zone 

 close to the coast of the sea and at depths of up to 2 meters. For the understanding of 

 the life cycles of Pr. strelkowi it is necessary to explain briefly the data concerning the 

 biology of Its host, the Zheltoperaya flounder. 



The Zheltoperaya flounder is widely distributed in the Far East and is 

 encountered at different times of the year at different depths starting from the littoreal 

 zone to 180-200 meters and even deeper. The mature individuals, i. e. , the age cate- 

 gories from four years and above, maintain themselves in the winter at great depths and 

 migrate into shallow waters with the arrival of spring where at depths of from 8 to 20 

 meters they begin to spawn. Spawning usually takes place in June -July, after which the 

 adult individuals spend a certain time in the same region feeding vigorously 



114 



