Ancyrocephalus paradoxus Creplin--During our work at Saratov 

 in July 1947 we succeeded in hatching a free-swimming larva of Anc. para- 

 doxus. Creplin from the eggs of the parasite from the gills of Sandre 

 [ L/Ucioperca lucioperca (L. )] . The development of the larva in the egg D, 152 



took place in four days at temperatures of 20 to 24°. The larva which had 

 emerged from the egg had a length of about 0. 15 mm with a width of about 

 0. 05 mm (the egg having the length of about 0. 10 and the width of about 

 0.06 mm). The mature adult worm has an average length of about 2 mm, 

 i.e., 13-14 times longer than the larva. The latter have a ciliary epi- 

 thelium located in essentially the same fashion as among the larvae of 

 Dactylogyrus, i.e. , in three zones or belts. The attaching disc of the 

 larva is not at all delineated from the body and is equipped with 14 edge 

 hooks beside which there are no traces of chitinous formations so that the 

 inception of the middle hooks takes place later. The edge hooks have the 

 length of about 0.015- 0.018 mm; their hooked part is well-developed but 

 the handle is weak with a small widening at its free end (Fig. 151). 

 Among adult worms (Fig. 152) the edge hooks have the length of about 



O.OIkm, 



Fig. 151. Ancyrocephalus paradoxus 

 Creplin, attaching armature of the 

 free -swimming larva. 







0.0l6to 0.019 mm, i.e., they are 



almost completely of the same sizes 



as in the larva. Judging from the 



observations on live mature worms, 



their edge hooks hardly function 



whereas among the young forms, 



which have fully formed middle 



hooks, the edge hooks still function 



fairly actively. The larvae have 



two pairs of relatively large eyes. 



The internal structure of the larva 



is completely analogous to that of 



the larva of Dactylogyrus. Further 



development has not been followed 



through. The youngest known individuals from the hosts which were at our 



disposal are about 0, 5 mm in length and already have fully formed attaching 



and sex armatures. 



Fig. 152. Ancyrocephalus para - 

 doxus Creplin, adult worm from 

 the gills of Lucioperca lucioperca 

 from Ahchtarin estuaries (Sea of 

 Azov). 



163 



