CHAPTER n 



OCCURRENCE OF SPECIES OF MONOGENETIC TREMATODES 

 ON THE SPECIES AND GENERA OF THEIR HOSTS --FISHES 



The data concerning the occurrence of the 958 species of p. 222 



monogenetic trematodes known to us at the present time, composed on 

 the basis of literary sources (including our own works), are represented 

 in Table IV. Examining them we see that 806 species or 84. 1 % of the 

 total number of monogenetic trematodes are encountered on representa- 

 tives of one genus of fishes. Those discovered on two genera of fishes 

 are indicated as 100 species or 10.4%, on three genera of fishes--30 

 species or 3. 2%, and finally on four and more genera of fishes --2Z species 

 or 2. 3% species of Monogenoidea. Thus only 152 species of monogenetic 

 trematodes, that is 15. 9% of their total number, are encountered on other 

 than one genus of fishes, a fact which in itself indicates the strong 

 adaptation of the worms to their hosts. Furthernnore, as is seen from 

 the table, among the ones (hosts, nobis ) related to the same family, that 

 is, indisputably related with each other, 903 species of monogenetic 

 trematodes are encountered on 94. 2% and only less than 6% are encountered 

 as parasitizing species of different families of fishes. If one takes into 

 consideration that from the latter nunnber more than two-thirds were 

 found on fishes of one order, that is--fishes which are distantly related to 

 each other, so to speak, then all these numbers underscore still more 

 the high adaptation of the species of monogenetic trematodes to the genera 

 and species of their hosts --fishes. 



In connection with the above -nnentioned, special interest is 

 occasioned by the cases in which monogenetic trennatodes are indicated 

 as occurring on several fishes of different families, and especially those 

 that occur on a large number of species belonging to different families of 

 various orders of fishes. In order to understand and evaluate these cases, 

 let us get acquainted more in detail with each one of them. 



Five species of monogenetic trematodes specifically: 

 Ancyrocephalus alatus Chauhan, Gyrodactylus arcuatus Bychowsky, 

 Benedenia melleni (MacCallum), Tristoma coccineum Cuvier, and 

 "Cyclocotyla" bellones Otto are indicated on more than three species and 

 genera of different orders. 



Ancyrocephalus alatus was described by Chauhan (Chauhan, 

 1945) from Muraenesox talabanoides Bleck. (Muraenesocidae, Anguilli- 

 formes), Arius falcarius Rich. (Ariidae, Cypriniformes), Mugil parsia 

 Bleck. (Mugilidae, Mugiliformes), and Harpodon neherius Ham. and 

 Buch. (Scopelidae, Scopeliformes). Chauhan writes that the first host 

 was the most infected, each of the specimens examined had individual 

 Anc. alatus on the gills. One can thus consider that Muraenesox 



242 



