A COMPARATIVE-STUDY OF THE FISH PARASITES PROTEOCEPHALUS-EXIGUUS AND PROTEOCEPHALUS-PERCAE (CESTODA, PROTEOCEPHALIDAE) - MORPHOLOGY, ISOENZYMES, AND KARYOTYPE

The two closely related cestodes Proteocephalus exiguus (= P. neglectu s) and P. percae, parasites of coregonid and salmonid fishes and of pe rch, respectively, were compared using morphological, biochemical, and cytogenetic methods. Three morphological forms of similar appearance were observed in both P. exiguus and II percae. Although the two speci es were strikingly similar in general morphological appearance, some o f the features analyzed morphometrically (width of scolex, diameter of apical organ, length and width of hermaphroditic proglottis, length o f cirrus sac) exhibited consistent differences. Fixed genetic differen ces distinguish the species at five loci in EST, GOT, and PGM enzymes. Nei's interspecific genetic distance was 0.305. Both species have Is chromosomes with comparable absolute lengths. However, the morphology of most chromosome pairs differed. On the basis of these results, disc riminative characteristics for P. exiguus and P. percae are given.