AILMENTS AND DISEASES 



FIG. 90. 



Cucullartus eleganSy 

 a Nematod parasite. 

 Length of female 1 5 

 mm., male 8 mm. 



fishes. These are Cucullanus foveolatus of the sunfish, and C. elegans of 

 the perch and the Cyprinidae, Fig. 90. 



FiLARiD/E. These parasites are more common to 

 the marine fauna. Filaria ■piscius is found spirally coiled 

 within the tissues of the herring, cod and whiting. A 

 number of other species of this family occur in similar hosts 

 and in warm-blooded animals. 



GoRDiiD^. These parasites take up a free existence 

 in damp earth and penetrate the bodies of insects and their 

 larvae. Some gain access to fishes by this means, where 

 they become encysted in the tissues. 



Anguillulid^. These minute free intestinal thread- 

 worms usually have the higher Vertebrates as hosts, but some species are 

 parasitic in aquatic molluscs and in insect larvae. They are very widely 

 distributed; the so-called Vinegar-eel, Anguillus aceti, belongs to this order. 

 All the other families of this group are parasites of higher Vertebrates. 



AcANTHOCEPHALA OR Thorn-headed Worms. This group con- 

 sists of members having vermiform bodies and otherwise resemble the 

 Nematoda, but differ in having spine-covered heads by which they attach 

 themselves to their hosts. They are now included in the single family 

 Echinorhynchidae, which infests all classes of Vertebrates and are one of the 

 more frequent parasites of fishes and amphibia. Over 100 species have 

 been described, a considerable number in the Cyprinidae; and of these 

 Echinorhynchus proteus is the most abundant species, of which the 

 immature form inhabits the smaller crustaceans, especially Gammarus 

 and Asellus, to be transferred with them to freshwater fishes. Other 



FIG. 91. 



Echinorhynchus pro- 

 teut, an Acanthoce- 



phalous parasite. 



Intermediate and 

 Adult forms. 



Greatly enlarged. 



FIG. 92. 



Echinorhynchus 



angustatus, an 



Acanthocephalous 



parasite. Length 



22 to 25 mm. 



Enlarged. 



Fig. 93. 



Echinorhynchus 



anthurisj an Antho- 



cephalous parasite. 



Greatly enlarged. 



common forms are E. angustatus, E. clavaceps, E. anthuris, E. globulosus, 

 and E. tuberosus in the Salmonidse and similar fishes. Some of these and 

 E. clavula, E. fusiformis and E. pachysoma frequently occur in other fresh- 

 water fishes, principally the Cyprinidae. E. anthuris also occurs in the Water 

 newt, and E. inflexus in the Snapping turtle. The Echinorhynchidae cause 



150 



