38o 



FRESH-WATER BIOLOGY 



^2 (i^) Adhesive organ oval, composed of four rows of alveoli. 



Aspidogaster von Baer 1826. 



Ventral sucking disc large, cc^ual in breadth and nearly so in length 

 to entire body; oval in outline with four convergent longitudinal 

 rows of quadrangular sucking grooves. Margin notched, with sense 

 organs. Mouth terminal; intestine extending into posterior end. 

 Sexual pore median; in depression between ventral shield and fore- 

 body. Ovary small; testis single, same size as ovary. Uterus 

 moderately long; ova large. In fishes and mollusks. 



Representative American species. 



Aspidogaster comhicola von Baer 1826. 



The common North American species in fresh water, Aspidogaster 

 conchicola v. Baer, is also the most common parasite of the Union- 

 idae. From pericardial and renal cavities of various species of the 

 group; St. Lawrence River; Havana, Illinois; North Judson, In- 

 diana; Iowa; Pennsylvania. Kelly reported thirty-seven cut of 

 forty-four species of Unionidae and 41 percent of the 1577 individuals 

 examined were parasitized by this species. Occasionally found in 

 the intestine of various fishes into which it has been introduced 

 when its proper host, the mussel, was taken as food. 



Fig. 66r. Aspidogaster conchicola. Anterior end of ventral sucker as seen 

 from below combined with genital system, partly diagrammatic. Uterus 

 and yolk folUcles left out. Est. X 35. (After Stafford.) 



^^ (32) Adhesive disc oval, composed of three rows of alveoli 34 



34 (35) Mouth subterminal, not surrounded by buccal disc. 



Cotylaspis Leidy 1857. 



Ventral shield much as in Aspidogaster, save that the alveoU 

 are in three longitudinal rows, the central alveoli being elongated 

 transversely. Marginal sense organs present, also two eyes. 

 Ovary dextral, smaller than single testis m posterior end. Ova 

 not numerous, large. 



Of several species known, Cotylaspis insignis Leidy 1837, is 

 most frequent. It is adherent to surface of host in angle between 

 inner gill and visceral mass (Kelly) ; or branchial cavity (Leidy) 

 of many species of Unionidae: Havana, 111.; Grand Rapids, 

 Mich.; Lake Chatauqua, N. Y.; Cedar River, la.; Schuylkill 

 River, Penn. Kelly examined over 1600 individuals of 44 species 

 which belong in 24 separate host species and found 18 per cent 

 infected. The number in a single host is small. 



Representative American species. 



Cotylaspis cokeri Barker and Parsons 1914. 



C. cokeri Barker and 

 Malacoctemmys lesueurii. 



Parsons occurs in the intestine of 



Fig. 66a. Cotylaspis cokeri X30. a. Ventral view of sucking disk Xis- 



