A CASE OF DEFENSIVE SELF - MUTILATION IN 



CR YPTOBRANCH US. 



Bertram G. Smith. 



One of the worst enemies of aquatic vertebrates in captivity 

 is the water-mold, Saprolegnia. . Recovery from a severe infection 

 is so rare that this alone would attract attention ; but recovery by 

 means of the automatic amputation of infected members is a 

 phenomenon that I have never seen described, and have recently 

 observed for the first time. 



During the latter part of November, 1909, seven hellbenders 

 of various sizes were shipped from their native habitat in north- 

 western Pennsylvania to the Zoological Laboratory of the LTni- 

 versity of Wisconsin. Placed in an aquarium with shallow run- 

 ning water pumped from Lake Mendota, all but one were 

 promptly attacked with the "nitrogen disease" familiar to fish 

 culturists, and five of them quickly died. The remaining affected 

 specimen displayed remarkable powers of resistance to the disease 

 and, though swollen with bubbles almost past recognition, after 

 three months entirely recovered from this attack. 



This specimen, a young adult 35 cm. long, is the subject of 

 the present note. Perhaps because rendered vnunerable by the 

 bursting of the epidermis by nitrogen bubbles, it became infected 

 with Saprolegnia. The fungus completely covered the toes of the 

 hind legs, and the last two inches of the tail, but seemed to be 

 confined to these regions. 



A crack or fissure, accurately separating the infected from the 

 uninfected portions of the integument, soon appeared ; this 

 deepened until it reached the bone, after which the infected 

 extremities of ,the limbs and tail dangled for several weeks 

 connected with the animal only by the bone. The fissures 

 appeared as sharp and clean as if cut with a knife ; on one 



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