AILMENTS AND DISEASES 



epidemics in fishes and in immature and adult forms have been found in 

 such numbers in the gills of young goldfishes as to cause the death of en- 

 tire hatchings. These worms grow to such size that they force the 

 operculae from the sides of the head and produce death from exhaustion 

 and inability of the fishes to breathe. No preventive means or parasiticides 

 have been devised to eradicate these destructive parasites, most of the 

 species of which do not exceed i cm. in length, and many of them are 

 much smaller. 



HiRUDiNiD^ OR Leeches. These parasites are divided into two 

 groups, the Rhynchobdellidte which pierce the tissues of their hosts by 

 means of a fine protrusile stomodaeum or proboscis, and the Gnathobdellida 



which bite their prey by means of 

 triangular horny jaws. They are carniv- 

 orous oblong . and generally depressed 

 contractile worms, having the mouth 

 encircled with a lip and a flat disc at 

 the posterior end, both adopted to ad- 

 here to other bodies and to serve as 

 organs of locomotion. Leeches abound 

 in both fresh and salt water and in 

 tropical countries some forms live on 



Fishes, 

 frogs and turtles are most frequently 

 attacked, but they also attach themselves to other animals which come to 

 the water to drink. The larger blood-sucking forms are Hirudo and 

 Macrobdella; and the true parasitic forms belong to Ichthyobdella, 

 Cystobranchus and Clepsine which feed principally on fishes, 

 and Nephilis and Aulastomus on snails and worms. The 

 North American leeches which prey on freshwater fishes 

 and amphibia are the species Piscicola funduli, known as the 

 Carp-leech, Figs. 94 and 95, P. punclata, Actinobdella 

 inequiannulata, Philobdella gracile, Clepsine elegans, and C. par- 

 asitica. Young leeches infest the gills of fishes, especially 

 the fry, literally packing them solid, and gorge themselves 

 with the blood, causing the death of their hosts. These 

 epidemics sometimes occur with broods of goldfishes. The only remedy 

 is to clean the tanks and destroy the aquatic plants. Cures of leech 

 infested fishes have been made by the brackish water treatment and by 

 injecting salt water into the gills. 



A very minute leech-like polyp Trichodina pediculus. Fig. 96, is 

 usually parasitic on freshwater polyps but frequently changes to fishes as 



^Bi*' 



u . u u Pf'f''fi'"'"'J' "^f Carp-leech at- ^^g j^nd secretcd among leaves. 



tacned to the head of a young Small-mouthed Black ^ 



Slighty enlarged. 



FIG. 94. 



FIG. 95. 



Pi scioia funduli 

 Enlarged 4 diameters 



151 



