AILMENTS AND DISEASES 



in breathing and the sloughing away of the skin. The following are the 

 recognized most common freshwater species likely to be encountered by 

 the aquariist. 



IcHTHYOPHTHiRius MULTiFiLiis. This infusotian, Figs. 105 and 106, 

 first forms round milky spots on the skin, fins, eyes and gills of freshwater 

 fishes. A microscope examination will reveal that each spot is caused by 



FIG. 105. Ichthyophth'irius multifilvs, an 

 Infusorian parasite. Greatly enUrged. 



1. Ciliated spore, 



2. Segmentation upon encystment. 



3. Adult infusorian. 



Head of a Catfish affected with Ichthyophthirius 

 multifiliit. 



the presence of a ciliated infusorian, the epidermis of the fish forming a 

 considerable protuberance over the parasite. Sometimes two or three 

 infusoria inhabit the same cyst, the form of the younger differing from 

 that of the grown individuals. The fishes soon appear completely ema- 

 ciated, the skin becomes thickened where the parasite is encysted, a scum 

 forms on the surface and deaths occur in ten days to two weeks. 



Pantotrichum i.AG'e.-^VLA. {U. lagenula.) This infusorian. Fig. 107, 

 is parasitic on the skin and in the gills of freshwater fishes and produces 



the "Spot-disease" or "Pox," by living in the 

 pulp cavity of the scales and absorbing their con- 

 tents, pigment cells, etc., producing colorless 

 patches on the skin. These spots first appear 

 as slimy excrescences, later assume a funguslike 

 appearance, and finally cause the death of the fish 

 by emaciation and destruction of the tissues. 

 The infusorian has an oval body with a sucking disc and swimming appen- 

 dage, and the cuticle is covered with very fine evenly-developed cilia. 



Trachelocercid^. Of these infusoria the most frequently occur- 

 ring freshwater species, is the ciliate Holotricha,i/.wjyj/flcctf,Fig. io8,a more 

 or less elongated or flask-shaped infusorian, entirely covered with cilia; 

 with delicate flexible cuticle and the anterior part of the body at times 



FIG. 107. Pantotrichum lagenuia, 



( Urotricha iagenuia,)nn Infusorian 



parasite. Greatly enlarged. 



Dorsal and lateral views. 



157 



