iqi3.] T. vSouthwfi.l: Parasites from Fish 8i 



ON SOME TREMATODE AND CESTODE PARASITES 

 FROM FISH. 



The only work done as yet on the parasites of Indian fish 

 consist of the reports of : — 



I. Shipley and Hornell who worked out the collection of 

 Cestodes made by Prof. Herdman in Ceylon. 



II. The present writer who continued and extended that 

 work and described his own collections in the Ceylon Marine 

 Biological Reports, [ly). 



III. Max Liihe who described the Trematodes collected by 



Prof. Herdman. (5). ■ - >r^u 



These reports all deal with parasites from marine fish. The 



present paper is the first one dealing with parasites mostly from 

 freshwater fish, either in India, Burma or Ceylon. 



Cestoda. 



The two species of Cestode parasites to be described, viz. 



Ophryocotyle bengahnsis, n. sp., and Bothriocephaliis (Anchistrocep- 



halus) polyptera (Leyd) constitute the first record of any adult 



Cestode found in any Teleostean fish in Indian waters. Southwell 



in his examination of marine Teleosts in Ceylon over a period 



of five vears never obtained a single adult Cestode parasite, although 



encvsted larval forms were extremely common. The above two 



species were obtained from (a) Ophiocephahis striatus (Bengah, 



Sol) and (6) Lahco rohita (Bengali, Rohu). Both species of parasites 



occurred in each species of fish. Those from Labeo rohita were few 



in number. Those from Ophiocephaliis striatus occurred in such 



large numbers, along with some undescribed Trematodes, that 



the lumen of the intestine of this fish in one particular case 



appeared entirely choked. Specimens of Ophryocotyle bengalensis, 



n. sp. were numerous. Only two specimens of Bothriocephaliis 



{Anchistrocephaliis) polyptera (Leyd.) were obtained. It has been 



noted that cystic forms of Cestoda in general are exceedmgly 



common amongst marine Teleosts. On the other hand such cysts 



are quite rare in freshwater forms. Up to the present I have 



been unable to discover any except the larva of Ligula simplicissima, 



which will be referred to later, and this was not encysted, but free 



in the coelom. Contrary to what occurs in marine fish, adult 



Cestodes are fairly common in freshwater Teleosts in Bengal, and 



our examples were obtained from the first fish of the precedmg 



species which we examined. This diflterence finds an explanation 



in the widely different conditions existing normally in the sea, 



and in fresh water. In the sea, adult Cestodes are always found 



in fish of the shark and ray tribe, which, on the whole, are not 



subject to the ravages of other predatory fish. In such an host 



the adult tapeworms find a safe and secure retreat, from which 



abode an unending stream of eggs are liberated. 



