161 
VII, 
NOTE ON A TREMATODE FROM RAINBOW TROUT. 
By W. Rushton, A.R.C.Sc., D.I.C., B.Sc., F.L.S. 
{Bead April 19, 1922.) 
Two Text-Figuees. 
During the month of July 1921 a report was received from Jersey 
that an unusual number of rainbow trout, weighing up to a pound 
in weight, were being found dead on the surface of one of the 
waterworks reservoirs, and an investigation of some of these dead 
trout, and careful inspection on the spot, led to the discovery that 
the gills of most of the dead trout were infected with a trematode 
worm and the detection in the gut of two species of Acantho- 
cephalus worms. 
During January 1922 the reservoir was run dry and all the 
fish netted out, and in many cases where the fish had the appear- 
ance of being abnormal it was found that the gills showed the 
presence of a large number of these trematodes, from 200-300 
being taken from one fish. The trematode, or fluke, has not, so far 
as I am aware, been reported from this area or in England, but 
occasional epidemics in hatcheries have been reported from America. 
The trematode belongs to the genus “ Octocotylidse ” (Van 
Benenden and Hesse, 1863), and was identified as Discotyle 
sagittatum Liihe, the old name being Octobothrium sagittatum. The 
characters given for identification are : — 
“Elongate; flattened ectoparasitic trematodes. The posterior 
organ of attachment has, usually in two parallel rows, eight, more 
rarely four or six, small suckers braced with a characteristic 
chitinous framework or armed with hooks. Extra hooks often 
occur on the disc. Genital pore armed with hooks. Eggs supplied 
with one or two long filaments. Occurring on gills of marine and 
fresh-water fishes. These parasites are very rare in fresh water. 
American and European representatives are not well known.” 
The trematode under examination agrees in all essentials with 
the above description. 
The peculiarity about this trematode is its appearance in an 
inland reservoir with no outlet to the sea up which migratory fish 
might find their way, and further the detrimental effect on the fish 
on which it got a hold. The only way it could have reached the 
reservoir was by sea birds carrying the eggs on their feet or by the 
contents of the gut, or by some mollusca acting as a carrier and 
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