LAKE DWELLING TRICLADS
37
TABLE I X
Positive Reaction to Rabbit anti-Asellus Serum by Squashes of Field
Specimens of Triclads. (Reproduced with permission frowi Young
et al., 1964.)
Beaumaris
The Mere
Cole Mere
Newton Mere
Reservoir
No.
N O .
No.
No.
Species
tested %+ve tested %+ve tested %+vr
tested %+ve
Dendrocoelurn
lacteum
50
100
50
68.0
50
8.0
-
-
Eugubria
56
5-4
48
0
12
0
Dugesia
Polycelis
Polycelia
nigra
-
-
tenuis
52
9.6
48
8.3
48
8.3
-
-
-
-
-
.__
__
36
2.0
field by the squash method. These experiments confirmed that gastropods are not important in the diet of any species except Dugesia. The
results from the serological approach (Young et al., 1964) showed conclusively that Dend. lacteum fed much more on Asellus (Table IX) and
probably arthropods in general, than the planariid species. They support
the laboratory data and indicate that bias occurred in the results from
the squashes.
These various approaches to a study of the food of trirlads show that
there is considerable overlap in the type of prey eaten by the four species. However, the Polycelis species take a larger proportion of oligochaetes than of other prey, Dugesia alone feeds on gastropods, and
Dendrocoelum eats a greater proportion of arthropods, especially Asellus.
An outstanding feature of the laboratory approach is the contrast
between the planariid species and Dendrocoelum in the number of prey
eaten. The behaviour patterns of the former seem to be such that they
do not react very markedly to the presence of intact prey behaving
normally. Although these triclads had been starved prior to the experiment and fed readily afterwards on punctured animals, they largely
failed to recognize intact organisms a s potential food; a total of 1531840
only were eaten. I n contrast Dendrocoelum devoured 331/510 prey; if
gastropods are excluded this becomes 331/360. Further experiments
were made to study the behaviour of the triclads when damaged animals from which the body fluids had leaked were exposed to them, and
in the case of the planariid species, to organisms trapped in vaseline. In
37
TABLE I X
Positive Reaction to Rabbit anti-Asellus Serum by Squashes of Field
Specimens of Triclads. (Reproduced with permission frowi Young
et al., 1964.)
Beaumaris
The Mere
Cole Mere
Newton Mere
Reservoir
No.
N O .
No.
No.
Species
tested %+ve tested %+ve tested %+vr
tested %+ve
Dendrocoelurn
lacteum
50
100
50
68.0
50
8.0
-
-
Eugubria
56
5-4
48
0
12
0
Dugesia
Polycelis
Polycelia
nigra
-
-
tenuis
52
9.6
48
8.3
48
8.3
-
-
-
-
-
.__
__
36
2.0
field by the squash method. These experiments confirmed that gastropods are not important in the diet of any species except Dugesia. The
results from the serological approach (Young et al., 1964) showed conclusively that Dend. lacteum fed much more on Asellus (Table IX) and
probably arthropods in general, than the planariid species. They support
the laboratory data and indicate that bias occurred in the results from
the squashes.
These various approaches to a study of the food of trirlads show that
there is considerable overlap in the type of prey eaten by the four species. However, the Polycelis species take a larger proportion of oligochaetes than of other prey, Dugesia alone feeds on gastropods, and
Dendrocoelum eats a greater proportion of arthropods, especially Asellus.
An outstanding feature of the laboratory approach is the contrast
between the planariid species and Dendrocoelum in the number of prey
eaten. The behaviour patterns of the former seem to be such that they
do not react very markedly to the presence of intact prey behaving
normally. Although these triclads had been starved prior to the experiment and fed readily afterwards on punctured animals, they largely
failed to recognize intact organisms a s potential food; a total of 1531840
only were eaten. I n contrast Dendrocoelum devoured 331/510 prey; if
gastropods are excluded this becomes 331/360. Further experiments
were made to study the behaviour of the triclads when damaged animals from which the body fluids had leaked were exposed to them, and
in the case of the planariid species, to organisms trapped in vaseline. In