36
T . B . REYNOLDSON
oligochaetes appeared to be the main diet of all species except Dugesia
which also fed extensively on gastropod molluscs; arthropods seemed
to be of lesser importance in all four species. The food range of young was
similar to that of adults and because communal feeding occurred on large
prey, the size-ranges of the food of young and adults also overlapped
(Young, 1963). When these results are compared with those from
laboratory experiments (Table VIII) based on summation of data where
single species were exposed, and data where several were exposed together (Reynoldson and Young, 1963)) the main conclusions based on
squashes are confirmed for P. tenuis and Dug. lugubris, but in the case of
P. nigra it was surprising how few oligochaetes were eaten. Dendrocoelum showed a very different result; in the laboratory it fed extensively on both arthropods and oligochaetes, in the field specimens only
the latter were detected. When both Asellus and the oligochaete Lumbriculus were exposed to this species the former were all eaten in 3 days,
the latter not until eight days had elapsed. The greater emphasis on
arthropods in the laboratory shown by all species, although only slight
for P. tenuis and Dug. lugubris, was undoubtedly due in part to the
difficulty of detecting triclads which had fed on this sort of prey in the
TABLE VIII
The Kinds a d Number of Organisms Eaten by Triclud.s in Laboratory
Experiments. (Reproduced with permission from Reynoldson and
Young, 1963.)
No. oaten by
I’olycelia
Diigesin Deridrocoelum
Prey
iaigra.
1’. teri rcis
lucpbris
lncteum
Oligochaeta
Lumbriculus variegatus
2/90
17/90
22/90
54/60
Arthropods,
Asellus meridianus
81150
11/150
20jl.50
100/100
Gammarus p u k x
0150
0150
0150
35/50
Cloeon dipterum
0160
0150
0150
47/50
Diura bicaudata
9/50
4/50
3/50
50150
Chironomus sp. larvae
6/50
6/50
3/50
45/50
Total Arthropoda
1 3
21
26
277
Mollusca
H?jdrobia jer ik ir 1 s i
0/50
1 /a0
15/60
0150
Tot a1 Molliiwa
0
2
B o
0
Lymiucea pereger
01150
1/150
1 Fi/15O
o/ 100
T . B . REYNOLDSON
oligochaetes appeared to be the main diet of all species except Dugesia
which also fed extensively on gastropod molluscs; arthropods seemed
to be of lesser importance in all four species. The food range of young was
similar to that of adults and because communal feeding occurred on large
prey, the size-ranges of the food of young and adults also overlapped
(Young, 1963). When these results are compared with those from
laboratory experiments (Table VIII) based on summation of data where
single species were exposed, and data where several were exposed together (Reynoldson and Young, 1963)) the main conclusions based on
squashes are confirmed for P. tenuis and Dug. lugubris, but in the case of
P. nigra it was surprising how few oligochaetes were eaten. Dendrocoelum showed a very different result; in the laboratory it fed extensively on both arthropods and oligochaetes, in the field specimens only
the latter were detected. When both Asellus and the oligochaete Lumbriculus were exposed to this species the former were all eaten in 3 days,
the latter not until eight days had elapsed. The greater emphasis on
arthropods in the laboratory shown by all species, although only slight
for P. tenuis and Dug. lugubris, was undoubtedly due in part to the
difficulty of detecting triclads which had fed on this sort of prey in the
TABLE VIII
The Kinds a d Number of Organisms Eaten by Triclud.s in Laboratory
Experiments. (Reproduced with permission from Reynoldson and
Young, 1963.)
No. oaten by
I’olycelia
Diigesin Deridrocoelum
Prey
iaigra.
1’. teri rcis
lucpbris
lncteum
Oligochaeta
Lumbriculus variegatus
2/90
17/90
22/90
54/60
Arthropods,
Asellus meridianus
81150
11/150
20jl.50
100/100
Gammarus p u k x
0150
0150
0150
35/50
Cloeon dipterum
0160
0150
0150
47/50
Diura bicaudata
9/50
4/50
3/50
50150
Chironomus sp. larvae
6/50
6/50
3/50
45/50
Total Arthropoda
1 3
21
26
277
Mollusca
H?jdrobia jer ik ir 1 s i
0/50
1 /a0
15/60
0150
Tot a1 Molliiwa
0
2
B o
0
Lymiucea pereger
01150
1/150
1 Fi/15O
o/ 100