107
Table 3. Presence (+) or absence (-) of the potential competitors and predators in the study ponds. Dm + Dp = Daphnia magna; Do +
Dp = Daphnia obtusa + Daphnia pulex Mb = Moina brachiata Ac = Aeschna cyanea (larvae) Ld = Libel/ula depressa (larvae) Sd =
Sympetrum danae (larvae) Ls = Lestes sponsa (larvae) As = Acilius sulcatus Dma = Dytiscus marginalis AB = Agabus bipustulatus
An = Agabus nebulosus; Gp = Guignotus pusillus; Hm = Hydroporus marginatus; Hp = Hydroporus palustris; T:o Triturus alpestris
(adults and larvae). Pond 12 and 13 contain no Branchipus schaefj"eri.
Competitors
Predators
Crustaceans
Dragonflies
Beetles
Amphibians
Pond no.
Dm
Do+Dp
Mb
Ac
Ld
Sd
Ls
As
Dma
Ab
An
Gp
Hm
Hp
T
5
+
+
+
+
+
+
+
+
12
+
+
+
+
+
+
+
+
+
+
+
+
13
+
+
+
+
+
+
+
+
+
+
+
+
+
+
15
+
+
+
+
+
+
+
+
+
+
+
+
16
+
+
+
+
+
+
+
+
20
+
+
+
+
+
+
+
+
27
+
+
+
+
+
+
+
+
35
+
+
+
+
+
+
+
+
Table 4. Prey density (total numbers) and consumption rate per predator during a 24 hour experiment.
Ni = initial prey density; Nf= final prey density; D:o Daphnia sp. Os = Ostracods: Tu = Tubifex sp.; B
= Branchipus schaefferi (size class 1-5 mm and >5 mm); Total = total no. of prey consumed.
Prey density
Predators
Ni(l-l)
Nf(l-l)
Chaoborus sp.
12.3
6.0
Aeschna cyanea
13.2
8.8
Lestes sponsa
12.8
8.1
Triturus alpestris (ad.)
12.8
6.7
Triturus alpestris (1)
12.8
6.5
dominant crustaceans Moina brachiata, and Daphnia
obtusa.
Methods
Presence and proportion of nauplii, juveniles, adult
males and adult females and thus duration and number
of the various generations of B. schaefferi in the ponds
was examined at least 3 times per week from February
until December 1984. Samples were collected with all
beaker (for the nauplii) which was rapidly dipped into
the water at several places spaced over the pond areas
and a 1 mm net (for juveniles and adult individuals)
which was pulled horizontally through the water. The
samples were combined and filtered through a 150 /Lm
No. of prey consumed
D
Os
Tu
Branchipus
Total
1-5mm 5mm
2.4
0
6.2
0
8.6
3.6
12.0
6.0
0
8.4
30.0
8.4
12.0
3.6
2.4
4.8
31.2
12.0
12.0
6.0
4.8
9.6
44.4
9.6
12.0
3.6
14.4
3.6
43.2
plankton gauze. The different instars were immediately
analyzed and, thereafter, placed back into the pond.
Total abundances of B. schaefferi in a permanent
pond (P 15) and a temporary pond (P 16) were studied
once per month. Horizontal net hauls were carried out
until no more animals were present in a pond. The captured juveniles, males, and females were counted separately and, thereafter, placed back into the pond.
Lengths of adults were measured 3 to 4 times from
June to November. 40 adults (20 males and 20 females)
were collected in each of the 8 ponds, preserved in 4%
formalin-sugar solution and in the laboratory measured
from the anterior end of the prosome to the tips of the
furcal rami.
To study the starvation resistance, 80 B. schaefferi
(40 individuals with a body length of 10 mm and 40
individuals with a body length of 20 mm) were placed
Table 3. Presence (+) or absence (-) of the potential competitors and predators in the study ponds. Dm + Dp = Daphnia magna; Do +
Dp = Daphnia obtusa + Daphnia pulex Mb = Moina brachiata Ac = Aeschna cyanea (larvae) Ld = Libel/ula depressa (larvae) Sd =
Sympetrum danae (larvae) Ls = Lestes sponsa (larvae) As = Acilius sulcatus Dma = Dytiscus marginalis AB = Agabus bipustulatus
An = Agabus nebulosus; Gp = Guignotus pusillus; Hm = Hydroporus marginatus; Hp = Hydroporus palustris; T:o Triturus alpestris
(adults and larvae). Pond 12 and 13 contain no Branchipus schaefj"eri.
Competitors
Predators
Crustaceans
Dragonflies
Beetles
Amphibians
Pond no.
Dm
Do+Dp
Mb
Ac
Ld
Sd
Ls
As
Dma
Ab
An
Gp
Hm
Hp
T
5
+
+
+
+
+
+
+
+
12
+
+
+
+
+
+
+
+
+
+
+
+
13
+
+
+
+
+
+
+
+
+
+
+
+
+
+
15
+
+
+
+
+
+
+
+
+
+
+
+
16
+
+
+
+
+
+
+
+
20
+
+
+
+
+
+
+
+
27
+
+
+
+
+
+
+
+
35
+
+
+
+
+
+
+
+
Table 4. Prey density (total numbers) and consumption rate per predator during a 24 hour experiment.
Ni = initial prey density; Nf= final prey density; D:o Daphnia sp. Os = Ostracods: Tu = Tubifex sp.; B
= Branchipus schaefferi (size class 1-5 mm and >5 mm); Total = total no. of prey consumed.
Prey density
Predators
Ni(l-l)
Nf(l-l)
Chaoborus sp.
12.3
6.0
Aeschna cyanea
13.2
8.8
Lestes sponsa
12.8
8.1
Triturus alpestris (ad.)
12.8
6.7
Triturus alpestris (1)
12.8
6.5
dominant crustaceans Moina brachiata, and Daphnia
obtusa.
Methods
Presence and proportion of nauplii, juveniles, adult
males and adult females and thus duration and number
of the various generations of B. schaefferi in the ponds
was examined at least 3 times per week from February
until December 1984. Samples were collected with all
beaker (for the nauplii) which was rapidly dipped into
the water at several places spaced over the pond areas
and a 1 mm net (for juveniles and adult individuals)
which was pulled horizontally through the water. The
samples were combined and filtered through a 150 /Lm
No. of prey consumed
D
Os
Tu
Branchipus
Total
1-5mm 5mm
2.4
0
6.2
0
8.6
3.6
12.0
6.0
0
8.4
30.0
8.4
12.0
3.6
2.4
4.8
31.2
12.0
12.0
6.0
4.8
9.6
44.4
9.6
12.0
3.6
14.4
3.6
43.2
plankton gauze. The different instars were immediately
analyzed and, thereafter, placed back into the pond.
Total abundances of B. schaefferi in a permanent
pond (P 15) and a temporary pond (P 16) were studied
once per month. Horizontal net hauls were carried out
until no more animals were present in a pond. The captured juveniles, males, and females were counted separately and, thereafter, placed back into the pond.
Lengths of adults were measured 3 to 4 times from
June to November. 40 adults (20 males and 20 females)
were collected in each of the 8 ponds, preserved in 4%
formalin-sugar solution and in the laboratory measured
from the anterior end of the prosome to the tips of the
furcal rami.
To study the starvation resistance, 80 B. schaefferi
(40 individuals with a body length of 10 mm and 40
individuals with a body length of 20 mm) were placed