Referenţi ştiinţifici - Muzeul Judeţean Satu Mare

Satu Mare – Studii şi Comunicări Ştiinţele Naturale -– Vol. VI (2005)
Table 2. The number of prey items, the average and the maxim number of preys / sample, the
weight of aquatic and terrestrial preys
No. of preys Average no.
of preys /
sample
Maxim no. of
preys /
sample
108
% of
terrestrial
preys
% of aquatic
preys
698 53.69 224 20.91 79.08
To estimate the intensity of feeding we calculated
the average and the maximum preys / samples
(Tab. 2). The high value in the average and
maximum number of preys / sample appears
because of the presence of small–sized taxon
preys with a gregarious life style such as
Cladocera and Diptera larva in certain stomach
contents. The value of the average number of
preys / sample at Triturus dobrogicus are higher that
those noted at the Triturus cristatus species
(Covaciu-Marcov et al. 2002a; Tab. 4) and at the
Triturus vulgaris species (Cicort-Lucaciu et al. in
verbis).
During our study we watched the differences of
the weight and the frequency of consumption of
the taxon preys by the studied population of
newts. Thus, from the number of preys that
belong to diverse taxons we determined their
percentage (weight) in the trophic spectrum of the
Triturus dobrogicus (Tab. 3).
Crustacea Cladocera represent the taxon prey
consumed in the highest amount by the Danube
Crested Newt. They are a small–sized taxon prey
with gregarious life style and thus a single Triturus
dobrogicus individual can consume them in great
number. The newts are trying to capture as many
as possible of them in order to supply their
bodies with the necessary energy. In addition to,
Dolmen & Kokvsik (1983) found that the major
preference of Triturus vulgaris and Triturus cristatus
was also Cladocera. Similar situations when
certain small–sized taxon preys with gregarious
life style are predominant in the stomach contents
were noticed in case of other species of newts like
Triturus cristatus (Covaciu-Marcov et al. 2001,
2002a), Triturus vulgaris (Cicort-Lucaciu et al. 2004b)
(Tab. 4), Triturus vittatus ophryticus (Kutrup & Çakir
2005). On the second position are the Coleoptera
larva. The group of Coleopterans is one of the most
important prey for amphibians due to their high
trophic value. The samples studied by us had
consumed only aquatic larva of bugs. Diptera larva
represent another taxon prey consumed in a high
amount by the newts. There are other amphibian
populations where Nematocera larvae occupy a very
important place in the trophic spectrum such as,
Triturus cristatus (Covaciu-Marcov et al. 2002a; Tab.
4), Bombina bombina (Sas et al. 2003).
Table 3. The weight and the frequency of prey taxa in the stomach contents
Beside the amount of preys, an important
parameter for the study of the trophic spectrum is
the frequency of their consumption (Tab. 3). The
frequency can be defined as the ratio between the
number of stomachs that contain a certain taxon
prey and the total of analyzed stomachs, the
obtained value being expressed in percentages.
The amount of a prey does not always correspond
with the frequency of its consumption. Thus
while the samples consume in the highest number
Cladocera (46.41), their frequency is smaller
(30.76) than those of Isopoda (100) or Coleoptera
Amount Frequency
Nematoda 0.42 7.69
Hirudinea 0.28 7.69
Crustacea Cladocera 46.41 30.76
Crustacea Ostracoda 8.88 23.07
Crustacea Izopoda 7.3 100
Crustacea Amfipoda 0.14 7.69
Miriapoda hilopoda 0.42 7.69
Coleoptera larva 20.48 92.3
Diptera larva 15.61 69.23
larva (92.3) and Diptera larva (69.23). Despite of
the low amount of Isopoda they represent an
important prey type for Triturus dobrogicus, because
they are accessible to all samples. Also, they are
much more important preys quantitatively
speaking. The lower importance of Crustacea
Cladocera can be explained by the fact that they
form congestion in certain parts of an aquatic
pond thus being accessible for only a few
samples. In context, for the population are much
more important those taxon preys which are
spread homogenous in the pond.