VOLUM OMAGIAL - Facultatea de Ştiinţe ale Naturii şi Ştiinţe Agricole

Aspects regarding the biodiversity... / Ovidius University Annals, Biology-Ecology Series 14: 171-175 (2010)
The banks of the river are covered with willows
(Salix alba, S. triandra, S. fragilis), which make the
banks more stable and also give shadow to the water.
SO4: Netuş
The Netuş Lake is situated in the Hârtibaciu
Plateau having the coordinates as follows: 46 0 03’
55’’ N, 24 0 47’ 55’’ E, at an altitude of 484m.
The lake was arranged by people, its purpose
being to reduce the flood. It also has a fish breeding
interest, being placed in the major riverbed of the
Hârtibaciu River. The vegetation is undeveloped.
2. Material and Methods
The biologic material was gathered during
September-October 2001, September 2002, August
and September 2004, From three stations there were
gathered two samples: in September and October
2001 from SO!, in September 2002 and August 2004
from SO2, in September and October 2001 from
SO3. From the station SO4 there was done only one
gathering (October 2004). For the identification of
the species we used the determination key of the
following authors: [1], [2], and [3].
There was calculated the relative abundance of
each and every species from the researched habitats,
diversity indexes ά - Margalef (for general aspects,
such as the number of species and the number of
individuals) and Lloyd-Ghelardi (for the evaluation of
heterogeneity) – and the indicator of percentage
similitude Renkonen, in accordance with [4].
3. Results and Discussions
As a result of the gatherings done during the
periods mentioned before we identified a number of
20 species, from which 13 species are aquatic
heteroptera (Heteroptera: Nepomorpha) and 7 species
are semi aquatic heteroptera (Heteroptera:
Gerromorpha), belonging to 9 families, presented in a
number of 724 samples (table 1).
The Corixidae family is the best represented
taking into account the number of species (8 species),
but considering the number of the gathered
individuals the Naucoridae family is on the first place
(202 samples). At Mateiaş (SO1) we identified 17
species representing 50% from the total number of
species that were gathered in the middle basin of the
172
river Olt (Ilie, 2009). Here is the only station where
appeared the species Ilyocoris cimicoides, its
presence being linked to the under water vegetation.
Other species of aquatic heteroptera (Sigara striata,
Sigara iactans, Notonecta glauca, Plea minutissima)
are also well represented from the same reason. On
the other side, the vegetation above the water is
favorable for the semi aquatic species (Microvelia
reticulata, Mesovelia furcata and Mesovelia
vittigera).
The community of the aquatic and semi aquatic
heteroptera from Mateiaş is defined by high values of
the relative abundance of the species Ilyocoris
cimicoides (A=30.31%), Microvelia reticulata
(A=20.85%), Gerris argentatus (A=16.62%) and
Sigara striata (A=12.54%) and values less than 10%
for the other species. There is to be noticed an
equilibrate structure of the heteroptera community as
two species of aquatic heteroptera and respectively
two species of semi aquatic heteroptera represents
about 40% from the total of the community. On
assembly the aquatic heteroptera represent 60% and
the semi aquatic heteroptera about 40% from the
heteroptera community in the lake in Mateiaş (in the
terms of relative abundance). The species Notonecta
glauca is represented by an average number of
individuals, the dimensions of the population being
determined by the big size and the predator behavior,
which is extremely active.
At the Bâlea Lake (SO2) we identified only two
species of heteroptera although there was done the
some number of gatherings, the habitat being of the
same kind (natural lake) and the relief unit the same,
namely mountain. This fact is a result of the great
differences of altitude, which implies climate
differences (especially the temperature, on which
depends the existence and the development of the
insects) as well as the vegetation (this being mainly a
shelter against the predators). There was also noticed
the fact that the species that were present in the Bâlea
Lake are to be found in the Mateiaş Lake, too.
At Cincşor (SO3) there were identified 10
species of aquatic and semi aquatic heteroptera. The
most of the species belong to Corixidae family (4
species). The other families are represented by one or
maximum two species.
In the aquatic and semi aquatic heteroptera
community of the Cincşor Lake, Micronecta scholtzi