ACTA BIOLOGICA SLOVENICA 
LJUBLJANA 2004 Vol. 47, Št. 2: 83-94 
Sprejeto (accepted): 2004-09-17 
Respiration rate and respiratory electron transport system 
(ETS) activity of chironomid larvae from mountain lakes 
(NW Slovenia) 
Stopnja dihanja in aktivnost dihalnega elektronskega 
transportnega sistema (ETS) pri ličinkah trzač iz gorskih jezer 
(SZ Slovenija) 
Tatjana SIMČIČ 
National Institute ofBiology, Večna pot lll, Sl-1000 Ljubljana, Slovenia; 
tel: +386(0)14233388, e-mail: tatjana.simcic@nib.si 
Abstract. Respiration rate (R) and electron transport system (ETS) activity 
were measured in larvae offour chironomid species, Chironomus thummi (Kieffer), 
Paratanytarsus austriacus (Kieffer), Procladius (Holotanypus) spp., and 
Zavrelimyia barbatipes (Kieffer) from three mountain lakes. ETS activity and res-
piration rate, measured at a standard temperature of 20 °C, differed significantly 
between species (ANOVA: p<0.001). ETS activity ranged from 10.3 µL 0 2 mg- 1 
DW h- 1 for Zavrelimyia to 27.6 µL 0 2 mg-1DW h-1 for Paratanytarsus. The lowest 
respiration rate was observed for Procladius (4.0 µL 0 2 mg- 1DW h- 1) and the high-
est for Paratanytarsus (12.4 µLO2 mg-1 DW h- 1). ETS activity and respiration rate 
of chironomids decreased with increasing size of the animals (p<0.001); b values 
for ETS activity and respiration rate were 0.82 and 0.66, respectively. Respiration 
rate correlated significantly with ETS activity for ali four species investigated. This 
study revealed that the ETS/R ratio differed between species (ANOVA: p<0.001). 
A low ratio (0.98) was determined for Zavrelimyia, while Procladius showed the 
highest value (3 .88). The differences can be explained by body size, and the eco-
logical preference and tolerance of each chironomid species. 
Key words: Chironomidae, Diptera, benthos, ETS/R ratio, ETS activity, respi-
ration, metabolism 
Izvleček. Stopnjo dihanja in aktivnost elektronskega transportnega sistema 
(ETS) smo določali pri ličinkah štirih različnih vrst trzač , Chironomus thummi 
(Kieffer), Paratanytarsus austriacus (Kieffer), Procladius (Holotanypus) spp., in 
Zavrelimyia barbatipes (Kieffer), ki smo jih nalovili v treh gorskih jezerih. Aktivnost 
ETS in stopnja dihanja, ki smo ju merili pri standardni temperaturi 20 °C, sta se 
značilno razlikovali med vrstami (ANOVA: p<0.001). Aktivnost ETS se je gibala 
84 Acta Biologica Slovenica, 47 (2), 2004 
med 10.3 µL 0 2 mg·1DW h·1 pri ličinkah Zavrelimyia in 27.6 µL 0 2 mg-t DW h·1 pri ličinkah 
Paratanytarsus. Najnižjo stopnjo dihanja smo določili pri ličinkah Procladius (4.0 µL 0 2 mg-1DW h·1), 
najvišjo pa pri ličinkah Paratanytarsus (12.4 µL 0 2 mg· 1DW h· 1). Aktivnost ETS in stopnja dihanja 
ličink sta se zmanjševali z naraščajočo velikostjo živali (p<0.001); vrednosti b sta znašali 0.82 za 
aktivnost ETS in 0.66 za dihanje. Opazili smo pozitivno korelacijo med stopnjo dihanja in aktivnos-
tjo ETS pri vseh štirih vrstah. Raziskava je pokazala značilne razlike v razmerju ETS/R med vrsta-
mi (ANOVA: p<0.001). Nizko razmerje (0.98) je bilo določeno pri ličinkah Zavrelimyia, medtem ko 
je bilo pri ličinkah Procladius določeno najvišje razmerje (3.88). Različna razmerja so posledica raz-
lik v vrstno-specifični telesni velikosti ter različne ekološke preference in tolerance pri posamezni 
vrsti trzač. 
Ključne besede: Chironomidae, Diptera, bentos, razmerje ETS/R, aktivnost ETS, dihanje, 
metabolizem 
Introduction 
The family Chironomidae is widely distributed in ali types of aquatic environments, where they 
form the major part of nearly all freshwater communities, and they occupy a variety of niches. The 
relatively short life cycle and large total biomass of the numerous larvae confer ecological energetic 
significance on this taxon, as both consumers and prey, and the partitioning of ecological resources 
by a large number of species presumably enhances the biologic stability of aquatic ecosystems 
(MERRITI & CUMMINS 1984). 
As chironomid larvae play an important role in aquatic food webs, an estimation of their respi-
ratory energy loss is essential in order to estimate the energy flow through the ecosystems. Direct 
determination of respiration usually involves incubating animals in a controlled environment, and 
determining the time-dependent change in oxygen concentration. These methods are tirne consum-
ing and impractical. The development of enzymatic techniques, however, has allowed metabolic 
activity to be estimated from the electron transport system activity (OWENS & KING 1975, PACKARD 
1985). The electron transport system (ETS)-assay, based on the reduction of tetrazolium salt (INT) 
in the presence of a cell-free homogenate of the organisms and excess substrates of the ETS, has 
proved to be useful for estimating the metabolic activity of different organisms (PACKARD 1985, DEL 
GIORGIO 1992, G.-T6TH & AL. 1995). It is simple, rapid and extremely sensitive and has been used 
extensively with marine plankton (KENNER & AHMED 1975, BAMSTEDT 1980, VOSJAN & OLANCZUK-
NEYMAN 1991) and freshwater plankton (BORGMANN 1978, JAMES 1987, DEL GIORGIO 1992), benth-
ic organisms (CAMMEN & al. 1990, MusK6 & al. 1995, 1998), marine sediments (VOSJAN & 
OLANCZUK-NEYMAN 1977, RELEXANS 1996), and freshwater sediments (TREVORS 1984, G.-T6TH & 
AL. 1994). The slow response ofETS activity to short-term variations in environmental factors makes 
the method superior to direct respiratory measurements on incubated animals (BAMSTEDT 1980). It 
is, however, necessary to determine empirically the relation between the highest potential metabolic 
activity and realised oxygen consumption in order to interpret the ETS <lata properly (DEL GIORGIO 
1992). Much has been published on the respiration of chironomids (ERMAN & HELM 1970, 
KONSTANTINOV 1971, BAIRLEIN 1989, HAMBURGER & DALL 1990, HAMBURGER & AL. 1994), but there 
is no study conceming their ETS activity. 
Previous investigations have shown that the chironornid larvae are the dominant group of the 
macrozoobent_hos in mountain lakes in NW Slovenia (SIMČIČ unpubl. data). These lakes are shallow 
T. Simčič: Respiration rate and respiratory electron transport system ... 85 
and, except the eutrophic lakes Krnsko jezero and Jezero na Planini pri Jezeru, transparent to the bot-
tom. Zoobenthos are reported to have a greater effect on energy flux through secondary production 
in shallow lakes than in deeper ones (J6NASSON & al. 1990, LINDEGAARD 1994). Therefore, chirono-
mids should be taken into account when energy flow through the food webs in these lakes is inves-
tigated. 
The purpose of this paper was to determine ETS activity and respiration rate of four different chi-
ronomid species from mountain lakes, and to calculate the ETS/R ratios of these species in order to 
contribute to the estimation of energy flux through secondary production of benthic organisms. 
Materials and methods 
Sampling of animals: ETS activity and respiration rate were measured in the laboratory for 
Paratanytarsus austriacus (Kieffer) and Procladius (Holotanypus) spp. from the oligotrophic lake 
Zgornje Kriško jezero, Zavrelimyia barbatipes (Kieffer) from the oligotrophic lake Srednje Kriško 
jezero, and Chironomus thummi (Kieffer) from the eutrophic lake Krnsko jezero. Zoobenthos sam-
ples were taken using van Veen grab (Eijkelkamp). It was important to handle the larvae as little as 
possible during identification. Single animals were used for each analysis. Different sets of animals 
were taken to be investigated separately in the respirometric measurements and separately in ETS 
activity measurements in the first part of experjments. To determine relationship between ETS activ-
ity and respiration rate, the individual animal was exarnined firstly by microrespirometer and then by 
ETS-assay. Before experiments animals were rinsed with filtered water to remove bacteria adhering 
to the body surface, and weighed on an electrobalance. The dry mass of animals was calculated using 
factors determined by drying five samples of animals for 24 h at 60°C. 
Respiration measurements: Respiration rate was estimated using a twin-flow microrespirome-
ter (CYCLOBIOS, Innsbruck, Austria) (GNAIGER 1983). In the open-flow system the concentration 
of oxygen was measured before and after the chamber containing the animal. Oxygen consumption 
was calculated from the reduction of oxygen concentration and the flow rate of the water with a com-
puter program Dat.Graf 2.1 Analysis. 
ETS activity measurements: ETS activity was measured using the method proposed by 
PACKARD (1971), modified by OwENS & KING (1975) and improved by G.-T6TH (1999). Each fresh-
ly weighed animal was homogenized in 4 ml of cold homogenization buffer (0.1 M sodium phos-
phate buffer pH = 8.4, 75 µM MgSO4, 0.15% (w/v) polyvinyl pyrrolidone, 0.2% (v/v) Triton-X-100) 
for 2 min. The homogenate was then sonicated using an ultrasound homogenizer (Cole-Parmer) for 
20 sec and centrifuged in refrigerated centrifuge (Sigma) for 4 min at O °C at 8500 x g. Three 0.5 ml 
samples from each homogenate were incubated in 1.5 ml substrate solution (0.1 M sodium phosphate 
buffer pH = 8.4, 1.7 mM NADH, 0.25 mM NADPH, 0.2% (v/v) Triton-X-100) with 0.5 ml of 2.5 
mM 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride (INT) solution for 40 min at 
a standard temperature of 20 °C. The reaction was stopped by adding 0.5 ml of stopping solution 
(formalin(conc.):H3POiconc.)=1: 1). Formazan production was determined spectrophotometrically 
from the absorbance of the sample at 490 nm against the blank (1.5 ml substrate solution and 0.5 ml 
INT solution were incubated as for the sam ples, and 0.5 ml of homogenate was added after the stop-
ping). ETS activity was measured as the rate of tetrazolium dye reduction and converted to equiva-
lent oxygen utilised per dry mass (DW) in a given tirne interval as described by KENNER & AHMED 
(1975). 
86 Acta Biologica Slovenka, 47 (2), 2004 
Analysis of data: ETS/R ratios were calculated as the ratio of the calculated maximum oxygen 
consumption (ETS), as measured by in vitro enzymatic rates, to the rate of respiration (R) in vivo 
(OWENS & KING 1975). An analysis of variance (ANOVA) was carried out to test for differences 
between species. Linear regression between dry mass (DW) and the parameters investigated (ETS 
activity, respiration rate, ETS/R ratio), and between ETS activity and respiration rate were calculat-
ed after logarithmic transformation of data, according the power function Y = a Xb (log Y = log a + 
b log X) (DEL GIORGIO 1992). The statistical tests were performed using Microsoft Excel. 
Results 
ETS activity 
ETS activity was found to differ significantly between species (Tab. 1). The highest value (27.6 
µL 0 2 mg· 1 h-1) was measured in Paratanytarsus (Fig. la). Significantly lower values were observed 
in Procladius (18.5 µL 02 mg-1 h· 1), followed by Chironomus (14.0 µL 0 2mg-l h- 1) and Zavrelimyia 
(10.3 µL 0 2 mg· 1 h-1). 
The relationship between ETS activity and body mass is shown in Fig. 2a. The mass-specific 
ETS activity of chironomids decreased with increasing size of the animals (log ETS = 1.06 - 0.18 
log DW; r=-0.53 ; n=68; p<0.001). The b value was 0.82. The body mass of the animals used in the 
experiments differed significantly between species (Tab. 1). The mean values (± SD) were 0.07 ± 
0.04 mg DW for Paratanytarsus, 0.08 ± 0.03 mg DW for Zavrelimyia, 0.35 ± 0.27 mg DW for 
Procladius and 1.06 ± 0.94 mg DW for Chironomus. 
Table 1: Results of analysis of variance applied to ETS activity, respiration rate (R), ETS/R ratio and body 
mass (DW) in chironomids with species as factor; d.f. - degree of freedom. 
Tabela 1: Rezultati analize variance za aktivnost ETS, stopnjo dihanja (R), razmerje ETS/R in telesno maso 
(DW) pri ličinkah trzač z vrsto kot faktorjem; d.f.-stopinje prostosti 
d.f. 
between group 
ETS 3 
R 3 
ETS/R 3 
DW 3 
d.f. 
within group 
64 
39 
38 
75 
F-value 
14.29 
7.94 
15.34 
17.94 
P-value 
<0.001 
<0.001 
<0.001 
<0.001 
T. Simčič : Respiration rate and respiratory electron transport system ... 87 
45 
40 a) 
35 
,-.., 
~ 30 
>, -..... ' ·;; ~ 25 ·.::: Cl 
(.) oIJ 
~ s 20 
E-< N 
i:i:i o 
...l 15 
:i. 
'-' 
10 
5 
o 
Chironomus Paratanytarsus Procladius Zavrelimyia 
20 
18 b) 
16 
- 14 2 -~ -
c<l - 12 ~ ~ 
.8 Cl 10 ..... oIJ _g s 
- - - ---
o. N 8 "' o <l) 
~ ...l 
:i. 6 '-' - - -
4 - + . 
2 
o 
Chironomus P aratanytarsus Procladius Zavrelimyia 
Figure 1: (a) ETS activity and (b) respiration rate of different chironomid larvae (mean ± standard devia-
tion) at 20 °c. 
Slika 1: (a) Aktivnost ETS in (b) stopnja dihanja pri ličinkah različnih vrst trzač (srednja vrednost ± stan-
dardna deviacija) pri 20 °C. 
88 Acta Biologica Slovenica, 47 (2), 2004 
Table 2: The ratios ETS/R for different species of chironomids, measured at 20 °C. 
Tabela 2: Razmerja ETS/R za različne vrste trzač, izmerjena pri 20 °C. 
n ETS/R ratio Standard deviation 
Chironomus thummi 
Paratanytarsus austriacus 
Procladius (Holotanypus) spp. 
'Zavrelimyia barbatipes 
18 
9 
8 
7 
2.73 
2.44 
3.88 
0.98 
60 r------------------, 
50 ~ 
l 
o 
o 0.5 
Body mass (mg) 
o o o o 
o 
o 
a) 
1.5 
60 .--------- ----------, 
b) 
50 
JO 
,, 
o 8 
~d>i,~. ; o 8 o~o o ~ o o 
o 
o 0.5 1.5 
Body mass (mg) 
• Procladius l!I Zavrelimyia i> Paratanytarsus o Chironomus 
0.93 
0.86 
0.75 
0.21 
Figure 2: The relationship between (a) ETS activity and body mass (DW), and (b) respiration rate (R) and 
body mass of different chironomid Iarvae at 20 °c. 
Slika 2: Razmerje med (a) aktivnostjo ETS in telesno maso (DW) ter (b) stopnjo dihanja in telesno maso pri 
ličinkah različnih vrst trzač pri 20 °C. 
T. Simčič: Respiration rate and respiratory electron transport system ... 89 
Respiration rate 
Respiration rate differed significantly between species (Tab. 1). The highest values were obtained for 
Paratanytarsus (12.4 µL 0 2 mg·1 h·1) and 'Zavrelimyia (11.9 µL 0 2 mg·1 h-1), while respiration rates of 
Chironomus (5.7 µL 0 2 mg-1 h-1) and Procladius (4.0 µL 0 2 mg- 1 h- 1) were approximately two and three 
times lower (Fig. 1 b ). The regression between respiration rate and body mass of chironornids was statis-
tically significant (log R = 0.60- 0.34 log DW; r=-0.71; n=43; p<0.001; Fig. 2b); b value was 0.66. 
The ETS/R ratio 
The ratio ETS/R differed significantly between species (Tab. 1). A relatively low value, close to 
1, was determined for 'Zavrelimyia, while the highest ratio of 3.88 was obtained for Procladius (Tab. 
2). Positive correlation between ETS/R ratios and body mass was observed (r=0.61; n=27; p<0.001). 
Respiration rate correlated strongly with ETS activity for all-four species (Fig. 3). Correlation 
coefficients and regression constants for relationships between ETS activity and respiration rate for 
each species are shown in Tab. 3. 
Table 3: Relationship between ETS activity and respiration rate of four chironomid species (<lata were log 
transformed). 
Tabela 3: Razmerje med aktivnostjo ETS in stopnjo dihanja pri štirih vrstah trzač (podatki so bili logarit-
mirani). 
Chi ronomus thummi 
Paratanytarsus austriacus 
Procladius (Holotanypus) spp. 
7.avrelimyia barbatipes 
2 
i 1,5 
§ 
~~ 
~ e 
10,5 
o 
o 0,5 
n 
18 
9 
8 
7 
Correlation b loga P-value 
coefficient (slope) (intercept) 
0.73 0.56 0.72 <0.001 
0.82 1.47 -1.02 <0.01 
0.71 0.41 0.09 <0.05 
0.85 0.74 0.30 <0.05 
1,5 2 
log ETS activity 
• Procladius • Zavrelimyia A Paratanytarsus o Chironomus 
Figure 3: The relationship between ETS activity and respiration rate of different chironomid larvae. 
Correlation coefficients and regression constants are given in Tab. 3. 
Slika 3: Razmerje med aktivnostjo ETS in stopnjo dihanja pri ličinkah različnih vrst trzač. Korelacijski in 
regresijski koeficienti so podani v Tab. 3. 
90 Acta Biologica Slovenica, 47 (2), 2004 
Discussion 
Results of the present study revealed that ETS activity and respiration rate differed significantly 
between chironomid species (Fig. 1; Tab. I ). Chironomid species vary significantly in body size 
(Tab. 1) and thus characters related to body size would be expected to vary between species. 
KONSTANTINOV (1971) reported that the mass-specific respiration rate of chironomid larvae was 
inversely related to body size. An effect of size on ETS activity was also found in previous investi-
gations, with larger species having lower ETS activities (SIMČIČ & BRANCELJ 1997, 2001). The larg-
er average body sizes of Chironomus and Procladius were probably one of the reasons for the lower 
metabolic activity than in the smaller larvae of Zavrelimyia and Paratanytarsus. The reasons for 
higher metabolic activity in smaller animals are well discussed in PETERS (1983). 
The significant correlations between body mass and ETS activity and between body mass and 
respiration rate confirmed the effect of body size on metabolic activity in chironomids (Fig. 2). A b 
value of 0.82 was found in the case of ETS activity and 0.66 for respiration rate. HAMBURGER & DALL 
(1990) found a value of 0.73 for respiration rate for four different species of chironomids. Similar 
values of ETS activity were reported for the benthic macrofaunal species Corophium volutator, 0.86 
(CAMMEN & al. 1990), for Nereis virens, 0.84 (CAMMEN & al. 1990), for Chelicorophium 
curvispinum, 0.66 (MusK6 & al. 1995), and for Anostraca Chirocephalus croaticus, 0.787 (SIMČIČ & 
BRANCELJ 2000). In general, b values ranged from 0.58 to 0.96 (see LAMPERT 1987). However, the 
distribution of ETS activity of Zavrelimyia compared to similar sized individuals of Paratanytarsus, 
Chironomus and Procladius (Fig. 2a) indicated that other factors, beside body size, had influenced 
on ETS activity. Larvae of Zavrelimyia are considered as cold-stenotherms (FERRARESE 1983, 
FITTKAU & ROBACK 1983). Therefore, one of the reasons for Iow ETS activities of Zavrelimyia was 
probably respiratory enzyme systems with narrow temperature optima which caused their inactiva-
tion at temperature of 20 °C. Contrary to ETS activities, respiration rates of Zavrelimyia were close 
to those of similar-sized individuals of Paratanytarsus. 
ETS activity correlated significantly with respiration race in all species investigated (Fig. 3). 
These results are in accord with those of KING & PACKARD (1975) and SIMČIČ & BRANCELJ (2001) 
who also found a correlation between ETS activity and respiration rate in invertebrate species. 
However, ETS activity is a direct enzymatic process, depending on the concentration (BAMSTEDT 
1980) and characteristics (PACKARD 1971) of the enzymes, whereas respiration is a complex physi-
ological process. It means that respiration is also influenced by the intact intracellular environment, 
substrate concentrations, and structure and properties of intact lipid membranes (WITHERS 1992). As 
investigated species differed in body size (Tab. 1) and their ecological tolerance (FITTKAU & R0BACK 
1983, PINDER & RE1ss 1983), the differences in the ETS activity-respiration rate relationship between 
them were expected. 
One of the purposes of the present study was to obtain an ETS/R ratio that could be used for esti-
mating actual metabolism in chironomids from ETS activity. As shown in Tab. 2 the values of this 
ratio differed significantly between cbironomid species (Tab. 1). In the present experiments, the basal 
metabolism and expenditure on locomotion were measured. The expenditure on feeding and specif-
ic dynamic action (SDA) was minimal, because the animals were not fed just prior to or during the 
experiments. The low ETS/R ratio in Zavrelimyia means tbat this species exploited 100% of its meta-
bolic potential for basal metabolism and locomotion. Procladius had a much higher ETS/R ratio, 
wbich means less intensive exploitation of metabolic potential for basal metabolism and activity 
(-25% ). These ratios are similar to the values found in other studies conceming invertebrate species. 
T. Simčič ; Respiration rate and respiratory electron transport system ... 91 
Ratios approaching 2 are characteristic of zooplankton (BAMSTEDT 1980, JAMES 1987, SIMČIČ & 
BRANCELJ 1997) but, in the case ofbenthic species, higher values were determined. MusK6 & al. (1995) 
found that the arnphipod Chelicorophium curvispinum exhibited an ETS/R ratio of 4.07 at 20 °C. 
CAMMEN & al. (1990) reported an ETS/R ratio for Corophium volutator of 2.38, and for the poly-
chaete Nereis volutator 11 .11 (measured at 10 °C). The latter extremely high value was explained by 
N. volutator 's low activity. ETS/R ratio was also influenced by the size of organisms. Present results 
are in accord with those of CAMMEN & al. (1990) who found that larger animals have higher ETS/R 
ratios. The reason for higher ETS/R ratios is the greater decrease in respiration relative to ETS activ-
ity with increasing body size. Previous studies have also shown that the ETS/R ratio differs between 
related species having different ecological tolerance and preference, and consequently they exploit 
their metabolic potential differently (MUSK6 & AL. 1995, SIMČIČ & BRANCELJ 1997). FANSLOW & al. 
(2001) reported that, in organisms with high ratios, the capacity for elevated metabolism is main-
tained so that maintaining the enzyme machinery for increased metabolic activity is an advantage. 
Investigated chironomid species have different temperature and food preference and tolerance 
(FITTKAU & R0BACK 1983, PINDER & REISS 1983), and it is reasonable to assume that ETS/R ratio is 
influenced by these differences as well. Low ETS/R ratio of Zavrelimyia suggest that its energy 
metabolism is less adaptable to environmental changes compared with the more widely distributed 
Chironomus, Paratanytarsus and Procladius. However, further studies will provide additional data 
in order to obtain detailed conclusions related to relationship between ETS/R ratio and different eco-
logical demands of chironomid larvae. Nevertheless, as ETS/R ratio differed significantly between 
chironomid species, the energy flux through macrozoobentos has to be estimated by using different 
conversion factors. Preliminary studies on the estimation of energy flow through respiration in 
mountain lakes revealed that contribution of chironomids to total respiration differed between shal-
low oligotrophic and eutrophic lakes. 
Conclusions 
l. ETS activity and respiration rate, measured at a standard temperature of 20 °C, differed 
between chironomid species; the body size of species is one of the factors that affected metabolic 
activity; b value was 0.82 for ETS activity and 0.66 for respiration rate. This indicates the greater 
decrease in respiration rate relative to ETS activity with increasing body size. 
2. The ETS-assay is shown to be a convenient method for estimating respiration rate in chirono-
mid larvae. 
3. ETS/R ratios differ between species, so the use of different conversion factors to calculate res-
piration rate from ETS activity in different chironomid species is recommended. The differences can 
be explained by different species-specific body size, and different ecological tolerance and prefer-
ence of chironomid species. 
Povzetek 
Ličinke trzač (Chironomidae) so široko razširjena skupina, ki ima pomembno vlogo pri pretoku 
energije skozi prehranjevalne splete, še zlasti v plitvih jezerih. Predhodne raziskave so pokazale, da 
ličinke trzač številčno prevladujejo v makrozoobentoški združbi gorskih jezerih SZ Slovenije, zato 
92 Acta Biologica Slovenica, 47 (2), 2004 
je pri oceni pretoka energije v jezeru potrebno upoštevati tudi njihov delež. Ker je neposredna 
določitev stopnje dihanja običajno zamudna in nepraktična, so razvili biokemijsko metodo, s katero 
merimo aktivnost dihalnega elektronskega transportnega sistema (ETS), ki predstavlja metabolni 
potencial organizmov. Številne raziskave so pokazale, da obstaja med aktivnostjo ETS in dihanjem 
pozitivna korelacija, tako da lahko na osnovi izmerjene aktivnosti ETS s pomočjo razmerja ETS/R 
hitro ocenimo intenzivnost dihanja organizmov. Stopnjo dihanja in aktivnost ETS smo določali pri 
ličinkah štirih različnih vrst trzač, ki smo jih nabrali v treh gorskih jezer: ličinke Chironomus thum-
mi v Krnskem jezeru, ličinke Paratanytarsus austriacus in Procladius (Holotanypus) spp. v 
Zgornjem Kriškem jezeru in ličinke Zavrelimyia barbatipes v Srednjem Kriškem jezeru. Aktivnost 
ETS in stopnja dihanja, ki smo jo določali pri standardni temperaturi 20 °C, sta se značilno razliko-
vali med vrstami. Aktivnost ETS in stopnja dihanja trzač sta se zmanjševali z naraščajočo velikostjo 
živali, kar kaže na vpliv telesne velikosti na intenziteto metabolizma. Opazili smo pozitivno 
korelacijo med stopnjo dihanja in aktivnostjo ETS pri vseh štirih vrstah, kar pomeni, da je metoda 
ETS primerna za oceno dihanja tudi pri ličinkah trzač. Raziskava je pokazala značilne razlike v 
razmerju ETS/R med preiskovanimi vrstami trzač. Različna razmerja so posledica razlik v vrstno-
specifični telesni velikosti trzač ter njihove različne ekološke preference in tolerance. 
Acknowledgements 
I would like to thank Dr. Pain for linguistic improvement of the manuscript and two anonymous 
reviewers for helpful comments. This work was financially supported by the Slovenian Ministry of 
Education, Science and Sport (Project SLO-Alpe2). 
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