Enzo Goretti

Macrobenthos in Montedoglio Reservior, central Italy

An investigation was carried out on the macrobenthos of Montedoglio Reservoir, an artificial lake in central Italy. Seven qualitative and quantitative samplings, performed by drag netting and airlifting at 5 stations, revealed a total of 48 taxa during 1992–94. The highest density and most frequent terms were Tubificidae, Chironomidae of the genera Procladius, Tanypus, Chironomus and Polypedilium and Chaoboridae. Tubificidae were found mainly at a depth of 7–9 m, Chironomidae at 1–3 m. The modest density and low biological diversity values are probably attributable to the substrate characteristics and a drop in hypolymnic oxygen during thermic stratification. The oxygen stress at the lake bed, which was unexpected given the scarce planktonic productivity, may have been caused by recent impoundment.

Deformities of chironomid larvae and heavy metal pollution: From laboratory to field studies

Mouthpart deformities of Chironomus riparius larvae (Diptera) have been investigated to evaluate the toxic effects of contamination by heavy metals in the Genna Stream (Central Italy), situated in an area subjected to intensive swine farms (40000 heads). The livestock farming (fertirrigation) contributes to metal pollution of the Genna Stream with an increase of copper, zinc, cadmium, chromium and nickel in the sediments of the downstream stations. The incidence of mentum deformities was very high at all sampling stations, about 56%. The highest values of deformities were found in the intermediate river reach (St. 3: 65%) and in March (66%), mainly due to an increase in severe deformities. The high incidence of severe deformities (30%) is attributed to the high pollution level by heavy metals in the sediments, in particular to copper and zinc, which showed the highest average value at St. 3 and in March. This field study reflected the relationships between sediment metal concentrations and chironomid mouthpart deformities, previously observed in laboratory tests, and highlighted these deformities as toxicity endpoints. This feature paves the way for their use as an effective tool in freshwater bioassessment monitoring programs to evaluate the toxic effects of metal contamination in freshwater ecosystems.

Induction of mouthpart deformities in chironomid larvae exposed to contaminated sediments.

The aim of the present study was to improve the cause-effect relationship between toxicant exposure and chironomid mouthpart deformities, by linking induction of mouthpart deformities to contaminated field sediments, metal mixtures and a mutagenic polycyclic aromatic compound metabolite (acridone). Mouthpart deformities in Chironomus riparius larvae were induced by both the heavy metal mixture and by acridone. A clear correlation between metal concentrations in the sediment and deformities incidence was only observed when the contaminated field sediments were left out of the analysis, probably because these natural sediments contained other toxic compounds, which could be responsible for a higher incidence of deformities than predicted by the measured metal concentrations only. The present study clearly improved the cause-effect relationship between toxicant exposure and the induction of mouthpart deformities. It is concluded that the incidence of mouthpart deformities may better reflect the potential toxicity of contaminated sediments than chemical analysis.

Sediment toxicity and deformities of chironomid larvae in Lake Piediluco (Central Italy).

The chemical analysis of the bottom sediments of the Lake Piediluco (Central Italy) has been carried out in order to individuate the potential correlation between the sediment toxicity and the high incidence of mouthpart deformities in chironomid larvae (biological indicators) found in this lake. The environmental contamination has been analyzed by determining the concentrations of the main heavy metals (lead, copper, cadmium, chromium, zinc and nickel), and the concentrations of organic compounds of anthropic source: PAHs, NPPs and OCPs. Heavy metals concentrations have pointed out a non-elevated contamination grade for the Lake Piediluco. The highest level of metals has been detected in the western area that feels the effect of the continuous tributaries incoming load. Also, concerning PAHs, NPPs and OCPs the lake does not present high values of pollution. The highest concentrations of the organic toxicants has been observed in the eastern sector of the lake, which presents typical lentic characteristics. A clear relationship has not found between the toxic substances present in the lacustrine sediments and the deformities incidence for chironomid larvae, which represent an index of environmental alteration. Probably, the mouthpart deformities found in the chironomid larvae of Chironomus plumosus are affected by a synergic action due to the whole toxic mixture present in the sediments of the Lake Piediluco.

Heavy metals bioaccumulation in selected tissues of red swamp crayfish: An easy tool for monitoring environmental contamination levels

In this paper we explored the heavy metal bioaccumulation (Cd, Cu, Pb and Zn) in Procambarus clarkii, a crayfish recently suggested as a potential bioindicator for metals pollution in freshwater systems. The present study is focused on crayfishes populations caught in a heavily polluted industrial and in a reference sites (Central Italy), though the results are generalized with a thorough analysis of literature metadata. In agreement with the literature, the hepatopancreas (Hep, detoxification tissues) of the red swamp crayfish showed a higher concentration of heavy metals in comparison to the abdominal muscle (AbM, not detoxification tissues) in the sites under scrutiny. Hep/AbM concentration ratio was dependent on the specific metal investigated and on its sediment contamination level. Specifically we found that Hep/AbM ratio decreases as follows: Cd (11.7)>Cu (5.5)>Pb (3.6)>Zn (1.0) and Pb (4.34)>Cd (3.66)>Zn (1.69)>Cu (0.87) for the industrial and reference sites, respectively. The analysis of our bioaccumulation data as well as of literature metadata allowed to elaborate a specific contamination index (Toxic Contamination Index, TCI), dependent only on the bioaccumulation data of hepatopancreas and abdominal muscle. In the industrial site, TCI expressed values much higher than the unit for Cd and Cu, confirming that these metals were the main contaminants; in contrast for lower levels of heavy metals, as those observed in the reference site for Cu, Zn and Pb, the index provided values below unit. TCI is proposed as a useful and easy tool to assess the toxicity level of contaminated sites by heavy metals in the environmental management.

Larval development of Libellula depressa (Odonata, Libellulidae) from pools in central Italy

Abstract The developmental stages of the larvae of Libellula depressa were investigated for three years in permanent freshwater pools in central Italy. Eleven instars (F‐0 ‐ F‐10) of L. depressa were discriminated by size and scatter plot. Scatter plots were constructed using the following measurements: labium length, head width, metafemur length, forewing‐pad length, and total larval body length. Prolarvae instar was derived by Dyars law. The mean growth rate coefficient values were about 0.77 for isometric parameters and 0.51 for the forewing‐pad allometric parameter. L. depressa appeared to be a ‘spring species’, as defined by Corbet, and the population we studied had a mainly semivoltine life history and, probably, a small proportion of the larvae a univoltine cycle. Eggs showed direct development.

Genetic analysis of the species of sigara s. str. (Heteroptera, Corixidae) in the Italian Peninsula

Abstract The genetic differences in three populations of Sigara s. str. belonging to S. striata, S. dorsalis, and S. basalis, distributed in northern (Veneto, South Tyrol) and central (Umbria, Molise) Italy, were assayed by horizontal starch electrophoresis. Adult specimens were examined. Twelve enzymes were assayed, eight of which gave satisfactory results. Five of the eight alloenzymes were further investigated to differentiate the three species: phos‐phoglucomutase (Pgm‐1, Pgm‐2), esterase (Est‐1, Est‐2, Est‐3), su‐peroxide dismutase (Sod‐1, Sod‐2), phosphoglucose isomerase (Pgi‐1, Pgi‐2), isocitrate dehydrogenase (Idh) coding for 10 studied loci. A total of 208 adults of the three taxa (142 for S. basalis, 49 for 5. dorsalis, and 17 for 5. striata) were analysed. Neis unbiased genetic distances were calculated and values between congeneric species ranged from 0.009 to 0.25, as illustrated in a phenogramme constructed by the unweighted pair‐group cluster analysis method. Sigara basalis presented the h...

Artificial light device for attracting pestiferous chironomids (Diptera): A case study at Lake Trasimeno (Central Italy)

Abstract In recent years, Lake Trasimeno (Central Italy) has been affected by massive chironomid swarms that have been a serious nuisance to inhabitants and tourists. The introduction of ‘tofo lamps’, to divert chironomid midges from inhabited areas, has exploited the natural attraction that these insects have for artificial light. These tofo lamps had a high white light intensity (450 W) and were equipped with an external net that imitates the fish net, called ‘tofo’. The attractive efficiency of such lamps was tested in the summers of 2007, 2008 and 2009 by monitoring these devices in areas on eastern (S. Feliciano) and western (Castiglione del Lago) sides of Lake Trasimeno. The most attracted taxa included the species causing a serious nuisance, i.e. the large-sized Chironomus plumosus, and the small-sized Tanypus punctipennis and Procladius sp. In summer, massive swarms of the last two taxa preceded those of C. plumosus. Female chironomids were much more attracted than were males by the artificial white light, with a sex ratio much lower than 1. In addition, the percentage of gravid females of C. plumosus was higher than that of females not carrying eggs. Artificial lights were confirmed as effective in diverting the pestiferous chironomids, a feature that should be carefully considered in order to limit the nuisance from these insects and to avoid spreading insecticides in natural environments.

Oxygen consumption in two aquatic coleoptera species: Hydrous piceus and Dytiscus marginalis

Abstract The respiratory activity in adults of two species of aquatic Coleoptera, Hydrous piceus and Dytiscus marginalis, was examined to assess the physiological responses of the oxygen content variations of their air stores, called physical gills. The respiration rates were measured at two temperature ranges between 19° C and 30° C by means of a dissolved oxygen metre. The two species showed no significant differences in oxygen consumption, but water temperature affected oxygen gains in the bubbles. The effect of body weight on respiration level did not differ significantly within the two temperature ranges in either species because of the similar weights among individuals. The oxygen exchange between the physical gills and the surrounding water can be used as a measure of the respiratory metabolism of these insects and of their interactions with the surrounding environment.

Invertebrate diversity in relation to chemical pollution in an Umbrian stream system (Italy)

We used self-organizing maps (SOM, neural network) to bring out patterns of benthic macroinvertebrate diversity in relation to river pollution. Fourteen stations were sampled over various seasons in the Nestore drainage basin (Central Italy) and characterized for macroinvertebrate communities, nutrient and heavy metal concentrations. Physicochemical variables were introduced into a SOM previously trained with macroinvertebrate data. Patterns of communities matched spatial and seasonal changes in environmental conditions, including water chemistry related to economic activities in the catchment. Although our analyses did not allow us to establish the specific effect of any given environmental parameter upon macroinvertebrate community composition based on the field study, they enabled us to map the ecological health of river ecosystems in a readily interpretable manner.