Maria Vittoria Di Giovanni

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...

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.

Sigara basalis (Costa) (Heteroptera, Corixidae), a valid species: Diagnostic characters and comparative observations

Abstract Investigation of the extensive Italian and European material of the subgenus Sigara provided definitive evidence that Sigara basalis is a valid species. This taxon, whose neotype has been designated, is described again and its distribution, of an endemic type (Apennines), is established. Comparative observations of the three species of Sigara living in the Italian peninsula (S. basalis, S. dorsalis, and S. striata) revealed that the characters useful for specific identification are primarily related with the morphology of the parameres and the 8th dextral abdominal tergite.

Reservoir management and its effects on the trophic organization of the macrobenthic community in a river in central Italy

The Chiascio River (central Italy) macrobenthic invertebrate community is analysed in relation to the management of a recently constructed reservoir located about halfway along the watercourse. The dam was originally planned for irrigation purposes, but since 2005 has only been used to regulate the minimum flow of the river, with partial filling in spring and total discharge in autumn. Seasonal sampling surveys, conducted from 1996 to 1999 at 13 stations along the river, yielded 45,744 specimens of benthic macroinvertebrates belonging to 109 taxa. The functional feeding analysis revealed a zone of discontinuity downstream of the dam, with high values of shredders and low values of collectors. The discontinuity is probably due to the reintroduction, in autumn, of the stored particulate organic matter. This altered the trophic structure of the benthic community just downstream of the dam, moving it towards a facies of lower stream order.

Trichoptera populations in the water system of the river tiber in Tuscany and Emilia Romagna (Italy)

Abstract Investigations were carried out during the summer of 1992 at 32 sampling stations situated on 19 rivers and streams of the River Tiber watershed in Tuscany and Emilia; of these, 31 were located upstream and one downstream from the Montedoglio Dam. Water quality was good and there were no environmental alterations upstream in the sampled streams. The Trichoptera study identified 33 species and 2 subspecies, 7 of which were new records for the area. Taxa abundance was evaluated by grouping into classes the individuals collected by semi‐quantitative sampling. Aquatic stages of Trichoptera, which had a wide range of habitat and trophic categories, were used as indicators of resource distribution along the longitudinal profile of the streams. The results concur with the ≪River Continuum≫ model. Because the reservoir affects the faunistic communities in the downstream reaches of the three immissaries, the Trichoptera population is typical of tracts of higher order water courses.

Morphometric pattern and biometry of adult Trichoptera (Italian species)

Abstract Morphometric characters of 961 adult caddisflies, belonging to 327 taxa of the Italian Trichopteran fauna were observed and measured. Sexual dimorphism is reflected in the smaller mean size of males, with mean differences in body length of 12.57%. For the order Trichoptera, regressions of the relationships among body dimensions have been used to estimate the value of exponent b and coefficient a of the allometric function y = a * xb , a power function that describes these relationships very well. The lengths (forewing, head‐wing, metafemur, and head) versus body length relationships displayed a high degree of isometry among species, with head‐wing and forewing having the highest correlation values (especially in males). The results show that most of the variance depends on isometric size variation and not on allometric shape variation among the different species. For adult caddisflies, this demonstrates constancy of the morphological model in the Italian Trichoptera.

Macrobenthos structure in the watershed of a river of central Italy

Abstract A study was undertaken to define the benthic populations, the environmental‐ecological variability and trophic aspects according to the functional feeding groups in the upper reaches of the Nera River, a tributary of the Tiber, in central Italy. A total of 12 681 individuals was collected and 83 taxa were identified; 11 proved to be endemic for Italy, 7 of them typical of the central Apennines. The greatest number of taxa (58), and the highest values of diversity were recorded at the lowest sampling station, 37 km from the source. A dendrogram constructed by the UPGMA method based on values of similarity revealed two main clusters, one identified with crenon (at the source) and the other with rhithron (the downstream stations) fluvial typology. Correspondence analysis on the environmental matrix parameters confirmed this finding. Taxa abundance was evaluated by grouping the individuals collected into classes using semi‐quantitative sampling. The results of trophic‐functional analysis, calculated ...

Esponenti endofitici, epifitici e fitosaprobi del Lago Trasimeno: Facies autunnale

Summary The progressive developement of hydrophytie colonies has increased the importance of the phytopbil communities existing in Lake Trasimeno and has transformed the whole lake into a single, extended, homogeneous, litoral region. Observations carried out in the month of October on the single species of water plants have brought to light a series of phytophil animals, the analysis of wich aims to establish their exact relationship with the substratum. The present work stresses in particular the representatives of the zoological world neglecting those of the algal, to wich will be dedicated a further note. The analysis of the communities, from specimens taken at stated distances, shows a certain wealth of composition, but at the same time a notable monotony of distribution. The types founded (Protozoa, Rotifera, Nematoda, Crustacea, Hydrachnida. Insecta, Mollusca) are more in evidence to epiphylon and periphyton, but there exist also a certain number of endophytic forms present especially in the Potamo...

Structure and meaning of the ≪G. P. Moretti≫ trichopterological collection

Abstract 28 June 1989 to 20 Dicember 1990: a hundred years of collecting italian Trichopteran fauna. This work arranges the ≪G.P. Moretti collection≫ that includes 14341 regularly labelled specimens derived from 3922 sampling days in the peninsula and on the islands (Sardinia, Sicily, Caparaia and Elba). The most part (99.6%) of the samples were determined by G.P. Moretti and by other taxonomists (0.4%). The collection comprises larvae, pupae, adults and their esuviae dipped in 80% alcohol and also several dry specimens and some anatomical pieces fixed on slides. Samplings wer done mostly in lotic ecosystems (3077) but also stagnant waters (539) and other different habitat (306) were widely investigated. On the whole the collection presents 311 species and 26 subspecies including 31 species and 15 subspecies all new to science. A different and significative presenc of species is clearly evident in the 22 territories sampled. The specific composition of the italian subtroglophil aphiletic Trichoptera is we...