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Description of some unknown larvae of Diamesa genus and correction to previous descriptions (Diptera, Chironomidae)
No full textMid-Po river zooplankton : a seven year study
No full textThe temporal crustacean-zooplankton variation in the mid-Po River (Italy) was analyzed from November 1974 through November 1982. Samples were collected at three stations at monthly intervals. Separate taxon-by-taxon multiple regression analyses (MLTRG) were carried out with zooplankton taxa as the criterion variable and river depth, river discharge and water temperature as the predictor variables. Moina brachiata and Eucyclops serrulatus were correlated with water temperature, Cyclops vicinus inversely correlated with temperature, Eudiaptomus padanus, C. vicinus and Daphniidae with river discharge; Copepodites inversely correlated with river depth. MLTRG showed that water temperature and river discharge account for about 15% of total zooplankton variation. Factorial analysis of variance (ANOVA) was carried out on residuals calculated from MLTRG. Among-years and among-months variation were significant for all the examined taxa. Significant years × months interactions indicated that seasonal variations were also different in different years. ANOVA stressed that there were still unexplained significant residuals in years and months variations. Weekly and daily samples collected in Summer 1979 were submitted to MLTRG and ANOVA as above. Among-week variations were significant for all the examined taxa, whereas among-days were significant for Daphiidae and M. brachiata (Cladocera), and not significant for any of the other taxa. Caution is recommended in interpreting the results of river zooplankton studies. Differences between species responses warn us not to pool species into larger taxa. Temporal variation changes from year to year, so long-time series are necessary to clarify the most important trends of river zooplankton
Stilocladius montanus n. gen. n. sp.: descrizione di un nuovo genere e di una nuova specie di Orthocladiinae dalle Alpi italiane (Diptera, Chironomidae)
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Revision of West Palaearctic Species Belonging To Orthocladius Orthocladius)s. str. van der Wulp, 1874 (Diptera: Chironomidae: Orthocladiinae), With A New Key To Species
No full textA key to larvae of Diamesa Meigen, 1835 (Diptera, Chironomidae), well known as adult males and pupae from Alps (Europe)
Full text linkA key to species belonging to the genus Diamesa Meigen, 1835 (Diptera, Chironomidae) well known as adult males and pupal exuviae from European Alps, is presented; the characters useful in species identification are pictured. The key considers both qualitative and quantitative characters. Thirteen morpho-species are distinguished, probably more species have a very similar larva and can be separated only in the adult or pupal stage. The most discriminant quantitative characters are the length and thickness of anal setae, among qualitative characters the most discriminant ones are the head capsule colour and the split of setae anteriores of labrum. The shape of mental and mandibular teeth are good taxonomic characters, but can be rarely used because teeth are often worn out in samples collected in the field. Quantitative characters show variability within each species, differing according to the sampled site and season, and must be used with caution. The following species groups can be easily separated in the larval stage: i) dampfi, including D. dampfi and D. permacra; ii) latitarsis including D. modesta and D. latitarsis; iii) zernyi including D. zernyi and D. vaillanti. D. starmachi, D. steinboecki, D. goetghebueri, D. bertrami, D. aberrata, D. incallida, D. cinerella, D. tonsa and D. insignipes can be separated from all the other known species in larval stage, but some of them, D. cinerella and D. insignipes for example, have a very similar larva, so are better separated on the basis of their distribution and collection of adults and pupae are strongly recommended to support identifications. A new character bound to head capsule colour is proposed to separate D. insignipes, D. cinerella, D. tonsa and D. zernyi.</em
Thoracic horn structure in Orthocladiini pupae (Diptera: Chironomidae: Orthocladiinae)
No full textThe pupal thoracic horn in Chironomidae is a respiratory organ specialized for oxygen adsorption and the horn surface was suggested as a measure of a species’ oxygen requirements. This structure was analyzed in 31 species belonging to the tribe Orthocladiini within the genera
Cricotopus, Eukiefferiella, Orthocladius and Tvetenia. Optima for dissolved oxygen and water temperature were calculated for each
taxon using information from a large database. The species with extensive horn are the most resistant to low oxygen levels and
high temperature, and no significant correlation was detected between horn surface and species optima. The species of the genus
Cricotopus, characterized by reduced thoracic horn, tolerate lower oxygen levels then Orthocladius: it is suggested that higher
tolerance is bound to more frequent respiratory undulations. At taxonomic levels below tribes behavioural and physiological
adaptations more than morphological ones may explain the result
The effects of tricyclazole treatment on aquatic macroinvertebrates in the field and in laboratory
Full text linkThe effects of tricyclazole treatments on benthic macroinvertebrates in the field and in laboratory were studied. In field conditions, low density of benthic populations was observed, both in treated and untreated plots, which was attributed to the short period of submersion of the rice field and high water temperature, fungicide treatments had no significant effect. Both laboratory acute toxicity test and a test using a mesocosm suggested a low toxicity of tricyclazole on invertebrates. A reduction of the macroinvertebrate density was observed only when tricyclazole concentration was applied at concentrations 100 times the ones tested in the field, acute toxicity test gave an LC50 after 48 h of 26 mg*L–1, in agreement with data obtained for other species
A key to larvae of species belonging to the genus Diamesa from Alps and Apennines (Italy)
Full text linkA key to species belonging to the genus Diamesa Meigen, 1835 (Diptera, Chironomidae) from the Alps and Apennines (Italy) is presented
using characters observable in the fourth-instar larva.
The larvae are separated on the basis of qualitative and quantitative characters.
At present fifteen species from the Italian Alps are described in all three life stages, but only twelve species groups can be separated as
larvae. The separation is based on the length and thickness of anal setae, antennal ratio, head capsule color and few other characters of the
labrum and mentum. The shape of mental and mandibular teeth is still a valid taxonomic character, but unfortunately these characters can
be rarely used because teeth are often excessively worn in samples collected in the field. Quantitative characters show variability within
each species, differing according to the duration of larval development and must be used with caution.
The species groups which can be separated in the larval stage are: the dampfi group, which includes D. dampfi and D. permacra, the latitarsis
group including D. modesta and D. latitarsis, the zernyi group including D. zernyi and D. vaillanti. The species within each of these groups
at present cannot be separated. D. starmachi, D. steinboecki, D. goetghebueri, D. bertrami, D. aberrata, D. incallida, D. cinerella, D. tonsa and
D. insignipes can be separated from all the other known species in larval stage
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