Preimaginal feeding habits of Dictyogenus fontium (Plecoptera, Perlodidae) in an alpine brook in NW Italy

The feeding habits of Dictyogenus fontium nymphs were investigated in the Rio Olen, an alpine brook in NW Italy. In an analysis of the gut contents of 84 nymphs, we detected evident trophic preferences: Chironomidae (Diptera) were the major component of the prey ingested, independently of their availability in the substratum. Plant detritus and algae were also an important part of the diet of this carnivorous stonefly. The findings are discussed on the basis of ecological considerations

Contribution of beta diversity in shaping stream macroinvertebrate communities among hydro-ecoregions

AbstractRivers are heterogeneous and patchy-structured systems in which regional biodiversity of aquatic communities typically varies as a function of local habitat conditions and spatial gradients. Understanding which environmental and spatial constraints shape the diversity and composition of benthic communities is therefore a pivotal challenge for basic and applied research in river ecology. In this study, benthic invertebrates were collected from 27 sites across three hydro-ecoregions with the aim of investigating patterns inα- andβdiversity. We first assessed the contribution to regional biodiversity of different and nested spatial scales, ranging from micro-habitat to hydro-ecoregion. Then, we tested differences inαdiversity, taxonomic composition and ecological uniqueness among hydro-ecoregions. Variance partitioning analysis was used to evaluate the mechanistic effects of environmental and spatial variables on the composition of macroinvertebrate communities. Macroinvertebrate diversity was significantly affected by all the spatial scales, with a differential contribution according to the type of metric. Sampling site was the spatial scale that mostly contributed to the total richness, while the micro-habitat level explained the largest proportion of variance in Shannon–Wiener index. We found significant differences in the taxonomic composition, with 39 invertebrate families significantly associated with one or two hydro-ecoregions. However, effects of environmental and spatial controls were context dependent, indicating that the mechanisms that promote beta diversity probably differ among hydro-ecoregions. Evidence for species sorting, due to natural areas and stream order, was observed for macroinvertebrate communities in alpine streams, while spatial and land-use variables played a weak role in other geographical contexts

Vertical Distrubution in the Water Column of Drifting Stream Macroinvertebrates

ABSTRACT We examined the macroinvertebrate composition and drift density in a Mediterranean lotic system, the Erro River (northwestern Italy). Drift density and composition were sampled for one year at three levels of the water column; temperature and flow velocity were also measured. We found that drift density was generally highest near the bottom. We also noticed that various taxa tended to drift at preferential levels of the water column, with 41.4 % of taxa mainly at the bottom level and 31.0 % mainly at the top. Drift density decreased with increasing water temperature. Both taxa richness and macroinvertebrate abundance in the drift were positively associated with natural riverbed richness and abundance

Feeding on the roof of the world: the first gut content analysis of very high altitude Plecoptera

The biology of Plecoptera from high altitude Himalayan freshwaters is almost unknown. Very few and sporadic studies have been devoted to these insects, and exclusively with a taxonomic approach. We provide information on the feeding of Capnia nymphs from three lakes localized above 4,800 m a.s.l. (NE Nepal). Nymphs from these high altitude lakes feed mainly on fine detritus, acting as collector- gatherers, with the accidental ingestion of mineral matter, mostly in larger specimens. It is likely that the harsh environmental conditions in our study area create an environment unfavorable to both the allochthonous input of coarse particulate organic matter (such as terrestrial leaves) and the autochthonous input related to aquatic primary productivity, so that these nymphs feed on small organic particles that originates mainly from the catchment

Trophic behaviour of the dragonfly Cordulegaster boltoni (Insecta: Odonata) in small creeks in NW Italy

The order Odonata comprises many predaceous species that inhabit aquatic systems, and a few that are restricted to flowing waters. Cordulegaster boltoni is a widespread Odonata in Europe, which usually inhabits small lotic systems. In this study we analysed the gut contents of C. boltoni immature stages, collected in the Rocchetta Tanaro Natural Park (Italy, Piemonte). Two hundred and eleven individuals were collected, and their diet analyzed by dissection or clearing. Larvae appeared to be opportunistic predators, feeding on a variety of prey. Aquatic insects dominated their diet, while crustaceans, annelids, molluscs and terrestrial invertebrates were sporadically observed in the gut contents. An ontogenetic shift in the diet was detected, as small larvae consumed different prey than large ones. Our study suggests that C. boltoni is one of the dominant predators in the benthic communities of lowland small order streams of Piemonte, which, because of their environmental characteristics, are devoid of fish and stoneflies

Nymphal biology of Brachyptera risi (Morton, 1896) (Plecoptera: Taeniopterygidae) in a North Apennine stream (Italy)

Some aspects of the life history of a population of Brachyptera risi were investigated in a North Apennine stream and compared with previously studied European populations. In our study area, this species showed a univoltine fast seasonal life cycle. Nymphs were present from January to the beginning of May, probably spending the rest of the year mainly in egg diapause. Fine particulate organic matter was the principal component of the diet, while diatoms and other algae were also found in the guts. This finding suggests the existence of greater trophic plasticity of the species. Individuals of this population act as gatherer-collectors but not as scrapers as usually pointed out for other European populations. We also detected considerable amounts of animal matter in the gut contents. The density of B. risi nymphs in the study area was very variable during the study period, ranging from 0 to 2,348 ind/m2