Hydrobiologia - In shallow lakes, macrophytes have important effects on food webs, community structure and nutrient dynamics. For this reason they play a significant role in the restoration of... 相似文献
The species composition of the damselfly assemblage and the life history patterns of two Coenagrionidae (Ischnura elegans
and Cercion lindeni) were investigated along the urban tract of a river characterized by increasing organic pollution. The
assemblage was dominated by generalist species, usually recorded in lentic habitats, rather than by typical riverine species
and the proportion of the latter decrease at the most polluted sites. At the end of Winter, the mean size and in star distribution
were different between the sampling sites showing that the life history of both species examined were influenced by a degradation
of the environmental quality. A longer reproductive period, absence of diapause, and tolerance of low oxygen concentration
appear to be key factors that allow generalist species I. elegans and C. lindeni to predominate at the polluted sites.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
The chironomid midges Belgica antarctica, Eretmoptera murphyi (subfamily Orthocladiinae) and Parochlus steinenii (subfamily Podonominae), are the only Diptera species currently found in Antarctica. The relationships between these species
and a range of further taxa of Chironomidae were examined by sequencing domains 1 and 3–5 of 28S ribosomal RNA. The resulting
molecular relationships between B. antarctica and E. murphyi, within Orthocladiinae, were highly supported by validation analyses, confirming their position within Chironomidae, as generated
by classical taxonomy. Within Podonominae, P. steinenii from the Maritime Antarctic was more closely related to material from sub-Antarctic South Georgia than to material from Patagonia.
Taking advantage of the availability of a molecular substitution rate calculated for this gene in Diptera, a dating of divergence
between our study taxa was tentatively established. The divergence dates obtained were 49 million years (Myr), between B. antarctica and E. murphyi, and 68.5 Myr between these species and the closest Orthocladiinae taxon tested from Patagonia, suggesting that B. antarctica and E. murphyi were representatives of an ancient lineage. As both are endemic to their respective tectonic microplates, their contemporary
distribution is, therefore, likely to have been shaped by vicariance rather than dispersal. 相似文献
The absence of a rapid and inexpensive method for estimating macroinvertebrate individual biomass is a limit to the study of freshwater communities, given that traditional methods are time- and money-consuming. We propose an inexpensive method to quickly estimate individual biomass from video-recorded images of pond macroinvertebrates. We used a software that automatically measures several body dimensions (area, perimeter, minor and major axes) on each individual and linear regression to relate these body dimensions to dry weight. Area was found to be the best predictor of dry weight. The method allows individual measures of macroinvertebrates at a reasonable speed and accuracy, and may be useful for biomass size spectra or secondary production studies. 相似文献
Fluctuating asymmetry (FA) is thought to be an indicator of developmental stability and negatively related to male mating success in many animal taxa. We investigated the relationships between mating success of males, body size and FA for both wing length and number of setae on the legs in the damselfly Ischnura elegans. Males were classified as mated or unmated at the time of sampling. Fluctuating asymmetry, expressed as right-left differences, showed normal distributions without evidence of directional asymmetry or antisymmetry. Univariate analyses showed a significant negative correlation between size and mating success, and significant negative correlations between FA and mating success for both characters. On the other hand, with a multivariate analysis, new to studies on FA, the effect of body size was still significant but FA did not reach significance for either character. We conclude that the multivariate analysis should be used to assess the role of the different factors affecting mating success. Copyright 2000 The Association for the Study of Animal Behaviour. 相似文献
Polygordius antarcticus sp. nov. is described from benthic material collected at depths ranging between 31 and 61 m in Terra Nova Bay, Ross Sea,
during the 1987–1988 and 1988–1989 expeditions of the Italian National Research Program in Antarctica. This is the first named
species of the genus from Antarctic waters. Although no fully mature specimens were available, the new species appears unique
in combining the following features: a regular pygidium, inflated and with a single ring of round adhesive pads, a conical
prostomium with short antennae (only half as long as the prostomium) and shallow head fold, and a well-developed circulatory
apparatus, with circumoesophageal commissures entering the prostomium and long intersegmental commissures insinuating into
the ventrolateral compartments of the trunk. These and other significant features were investigated by light and scanning
electron microscopy. In the construction of the head and the scheme of the blood system, the new species resembles Polygordius triestinus Woltereck, described by Hempelmann in 1906, an aberrant species inhabiting muddy, anoxic sediments in the Adriatic Sea, but
it differs significantly from it in the shape of the mouth (in P. triestinus the upper lip is hypertrophied and strongly protruding) and the pygidium (in P. triestinus this region is stump-like and non-adhesive). The pygidium of P. antarcticus sp. nov. is encircled by 28–30 small adhesive pads, each with 15–20 glandular openings. Preterminal cirri are lacking, as
are perianal appendages. The anus is surrounded by six to seven lobes of which the midventral is largest and longest. A world
distribution map of the genus is provided.
Accepted: 27 August 1998 相似文献
The construction of an aquatic system to recycle the wastewater coming from an experimental aquaculture plant provided the opportunity to follow the evolution of structural and functional properties of a community in a new eutrophic shallow lake. Specific aims of this study were to describe the temporal patterns of diversity and production of the macroinvertebrate assemblage in different habitats. The benthic assemblage was sampled monthly for 3 years starting 1 month after pond filling. Each month, replicate samples of invertebrates were collected with quantitative methods from 3 habitats: unvegetated bottom, submerged vegetation and emergent vegetation of the littoral zone. We collected a total of 48 macroinvertebrate taxa belonging to 38 families. The number of taxa increased rapidly during the first phase of colonization (93% of taxa were already recorded within 14 months from pond filling) and then slowly decreased through the next 2 years. Diversity pattern through time was not consistent among habitats, being higher in the unvegetated bottom during the first year and on the submerged vegetation and the littoral vegetation in subsequent years. Slopes of rank-abundance curves showed differences among years and habitats, even though all habitats showed a trend towards the increase of the relative dominance of few taxa (e.g. diminishing of slopes). Macroinvertebrate production changed with time and was different among habitats. The development of submerged and emergent macrophytes greatly increased not only the diversity, but also the production of the whole macroinvertebrate assemblage. %
The lack of biological systems for the assessment of ecological quality specific to mountain ponds prevents the effective
management of these natural resources. In this article we develop an index based on macroinvertebrates sensitive to the gradient
of nutrient enrichment. With this aim, we sampled 31 ponds along a gradient of trophy and with similar geomorphological characteristics
and watershed use in protected areas of the central Apennines. A bioassessment protocol was adopted to collect and process
benthic samples and key-associated physical, chemical, and biological variables during the summer growth season of 1998. We
collected 61 genera of macroinvertebrates belonging to 31 families. We calculated 31 macroinvertebrate metrics based on selected
and total taxa richness, richness of some key groups, abundance, functional groups and tolerance to organic pollution. The
gradient of trophy was quantified with summer concentrations of chlorophyll a. We followed a stepwise procedure to evaluate the effectiveness of a given metric for use in the multimetric index. Those
were the pollution tolerance metric ASPT, three metrics based on taxonomic richness (the richness of macroinvertebrate genera,
the richness of chironomid taxa, and the percentage of total richness composed by Ephemeroptera, Odonata, and Trichoptera),
two metrics based on FFG attributes (richness of collector gatherer taxa and richness of scraper taxa) and the habit-based
metric richness of burrowers. The 95th percentile of each metric distribution among all ponds was trisected for metric scoring.
The final Pond Macroinvertebrate Integrity Index ranged from 7 to 35 and had a good correlation (R2 = 0.71) with the original gradient of environmental degradation.
Guest editors: R. Céréghino, J. Biggs, B. Oertli & S. Declerck
The ecology of European ponds: defining the characteristics of a neglected freshwater habitat 相似文献