1,720,971 research outputs found
The value of water mites (Hydrachnidia) as bioindicators of stream ecological status: an example from Abruzzo, central Italy
No full textBenthic invertebrate assemblages and leaf-litter breakdown along the eucrenal–hypocrenal ecotone of a rheocrene spring in Central Italy: Are there spatial and seasonal differences?
No full textTo better understand the pattern of variation in biocomplexity of springs and first-order streams, it is essential to explore how the characteristics of spring communities may vary from the spring source (eucrenal) to the first reach of the originating springbrook (hypocrenal). For these reasons, we assessed spatial and temporal variation of crenic assemblages and leaf-litter breakdown along a 45-m reach of a spring–springbrook system in Central Italy. We found that physicochemical and hydrological parameters of Vera Spring did not vary significantly along the 45-m reach investigated. In contrast, total richness of assemblages was significantly higher at 20 and 45 m from the spring source, while abundances were more variable and did not show significant differences between seasons and among sites. The composition of assemblages did not show significant temporal trends in all sites investigated, while spatial differences along the eucrenal–hypocrenal ecotone were more prominent. The functional organization of assemblages was relatively stable in both space and time, and no spatial differences were observed in the rate of leaf-litter breakdown, though the dry mass loss of poplar leaves was slightly higher at the most downstream site. We conclude that immediately after groundwater emergence, spring communities are less stable and more variable while they tend to be better organized at short distance downstream. Small and gradual spatial changes in the strength of competitive interactions and predation pressures may have a fundamental role in structuring spring communities more than variation in abiotic parameters and/or differences in quantity and quality of food resources
Lenght-weight relationships for some plecoptera and ephemeroptera from a carbonate stream in central Apennine (Italy)
No full textThe relationship between dry weight and
body length for larvae of Plecoptera (Leuctra spp.,
Isoperla grammatica, Nemoura cinerea) and
Ephemeroptera (Baetis spp., Habrophlebia fusca,
Paraleptophlebia submarginata, Ecdyonurus helveticus,
Rhithrogena semicolorata), collected from a
carbonate stream in the Apennine (central Italy), is
reported. The power equation f(x) = AxB has been
applied to fit the curves of dry weight vs. body size
(length) in the ranges 0.03–13.00 mg and 2–14 mm,
respectively; a total of 674 larvae were examined.
The power model was in very good agreement with
experimental data. Moreover, the error between
measured and estimated weight was in the 4–20%
range. The data on Isoperla grammatica, Leuctra
spp., Rhithrogena semicolorata and Baetis spp. were
compared to those in a previous study in a different
geographical setting (south-western Germany’s Black
Forest) obtaining similar results but with lower
errors. We used and compared two methods: the
weighted least-square method (WLS) and an analysis
of covariance (ANCOVA). The values of the A and B
coefficients obtained with the two methods were very
similar (\6% discrepancy for either A or B). We
found the best fits for all the examined Plecoptera
(species, genus, and order level), while the results for
Ephemeroptera were varied, with loose fits at the
order level and also for Leptophlebiidae collectively
considered
Diel activity cycles of freshwater gastropods under natural light: Patterns adn ecological implications
No full textThough much is known about freshwater snail ecology, their circadian rhythms remain poorly
investigated. Well-fed, stress-free, mid-size adults of six species common in central Italian lakes were exposed
to natural sunlight and photoperiod, and their activity status was recorded at 3-h intervals during a 9-d indoor
experiment. All species exhibited evident diurnal habits despite high individual variability, with middayto-
early-afternoon activity peaks. Activity was correlated with diel light conditions but not with short-term
changes in albedo. The prosobranch Bithynia (=Codiella) leachii and the pulmonates Physa (=Physella) acuta
and Planorbis planorbis were the most active species and exhibited the longest-lasting response to daytime
food addition. The prosobranch Valvata piscinalis exhibited long periods retracted in its shell with the operculum
shut, and the remaining taxa (the pulmonates Galba (=Lymnaea) truncatula and Radix (=Lymnaea)
auricularia) exhibited an intermediate degree of activity. P. acuta was the most active species at night and
exhibited the quicker response to nighttime food addition. Alertedness to (diurnal) predators may be highest
for the highly active P. acuta and P. planorbis, whose antipredator defenses are mainly behavioral. Diel activity
patterns and other ecological characteristics suggest that P. acuta may be favored in food-rich habitats,
while V. piscinalis may not be able to fully exploit food resources, especially if in limiting quantities. All snail
species – and P. acuta in particular – may stimulate periphyton metabolism while keeping its biomass low by
grazing mainly during the time of maximum photosynthesis
Planarian (Dugesia polychroa) predation on freshwater gastropod eggs depends on prey species, clutch morphology, and egg size
No full textFine-scale differences in diel activity among nocturnal freshwater planarias (Platyhelmithes: Tricladida)
No full textIndicator value of lotic water mites (Acari: Hydrachnidia) and their use in macroinvertebrate-based indices for water quality assessment purposes
Full text linkThe Water Framework Directive (WFD) of the European Union includes benthic macroinvertebrates for the ecological assessment of running waters. The invertebrate-based Star-ICMi index, adopted in 2010, does not include Hydrachnidia (water mites) in its complex formulation. However, Hydrachnidia are associated with many environmental variables and may be useful for stream ecological characterization. We have therefore assessed the bioindicator value of Hydrachnidia in streams of central Italy, and the ability of two mite-containing (the PTH and the newly formulated PTHfam indices) and four mite-excluding biotic indices (Star-ICMi, BMWP, ASPT, and IBE) to characterize 216 sites ranging from semipristine to impacted. Mite bioindicator value was high at family level. Index reliability was consistently low for the PTH and ASPT indices. Distribution of mite families across quality classes (QCs) was fully separated only for the PTHfam index. QC assignment remained reliable at high index values (i.e., at high ecological status) for the PTHfam and BMWP indices, while logarithmic correlations between the PTHfam and the other indices suggest that the latter may misrepresent sites in high, good, and moderate ecological status sensu WFD. Further studies on the PTHfam index are warranted in light of its simplicity, high reliability, and low sampling and taxonomic identification effort
Diversity, distribution and ecology of water mites (Acari: Hydrachnidia and Halacaridae) in high Alpine lakes (Central Alps, Italy)
No full textInformation on water mite assemblages from high elevation lentic biotopes is scant. A
survey of 14 small Alpine lakes located between1900 and 2400 m a.s.l. in Italy resulted in the
discovery of 17 species of Hydrachnidia and a single species of freshwater Halacaridae. Arrenurus
conicus and Lebertia tuberosa were the most widespread and abundant species; Lebertia sefvei,
Lebertia rufipes, Oxus setosus, Panisus torrenticolus and Sperchon glandulosus were also widely
distributed but relatively less abundant. Atractides fissus and Arrenurus conicus are recorded for the
first time from Italy. In contrast to mid/low elevation lakes and ponds, water mite assemblages of
alpine lakes are less diverse and are composed mainly of rheo- and crenobiontic taxa, most of which
are cold-stenothermic. Typical standing water dwellers represented only a small fraction (23%) of
the species sampled. A principal component analysis conducted on lake environmental variables
resulted in a clear separation of the lakes mainly based on ionic contents, pH and temperature.
Water mites seem to be less influenced by these factors than by temperature fluctuations and
habitat stability and heterogeneity. We conclude with some considerations of the influence of
abiotic and biotic factors on the altitudinal and latitudinal distribution pattern of water mites
Biodiversità e distribuzione degli acari acquatici (Acari, Hydrachnidia) nelle acque interne dell'Appennino centro-settentrionale
No full text- …
