Search results for "Seasons"
showing 10 items of 361 documents
Human fascioliasis in Argentina: retrospective overview, critical analysis and baseline for future research
2010
Abstract In Argentina, human fascioliasis has never been adequately analysed, although having a physiography, climate, animal prevalences and lymnaeids similar to those of countries where the disease is endemic such as Bolivia, Peru and Chile. We performed a literature search identifying 58 reports accounting for 619 cases, involving 13 provinces, their majority (97.7%) from high altitudes, in central mountainous areas and Andean valleys, concentrated in Cordoba (430 cases), Catamarca (73), San Luis (29) and Mendoza (28), the remaining provinces being rarely affected. This distribution does not fit that of animal fascioliasis. Certain aspects (higher prevalence in females in a local survey,…
Seasonal dynamics of egg laying and egg-laying strategy of the ectoparasite Argulus coregoni (Crustacea: Branchiura).
2004
Substrate preferences, spatial aggregation patterns and seasonal dynamics in the egg laying of ectoparasiticArgulus coregoniwere studied at a commercial fish farm in Finland. Pilot experiments showed thatA. coregonifemales selected specific types of substrates for egg laying. Significantly moreA. coregonieggs were laid on dark substrates than on light ones suggesting the use of visual cues. Therefore, egg-laying plates of dark colour were constructed for further experiments. MostA. coregonieggs were deposited in locations in shadow and in the deepest water in a 2 m deep farming canal. Relatively more eggs were laid on bottom stones situated near each egg-laying trap than on artificial egg-l…
Response of an arctic predator guild to collapsing lemming cycles
2012
6 pages; International audience; Alpine and arctic lemming populations appear to be highly sensitive to climate change, and when faced with warmer and shorter winters, their well-known high-amplitude population cycles may collapse. Being keystone species in tundra ecosystems, changed lemming dynamics may convey significant knock-on effects on trophically linked species. Here, we analyse long-term (1988-2010), community-wide monitoring data from two sites in high-arctic Greenland and document how a collapse in collared lemming cyclicity affects the population dynamics of the predator guild. Dramatic changes were observed in two highly specialized lemming predators: snowy owl and stoat. Follo…
Seasonal changes in predator community switch the direction of selection for prey defences
2014
Insect communities consist of aposematic species with efficient warning colours against predation, as well as abundant examples of crypsis. To understand such coexistence, we here report results from a field experiment where relative survival of artificial larvae, varying in conspicuousness, was estimated in natural bird communities over an entire season. This takes advantage of natural variation in the proportion of naive predators: naivety peaks when young birds have just fledged. We show that the relative benefit of warning signals and crypsis changes accordingly. When naive birds are rare (early and late in the season), conspicuous warning signals improve survival, but conspicuousness b…
Whole-lake experiments reveal the fate of terrestrial particulate organic carbon in benthic food webs of shallow lakes
2014
Lake ecosystems are strongly linked to their terrestrial surroundings by material and energy fluxes across ecosystem boundaries. However, the contribution of terrestrial particulate organic carbon (tPOC) from annual leaf fall to lake food webs has not yet been adequately traced and quantified. In this study, we conducted whole-lake experiments to trace artificially added tPOC through the food webs of two shallow lakes of similar eutrophic status, but featuring alternative stable regimes (macrophyte rich vs. phytoplankton dominated). Lakes were divided with a curtain, and maize (Zea mays) leaves were added, as an isotopically distinct tPOC source, into one half of each lake. To estimate the …
Plants in the UK flower a month earlier under recent warming.
2022
Global temperatures are rising at an unprecedented rate, but environmental responses are often difficult to recognize and quantify. Long-term observations of plant phenology, the annually recurring sequence of plant developmental stages, can provide sensitive measures of climate change and important information for ecosystem services. Here, we present 419 354 recordings of the first flowering date from 406 plant species in the UK between 1753 and 2019 CE. Community-wide first flowering advanced by almost one month on average when comparing all observations before and after 1986 ( p < 0.0001). The mean first flowering time is 6 days earlier in southern than northern sites, 5 days earlier…
High Diversity of the Viral Community from an Antarctic Lake
2009
Viruses are the most abundant biological entities and can control microbial communities, but their identity in terrestrial and freshwater Antarctic ecosystems is unknown. The genetic structure of an Antarctic lake viral community revealed unexpected genetic richness distributed across the highest number of viral families that have been found to date in aquatic viral metagenomes. In contrast to other known aquatic viromes, which are dominated by bacteriophage sequences, this Antarctic virus assemblage had a large proportion of sequences related to eukaryotic viruses, including phycodnaviruses and single-stranded DNA (ssDNA) viruses not previously identified in aquatic environments. We also o…
Using genetic markers to unravel the origin of birds converging towards pre-migratory sites
2018
AbstractIdentifying patterns of individual movements in spatial and temporal scales can provide valuable insight into the structure of populations and the dynamics of communities and ecosystems. Especially for migrating birds, that can face a variety of unfavorable conditions along their journey, resolving movements of individuals across their annual cycle is necessary in order to design better targeted conservation strategies. Here, we studied the movements of a small migratory falcon, the Lesser Kestrel (Falco naumanni), by genetically assigning feathers from individuals of unknown origin that concentrate in large roosts during the pre-migratory period. Our findings suggest that birds fro…
Insensitivity of Tree-Ring Growth to Temperature and Precipitation Sharpens the Puzzle of Enhanced Pre-Eruption NDVI on Mt. Etna (Italy)
2017
On Mt. Etna (Italy), an enhanced Normalized Difference in Vegetation Index (NDVI) signature was detected in the summers of 2001 and 2002 along a distinct line where, in November 2002, a flank eruption subsequently occurred. These observations suggest that pre-eruptive volcanic activity may have enhanced photosynthesis along the future eruptive fissure. If a direct relation between NDVI and future volcanic eruptions could be established, it would provide a straightforward and low-cost method for early detection of upcoming eruptions. However, it is unclear if, or to what extent, the observed enhancement of NDVI can be attributed to volcanic activity prior to the subsequent eruption. We conse…
Identification of sapovirus infection among Japanese infants in a day care center.
2005
A total of 921 fecal specimens collected from 44 infants in a day care center in Tokyo, Japan during June 1999 to July 2000 were tested for the presence of sapovirus by reverse transcription-polymerase chain reaction (RT-PCR). Of 88 fecal specimens from infants with acute gastroenteritis, 2.3% (2) were found to be positive for sapovirus. Twenty-two of 833 (2.6%) fecal specimens collected from asymptomatic infants were also infected with this virus. Another interesting feature was the demonstration of high incidence of sapovirus infection (95.5%, 21 of 22) identified in a single day care center, which was not due to viral shedding after the latest acute gastroenteritis. Sapovirus was subject…