998 resultados para 060808 Invertebrate Biology


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The Nyirkai-Hany wetland reconstruction area in northwestern Hungary is now designated as a Ramsar and a Natura 2000 site. It was created in 2001–2002 by the Fertő-Hanság National Park Directorate to restore a part of the formerly drained large wetland called Hanság and to offer waterbirds a suitable habitat for feeding and breeding. We focused on this aim of the restoration project and studied the temporal and spatial variation in abundance of birds and their invertebrate prey in this newly created wetland. From April 2007 until May 2008, we sampled plankton, nekton and benthos of different habitats monthly and monitored waterbirds weekly on the three different areas of the Nyirkai-Hany. During our investigations, 135 invertebrate and 53 waterbird species were recorded. Benthos and macrophyte decomposition accelerating guilds were the most abundant waterbird guilds—besides the dominant grazing importer material transporter guild, represented primarily by geese—in the Nyirkai-Hany. Zooplankton assemblages primarily consisted of small species not easily used as a food by planktivorous waterbirds. The low density of zoobenthic biomass and the small extent of shallow water mudflats probably accounted for the scarcity of the bioturbing guild group of birds. Nektonic biomass varied greatly among locations having different vegetation types, was greatest in the shallow water areas dominated by Typha, Carex and Phragmites species and lowest at offshore vegetation-free sites. Chironomids, mayflies and odonates were especially abundant and their biomass significantly correlated with several waterbird species, mainly belonging to the macrophyte decomposition accelerating guild (e.g. Anas platyrynchos, Fulica atra). This guild itself, which has increased in abundance in recent years, showed an exceptionally strong correlation with odonate abundance. These results indicate the growing importance of the Nyirkai-Hany wetland area as a foraging site for waterbirds.

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The biology of three landlocked and a riverine population of Galaxias maculatus were examined in western Victoria, Australia. All systems supported reproducing populations of these fish, including Lake Corangamite which had salinities that on occasion reached 82. Spawning sites in Lake Corangamite were located in adjacent tributaries and not in the main lake as was the case for other populations. The smallest fish were found in the fresh water Lake Purrumbete and the largest in the hypersaline Lake Corangamite. The size at which 50% of the population attained sexual maturity varied across sites, with fish maturing at a smaller size in Lake Purrumbete, followed by the Merri River, Lake Bullen Merri and Lake Corangamite. Condition was higher in the freshwater Lake Purrumbete and there was no relationship between condition and temperature, conductivity, turbidity and pH; but there was a positive relationship between condition and dissolved oxygen. Length frequency analysis suggested that the majority of fishes live for a year.

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Endemic asp, Aspius vorax, from the middle section of the Euphrates River flowing through eastern Syria were studied to determine the main characteristics of their population structure, morphological parameters and reproductive biology. Samples ranged between 0+ and 4+ years of age and were dominated by 2+ years old group. Total length (TL) ranged between 19 and 70 cm corresponding with 46 to 2824.5 g weight, respectively. Fish growth has isometric pattern and the overall sex ratio was unbiased. Seasonal changes in the condition factor were related with the water temperature as well as the spawning season. Annual cycle of gonadosomatic index (GSI) readings indicated that spawning season occur around March when fish longer than 36 cm can mate. Average pre-spawning GSI was greater in individuals older than 2 years. Meanwhile, female fecundity was highly related to TL and weight. These findings did not always concur with previous observations from other asp populations, mainly in southern and northern Mesopotamia. Our results highlighted basic biological aspects of the local population and indicated differences between populations which can assist in fisheries management, conservation and commercial culture of the investigated species.

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The structure and function of agricultural stream reaches with sparse riparian and floodplain vegetation differ from those of forested reaches, but may be ‘reset’ as these streams flow through reaches with forested riparian zones. We investigated whether invertebrate colonisation of River Red Gum (Eucalyptus camaldulensis) leaf packs in lowland intermittent streams was influenced by the adjacent reach-scale landuse (cleared farmland or forested reserve) within an agricultural catchment in Victoria, Australia. Further, we examined the influence of seasonal changes in hydrology and associated changes in abiotic conditions on the colonisation of leaves by repeating experiments over two summers and one spring. Across these experiments, there were no consistent differences in the structure of communities that colonised leaves in farmland and reserve reaches. In both seasons, most leaf colonists were collectors and few were shredders in both farmland and reserve reaches. Relative abundances of gastropod grazers were much higher in summer than in spring. The structure of invertebrate communities colonising leaves in the different reaches converged over time when streams flowed in spring, but diverged over time as the streams dried and abiotic conditions within disconnected pools became increasingly harsh in summer. Thus, patterns of leaf pack colonisation were influenced by the regional climate causing large seasonal changes in hydrology, but not by reach-scale landuse. The large-scale disturbances of agricultural landuse across the catchment and a supra-seasonal drought probably contributed to low diversities of invertebrate communities in the streams.

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We present four case studies of the literature discussing the effects of physical forces on biological function. While the field of biomechanics has existed for many decades, it may be considered by some a poor cousin to biochemistry and other traditional fields of medical research. In these case studies, including cardiovascular and respiratory systems, we demonstrate that, in fact, many systems historically believed to be controlled by biochemistry are dominated by biomechanics. We discuss both the previous paradigms that have advanced research in these fields and the changing paradigms that will define the progressions of these fields for decades to come. In the case of biomechanical effects of flowing blood on the endothelium, this has been well understood for decades. In the cases of platelet activation and liquid clearance from the lungs during birth, these discoveries are far more recent and perhaps not as universally accepted. While only a few specific examples are examined here, it is clear that not enough attention is paid to the possible mechanical links to biological function. The continued development of these research areas, with the inclusion of physical effects, will hopefully provide new insight into disease development, progression, diagnosis and effective therapies.

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1We censused ectoparasite populations of adult and nestling swifts over the course of the host's breeding season. Nearly all of the birds were infested with chewing lice and two-thirds of the nests were infested with louse flies. Feather mites were observed but not quantified.2Lice and louse flies both showed aggregated distributions among hosts. Louse eggs, hatched lice and adult louse flies had negative binomial distributions, whereas the aggregated distribution of louse fly pupae was not adequately described by negative binomial or Poisson models.3Transmission of lice from parents to offspring was documented. A comparison of the age structure of lice on parents and offspring indicated that most transmission was by nymphal lice.4Host reproductive success and survival appeared to be independent of the number of lice or louse flies. Neither parasite correlated with the number, body mass, or date of fledging of young birds, nor with the overwinter survival of adults. We caution, however, that experimental manipulations of parasite load are required for a definitive test of the impact of ectoparasites on evolutionary fitness components.

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Relatively little is known about the biology and ecology of the world’s largest (heaviest) bony fish, the ocean sunfish Mola mola, despite its worldwide occurrence in temperate and tropical seas. Studies are now emerging that require many common perceptions about sunfish behaviour and ecology to be re-examined. Indeed, the long-held view that ocean sunfish are an inactive, passively drifting species seems to be entirely misplaced. Technological advances in marine telemetry are revealing distinct behavioural patterns and protracted seasonal movements. Extensive forays by ocean sunfish into the deep ocean have been documented and broad-scale surveys, together with molecular and laboratory based techniques, are addressing the connectivity and trophic role of these animals. These emerging molecular and movement studies suggest that local distinct populations may be prone to depletion through bycatch in commercial fisheries. Rising interest in ocean sunfish, highlighted by the increase in recent publications, warrants a thorough review of the biology and ecology of this species. Here we review the taxonomy, morphology, geography, diet, locomotion, vision, movements, foraging ecology, reproduction and species interactions of M. mola. We present a summary of current conservation issues and suggest methods for addressing fundamental gaps in our knowledge.

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Human impacts through habitat destruction, introduction of invasive species and climate change are increasing the number of species threatened with extinction. Decreases in population size simultaneously lead to reductions in genetic diversity, ultimately reducing the ability of populations to adapt to a changing environment. In this way, loss of genetic polymorphism is linked with extinction risk. Recent advances in sequencing technologies mean that obtaining measures of genetic diversity at functionally important genes is within reach for conservation programs. A key region of the genome that should be targeted for population genetic studies is the Major Histocompatibility Complex (MHC). MHC genes, found in all jawed vertebrates, are the most polymorphic genes in vertebrate genomes. They play key roles in immune function via immune-recognition and -surveillance and host-parasite interaction. Therefore, measuring levels of polymorphism at these genes can provide indirect measures of the immunological fitness of populations. The MHC has also been linked with mate-choice and pregnancy outcomes and has application for improving mating success in captive breeding programs. The recent discovery that genetic diversity at MHC genes may protect against the spread of contagious cancers provides an added impetus for managing and protecting MHC diversity in wild populations. Here we review the field and focus on the successful applications of MHC-typing for conservation management. We emphasize the importance of using MHC markers when planning and executing wildlife rescue and conservation programs but stress that this should not be done to the detriment of genome-wide diversity.