971 resultados para Evolutionary ecology


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Six species of spiny lobsters of the genus Panulirus have been recorded in Ceylon waters. It is clear, therefore, that species dominance and ecological separation in the genus Panulirus is demonstrable and that the separation is dependent on the particular ecological preferences of the different species. In order to determine the factors governing the ecological separation, it was decided to make a detailed study of the environments in which the different species were found. Diving operations constituted the chief method of investigation. However, information was also obtained from commercial skin-divers, trap fishermen, bottom-set net fishermen and trawling operations. The period of investigations extended from 1962-1968.

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The Austrian-Ceylonese hydrobiological mission studied 38 biotopes; 28 of which contain Odonata. From the Zygoptera the Calopterydoidea seem to be the dominant form (22 habitats), while the Coenagrionoidea are scarcer (11 habitats). The most frequent species was Euphaea splendens (Epallagidae - 16 habitats) followed by Vestolis apicalis nigrescens (Calopterygidae, 8 habitats) and Neurobasis chinensis (Calopterygidae, 6 habitats). From the Anisoptera Zygonyx ceylanica (Libellulidae: Zygonictinae) was the dominant form (8 habitats), but some Libellulinae remain undescribed. The number of species varied greatly between different biotopes. The biotopes containing Odonata are small brooks, in which the pH was mostly on the limit between acid and alkaline reaction. They are fast running waters, situated in most cases on lower or middle elevations, only three species being found in higher elevations (1800-2000 m). Adaptations to fast currents and other factors are described.

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The survey covered by this report was undertaken between 6 th and 9th October 2009 as a follow-up on the during construction surveys of the Bujagali Hydropwer Project (BHPP). In addition to two pre-construction baseline surveys in April 2000 and April 2006, four monitoring surveys have so far been undertaken i.e. in September 2007, April 2008, April 2009 and the present one, in October 2009. The 2009 biannual monitoring surveys were conducted at an upstream and a downstream transect of the BHPP with emphasis on the following aspects: 1. water quality determinants 2. biology and ecology of fishes and food webs 3. fish stock and fish catch including economic aspects of catch and 4. sanitation/vector studies (bilharzias and river blindness)

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The result reported were from a monitoring survey no.8 undertaken between 6th and 10th April 2011 during construction period of the Bujagali Hydropwer Project (BHPP). Two pre-construction, baseline surveys in April 2000 and April 2006 were conducted and so far,durin construction phase of the project, seven monitoring surveys have been undertaken i.e. in September 2007, April 2008, April 2009,October 2009, April 2010, September 2010 and the present one, in April 2011. Since 2009 biannual monitoring surveys have been conducted at an upstream and a downstream transect of the BHPP with emphasis on the following aspects: Water quality determinants Biology and ecology of fishes and food webs Fish stock and fish catch including economic aspects of catch and Sanitation/vector studies (bilharzias and river blindness)

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Forty chromosome-specific paint probes of the domestic dog (Canis familiaris, 2n = 78) were used to delineate conserved segments on metaphase chromosomes of the American mink (Mustela vison, 2n = 30) by fluorescence in situ hybridisation. Half of the 38 canine autosomal probes each painted one pair of homologous segments in a diploid mink metaphase, whereas the other 19 dog probes each painted from two to five pairs of discrete segments. In total, 38 canine autosomal paints highlighted 71 pairs of conserved segments in the mink. These painting results allow us to establish a complete comparative chromosome map between the American mink and domestic dog. This map demonstrates that extensive chromosome rearrangements differentiate the karyotypes of the dog and American mink. The 38 dog autosomes could be reconstructed from the 14 autosomes of the American mink through at least 47 fissions, 25 chromosome fusions, and six inversions. Furthermore, comparison of the current dog/mink map with the published human/dog map discloses 23 cryptic intrachromosomal rearrangements in 10 regions of conserved synteny in the human and American mink genomes and thus further refined the human/mink comparative genome map. Copyright (C) 2000 S. Karger AG, Basel.

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Cross-species painting (fluorescence in situ hybridization) with 23 human (Homo sapiens (HSA)) chromosome-specific painting probes (HSA 1-22 and the X) was used to delimit regions of homology on the chromosomes of the golden mole (Ghrysochloris asiaticus) and elephant-shrew (Elephantulus rupestris). A cladistic interpretation of our data provides evidence of two unique associations, HSA 1/19p and 5/21/3, that support Afrotheria. The recognition of HSA 5/3/21 expands on the 3/21 synteny originally designated as an ancestral state for all eutherians. We have identified one adjacent segment combination (HSA2/8p/4) that is supportive of Afroinsectiphillia (aardvark, golden mole, elephant-shrew). Two segmental combinations (HSA 10q/17 and HSA 3/20) unite the aardvark and elephant-shrews as sister taxa. The finding that segmental syntenies in evolutionarily distant taxa can improve phylogenetic resolution suggests that they may be useful for testing sequence-based phylogenies of the early eutherian mammals. They may even suggest clades that sequence trees are not recovering with any consistency and thus encourage the search for additional rare genomic changes among afrotheres.

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< p > The past population dynamics of four domestic and one wild species of bovine were estimated using Bayesian skyline plots, a coalescent Markov chain Monte Carlo method that does not require an assumed parametric model of demographic history. Four dom

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Identification of conserved genomic regions within and between different genomes is crucial when studying genome evolution. Here, we described regions of strong synteny conservation between vertebrate deuterostomes (tetrapods and teleosts) and invertebrat

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This study deals with seasonal variations, natural correlations and similarities of fouling assemblages on exposure panels in the Suez Bay during January 1992 to January 1993. Three main sources of pollutions flow into the bay; industrial waste products, domestic drainage of Suez city and ships' oil and refuse.The fouling assemblages on the test pan els after various periods (1, 2 and 3 months) belonged mainly to the algae (Ulva rigida), polychaetes (Hydroides elegans), Cirripedes (Balanus amphitrite) and amphipods. The fouling at the lst station was relatively more dense than at the 2nd station during the summer and autumn seasons. The lowest productivity was achieved at the 3rd station which was considered less polluted being offshore water. The overall paucity of fouling in the bay is because of the silt covering the submerged surfaces, particularly at the 2nd station, leading to the prevention of the settlements or establishment of fouling organisms. The seasonal changes in the intensity of fouling assemblages on submerged surfaces in seawater seems to be closely related to seasonal variations in water temperature. The great fouling communities on the buoys and long exposure panels showed a remarkable variety of species and density rather than on short term exposures, which were more dense during warmer months.

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The bed Shakla, comprising an average area of 75.0 ha is located in the northeastern region (Brahmanbaria district) of Bangladesh. The study was carried out to assess the ecological aspects of bed ecosystem. Surface run-off and increase inflow of rain water from the upper stretch during monsoon cause inundation and resumption of connection between beel and parent rivers. The range of dissolved oxygen (DO) content ( 4.5-8.9 mg/L) was found congenial for aquatic life. pH was in the alkaline range (7.3-8.5) and free C02 was reletavely high. Lower values of total hardness and total alkalinity indicated less nutrients in the beel water. A wide variation (1.4-27.2 x 103 ceHs/L) in the standing crop of total plankton was recorded during study period of which phytoplankton alone contributed about 90%. Phytoplankton diversity in the beel represented by three groups viz. Chlorophyceae, Myxophyceae and Bacillariophyceae in order of abundance. A total of 52 fish species belonging to 36 genera, 20 families and 1 species of prawn were identified so far from the beel. About l3 types of fishing method were found in operation. Seine nets (moshari berja, ghono berjal) and gill net (current jal) were identified as detrimental gear killing juveniles of different species during post spawning period. Kua fishing was also found harmful due to dewatering nature. A total of 11 species belonging to 11 genera and 10 families of aquatic weeds were identified from the beet The eggs of Macrobrachium Jamarrei were identified into the Najas najas vegetation during April-September.

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Geo-morphology, ecology and fish production of the 92 rivers of Rajshahi division have been presented in this paper. Fifteen rivers are dead and 11 rivers have severe erosion problem. Siltation has increased in 66 rivers and depth has decreased in 11 rivers. Sixty nine rivers are suffering from low flow conditions. Fish diversity has decreased in 20 rivers while fish production has declined in 75 rivers. A total of 31 fish species have extinct, 25 species are under threat of extinction and 43 species have low production. Siltation and pollution are the major causes of fish habitat loss. Recommendations are made to protect and conserve fish habitat and riverine fisheries of Rajshahi division.