Previous studies on the influence of abiotic factors on the distribution of bilharzia intermediate host snails of the family Planorbidae are reviewed. Much of this work is basically descriptive and relatively few attempts have been made to examine the effects of these factors on snails in their natural habitats - to identify the factors precisely and to measure their critical levels. An account is given of recent studies on Eiomphalaria pfeifferi (Krauss) in two climatically different regions of southeastern Africa, at 6S5m altitude on the eastern Transvaal escarpment and 19m on the coastal peneplain of northern Zululand. These have shown the species to undergo a similar annual life-cycle of three overlapping generations in both areas. Further, in these areas where the snail has a discontinuous distribution, two abiotic factors, stream geology and water temperature, were found to be important in limiting its distribution. The longitudinal distribution of B. pfeifferi and another host snail Bulinus (Physopsis) globosus (Morelat), extended upstream in a perennial watercourse, the Gladdespruit, on the escarpment only as far as permanently lentic habitats were available. These habitats, usually detached from the channel, characterized the stream's lowest physical zone with its substratum of exposed granite, as opposed to the sandy-bottomed lotic zones upstream. The limit of the snails' occurrence lay close to the junction of these two substratum types. Granite is resistant to erosion but contains soft inclusions which erode more quickly than the hard matrix causing uneven weathering. This results in the formation of depressions in the stream bed (i.e. pools, potholes and backwaters) which provide the permanently lentic conditions necessary for the snails' survival. Temperature recordings made on this plain, upstream of the snails' limit, suggest that the water temperature here exceeded the critical lower levels required for a positive intrinsic rate of natural increase sufficiently often to permit the species to survive here, though not optimally. Above this point however, current velocities are continually in excess of the maximum tolerated (0.3 m/sec.) so that in this situation at least, current velocity is a dominant factor. A contrasting situation exists on the coastal peneplain of northern Zululand where B. pfeifferi occurs in some lentic habitats and not in others. This discontinuous distribution is shown to be related to the prolonged duration of temperatures above the level for optimal increase. The apparently suitable habitats from which B. pfeifferi was absent were found to be both very shallow and to experience these prolonged high temperatures during spring and early summer. This corresponds to the maturation period of the B. pfeifferi 1st generation as defined by Appleton (1974) and causes reduced fecundity probably through impaired gonad development. The density of its filial (2nd) generation is correspondingly reduced. A statistically significant partial-correlation (at a 1% level) was found between the fecundity of the 1st generation and increasing periods of temperatures above the species' optimal limit in the habitats involved during its maturation period (spring). It is interesting to nate here that B. (Ph.) globosus, which is known to be better adapted to high temperatures than B. pfeifferi (Shiff & Husting, 1966) occurred in all the waterbodies concerned. Both these factors therefore play important roles in determining the country-wide distribution pattern of the host snails. This distribution is closely correlated with the availability of permanently lentic habitats. In river systems, which form the main environment for these snails, such stable habitats occur almost entirely in low-gradient reaches over hard bed-rock which is resistant to erosion. Current velocities above 0.3 m/sec. render steeper reaches and those over soft, non-resistant rock and sand (unstable substrata) unsuitable and therefore constitute a most important limiting factor. Temperature however becomes a dominant factor in permanently lentic waterbodies. Biomphalaria pfeifferi is adversely affected by high temperature regimes and where such regimes occur in waterbodies which are too shallow to permit temperature gradient to develop, the species cannot survive whereas B. (Ph.) globosus can do so. This intolerance of high temperature regimes on the part of B. pfeifferi accounts for the species' adoption of a discontinuous distribution over the coastal plain of south-eastern Africa. A comparable pattern has been reported for the species over this plain northwards to approximately 16°S latitude in Mozambique and is probably due to a similar high-temperature effect. Further northwards in equatorial latitudes B. pfeifferi is restricted to the more elevated and cooler areas above an altitude of 500 - 600 m, probably because the very high temperature regimes prevailing in the lowlands there exclude the species altogether.

Anguispira is a group of common land snails found primarily in eastern North America. There are currently thirteen species recognized within Anguispira. A considerable amount of morphological variation is seen within and among these species, which has lead to much taxonomic confusion within the group. Additionally, because Anguispira species descriptions are based almost exclusively on shell shape and color characteristics, identifying specimens to species is often problematic. In an attempt to delimit species and clarify relationships within Anguispira, regions of the mitochondrial cytochrome oxidase subunit I (cox1), 16S ribosomal RNA (rrnL), and cytochrome b (cob) genes were sequenced from ninety-three individuals representing eleven putative Anguispira species. Variation in shell morphology was also investigated using multivariate analyses of variance. Molecular analyses revealed two currently recognized species (A. alternata and A. cumberlandiana) to be polyphyletic. Evidence also suggested that A. columba, previously synonymized with A. mordax, should be recognized as A. columba and no longer remain synonymized. In addition, several individuals belonging to four strongly supported lineages (which are currently questionable/unidentified) could result in new species.

No description available.

No description available.

This study utilized freshwater mussel shells to assess the role of mercury contamination in the North Fork Holston River, an aquatic habitat affected by extensive extirpations of mussel populations starting in the early 1970's. Mussel shells (n=366) collected from 5 sites, upstream and downstream of Saltville (where mercury was used from 1950-1972) were analyzed to test if: (1) geochemical signatures of shells record variation in mercury levels relative to the contamination source; and (2) shell taphonomy could be used to differentiated affected and unaffected sites. Analysis of 40 shells for geochemical signatures using atomic absorption spectroscopy indicated a strong longitudinal pattern. Mercury content was as follows: upstream sites had low Hg concentrations (<5 to 31ppb), shells directly below Saltville had high concentrations (23-4,637ppb), shells 18km downstream of Saltville displayed intermediate values (7-115ppb), and those 38.4km downstream were comparable to upstream sites (<10ppb). Two pre-industrial shells collected from Saltville in 1917 also yielded Hg estimates (5-6ppb) comparable with upstream estimates. The Hg content was not correlated with shell length (r=-0.3; p=0.2) or degree of taphonomic alteration (r=0.18; p=0.28). Analysis of 366 shells for taphonomic signatures indicated that shells are most heavily altered and fragmented directly downstream of Saltville. In contrast, upstream sites, inhabited by reproducing mussel populations, contain many fresh-dead shells. Taphonomic signatures can thus be used to differentiate sites with different extirpation histories. Relic mussel shells can provide useful spatial and temporal data on Hg concentrations in polluted ecosystems and offer a tool for delineating areas with unknown extirpation histories. / Master of Science

The aim of the present study was to determine the potential impact of intertidal grazers on the distribution of macro algae on the south coast of South Africa. Particular attention was paid to the large patellid limpet, Patella oculus, which is found thoughout the intertidal zone. Studies of gut contents revealed that Patella oculus was capable of ingesting not only the thallus of foliose (eg. Ulva spp.) and encrusting coralline macroalgae, but also spores and diatoms. The inclusion of these relatively small particles in the diet was surprising, as electron micrographs of the radula of P.oculus revealed that it is typically docoglossan in structure. Such radulae are thought to be poorly suited for collecting small food particles. Sand made up a significantly higher proportion of the gut contents than other particles at all shore heights, which suggests that P.oculus might be capable of excavating the rocky substratum, or of sweeping up sand, while searching for food. Analysis of the gut contents of other local herbivorous molluscs, was also carried out. These species included the winkles, Oxystele variegata and O.sinensis, and the small pulmonate limpets, Siphonaria concinna, S.capensis, and S.serrata. The guts of all species contained mainly spores and diatoms, although small fragments of Ulva sp. were found. The population structure of Patella oculus was investigated at two sites, Cannon Rocks and Old Woman's River. At Cannon Rocks, mean shell length of low-shore animals was significantly lower than that of both mid- and high-shore animals, while at Old Woman's River, no significant difference was found among shore heights. A regression equation for In (shell length) vs In (dry weight) was calculated, and based on length data, the biomass density (g dry mass.m⁻²) of P.oculus at Old Woman's River was estimated. Values ranged from 2.8 on the low- and midshore to 0.37 on the high-shore. A manipulative field experiment was used to determine the impact of mesograzers and macrograzers (such as Patella oculus) on the distribution of intertidal macro algae on the mid- and low-shore at Old Woman's River. Grazers were excluded using mesh cages (mesh size = 3mm), in two separate experiments, one in winter and the other in spring. Percentage cover of macroalgal species and sessile invertebrates was estimated at approximately 6 week intervals for up to 3 months. MANOV A showed that treatments did not significantly affect cover of macroalgae or barnacles during winter. However, towards the end of the spring experiment (midshore only) cover of barnacles and green foliose turfs did increase in those plots from which mesograzers and/or macro grazers were excluded. The failure of the statistical tests to detect significant differences at some time intervals may have been caused by high levels of variation among replicates. This suggests that factors other than grazing are of overriding importance in determining the distribution of local macroalgae. The existence of a possible symbiotic relationship between Patella oculus and the red foliose alga, Gelidium pristoides, was investigated. The availability of various substratum types, including rock, limpet shells, barnacles etc., and the proportion of the total cover of G.pristoides on each, was calculated. It was shown that a significantly higher proportion of the alga grew on limpet shells, although the availability of this substratum type was low. It is thought that the aggressive behaviour of P.oculus prevents all but juvenile Patella longicosta from grazing on its shell, thus providing a refuge from grazing for G.pristoides.

Endocrine disrupting compounds (EDCs) together with potentially toxic metals (PTMs), are present in large amounts in sewage sludge which was used as a tool to expose terrestrial molluscs to environmental concentrations of these pollutants. Pastures fertilised with sewage sludge had significantly fewer adult slugs collected per replicate (C: 58.4; T: 26.2; S.E.D. 0.14; p&lt;.05) and eggs (C: 16.6; T: 9.1; S.E.D. 0.17; p&lt;0.05).  No differences with treatment, in tissue concentrations of EDCs or PTMs or in hepatopancreas or gonad structure, were detected.  However, hepatopancreatic proteins (cyclophilin, paramyosin and trypsin) were significantly altered (p&lt;0.01). In a laboratory study, exposure, via feed, to 0x (Control), 1x (T1), 10x (T2) or 110x (T3) the environmental dose of sludge extract resulted in a dose-related increase in mean mortality rates (relative to controls) in adult slugs (<i>Deroceras reticulatum</i>).  Exposure for 3 weeks induced no measurable differences in tissue pollutant concentrations or hepatopancreas or gonad histology. Fewer slug eggs exposed to sludge and/or dehydration (2x2; 10 eggs/replicate); hatched following sludge exposure (C hydrated 64.5%;T hydrated 24.5%; p&lt;0.05; S.E.D. 2.169; C dehydrated 48.9%; T dehydrated 17.4%; p&lt;0.05; S.E.D. 4.256) but not following dehydration.  There was no significant interaction between sludge exposure and dehydration but survival was lowest in animals exposed to both. Slug behaviour was affected by exposure to sludge, including increasing avoidance and huddling behaviours. The results indicate that terrestrial molluscs may be used as invertebrate sentinels to assess the effects of ECD and PTM exposure.

Slugs are major pests of oilseed rape and wheat. Current chemical control measures often do not give adequate protection to plants, and pose an environmental hazard. Laboratory experiments investigated the potential of seed treatments to control slug damage in oilseed rape. Four compounds: metaldehyde, methiocarb, cinnamamide and 3,5-dimethoxycinnamic acid (DMCA) were tested for phytotoxicity and ability to reduce damage. Metaldehyde and methiocarb seed treatments protected seedlings as well as or better than baited pellets. A broad-spectrum insecticide imidacloprid was tested as a seed treatment to control slug damage to oilseed rape and winter wheat in laboratory experiments. Imidacloprid did not reduce slug damage to oilseed rape at any dose or to wheat at low doses. Higher doses of imidacloprid on winter wheat significantly reduced slug damage. In a field experiment with winter wheat, imidacloprid seed treatments reduced slug damage to a lower level than bait pellets but had inconsistent and short lived activity. The most promising seed treatments, metaldehyde and methiocarb, were tested in semi-field trials and found to have a reduction in efficacy in comparison to laboratory trials. To determine why field efficacy was reduced, seedlings were grown under a range of environmental conditions. The metaldehyde content of seedlings was measured using a novel method of GC-FID analysis. Data suggested that reduced field efficacy results from microbial breakdown and/or loss of active ingredient caused by percolating soil water. Once seedlings had emerged, neither volatalization nor simulated rainwater reduced the metaldehyde content of seedlings. New seed treatment formulations were developed and tested in 3 mini-plot trials on oilseed rape and wheat. In 2 of the mini-plot trials the industry-produced metaldehyde seed treatment protected seeds and seedlings, as well as bait pellets. In the third mini-plot trial, very heavy rainfall at sowing resulted in only bait pellets successfully reducing slug damage.

A educação em ciências é uma prática social que vem sendo cada vez mais ampliada e desenvolvida e, nesse aspecto, os museus ganham destaque como locais de divulgação e de educação não formal. Neste sentido, é evidente a atual e gradual mudança que a natureza e o papel educacional dos museus vêm sofrendo, o que leva a questionar os pressupostos teóricos e práticos que fundamentaram e fundamentam as ações em educação não formal nesses locais. Assim, tendo em vista a fundamentação do trabalho de divulgação que o Laboratório de Malacologia do Instituto de Biociências da USP inicia, pretendia-se verificar como os moluscos são abordados nas exposições de dois museus universitários de ciências, discutindo algumas abordagens científicas, comunicacionais e museológicas que norteiam a práxis expositiva desses locais. Para tanto, optou-se por uma abordagem metodológica qualitativa por meio de dois instrumentos de pesquisa: observação com registros escritos e fotográficos e análise documental. A análise das abordagens científicas indicou que as duas instituições apresentam temáticas expositivas condizentes com os objetivos a que se propõem, ou seja, divulgar a pesquisa que ali é feita e, no caso do Museu de Zoologia, discutir também as idéias dominantes na Zoologia. Os textos, por sua vez, aparecem predominantemente na forma de impressos, cada instituição apresentando padrões de diagramação diferentes e conseqüentemente levantando questões diferentes. Com relação ao discurso empregado, fica evidente que o texto apresentado é um híbrido de diversas categorias de discurso. Por fim, as exposições revelaram corresponder preponderantemente ao tipo Educativas descrito por DEAN (2003), fazendo amplo uso de objetos reais embora estes estivessem sempre distantes do visitante e com função geralmente de ilustração. Quanto aos níveis de interatividade descritos por WAGENSBERG (2000), chama atenção o fato de nenhum dos museus trabalharem os três níveis, e a interatividade mental, única trabalhada pelos dois museus, sendo timidamente explorada. / Science Education is a growing and developing social practice and, in this respect, museums have gained prominence as places for doing public communication of science and non-formal education. In this sense, the nature and educational role of museums are clearly suffering gradual changes, what leads to questions about the theoretical and practical pre-assumptions that formed and still form the basis for actions in non-formal education occurring in these places. Thus, having in mind the fundamentals of the science communication work that the Malacology Lab (Institute of Biosciences-USP) has begun, the intention was to verify how mollusks are approached in the exhibitions of two universitary science museums, discussing some of the scientific, communicative and museological approaches that guide the expositive praxis of these places. For doing so, a qualitative methodological approach by means of two research instruments was chosen: observation, producing written and photographic records, and documental analysis. The analyses of scientific approaches indicated that both institutions have expositive subjects that meet their objectives of divulging the research they do and, in the case of the Zoology Museum, of discussing the dominant ideas in Zoology. The texts, in turn, appear predominantly as printouts, with each institution presenting different diagramming patterns and, consequently, bringing up different questions. As for the discourse used, it is clear that the text presented is a hybrid of several discourse categories. Finally, the exhibitions showed to be predominantly of the Educative type as described by Dean (2003), making wide use of real objects even though these were always far from the visitors and used for illustrative purposes. As for the levels of interactivity described by Wagensberg (2000), what calls the attention is the fact that none of the museums works all three existing levels and the only one worked by both museums, mental interactivity, is timidly explored.

Orientador: Carmem Silvia Fontanetti Christofoletti / Banca: Gisela de Aragão Umbuzeiro / Banca: Juliana da Silva / Banca: Denis Moledo de Souza Abessa / Banca: Maria Izabel Souza Camargo / Resumo: O estuário de Santos já foi um exemplo de degradação ambiental, porém medidas dos órgãos responsáveis pelo saneamento ambiental resultaram em melhoria na qualidade das águas, mas os sedimentos e a biota continuam contaminados. Os moluscos bivalves são bons bioindicadores de poluição ambiental, devido a seu hábito séssil e filtrador, e à capacidade de acumular diversas substâncias. Mytella falcata é uma espécie comum em regiões tropicais, encontrada semi-enterrada no sedimento, podendo fornecer dados sobre as condições do mesmo. Neste trabalho, bivalves da espécie Mytella falcata residentes em três pontos do estuário de Santos com diferentes níveis substâncias potencialmente poluidoras, foram analisado a fim de caracterizar a população residente nestes pontos. As técnicas utilizadas foram o ensaio do cometa, o teste do micronúcleo e a análise histopatológica das brânquias, incluindo técnicas histoquímicas, ultramorfológica e ultra-estrutural. As análises demonstraram que a espécie pode ser para avaliar danos genotóxicos, mutagênicos e citotóxicos. Utilizando o ensaio do cometa os indivíduos dos pontos B e C mostraram níveis significativamente maiores de danos ao DNA quando comparados aos animais do ponto A. Quanto a análise dos micronúcleos os animais de todos os pontos apresentaram resposta muito semelhante. A morfologia dos filamentos branquiais desta espécie mostrou-se muito similares a de espécies próximas e na análise histopatológica foram observadas alterações nos pontos B e C; as principais foram o desprendimento do epitélio da região lateral do filamento, modificação na morfologia deste epitélio, aumento na produção de muco e processos envolvidos na eliminação de células e renovação das mesmas. Os dados obtidos mostraram que todas as técnicas resultaram no diagnóstico de que os animais residentes no ponto... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The Santos estuary which is located in São Paulo, Brazil, was considered one of the major examples of coastal degradation. Nowadays the quality of this environment has improved, but the sediment and the biota are still contaminated. Bivalve mollusks are sedentary, filter-feeding invertebrates that have been widely used to monitor aquatic habitats. Mytella falcata is very common in tropical areas and lives buried in the sediment. In this study, the mussel Mytella falcata, from three sites of Santos estuary, were analyzed; the three sites presented different levels of harmful substances. The aim of this analysis was to characterize the animals that live in this area. The techniques applied were the comet assay, micronucleus test and histopathological analysis of the gill filaments, including the histochemistry and scanning and transmission electron microscopy. Laboratory tests demonstrated that the species can be used as bioindicator. The analyzed specimens from sites B and C, showed higher levels of DNA damage when compared to those from site A. The micronucleus test presented no difference between the three sites. Mytella falcata gill filaments showed high similarity to other Mytilidae species. The histopathological analysis demonstrated some alterations in sites B and C. The major alterations were the detachment of epithelial cells from the lateral surface, changes in the morphology of this epithelium, increase in mucous production and processes involved in cell elimination and renovation. The damages found in animals from sites B and C were considered as adaptations to the exposition to pollutants. The lack of difference between animals from sites B and C were related with the distance between animals and sediment. In conclusion, this study confirm that sediments act as a deposition site for pollutants and alert the authorities for the manner of dealing with this sediment... (Complete abstract click eletronic access below) / Doutor