The population density of Lymnaea columella (Say, 1817) (Mollusca, Lymnaeidae) an intermediate host of Fasciola hepatica (Linnaeus, 1758), in the Caparaó microregion, ES, Brazil / Densidade populacional de Lymnaea columella (Say, 1817) (Mollusca, Lymnaeidae) hospedeiro intermediário de Fasciola hepatica (Linnaeus, 1758) na Microrregião do Caparaó, ES, Brasil

Abstract The aim of this study was to monitor the population density of Lymnaea columella, an intermediate host of Fasciola hepatica, in various aquatic habitats and in drinking water in the area of the Instituto Federal de Educação, Ciência e Tecnologia do Espírito Santo, on Caparaó Microregion, municipality of Alegre, state of Espírito Santo, Brazil. Monthly samplings were performed at certain points between drainage areas and drinking water in cattle and goat production systems during the years 2010 to 2013. The mean temperature, precipitation and the frequency of samples of L. columella were analysed graphically according the monthly average during the study period. A total of 2,038 molluscs were collected, 1558 of which were L. columella, that predominated in all sampled points. The highest average of specimens observed for L. columella was in the years 2010 and 2013 (51.0), and occurred decreased in 2011 (19.8). The temperature and precipitation averaged is 23.7 °C and 141 mm/year, respectively. Rainfall peak occurred in March (2011, 2013) and November (2012), during these periods the population of L. columella growth. There was no significant difference in the relationship between the specimens observed with seasons (dry-wet), thus the population of L. columella remained stable and can be found throughout the year.

Resumo O objetivo deste estudo foi acompanhar a variação da densidade populacional de Lymnaea columella, hospedeiro intermediário de Fasciola hepatica, em diferentes tipos de coleções hídricas e bebedouros na área do Instituto Federal de Educação, Ciência e Tecnologia do Espírito Santo, na microrregião do Caparaó, município de Alegre, estado do Espírito Santo, Brasil. Foram realizadas coletas mensais em pontos determinados entre áreas de drenagem e bebedouros de animais nos setores de bovinocultura e caprinocultura durante os anos de 2010 a 2013. As médias de temperatura, precipitação e a frequência de exemplares de L. columella foram analisadas graficamente de acordo com a média mensal ao longo do período avaliado. Foram coletados 2.038 moluscos, sendo 1558 de L. columella, espécie predominante em todos os pontos amostrados. A maior média de espécimes observadas para L. columella foi nos anos de 2010 e 2013 (51,0), ocorrendo um decréscimo em 2011 (19,8). A temperatura apresentou média de 23,7°C e precipitação de 141 mm/ano. Picos de precipitação ocorreram em Março (2011, 2013) e Novembro (2012), nestes períodos foi observado aumento populacional de L. columella. Não houve diferença significativa na relação entre as espécimes observadas com as estações do ano (seca-chuvosa), dessa forma, a população de L. columella se mostrou estável, podendo ser encontrada durante todo ano.

The effect of isolation on the life-history traits of Pseudosuccinea columella (Pulmonata: Lymnaeidae)

A population of Pseudosuccinea columella was raised under laboratory conditions and its life tables were determined in isolated and paired snails. Isolated snails were significantly larger in shell size than paired snails from five weeks of age onward. Also, statistically significant differences were found for the number of eggs per mass per individual from week 5 to 9, isolated snails exhibiting the highest values. The intrinsic and finite rates of increase were greater in isolated than in paired snails. Either an inhibition of the reproductive output between individuals or the advantage of selfing may be the cause of the differences in this species, acting as a possible mechanism that increase the fitness of isolated snails

Rearing of Lymnaea columella (Say, 1817), intermediate host of Fasciola hepatica (Linnaeus, 1758)

The intermediate host of Fasciola hepatica, Lymnaea columella, collected in Belo Horizonte, Minas Gerais, Brazil, was reared in our laboratory. The aim of the current study was to standardize a rearing and maintenance technique. Two kinds of diet were tested: fresh lettuce (A) and rodent ration + 10 percent CaCO3 plus fresh lettuce (B). The age for the beginning of oviposition ranged from 27 to 57 days. Ten days after oviposition at 24.7§C, 100 percent eclosion occurred. The complete life cycle varied from 37 to 67 days. The average numbers of eggs per egg mass were 26.3 and 31.1 with diets (A) and (B), respectively. The lettuce and ration fed snails presented a increased growth although the difference was not statistically significant (p > 0.05). The mortality rate varied from 40 to 64 percent after 90 days. The maximum longevity was 183 days, 21.5 mm length and 11 mm wide. The methodology to mass breed and maintain these snails was found to be suitable in the laboratory.

Lymnaea cousini Jousseaume, 1887, from Ecuador (Gastropoda: Lymnaeidae)

A description is given of the shell, renal organ, reproductive system and radula of topotypic specimens of Lymnaea cousini Jousseaume, 1887. A diagnosis between it and four other lymnaeids which also occur in South America and were previously studied by the author (L. columella, L. diaphana, L. viatrix and L. rupestris) is presented.

Atraçäo miraxonal exercida por Biomphalaria straminea, Lymnaea columella e Physa sp, sobre miracídios de Schistosoma mansoni da linhagem BH / Miracidial atraction by Biomphalaria straminea, Lymnaea columella and physa sp upon miracidia of Schistosoma mansoni BH strain

Utilizando-se um artefato de vidro composto de duas câmaras unidas por um canal, testamos a atraçäo miraxonal exercida por Biomphalaria straminea, Lymnaea columella e Physa sp, sobre larvas de Schistosoma mansoni da linhagem BH. Os moluscos, ou suas águas de condicionamento (SCW), foram colocadas aleatoriamente em uma das câmaras, contendo o restante do artefato somente água declorada. Dez miracídios foram depositados no centro do canal. O comportamento dos miracídios foi observado por 15min. Foram feitas dez replicaçöes de cada experimento, utilizando-se espécimens de moluscos e miracídios diferentes. Verificou-se que todos os moluscos e suas SCW exerceram atraçäo miraxonal, sendo que Physa sp atraiu mais que Lymnaea columella. Foi isolado um único exemplar de B. straminea que exerceu efeito repulsivo sobre os miracídios de S.mansoni