ABSTRACT
We examined aspects of the population ecology of the gastropod Stramonita haemastoma at Ilhéus, Bahia, Brazil. We collected monthly from October 2007 through September 2008 on a sandstone bank 1.5 km long, on which two points and two sampling levels were defined. We took five previously randomised replicates at each level, using a square enclosing an area of 0.0625 m². The snails were photographed, counted, and measured at the site. Both recruits and other individuals in the population preferentially inhabit the regions closer to the lower shore, where they are submerged for longer periods and are less subject to physiological stresses caused by temperature variation and desiccation. The cracks and holes in the bank serve as refuges and places for S. haemastoma to lay their egg capsules. Recruits were observed throughout the study period, and the population showed continuous reproduction.
Neste estudo objetivou-se analisar aspectos da ecologia populacional do gastrópode Stramonita haemastoma em Ilhéus (Bahia). As amostragens foram realizadas mensalmente, entre outubro de 2007 e setembro de 2008, em um banco arenítico com 1,5 km de extensão, no qual foram estabelecidos dois pontos e dois níveis amostrais. Em cada nível foram feitas cinco repetições previamente aleatorizadas, utilizando-se um delimitador quadrado com 0,0625 m² de área. Os animais foram fotografados, quantificados e mensurados no local. Foi evidenciado que tanto recrutas quanto os demais indivíduos da população habitam preferencialmente as faixas mais próximas do infralitoral, onde, em função do maior tempo de submersão, os animais ficam menos sujeitos a estresses fisiológicos decorrentes de variação térmica e dessecação. Por apresentarem fendas e buracos, esses locais servem ainda de refúgio e ambiente para posturas de S. haemastoma. Foram observados recrutas ao longo de todo o período, evidenciando reprodução contínua.
Subject(s)
Animals , Demography , Gastropoda/growth & developmentABSTRACT
The samples of Tagelus plebeius and Iphigenia brasiliana were manually collected on the Cachoeira River estuary region (Ilhéus, BA, Brazil) between August 2005 and August 2006, with a periodicity of 15 days, with 20 animals collected/sampled, performing 500 samples from each species. The animals were measured, eviscerated and kept in solution of Davidson and after 24-30 hours, they were transferred to ethanol 70%. The material was processed for routine histology, with paraffin embedding, obtaining 7 microm thick slices, stained with Harris hematoxilin and Eosin (HE). By light microscopy analysis, 2 cases of hermaphroditism (0.4%) in T. plebeius samples and one case (0.2%) in I. brasiliana were registered with predominance of female over male follicles.