Population Dynamics of Pinnixa patagoniensis Rathbun, 1918 Brachyura: Pinnotheridae a Symbiotic Crab of Sergio mirim Thalassinidea: Callianassidae in Cassino Beach, Southern Brazil |
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| Authors: | Eliana dos Santos Alves Paulo Ricardo Pezzuto |
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| Institution: | Fundação Universidade do Rio Grande FURG, Depto. de Oceanografia, Cx. Postal 474, CEP 96201-900, Rio Grande, RS, Brazil;Universidade do Vale do Itajai, Faculdade de Ciências do Mar FACIMAR, Cx. Postal 360, CEP 88302-202, Itajai, SC, Brazil |
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| Abstract: | Abstract. Pinnotherid crabs are typically found associated with many benthic invertebrates. On sandy beaches of southern Brazil, Pinnixa patagoniensis R athbun , 1918 inhabits burrows of the ghost shrimp Sergio mirim R odrigues , 1971. The population dynamics of this crab were studied from monthly samples taken between March 1989 and November 1991 near the Patos Lagoon outlet, southern Brazil ca. 32°13'S; 52°15'W. There was no correlation between the number and size of the crabs and the size of their respective hosts. Mean densities and incidence reached 3.1 indiv. opening-1 range: 0 to 29 and 83.9%. respectively. Sex-ratios were not significantly different from 1:1 for the different size classes and sampling dates. Ovigerous females were found between October and March, showing an average fecundity of 1529 eggs per female. The annual recruitment pattern was bimodal, with a minor peak in summer and a fall peak that accounted for almost 70% of the population maintenance. Males and females both reached a maximum carapace width of 11.5 mm and had a life span of nearly two years as estimated from fitted von B ertalanffy growth curve parameters. |
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| Keywords: | Population dynamics Brachyura Pinnotheridae sandy beaches Brazil |
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