ABSTRACT. Density distribution and population structure of Pilumnus dasypodus Kingsley (Crustacea, Decapoda, Xanthidae) from Farol Isle, Matinhos, Paraná, Brazil. A study of the population of the xanthid crab Pilumnus dasypodus Kingsley, 1879 from rocky shore at the Farollsle (25°51 'S and 48°32' W) was calTied out in the following aspects: temporal and spatial distributions of density, annual fluctuation of the sex ratio, size. composition of the population and reproductive activities of the species. Monthly, four levei s in relation to emmersion time within intertidal zone were sampled, from May/90 to Aprill91 , but Pilumnus dasypodus was obtained only in the leveis 2, 3 and 4. The surface water temperature ranged from 16.0°C (July/90) to 28.0°C (February/91). A total of 775 individuais of Pilumnus dasypodus were collected amon § which, 92 were ovigerous females. The population density ranged from 14.63 ind.m· (February/91) to 148.00 ind.m· 3 (March/91). Higher densities were observed in the levei 4, a local of permanent submersion. The sex ratio was I: I in almost ali 1110nths. The carapace width varied from 1.0 I to 8.28 111m for males, from 1.0 I to 7.18 mm for females and 0.0 I to 1.00 mm for juveniles. The fecundity ranged from 81 to 1834 eggs per femal e. The species has continuous reproduction with two peaks of recruiting in the year. Thel'e was a positive relationship, with weak correlation rate, between the carapace width ofthe ovigerous females and the number of eggs in the abdomen . The rocky shore at Farol lsle is a complex environment which harbor the decapod Pilumnus dasypodus, for breeding and survivingo KEY WORDS . Pilumllus dasypodus, population structure, Farol lsle, Paraná State A distribuição espacial e a flutuação temporal da abundância dos organismos são dois dos aspectos ecológicos mais relevantes, e o conhecimento dos mesmos constitui um passo fundamental no entendimento dos processos de interrelação com o meio ambiente (BREWER 1994).A zonação na faixa entremarés em costões rochosos do litoral marinho é universal, envolvendo na maioria das vezes o mesmo grupo de seres vivos em qualquer parte do mundo, dos trópicos aos polos (BARNES & HUGHES 1988). A zonação é mais evidente dentre os organismos sésseis, porém, aqueles vágeis como os decápodos também têm uma distribuição zonada, devido ao tempo diferenciado de emersão, o qual constitui um estresse térmico, de dessecação e de acesso reduzido ao oxigênio dissolvido e ao alimento (LEVrNTON 1982).