Population structure and growth of the hermit crab Pagurus brevidactylus (Anomura: Paguridae) from the northern coast of São Paulo, Brazil

Abstract

The hermit crab Pagurus brevidactylus (Crustacea: Anomura: Paguridea) from the infralittoral area of Anchieta Island, Ubatuba, was characterized by population structure (size, sex ratio, reproduction and recruitment) and growth. Animals were collected monthly during 1999 by SCUBA diving. A total of 1525 individuals was collected (633 males and 892 females), 695 of them were ovigerous females. Overall sex ratio was 0.7:1 in favour of females. The crabs showed a unimodal distribution with males signi¢cantly larger than females. Ovigerous females were collected during all months and in high percentages from 1.0 mm of shield length, demonstrating intense and continuous reproduction. The longevity was approximately 24 months for males and 18 for females, which showed larger growth rate and reached sexual maturity earlier (two months) than males. The low number of males in this population may be due to the longer life span. Moreover, the sexual dimorphism favours males during the intra-and interspeci¢c ¢ghts by shell, food, reproduction and territory. Females demonstrated a short life cycle and intense reproduction.Pagurus brevidactylus (Stimpson, 1859) is a small abundant hermit crab found in the infralittoral zone of Anchieta Island (Mantelatto & Garcia, 2002), as well as in the northern coast of Sa‹ o Paulo State. The biological aspects of this species in the western Atlantic region are poorly known (Mantelatto & Meireles, 2004). Therefore, the objective of the present study was to describe the population structure (size, sex ratio, reproduction and recruitment) and the growth in the ¢eld of the population inhabiting Anchieta Island, Brazil.Hermit crabs were collected monthly from January to December 1999 in the infralittoral area of Anchieta Island (23832 0 S 45804 0 W), which is an ecological reserve of the northern coast of Sa‹ o Paulo State, Brazil. Animals were collected in the daytime by two people during 30 minutes of SCUBA diving.Animals were frozen and transported to the laboratory where they were removed from their shells and immediately weighed. Sex was determined from the gonopore position; the presence of eggs at the pleopods determined ovigerous females, being the maturity of males and females based on the size of the smallest ovigerous females. Shield length (SL, from the tip of the rostrum to the V-shaped groove at the posterior edge), measured under a compound light microscope equipped with a camera lucida (50Â), was the measurement of size of the hermit crabs.Hermit crabs were grouped in size-classes of 0.2 mm SL, and the sex ratio for each was calculated. The reproductive period was evaluated by percentage of ovigerous females relative to the total number of females collected monthly. The KolmogorovŜ mirnov test was used to verify the normality of the sizef requency distribution of the individuals and the Pearson correlation to test for a correlation between the water temperature and the total of individuals collected monthly or the percentage of ovigerous females. The w 2 -test was used to evalu...

Population structure of the deep sea hermit-crab Catapaguroides microps (Paguroidea, Anomura) in the Campos Basin, RJ, Brazil

“…Catapaguroides microps is sexually dimorphic in relation to size, with males reaching larger shield lengths than females. A similar growth pattern has been observed in populations of shallow water hermitcrabs such as those of Calcinus tibicen (FRANSOZO; MANTELATTO, 1998), Dardanus insignis (BRANCO et al, 2002), and Pagurus brevidactylus (MANTELATTO et al, 2005) studied in São Paulo, and Diogenes puligator (MAJÓN-CABEZA; GARCIA-RASO, 1998) in the Strait of Gibraltar. Above the 2.2 mm CS, males become more abundant (Fig.…”

Pattern of shell occupation by the hermit crabPagurus exilis(Anomura, Paguridae) on the northern coast of São Paulo State, Brazil

“…The occupation of the largest shells by the males has been reported in other studies Mantelatto and Meireles 2004), and this occurs as a function of the size difference attained by the different sexes, as the males' investment on reproduction is lower than for females. Male Pagurus exilis attained larger sizes than females, evidencing sexual size dimorphism (Espósito et al forthcoming) as reported for Pagurus species such as P. criniticornis, P. brevidactylus, P. excavatus (Herbst, 1791), and P. filholi (De Man, 1887) (Faria 2004;Mantelatto et al 2005;Macpherson and Raventos 2004;Goshima et al 1998, respectively).…”

Ocupação de conchas de gastrópodes por ermitões (Decapoda, Anomura) no litoral de Rio Grande, Rio Grande do Sul, Brasil

“…Amostragens periódicas viabilizariam afirmações mais fidedignas quanto aos padrões populacionais das diferentes espécies. Com efeito, os machos atingem tamanhos maiores que as fêmeas [e. g. Clibanarius vittatus (Bosc, 1802) (REIGADA & SANTOS, 1997), Paguristes erythrops Holthuis, 1959(GARCIA & MANTELATTO, 2001, Calcinus tibicen (Herbst, 1791) (FRANSOZO et al, 2003), Pagurus brevidactylus (Stimpson, 1859) (MANTELATTO et al, 2005)] o que parece ser um padrão usual entre os ermitões da costa brasileira.…”