Shell occupation as a limiting factor forPagurus brevidactylus(Stimpson, 1859) in the Marine State Park of Laje de Santos, Brazil

Abstract

Hermit crabs are soft-abdomen decapods. They depend upon gastropod shells for protection, with the latter influencing growth rate, mortality and reproduction. The present work aims to provide information about the biology and reproduction of Pagurus brevidactylus in a conservation area in Brazilian southeastern littoral. The material was sampled through active searching by SCUBA diving and refuge traps. We analyzed population structure, fecundity, reproductive output (RO), reproductive periodicity and shell utilization for P. brevidactylus. In total, 54 males, 18 nonovigerous females, 34 ovigerous females and 10 juveniles were sampled. The females had a fecundity of 69.5 ± 65 eggs, which was lower than that compared to other populations from different localities. The RO ranged from 1.48% to 63.04%, with a mean of 26.75 ± 18.23%. There was a positive relationship between egg number and female size. The animals had continuous reproduction, but they reached smaller maximum sizes when compared with other populations. The shell occupation pattern was also different from other localities, the shells of Phrontis alba being the most occupied; this shell has a smaller size when compared to others that P. brevidactylus occupies in other localities. Therefore, P. alba could have had limited the growth and reproduction of P. brevidactylus.

The hermit crab–shell relationship through the lens of interaction networks: The use of network metrics and species role across communities

“…Ilha Anchieta and Laje de Santos have different characteristics as reflected in the shell availability discussed by da Silva et al (2018). Ilha Anchieta is an island close to the coast, which offers shelter from the hydrological features of the sea (e.g.…”

“…wave energy and strong currents); thus, creating a stable environment for different and larger shelled gastropods (Mantelatto & Garcia 2002). Laje de Santos is an exposed rock approximately 36 km from the coast that are subject to wave energy and hydrological features (da Silva et al 2018). Lunt et al (2017) found that the ocean wave energy and flow can reduce benthic invertebrate abundance and size; thus, Laje de Santos favours small‐shelled gastropods.…”

“…The P. diogenes species is bigger than other hermit crabs, reaching 40 mm of shield length (Bertini & Fransozo 1999; Turra et al 2002), while the other species reaches around 5 mm of shield length (Lima et al 2018; da Silva et al 2018). The bigger size of P. diogenes limits its shell usage because there are fewer gastropod species that reach a sufficient size to fit the hermit crab; this makes it a specialist species in most regions studied.…”

“…In Laje de Santos, the samples were collected with two combined techniques: the first is an active search performed by two divers with sample effort of 1 h/diver, the second was refuge traps. The samples from Laje de Santos were collected from June 2015 to September 2016 (please see da Silva et al (2018) for more information). In Ilha da Vitória, the samples were conducted seasonally from 2013 to 2014 by active search with sample effort of one diver per hour per diving session.…”

“…The quality of the shells can be compromised by epibiont infestation and broken parts (Buckley & Ebersole 1994; Carlon & Ebersole 1995). The shell’s characteristic such as internal volume and aperture width can impact the hermit crab growth, that is if the shell present in the environment has suboptimal size, the hermit crab will not grow as it should; also, the internal volume can limit the number of eggs produced; and mortality can be increased if the shell is broken or worn out which makes the hermit crab susceptible for predators (Reese 1969; Kellogg 1976; Bertness & Cunningham 1981; Brooks 1988; Hazlett 1989; Buckley & Ebersole 1994; Worcester & Gaines 1997; Angel 2000; da Silva et al 2018; Stanski et al 2018).…”