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

Abstract

ABSTRACT. Occupation of gastropod shells by hermit crabs (Decapoda, Anomura) in the littoral of Rio Grande, Rio Grande do Sul, Brazil. The present study aimed to characterize the shell occupation by hermit crabs at the Rio Grande city, state of Rio Grande do Sul. Animals were sampled at 14 radials in Rio Grande, between 12 and 50 meters depth. Each hermit crab and its respective shell were identified, weighted and measured. A total of 408 animals were captured, of families Paguridae and Diogenidae; the most abundant species were Dardanus insignis (de Saussure, 1858) and Loxopagurus loxochelis (Moreira, 1901). The animals occupied shells from 13 gastropod species, mainly of Buccinanops lamarckii (Kiener, 1834) and B. gradatum (Deshayes, 1844). Dardanus insignis utilized shells from 12 of the 13 mollusks species registered; L. loxochelis from nine ones. In a general way, the shell occupation patterns present a correlation between the hermit crab size and the shell size, in the case of the two most abundant species the strongest correlation was between their size/weight and shell aperture width, evidencing that shells occupation is given not only by their local availability, but also by the relationship between hermit crabs variables and gastropod shells. KEYWORDS. Shell preference, Dardanus insignis, Loxopagurus loxochelis, south Brazilian coast.RESUMO. O presente estudo teve como objetivo caracterizar a ocupação de conchas por ermitões no litoral da cidade de Rio Grande, Estado do Rio Grande do Sul. Os animais foram amostrados em 14 radiais em Rio Grande, entre 12 e 50 metros de profundidade. Cada ermitão e sua respectiva concha foram identificados, pesados e medidos. Um total de 408 animais foi capturado, pertencentes às famílias Diogenidae e Paguridae; as duas espécies mais abundantes foram Dardanus insignis (de Saussure, 1858) e Loxopagurus loxochelis (Moreira, 1901). Os ermitões ocuparam conchas de 13 espécies de gastrópodes, principalmente de Buccinanops lamarckii (Kiener, 1834) e B. gradatum (Deshayes, 1844). Dardanus insignis utilizou 12 das 13 espécies de moluscos registradas; Loxopagurus loxochelis utilizou nove. De um modo geral, o padrão de ocupação de conchas apresenta uma correlação entre o tamanho do ermitão e o tamanho da concha; no caso das duas espécies de ermitões mais abundantes, a maior correlação foi entre peso/tamanho do animal e o tamanho da abertura da concha, evidenciando, que a ocupação de conchas se dá não apenas pela disponibilidade local das mesmas, mas também pelas relações entre as variáveis dos ermitões e das conchas de gastrópodes. PALAVRAS-CHAVE.Preferência de conchas, Dardanus insignis, Loxopagurus loxochelis, costa sul do Brasil.

Shell use by the hermit crab <i>Calcinus californiensis</i> at different levels of the intertidal zone

“…For instance, females being more abundant than males has been reported for the species Coenobita scaevola (Forskäl, 1975;Sallam et al, 2008) and Clibanarius vittatus (Bosc, 1802;Sant'Anna et al, 2006), whereas a higher proportion of males has been reported for Pagurus exilis (Benedict, 1892;Terossi et al, 2006) and Paguristes calliopsis Forest andSaint Laurent, 1968 (Biagi et al, 2006). In contrast, a similar proportion of males and females has been reported for Dardanus insignis (De Saussure, 1858;Ayres-Peres et al, 2008). Variations in the sex ratio between seasons have been reported for Clibanarius longitarsus (De Haan, 1849;Litulo, 2005), C. vittatus (Lowery and Nelson, 1988), and Diogenes nitidimanus Terao, 1913(Asakura, 1995, though in our study similar sex distribution patterns were found in the different wave-action sites in March and August.…”

“…This shell type is relatively light, as shown by its weight/shield ratio (see Figure 3). It has been documented that females occupy lighter shells than males, for instance P. exilis, D. insignis, and Clibanarius erythropus (Latreille, 1818;Terossi et al, 2006;Ayres-Peres et al, 2008;Caruso and Chemello, 2009). Some authors suggest that the use of heavy shells may limit reproduction and growth in hermit crabs, for example in C. obscurus, Clibanarius albidigitus Nobili, 1901, and Pagurus sp.…”

Shell occupation by the hermit crab Dardanus insignis (Decapoda, Diogenidae) from the north Coast of São Paulo state, Brazil

“…Shells of the gastropod O. urceus were the most used by D. insignis in a region at higher latitude according to Ayres-Peres et al (2008). When compared to the present study, which also recorded O. urceus as the most occupied shell in all three bays (>50%) and, given its high occupation rate, we can assume that there is both a occupation and a better adaptation of the hermit crab D. insignis to occupy this species.…”

“…Hahn (1998) suggested that the occupation of the same shell species (in this case, O. urceus) decreases intraspecific competition, which has a positive influence at the population level. This fact might be associated with the competitive dominance of D. insignis in the sub-littoral region (see Fransozo et al, 2008Fransozo et al, , 2011Ayres-Peres et al, 2008). Hazlett et al (2005) suggests that male hermit crabs that use for the most part a given species of shell are considered specialists and allow for a higher effectiveness in the mating process in comparison to hermit crabs with generalist occupation patterns, occupying shells of different species according to their availability in the environment.…”

Shell occupation by the South Atlantic endemic hermit crab Loxopagurus loxochelis (Moreira, 1901) (Anomura: Diogenidae)

“…The shell of O. urceus is the most occupied by hermit crab species of unconsolidated substrate in the subtropical region of the Brazilian coast (Ayres-Peres et al, 2008;Fransozo et al, 2008). As well as the hermit crab Dardanus insignis (Saussure, 1858) and Isocheles sawayai (Forest and Saint Laurent, 1968) (Miranda et al, 2006;Fantucci et al, 2008;respectively), L. loxochelis mostly occupied the shell of O. urceus in the three bays.…”