Shell preference of the hermit crab Pagurus exilis (Anomura: Paguridae) from Brazil and Argentina: a comparative study

Abstract

Shell preferences, as shown by laboratory choice experiments, are important determinants of shell utilization under natural conditions. Size and shell species preferences of the hermit crab Pagurus exilis were determined and compared for the most occupied shell types (Olivancillaria urceus, Natica isabelleana and Buccinanops gradatum) in the Caraguatatuba region, Brazil, and for the two most occupied species (B. gradatum and N. isabelleana) in Mar del Plata, Argentina. All experiments were conducted under laboratory conditions, using glass aquaria where the hermit crabs were placed naked with a large number of shells of appropriate sizes. Animals often must compromise among different sets of demands when selecting resources (Yoshino et al. 1999). In hermit crabs particularly, shell selection is not by chance but based on adequacy and availability of resources (Reese 1962, Conover 1978, and is affected by both shell size and species (Abrams 1978, Conover 1978, Blackstone 1985, Lively 1988, Siu and Lee 1992, Ohmori et al. 1995, Hahn 1998, Rodrigues et al. 2000, Mantelatto and Dominciano 2002, Mantelatto and Meireles 2004.Moreover, the fitness of a particular shell may differ between hermit crab species, reflecting several selection pressures, which associated with different habitats, act in different ways on each crab species (Bertness 1981) in different areas. Although the shell selection process has been well investigated (Vance 1972, Elwood et al. 1979, Bertness 1980, Wilber 1990, Hazlett 1992, Ohmori et al. 1995, Wada et al. 1997, Garcia and Mantelatto 2001, Meireles and Mantelatto 2005, there is a scarcity of studies about the shell preferences of two different populations of the same species from different locations distantly removed from one another. Comparative studies of species known to occur over wide geographical

Predatory behavior of the paguroid Dardanus venosus (H. Milne-Edwards, 1848) (Anomura: Diogenidae) on the snail Aurantilaria aurantiaca (Lamarck, 1816) (Gastropoda: Fasciolariidae)

“…They use empty gastropod shells to protect themselves against predators, desiccation, and other environmental stresses (Reese, 1969;Bertness, 1981;Hazlett, 1981). In spite of the extensive literature on their behavior, most studies focus on how paguroids use their shelter, namely shell selection and assessment (Reese, 1963;Hazlett, 1966;Elwood and Neil, 1992;Mesce, 1993;Garcia and Mantelatto, 2001;Dominciano and Mantelatto, 2004;Turra and Leite, 2004;Biagi et al, 2006;Mantelatto et al, 2007;Meireles et al, 2008), shell fighting (Hazlett, 1981;Briffa et al, 1998), reproductive behavior (Hazlett, 1966;1968a;Turra, 2005), and clustering behavior (Turra and Leite, 2000a).…”

Shell preference in a hermit crab: comparison between a matrix of paired comparisons and a multiple-alternative experiment

“…The design of pair-wise choice trials commonly considers a matrix of shell-preference comparisons that is more restricted than the variety of shells occupied in the wild, which can be partially explained because these experiments require large numbers of hermit crabs, empty shells, and experimental trials. For instance, Pagurus exilis (Benedict, 1892) occupy 19 shell species on the northern coast of Sao Paulo State, Brazil (Terossi et al 2006), yet the preference for only three species from Brazil has been tested (Mantelatto et al 2007). The matrix of preference of three shell species tested by Mantelatto et al (2007) required 137 hermit crabs and 2,055 empty shells (see examples in Table 1).…”

“…For instance, Pagurus exilis (Benedict, 1892) occupy 19 shell species on the northern coast of Sao Paulo State, Brazil (Terossi et al 2006), yet the preference for only three species from Brazil has been tested (Mantelatto et al 2007). The matrix of preference of three shell species tested by Mantelatto et al (2007) required 137 hermit crabs and 2,055 empty shells (see examples in Table 1). In our study, to test the shell preference for six shell species through the traditional procedure required 300 hermit crabs and 1,800 shells, whereas for the multiple alternative procedure 14 hermit crabs and 252 shells where used, Wnding a high statistical signiWcance in the sequence of preference.…”

“…The results of our study support the use of a multiple-alternative test to establish the sequence of shell preference in hermit crabs. Additionally, here, we suggest new procedures to force hermit crabs to leave their shell instead of heating the shell (Kellogg 1977), submerging the crabs in warm water (Sato and Jensen 2005), breaking the shell (Dowds and Elwood 1985), the use of anesthetics (Mantelatto et al 2007), or electric shocks ). An important contribution of this study is the use of the plastic clamps as a less traumatic method of forcing the crabs to change to a diVerent shell.…”

“…The pattern of shell use is known to be dependent on shell availability (Turra and Leite 2001;Argüelles-Ticó et al 2010;Arce and Alcaraz 2011) and shell preference (Bertness 1980;Biagi et al 2006;Mantelatto et al 2007;Meireles et al 2008). Hermit crabs choose shells according to species or shape (Sato and Jensen 2005;Mantelatto et al 2007), size (Hazlett 1992), shell condition (McClintock 1985;Pechenik et al 2001), the previous experience of the crab (Meireles et al 2008;Alcaraz and Kruesi 2009), and the developmental and reproductive stage of the crab (Elwood et al 1979). The shells chosen have direct eVects on crab Wtness; consequently, hermit crabs have a shell selection behavior based on shell characteristics that match their requirements.…”