Background
Introduction Materials and Methods Graphs and Tables Results
Discussion Background Information Pictures References

Article A

Osorno, Contreras-Garduno, & Macias-Garcia (2005) studied C. compressus, a species of terrestrial hermit crab that lives in the high intertidal zone of the Pacific Coast of Mexico on Isla Isabel, a tropical habitat. By collecting and maintaining 27 crabs for one to seven months, and by remodeling their shells, the researchers were able to study four aspects of how shells relate to hermit crabs: shell weight on crab growth rate, shell weight/thickness on crab shell preference, shell thickness on shell mechanical resistance, and shell thickness on water retention. Their results show that the heavier the shell, the more compromised the growth rate of the crab is; however, the crabs refused to carry thin, light shells even if they did promote growth rate. Thus, it would seem that hermit crabs also assess thickness of shells in terms of resistance as a trade-off between growth (and reproduction) and protection from predators. Finally, the study showed that the thicker the shell, the more humidity it retained, thus decreasing the chances of desiccation. Overall, it would seem that even though heavy shells slow down crab growth, light thin shells provide less protection from both biotic and abiotic factors. Thus, shell preference of C. compressus is determined by various cost-benefit balances and by the life history of each species.

 

Osorno, J.L., Contreras-Garduno, J., & Macias-Garcia, C. “Long-term costs of using heaving shells in terrestrial hermit crabs (Coenobita compressus) and the limits of shell preference: an experimental study” (2005). Journal of Zoology, 266: 377-383.

 

Article B

Turra and Leite (2004) studied three species of hermit crabs – Clibanarius anteillensis, C. sclopetarius, and C. vittatus – to show that hermit crabs’ preference for shell size was not dependent on the type of the shell or on the species of the crab. The crabs were collected from an intertidal flat with two islands (Pernambuco and Pedroso) near Araçá in the São Sebastião Channel, a sub-tropical habitat. The strong correlation between the shell parameters (size and weight) indicates that the hermit crabs were not accessing particular shell characteristics during shell selection. A very intriguing discovery was that the hermit crabs studied chose relatively lighter shells in nature as opposed to in an experimental setting where they had free access to a variety of shell thicknesses. This seems to indicate that the hermit crab species are limited by shell availability. Finally, relative shell weight can be considered a measure of its architectural defense against predators, and shell aperture is also strongly related to shell architecture, which is likely to constrain crab morphology. Thus, selection of shells with larger apertures may prevent shell influences on crab form. Overall, the study shows that the preferred size of a given shell type is not necessarily dependent on the crab species; rather, it is dependent on the crab size or weight.

 

Turra, A., Leite, F.P.P. “Shell-size selection by intertidal sympatric hermit crabs” (2004). International Journal on Life in Oceans and Coastal Waters, 145.2, 251-257.

 

Article C

Botelho and Costa (2000) studied the intertidal hermit crab Clibanarius erythropus at three sites during low spring tides (zone unspecified) on São Miguel in the Azores, which has a temperate and moderate coastal climate. The researchers discovered that, out of the 19 shell species that were utilized by the hermit crabs, Littorina striata, Nassarius incrassatus, and Mitra species were the most frequent. Each shell species individually occurred most frequently at the three sites, Fenais da Luz, Agua de Alto, and Caloura, respectively. Overall, it appears that shell selection is determined by the respective sizes of the hermit crab and of the shell species. In addition to this finding, it would also seem that the small-size class crabs occupy more shells species than the larger crabs.

 

Botelho, A.Z., Costa, A.C. “Shell occupancy of the intertidal hermit crab Clibanarius erythropus (Decapoda, Diogenidae) on Sao Miguel (Azores)” (2000). Hydrobiologia, 440.1-3, 111-117.

 

Article D

The hermit crab Pagurus brevidactylus was used in a long-term study in Brazil to determine shell occupation and availability among hermit crabs. A total of 3,704 shells and 32 species were collected, monthly between January and December of 2000. It was observed that shell availability is the number one factor for crab utilization, and dimension is number two. The article discusses the idea that shell choice is not readily known so the following factors had to be considered while doing the research, “Almost every physical variable has been considered as being of primary importance: shell weight (Hazlett and Herrnkind, 1980), its weight/volume ratio (Markham, 1968), the angle of its columellar axis (Dowds and Elwood, 1983), the relationship between hermit weight and shell width (Vance, 1972a), the internal volume of the shell, its rugosity, aperture size or shape, and even its internal architecture (Lancaster, 1988).” It also states that shell choice will be different among hermit crab species as habitats are different for each. In southern Brazil, 93% of the total shells collected were inhabited. 41% of crabs collected were males, and they were larger than females. Cerithium atratum shells were most commonly occupied by small to medium sized crabs, while Pisania auritula shells were dominantly occupied by larger crabs. The article states, “The variables that best describe the association between hermit crabs and their shells were shield length (SL), hermit crab weight (HW), shell internal volume (SIV), and shell dry weight”  The article also discusses that although there may be high shell availability, occupation rates may not be high due to damage or a limiting size range.


                                                  
Mantelatto, Fernando Luis; Meireles, Andrea de Lucca. “THE IMPORTANCE OF SHELL OCCUPATION AND SHELL AVAILABILITY IN THE HERMIT CRAB PAGURUS BREVIDACTYLUS (STIMPSON, 1859) (PAGURIDAE) POPULATION FROM THE SOUTHERN ATLANTIC” Bulletin of Marine Science 75 no1 27-35 Jl 2004

 

Authors: Jenessa Hill & Jennifer Mordaunt| Ecology 450| Marine Discovery| Created November 20,2007| University of Arizona| Class Photos