The preference of the hermit crab, Calcinus californiensis, among six species of shells, was tested by two diVerent experiments. The Wrst experiment used pair-wise trials, analyzing the preference by Chi-square tests using two diVerent constructions of the null hypothesis. One hypothesis was based on a no-preference among shell species, the second on comparing the number of crabs changing for a particular shell species when two options were given versus the changing when no options were oVered. The second experiment was a multiple-alternative test based on a rank ordering of the shell preference. This method has both statistical and resource-saving advantages over the traditional pair-wise comparisons. The sequence of shell preference was similarly independent of the procedure used. The preferred shell species are heavy and might be associated with hydrodynamic advantages and with the protection against predation. The shell preference matches with the pattern of shell occupancy indicating that the shell use in nature is determined by the crab's preference. The information generated may be used for further research on shell preference as a methodological alternative.
SUMMARY:The gastropod shell use of the hermit crab Calcinus californiensis was studied at Troncones, Guerrero, Méx-ico. Hermit crabs were captured at two different levels of the intertidal zone, in wave-protected and wave-exposed sites. C. californiensis occupied shells of 18 gastropod species. At both wave-action sites, Cantharus sanguinolentus was the most occupied shell. Columbella sp. was used more by females than by males, and Nerita scabricosta was more used by males. The frequency of use of the shells was different between the different wave sites. N. scabricosta and Columbella sp. were occupied more at the wave-protected than at the exposed sites; C. sanguinolentus and Stramonita biserialis were occupied more at the exposed sites. The hermit crabs at the wave-exposed sites occupied heavier and thicker shells compared with the crabs from the protected sites. The Olmstead-Tukey diagram showed eight shell species as dominant in the wave-protected sites, and seven in the wave-exposed sites. Ten shell species were rare in the wave-protected sites, and six in the waveexposed sites. The rare shells occupied by the hermit crabs were relatively heavier than the dominant shells in both site types. Our results suggest that the shell weight is important in sites that are greatly affected by the hydrodynamics.Keywords: gastropod shell, hermit crab, Calcinus californiensis, waves, Olmstead-Tukey, intertidal. RESUMEN: Uso de conchas por el cangrejo ermitaño CalCinus Californiensis en diferentes niveles de la zona intermareal. -El uso de conchas de gasterópodo por el cangrejo ermitaño Calcinus californiensis fue estudiado en Troncones, Guerrero, México. Los cangrejos ermitaños se capturaron en dos niveles diferentes de la zona intermareal, en sitios protegidos y expuestos al oleaje. C. californiensis ocupó conchas de 18 especies de gasterópodo. Cantharus sanguinolentus fue la concha más ocupada considerando ambos sitios. Columbella sp. fue más ocupada por las hembras que por los machos y Nerita scabricosta fue más ocupada por los machos. La frecuencia de uso de las conchas de las diversas especies difirió entre ambos sitios. N. scabricosta y Columbella sp. fueron más ocupadas en la zona protegida al oleaje que en la zona expuesta; C. sanguinolentus y Stramonita biserialis fueron más ocupadas en los sitios expuestos. Los cangrejos ermitaños ocuparon conchas más pesadas y más gruesas en la zona expuesta al oleaje que en la zona protegida. El diagrama Olmstead-Tukey mostró como dominantes las conchas de ocho especies en la zona protegida del oleaje y siete en el sitio expuesto; como raras las conchas de diez especies en la zona protegida y seis en la expuesta. Las conchas agrupadas como raras en ambas zonas fueron relativamente más pesadas que las conchas agrupadas como dominantes. Los resultados sugieren que el peso de las conchas es un factor importante para los ermitaños en las zonas con alta influencia hidrodinámica.
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