Determining the optimal concentration of chemical cues that induce directional orientation in Clibanarius vittatus (Bosc)

Abstract

Orientation of the hermit crab Clibanarius vittatus (Bosc) to a black horizontal area was tested in a circular arena. Crabs were tested in the presence of chemicals that signal the potential availability of a gastropod shell. Only Investigating Crabs, those exhibiting chemically induced shell-investigation behavior, were tested. All trials were in the presence of chemical cues generated by freezing and thawing flesh from gastropods, Busycon carica or Cinctura hunteria. Directional orientation was absent when crabs were presented with the white background alone. The study tested the hypothesis that shell-seeking behavior would increase as the concentration of chemical cue increased up to a certain point, and then responsiveness would decline. We also hypothesized that gastropod odor prepared by leaching of the chemical cue from gastropod flesh into seawater rather than homogenizing the gastropod flesh would cause a higher proportion of crabs to be attracted to the target. Crabs displayed significant orientation toward the visual target in the presence of homogenized and leached odor from C. hunteria. For all odors the directional response declines significantly at higher concentrations. Leaching of the chemical cue from the flesh for an incubation time of 24 hours at 4°C increased the proportions of crabs attracted towards the visual target compared to all other odor types. Higher proportions of crabs were attracted to the target in the presence of odor from C. hunteria than from B. carica, which suggests an increased sensitivity to the chemical cue originating from C. hunteria.National Science FoundationDuke Marine LaboratoryNo embargoAcademic Major: Biochemistr