Abstract

Organisms living in the intertidal zone must adapt to environmental and physical stressors. One physical stressor that these organisms may face, and that may require specific behavioral and physiological responses, is burial by sediment. In this thesis I report the results of experiments in which I subjected the intertidal hermit crab, Pagurus samuelis, to burial and analyzed aspects of subsequent behavior and physiology. In the first set of experiments, hermit crabs were buried with the shell aperture facing either up or down, and at one of three depths (2, 4, or 6 cm). The factors hermit crab weight, shell weight, weight ratio, shell shape, aperture orientation, and depth of burial were analyzed by logistic regression to determine their influence on shell abandonment and survival. The results showed a significant number of hermit crabs abandoned their shells when compared with the control group. The only variable that influenced shell abandonment was aperture orientation. The aperture up position promoted shell abandonment, with 73.2 % of hermit crabs that abandoned their shells doing so from an aperture up position. A lighter shell weight, shell abandonment, aperture orientation, and shallower depth of burial were all found to be significant predictors of survival of P. samuelis when buried.

After being buried with sediment, hermit crabs were more likely to survive if they abandoned their shells. However, this would leave the soft abdomen vulnerable to predation or some other potential hazard. Additionally, I discuss that the behavior of abandoning the shell may be one possible reason for the paucity of hermit crabs found in situ in the fossil record. I suggest that whether or not the hermit crab survives the burial event, if it abandons the shell, the body and shell are less likely to be found fossilized together.

In the second set of experiments P. samuelis was subjected to burial treatments to determine if hemolymph lactate concentration increased due to hypoxic conditions in this species over time. Hermit crabs were buried with 6 cm of sand and excavated at 2, 4, 6, 8, 10, or 12 h. Burial duration and state (alive or dead) of the crabs were analyzed for group differences with regard to the accumulation of lactate in the hemolymph. A significant interaction was found between the independent variables duration and state concerning lactate concentration. There was a trend for lactate to be low (8.8 ± 2.7 mM) for those hermit crabs surviving the short durations, but higher (19.7 ± 5.0 mM) in crabs that died. Surprisingly, in the long durations, lactate was found to be very high (40.1 ± 5.0 mM) in surviving crabs, but lower (22.5 ± 2.4 mM) among the dead. I suggest variations in energy reserves and expenditure determined the outcome of survival and lactate concentration within the survival category. Shell weight, crab weight, weight ratio, lactate, and burial duration were analyzed to determine their affect on survival of P. samuelis. Burial duration negatively influenced survival, while none of the other variables had a significant influence. These results imply that the longer P. samuelis is buried, the less likely it will survive an acute, shallow burial event. Anaerobic respiration can provide a short term solution, as long as a substrate for glycolysis is available to meet metabolic demands. Glycogen stored in the hepatopancreas, and muscles is suggested as the substrate for anaerobic glycolysis.

LLU Discipline

Biology

Department

Biology

School

School of Science and Technology

First Advisor

Stephen G. Dunbar

Second Advisor

Danilo S. Boskovic

Third Advisor

Kevin E. Nick

Degree Name

Master of Science (MS)

Degree Level

M.S.

Year Degree Awarded

2010

Date (Title Page)

6-2010

Language

English

Library of Congress/MESH Subject Headings

Pagurus samuelis; Hermit crabs -- Behavior; Crabs -- Physiology; Adaptation (Biology); Intertidal ecology

Type

Thesis

Page Count

xil; 85

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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