Aspects of the ecology of Pagurus bernhardus are examined and
the strategies which enable this species to exploit two quite
different habitats are determined. The area of shell selection is
reviewed and mathematical indices of shell adequacy are rejected as
biologically flawed. A subjective index is proposed to more
accurately describe the quality of a hermit crab shell resource.
Shell preference is considered to be an artificial phenomenon and
shell selection is demonstrated to be an essentially random process.
Shell-limitation is considered one of the most common problems
facing all populations of hermit crabs, detrimentally affecting
growth, fecundity, and longevity.
The reproductive cycle of Pagurus bernhardus is examined, and
the period spent in the littoral zone is considered critical in the
life history. Breeding is shown to occur only during the winter
months in littoral populations, and is shown to require two
interacting stimuli. Low temperatures affect egg production in the
female; while reduced photoperiods affect breeding behaviour in the
male. Gestation is shown to require some 43 days at temperatures of
8-10°c, and most females will produce two broods during a breeding
season. Females are sexually mature in their first year and
precocious breeding is seen as a vital strategy to overcome the
restrictions of shell-limitation.
The monitoring of marked individuals indicates that Pagurus
bernhardus is not territorial, and that the distribution of
individuals on a shore is essentially random. The patterns of
movement, the non-breeding interactions between individuals, and the
residence times of these animals on a shore are suggested to be most
strongly influenced by the quantity and quality of their shell
contacts. Migration into the sublittoral is seen as an inevitable
consequence of this behaviour.
Date of Award | 1988 |
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Original language | English |
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Awarding Institution | |
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OPTIMISATION IN THE LIFE HISTORY OF THE HERMIT CRAB PAGURUS BERNHARDUS ( L.)
LANCASTER, I. (Author). 1988
Student thesis: PhD