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The behavior of the pea crab Fabia subquadrata in relation to its mussel host, Mytilus californianus

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Title The behavior of the pea crab Fabia subquadrata in relation to its mussel host, Mytilus californianus
Names Lidrich, Joseph Stanley (creator)
Wiens, John A. (advisor)
Date Issued 1969-08-14 (iso8601)
Note Graduation date: 1970
Abstract The pea crab Fabia subquadrata is frequently found as a symbiont
of mussels, living within the mantle cavity. This study examined
the nature of this symbiotic relationship by recording the pattern
of distribution of individuals in a mussel bed, testing responsiveness
to host secretions, and observing the feeding mechanics and behavior
of Fabia.
Individual pea crabs were unevenly distributed in an intertidal
bed of Mytilus californianus at Yaquina Head, near Newport, Oregon.
The greatest degree of infestation (25%) was in the largest mussels
which were subjected to the most nearly continuous water cover.
This pattern of distribution was attributed to a combination of the
feeding behavior of the crab and the effects of tidal level.
The responsiveness of Fabia to chemical secretions of the
mussels was tested by presenting liberated crabs with a choice
between sea water conditioned by live mussels and water drawn directly from Yaquina Bay. Tests were conducted to determine the role of
sex and maturation, by dividing the pea crabs into three groups: immature
females, adult females, and adult males. The effects of light,
darkness, and deprivation of its habitat (the host) were also tested.
Under these various test conditions, Fabia showed no measurable
response to any host factor from Mytilus.
When the crab was inside the mussel it faced the posterior and
fed by intercepting the major mucus strand in the food groove of a
ctenida. This behavior took full advantage of the feeding tracts of the
mussel. When outside the host in undisturbed aquaria, crabs fed on
feces and mucus ejected by mussels. This feeding behavior may play
a role in the selection and invasion of a host. Quantitative measurements
indicated that the feeding on Mytilus by adult female crabs had
no significant effects on five parameters used to determine the condition
of infested mussels.
The life span of adult female crabs was estimated to be more
than two years and less than eight years. The adult male's life span
was two years at best with most surviving only a year. Female crabs
were capable of producing live zoea from stored sperm for at least
two years and possibly more.
Genre Thesis/Dissertation
Topic Fabia subquadrata
Identifier http://hdl.handle.net/1957/45713

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