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Where
does this crab live? |
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At
vent sites in the eastern Pacific Ocean among dense
clusters of tubeworms at an average depth of 2.7
kilometers (1.7 mi). |
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What
does it eat? |
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Like
other crabs, the vent crab seems to have a very good sense
of smell. This is important in locating food. We’ve
observed it feeding on several species of deep-sea worms,
as well as clams and mussels. Also, some studies have suggested
that the adult crabs feed on bacterial mats. These are
colonies of bacteria so dense they are visible to the naked
eye. |
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How
abundant is this crab? |
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It’s present in such high numbers at vent sites
that Alvin’s pilots actually use it as
an indicator that we are approaching an active vent
field.
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It
appears that this crab has eyes. Can it see in the dark?
How does it find prey? |
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The
growth stage beyond the larval stage is called the megalopa. At
this stage, the crab has well-developed eyes that can sense
light levels expected at depths around 1,000 meters in
the water column. In contrast, once the megalopae develop
into adult crabs, they basically have night vision as can
be found in night-vision goggles. See
this recent news article. |
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Why
do you think the megalopa stage is red, and the
adult stage is white? |
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The bright red coloration seen in the megalopa (post-larval
stage) is due to high concentrations of carotenoid
pigments. In contrast, the adult crabs have low concentrations
of carotenoids.
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Why
are you studying it? |
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What
most intrigues me about this crab is how it colonizes new
vents. Vent fields may be separated by many hundreds of
kilometers, so how do new sites become colonized? To find
out what strategies or mechanisms this crab uses, we are
studying how its early life stages (larvae) disperse and
where they develop. |
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Do
these crabs inhabit vent sites in other oceans
in addition to the Pacific? |
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There are several genera and species of vent crabs.
For example, Bythograea thermydron, Bythograea microps, and Cyanograea are
found along the East Pacific Rise, while Austinograea
williamsi is common in the western Pacific. Segonzacia
mesatlantica is found in the Mid-Atlantic Ridge
in the Atlantic Ocean.
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Are
these crabs good swimmers? |
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When
we did our laboratory studies at atmospheric pressure (which
is more than 250 times less than the pressure of the deep-sea
environment), we found that megalopae are very good swimmers.
Speeds in warm water were comparable to those of the fastest-swimming
megalopae of shallow-water forms like the blue crab Callinectes
sapidus. Even at low temperatures typical of bottom
waters near the vents (2–5°C), megalopae are capable
of sustained swimming speeds of 4 centimeters per second.
That’s fast! |
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How
do you maintain them in the lab? |
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We
are able to maintain the larval stages and small
juveniles at room temperature and atmospheric pressure.
However, the adults are pressure-sensitive and do
not survive long at atmospheric pressure. Therefore,
we must keep them in pressure chambers. |
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Is
there anything else we should know about vent crabs? |
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There
are many interesting and important aspects of the biology
of these crabs that we do not know about. For example,
we do not know how long it takes for the larvae to develop
or where these larvae develop. We do not know how long
they live, and more importantly we still do not know how
they colonize new vents. |
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