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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 have much smaller, probably non-functional eyes.
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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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