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 The hydrothermal vent crab, Bythograea
thermydron,
is a top predator at vent sites in the Pacific Ocean. This crab is present in such high densities that scientists
actually use it as an indicator that they are approaching an active vent field.
The vent crab is typically found among dense clusters of tubeworms at an average depth of 1.7 miles and can
tolerate a temperature gradient that ranges from 77°F in the tubeworm clumps, to 36°F, which is the temperature
of the water surrounding the vent sites.
 Because vent fields may be separated by
hundreds of miles, scientists have many questions about how they are colonized by the crabs. At the University
of Delaware College of Marine Studies, scientists including graduate student Gina Perovich (right) are examining
the crab’s life stages and reproductive biology to look for clues.
Going Crabbing in the Deep Sea!
To collect a small number of adult crabs for laboratory study, scientists deploy modified minnow traps on the
seafloor with the help of the deep-sea sub Alvin. Younger crabs are captured indirectly by collecting clumps
of tubeworms at the vent site.
 To find out how
the crabs are maintained back in the lab at the University of Delaware, see the sidebar at right.
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