SULFIDE AS A CHEMICAL STIMULUS FOR DEEP-SEA HYDROTHERMAL VENT SHRIMP

Organisms dependent on deep-sea hydrothermal vents for their existence face extinction when their vents expire, unless they can establish po pulations on neighboring vents or on new vent sites. Propagules, inclu ding larvae and motile adults, are readily dispersed broadly by seaflo or currents, but how they recognize active hydrothermal sites is probl ematical. Compeling evidence that vent organisms can find and colonize hydrothermal sites has been provided by a series of observations on t he East Pacific Rise (1). New hydrothermal vents created there followi ng a volcanic eruption on the seafloor in March 1991 were colonized by sessile invertebrates in less than one year. On the Mid-Atlantic Ridg e, shrimp that normally cluster on sulfide surfaces have been observed to swim directly back to the surfaces when displaced from them. How d o vent animals locate new or existing vents? Passive transport by curr ents (2) or active swimming without guidance by some physical cue is n ot likely to result in success (3). Chemical present in hydrothermal f luids have been proposed as attractants. We provide the first evidence of a chemosensory response in a vent invertebrate to sulfides, which are prevalent in vent fluids and provide the energy for chemosynthetic primary production at vents.