The discovery of such huge numbers of shrimp swarming around hydrothermal vents must rank as one of the most surprising and awe-inspiring biological findings of the late 20th century. They say a picture tells a thousand words, so to demonstrate just how incredible the swarms are, please view the videos below.
Estimates for the number of individuals in these swarms varies however some researchers have suggested that there may be up to 40’000 individuals per m3 (Segonzac et al, 1993) meaning the swarms with be composed of hundreds of thousands if not millions of shrimp. Such a concentration of life at the bottom of the sea is (to my mind) incredible however, it does beg the question, just why the shrimps congregate in such numbers?
The answer (whilst still theory) brings together various ideas previously discussed and will form the conclusion of this blog. A major reason behind the swarming behavior is the simultaneous need for Rimicaris to provide its episymbionts with reduced chemical compounds whilst remaining in water of (approx) 25oC. Suitable areas which provide chemical rich yet cool water are fairly limited forcing Rimicaris to exist in a fairly narrow three dimensional space, contributing to swarming behavior. The unpredictability of vent hydrodynamics may also have led to selection for swarming behavior. Being in physical contact with neighboring individuals will help ensure that each shrimp remains in a suitable habitat. As Rimicaris can “see” the vents (even with their head in a swarm) tracking the movement of con-specifics (individuals of the same species) will ensure the shrimp neither starve nor sizzle.
Well done, you’ve come to the end of the blog. I would like to thank any determined readers who have made it this far and I hope that readers have learnt some new, interesting and surprising facts about the deep-sea hydrothermal vent shrimp Rimicaris exoculata, surely the most extreme vent organism.