Dancing for food in the deep sea: bacterial farming by a new species of Yeti crab.

Andrew R Thurber,William J Jones,Kareen Schnabel,Dirk Steinke

doi:10.1371/journal.pone.0026243

Abstract

Vent and seep animals harness chemosynthetic energy to thrive far from the sun's energy. While symbiont-derived energy fuels many taxa, vent crustaceans have remained an enigma; these shrimps, crabs, and barnacles possess a phylogenetically distinct group of chemosynthetic bacterial epibionts, yet the role of these bacteria has remained unclear. We test whether a new species of Yeti crab, which we describe as Kiwa puravida n. sp, farms the epibiotic bacteria that it grows on its chelipeds (claws), chelipeds that the crab waves in fluid escaping from a deep-sea methane seep. Lipid and isotope analyses provide evidence that epibiotic bacteria are the crab's main food source and K. puravida n. sp. has highly-modified setae (hairs) on its 3rd maxilliped (a mouth appendage) which it uses to harvest these bacteria. The ε- and γ- proteobacteria that this methane-seep species farms are closely related to hydrothermal-vent decapod epibionts. We hypothesize that this species waves its arm in reducing fluid to increase the productivity of its epibionts by removing boundary layers which may otherwise limit carbon fixation. The discovery of this new species, only the second within a family described in 2005, stresses how much remains undiscovered on our continental margins.

Highlights

From ants that use symbiotic bacteria to protect the fungi that they farm [1] to polychaetes that ‘‘garden’’ bacteria [2], animals have developed a diversity of mechanisms to increase their symbionts’ productivity and health
During June 2006, we discovered a second species of Yeti crab, which we formally describe here at Kiwa puravida n. sp, swinging its bacteria-laden chelipeds rhythmically at a Costa Rican methane seep (Figures 1A–C and 1F; Video S1)
We describe how this new species farms its epibiotic bacteria in a unique form of symbiosis

Summary

Introduction

From ants that use symbiotic bacteria to protect the fungi that they farm [1] to polychaetes that ‘‘garden’’ bacteria [2], animals have developed a diversity of mechanisms to increase their symbionts’ productivity and health. This crab had chelipeds (claws) covered in dense setae and epibiotic bacteria that lead to this species, Kiwa hirsuta, to be called the ‘‘Yeti crab’’ [9].

Results

Conclusion