University Park, Pa. -- With an incredible lifespan of up to 250 years, the deep-sea tube worm, Lamellibrachia luymesi, is among the longest-lived of all animals, but how it obtains sufficient nutrients -- in the form of sulfide -- to keep going for this long has been a mystery. In a paper just published in the online journal PLoS Biology, a team of biologists now provide a solution: By releasing its waste sulfate not up into the ocean but down into the sediments, L. luymesi stimulates the growth of sulfide-producing microbes, thus ensuring its own long-term survival.
The research team includes Erik E. Cordes, a postdoctoral researcher in the laboratory of Charles Fisher, professor of biology at Penn State, along with Katriona Shea, assistant professor of biology at Penn State, Michael A. Arthur, a professor of geosciences at Penn State, and Rolf S. Arvidson, an earth sciences research scientist at Rice University.
The sulfide this worm needs is created by a consortium of bacteria and archaea that live in the cold deep-sea sediments surrounding the seep where the worm lives. These organisms use energy from hydrocarbons to reduce sulfate to sulfide, which L. luymesi absorbs through unique rootlike extensions of its body, which tunnel into the sediments. However, current measurements of sulfide and sulfate fluxes in the water near the vents do not match either the observed size of the tubeworm colony or the observed longevity of its individuals, leading Cordes et al. to propose that L. luymesi also uses its roots to release sulfate back to the microbial consortia from which it draws its sulfide.
Without this return of sulfate, the model predicts an average lifespan of only 39 years in a colony of 1,000 individuals; with it, survival increases to more than 250 years, matching the longevity of actual living tubeworms.
To date, the proposed return of sulfate to the sediments through the roots is only a hypothesis, albeit one with much to support it, that still awaits direct confirmation. By providing a model in which this hypothetical interaction provides real benefits and explains real observations, the authors hope to stimulate further research into the biology of the enigmatic and beautiful L. luymesi.
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