The deep-sea tube worm, Lamellibrachia Luymesi, is among the longest-lived of all animals. It has a lifespan of 250 years, and now scientists from Penn State (Erik E. Cordes, Prof. Katriona Shea, Prof. Michael A. Arthur) and Rice (Rolf S. Arvidson) might have found out why. In a paper just published in the online journal PLoS Biology, the biologists say that the tubeworm releases its waste (sulfates) not up into the ocean but down into the ocean sediments. This stimulates the growth of sulfide-producing microbes, thus ensuring the tubeworm's long-term survival.

Close-up photo of tubeworms at 550 meters depth (Courtesy: Penn State)The worm needs sulfides to survive, which is created by a consortium of bacteria and archaea that live in the cold deep-sea sediments surrounding the seep where the worm lives. The bacteria use energy from hydrocarbons to reduce sulfate to sulfide, which the tubeworm absorbs through tube-like extensions that are rooted into the sediments. The tubeworms also use the same extensions to return its waste (sulfates) into the sediment.
The scientists used a colony of 1000 tubeworms, and found that without this return of wastes back to the sediments, the average age of the tubeworms reduce to 39 years, with it, it goes up to 250 years as observed in nature. Thus, there exists a symbiotic relationship between the tubeworm and its surrounding microbes, that ensures a long life for the worms.
Other scientists are doing studies on the tubeworm's genetic development (here, and here), and the goal is to learn the secret of their long life, and perhaps use it to better our chances of a long life.