GOFFREDI, S.K.; ROUSE, G.W.; VRIJENHOEK, R.C.; Monterey Bay Aquarium Research Institute; Earth and Environmental Sciences, University of Adelaide ; Monterey Bay Aquarium Research Institute: Bone-devouring worms: Ecological and reproductive novelty

We recently described a new genus of annelid, Osedax, discovered living on the carcass of a gray whale at ~3000 m depth off of California. Since the initial discovery in 2002, three species within the genus have been collected. These benthic marine invertebrates are unique in ecological and reproductive strategy from all animals known to date. The mouthless and gutless worms possess novel morphological specializations used to obtain nutrition from decomposing mammalian bones. Adult worms possess elaborate root-like extensions that invade the lipid-rich marrow of whale bones and contain a layer of bacteriocytes that house microbial symbionts, related to bacteria known for heterotrophic degradation of complex organic compounds. This unique symbiotic strategy has allowed for the exploitation of an environmental niche not available to most organisms. Additionally, all visible Osedax worms are reproductively prolific females. Each female contains numerous (up to 100) dwarf males within her tube. Highly skewed male-biased sex ratios are rarely observed in the animal kingdom, suggesting unique factors driving this uncommon reproductive mechanism. The potential role of this invertebrate-microbial symbiosis in the cycling of large organic inputs into the surrounding deep-sea community is particularly significant when one considers that remineralization of such a large amount of organic carbon, ~20,000 kg for a 10 m long whale, facilitated almost entirely by Osedax and its symbionts, takes place within only a few years. This time frame is ~2000 years faster than the typical avenue of carbon delivery to the deep seafloor, a habitat which covers ~50% of the Earth�s surface, making the study of this unusual group globally significant.