About the Cover
Cover
The cover shows a dense cluster of polychaete worms living more than 1000 m beneath the sea on a piece of bone from a blue whale. The bone is part of a carcass that was sunk in Monterey Canyon, off California, as part of a study of whale-fall communities. All the worms visible in the photo are female: males in this genus are dwarfs that live in the lumen of the transparent gelatinous tubes of the females and appear to be arrested larval forms. The pictured worms belong to a new species of Osedax, which is a group of annelids whose closest relatives include vestimentiferan tube worms in the family Siboglinidae. Like other siboglinids, Osedax uses symbiotic bacteria, though these are heterotrophic rather than chemoautotrophic, and the bacteria are found in root-like structures that ramify through vertebrate bones.
On pages 67–82 of this issue, Greg Rouse and coworkers describe this new species, a population that they sampled for several months after the whalecarcass was introduced into the Canyon. They found that the whalebone was rapidly colonized by female worms, but that these first occupants had relatively few dwarf males in their tubes. Over time, the size of the “harems” of males increased until the sex ratio was markedly male-biased. This pattern of initial female settlement followed by male accumulation is consistent with the hypothesis that male sex is environmentally determined in Osedax and depends on whether the larvae settle directly on bone (producing females) or on already settled females (producing males).
Credits: Photo, Monterey Bay Aquarium and Research Institute pilots, on ROV Tiburon Dive 932.
Cover design, Beth Liles, Marine Biological Laboratory.
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Copyright © 2008 by the Marine Biological Laboratory.
