On 6 December 2010 Monterey Bay Aquarium Research Institute (MBARI) released news of a study about the way whale carcasses are eaten on the ocean bottom. Five dead whales were towed out and sunk to various depths in Monterey Bay. These bodies where then visited regularly by remotely operated vehicles (ROVs) that photographed the sites.
Specialist Worm Bone Eaters
One genus of worm (Osedax) feeds exclusively on dead whales deep on the ocean floor, and in 2005 the wonderfully named species Osedax mucofloris (The Bone Eating Snot Flower!) was discovered on a dead Minke Whale.
The recent MBARI research has now discovered 14 new species of these 'Zombie Worms', and all exploit 'whale fall' (dead whale carcasses).
It is thought that these worms are the first to colonize the dead whale bones after other creatures have quickly removed the flesh, but they are not alone – there are also bone-eating snails.
Bone-eating Snails
MBARI's Shannon Johnson has described two new species of bone-eating snail, one of which (Rubyspira osteovora) is almost as common as the zombie worms at the deepest Monterey whale fall, and she is still trying to work out how these snails digest bone – i.e. whether they rely on symbiotic bacteria or not.
These are an ancient snail type, having survived unchanged from the time of the dinosaurs. Maybe their peculiar bone eating habit has kept them in a habitat where there is little competition from other snails, meaning there has been no need for change. Like other 'living fossils' there has been no need to alter a successful body plan and lifestyle ('if it ain't broke don't fix it').
Different Animal Communities at Different Depths
In very deep water whale bones can take a long time to disappear, maybe as long as a century, but in shallower water it takes only months. There are at least two reasons for this difference. One is that once the worm and snail specialists have begun the job in shallow conditions many other animals living nearby can move in, but in deeper water there are fewer species. The other reason is that there is very much less oxygen available at great depths so everything proceeds more slowly.
Once again a novel type of photographic recording has led to a new understanding of the natural world. In this case photographs taken remotely in the deep sea have made the way dead whales are consumed by deep-water specialists a bit clearer.
References: 'Fleshing out the life histories of dead whales', Monterey Bay Aquarium Research Institute and LabSpaces, 6 December 2010.
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