Archive for December, 2015

So that’s it. Christmas is over for another year. I hope you all go the presents you wanted, there were no family arguments, and that, depending on exactly which Christmas traditions you follow, the Offering to the Monolith went smoothly and you did not forget any chants.

 

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Seriously, for your sake, I hope you did not forget. The Monolith is not forgiving. 

Now, the animal we’ll be discussing this time is a deep sea dwelling worm that feeds on the rotting bones of once majestic whales. The link to Christmas is, I think, pretty obvious.

Christmas Fireplace

If you can see the link between Christmas and bone eating worms, you should probably be on some kind of medication. 

Osedax worms were only discovered in 2002 as part of science’s commitment to continually probe the dark corners of the world and see that which should not be seen. Consisting of eleven described species, including the wonderfully named Osedax mucofloris (which roughly translates from the Greek and Latin to ‘snot flower bone eater’ or ‘bone eating snot flower’) the Osedax worms live on whale fall.

O. frankpressi - whale-fall worm

The pinkish tentacles are the gills, and the green bits are the bacteria filled ‘roots’ of the worm that enter the bone. The screaming skull is, of course, simply a trapped damned spirit. (Image from mbari.org)

‘Whale fall’ is exactly what is sounds like. The seabed, assuming limited light reaches it and it is far from shore, is often nutrient and energy limited (aside from some unusual occurrences like the ecosystems found around hydrothermal vents). Far from shore, on the seabed, all of the nutrients and energy come, ultimately, from above, in the form of either prey or organic remains slowly sinking – what is called ‘marine snow’, as presumably ‘the soft fall of dead matter’, whilst more accurate, isn’t quite as catchy. Therefore, generally life on the seabed is rather less biodiverse than, for example, life on the shoreline, in a shallow seabed, or a coral reef. There simply are not enough resources available to support large, complex ecosystems.

This all changes when a whale dies. Whales, as you hopefully know, are big animals, and so full of nutrients and energy. A bit like an oasis in a desert, a dead whale provides enough resources to allow a thriving community to develop, feeding off the whale. Slightly unlike an oasis, the vast majority of these organisms are horrifying.

Osedax is no exception. It feeds on the whale bone, and pictures of dead whale carcasses show a writhing mass of red, 1 cm long worms covering them, which somehow makes a gigantic, rotting skeleton at the bottom of the abyss worse. They don’t have any eyes – they don’t need them – and also they have no mouths. Instead, they absorb a slurry of lipids and nutrients, obtained as bacteria break down the whale bones. The worms help with this by boring into the bones and creating a network of miniature tunnels. They don’t do this with teeth, though – instead, the secrete acids strong enough to melt through bone. Like many other polychaete worms, they have large, colourful feathery plumes which act as gills.

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Image from chess.myspecies.info. Worms on a whale bone.

Most scientists think eleven species in an understatement – these worms are found at a range of depths, from twenty five to thirty thousand metres and often occupy quite broad ranges in depths – O. roseus, for example, has a depth range of at least twelve hundred metres, as well as being found across the world. At any one time, there are thought to be nearly seven hundred thousand whale carcasses on the seabed – so despite the seabed being a fairly large place, there are enough carcasses to support large populations of Osedax worms.

Since Osedax worms are prolific breeders (a female O. rubiplumus can produce over three hundred eggs a day) the Osedax spread from carcass to carcass by simply producing huge numbers of offspring. These larvae float through the water and can survive for around two weeks, feeding from a small yolk sac attached to their bodies. The vast majority will never find a new home, but a lucky one may encounter another whale bone and start the cycle all over again. Curiously, the sex of Osedax worms does not seem to be determined at birth. The males are generally much smaller than the females and live inside the musuc tube that surrounds the female worm – each female might support several hundred males. Its thought that larvae which land on another Osedax worm (of the same species) become males. The one exception to this might be O. priapus, which has males and females of the same size. Since the males aren’t conveniently attached to the females they can extent to up to ten times their normal length to find (or, as this paper put it rather wonderfully, ‘roam across the bone’) and mate with a female.

And it isn’t just dead whales they feed on. Boring by Osedax worms cause readily identifiable patterns in bones. Such patterns have been seen in plesiosaur fossils dating back over 100 million years, to the early Cretaceous period. Molecular evidence suggests that these worms either originated around 40-45 million years ago, or much earlier, possibly in the late Jurassic or early Cretaceous*. After the KT mass extinction 65 million years ago, its thought these worms subsisted on giant turtles, until the whales and other cetaeans evolved and spread throughout the oceans, dramatically expanding the food supply of the Osedax worms and allowing them to speciate. They can also survive on bird bones and, in an experiment, they thrived on the bones of a deer, so it appears they aren’t too fussy.

 

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So long as its bone, they’re happy. (Image from deepseanews.com)

 

In theory, they’d be perfectly happy munching away at the bones of, say, a reindeer, that fell out of the sky and into the middle of the ocean one December night…

And there you have it. There is, indeed, a link between a bone eating snot flower at the bottom of the ocean, and Christmas.

 

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Truly, it is a Christmas miracle. 

*If you’re wondering why there’s such a gap between these estimates, its almost certain there was a radiation of Osedax species around 40 million years ago, which could have made determining the age of this species harder.

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