Deep in the sea, on the denuded carcasses of whales, there live humble little scavengers. They’re the snotworms, better known to researchers as various species of the polychaete worm Osedax. They pursue a very dedicated lifestyle. Female snotworm larvae settle onto the exposed bones of dead whales, sending down “roots” to tap into the fatty substances locked in the cetacean’s skeleton. Together with mats of bacteria and other organisms, they’re part of a whale deconstruction crew that can totally break down the world’s largest animals.
And the snotworms have been at this for quite some time. Their distinctive pockmarks have been found on fossil whale bones dating back to about 30 million years ago. And even though they’re most famous for feeding on decaying whales, the snotworms can be food, too. In a new Lethaia paper, University of Otago paleontologists Robert Boessenecker and Ewan Fordyce describe divots and scratches on a 28-23 million year old whale that show fish and sharks gobbled snotworms.
The whale in question – of an as-yet-unnamed prehistoric genus and species – was found on New Zealand’s South Island. There was quite a bit of the mammal in the rock, including the skull, vertebrae down to the torso, ribs, and additional bones left at the site. And upon those prehistoric bones are trace fossils that testify to the presence of other organisms. Among the most numerous are clusters of small circular holes that are concentrated on well-preserved bone – these are the signs of prehistoric Osedax, the first fossil occurrence from the southern hemisphere.
But in some spots there are other marks that cut across the snotworm holes. The snotworm burrows on the skull bones are associated with shallow, parallel scrape marks. The most likely culprits, Boessenecker and Fordyce propose, are fish and sharks that dragged their jaws across the whale carcass to snaffle the snotworms, roots and all.
The Osedax feast continues today. Boessenecker and Fordyce point out that ratfish and crabs have been seen eating whale bone covered in snotworms, too. As long as there have been snotworms, other creatures have turned to them for food. It’s another indication that, rather than being silent undersea tombs, whalefalls are sites of vibrant life.
Boessenecker, R., Fordyce, E. 2014. Trace fossil evidence of predation upon bone-eating worms on a baleen whale skeleton from the Oligocene of New Zealand. Lethaia. doi: 10.1111/let.12108