Pig Butt Worm


Chaetopterus pugaporcinus

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Matting color

The Pig Butt Worm is a deep-sea pelagic annelid closely related to the burrowing parchment worms common to Atlantic coasts. The "buttocks" are actually the inflated middle segment of the body, and the concentric rings in the middle are the rest of the body segments being smooshed against the enlarged segment. The cleft of the "buttocks" is created by a ciliated groove running along the dorsal surface of the body. The worm actually only contracts into this appearance when harassed. Normally it assumes that fat-caterpillar shape you see on the bottom left.

It isn't yet clear if the specimens sampled are adults or larvae. They are much larger than any other known Chaetopterus larvae and when placed in a laboratory they did not metamorphosize nor descend to the substrate (most Chaetopterus species will eventually sink to the bottom to assume a benthic lifestyle), indicating that they may be full-developed adults. On the other hand, all of the collected specimens lacked gonads, indicating that they had not reached sexual maturity.

I was a bit confused about which way to orient the creature. Most pictures show it with the head part and the crease of the "buttocks" facing downward. However, the article that describes the worm indicates that the mouth faces up, as does the ciliated groove. Thus, that's the way I've oriented them.

The article mentions that C. pugaporcinus produces a mucus-sac from its ciliated groove-- presumably for capturing and feeding on marine snow. Unfortunately, they didn't provide a picture of the sac, so I created my own version of what I imagine it looks like in the lower left. The researchers also mention that, when agitated, the head of a Pig Butt Worm will glow and the animal will release a small cloud of bioluminescent particles into its mucus sac.

Article sited:
Osborn et. al. "Description and Relationship of Chaetopterus pugaporcinus, an Unusual Pelagic Polychaete (Annelida, Chaetopteridae)" Biological Bulletin 212 (Feb 2007): 40-54


Pig Butt Worm  ©2013 John Meszaros.  All Rights Reserved