Worms are pretty odd compared to creatures we are more familiar with. Within that already weird group, some worms are weirder than others.
Giant Blue Earthworms
Terriswalkeris terraereginae is an Australian worm. In a land where an animal has to be pretty weird to be even noticed, the giant earthworm is not only a lovely shade of Prussian Blue, it also can grow up to two meters long!
Pig Butt Worm
One of the few things that worms all over the world have in common is that they are vermiform, or shaped like worms, right? Wrong! ConsIder the deep sea worm Chaetopterus pugaporcinus. It doesn't look so much like a worm as it does a pig's butt. That's why its common name is the Pig Butt Worm. This worm is segmented like other worms, but the middle segment is inflated while the front and rear segments are flattened against the midsection.
The Palouse earthworm is native to eastern Washington and western Idaho. They can grow up to three feet long and burrow 15 feet deep in the soil! Driloleirus americanus was first discovered in 1897 and was considered extinct in the 1980s. Two specimens were found last year, but were killed and somewhat damaged before a cautious identification.
A worm called Xenoturbella bocki is the master of minimalism in worms. It has no mouth, stomach, brain, or any internal organs! The only thing this primitive worm has in common with other worms is its shape. Scientists couldn't quite classify it on discovery. DNA tests indicated it was related to molluscs, but later testing indicated that the worms may have eaten the molluscs -somehow, even with no mouth or organs. The most organized internal feature is the "statocyst" which keeps it oriented, an important task when an animal doesn't know its head from its tail.
Bone Eating Worm
In 2002, deep sea explorers 9,400 feet down in the depths came upon a decomposing whale carcass with an entire ecosystem, living on it. The most numerous species was a raft of worms with distinct red plumage. The new species was named Osedax rubiplumus, after their appearance and their habit of eating the bones of dead animals. All the worms feeding on the whale were females. The males were discovered living inside the females! The males seem to be stunted developmentally, but they still provide sperm for reproduction. Osedax has no mouth or functional gut. Their "plumes" act as roots that extract nutrients from the bones they feed on. Since then, twelve different species of Osedax have been identified.
A video went around the internet last week with a plea to identify this weird worm. Commenters at Flickr believe it to be of the phylum Nemertea, or ribbon worm, sometimes called a proboscis worm. When it shoots out its proboscis, its length will stretch to many times its original length. There are around 1400 species of Nemertea.