Tubifex

Image: Matthias Tilly

It's Tubifex! Also known as Sludge Worms and Sewage Worms. For good reason. Yaaaaaaay!

Image: Ivo Antušek

There are about a dozen species in the Tubifex genus, including one called Tubifex tubifex, which is the most well-known of them all and can reach 20 cm (8 in) long.

Actually it's really difficult to tell the species apart. Water conditions effect their external appearance so a careful look at the sexual organs is the best way of discerning species. But the sexual organs are absorbed by the body when not in use, so even with a good microscope, a book entitled "How to Tell Tubifex Worms Apart" and an eyeful of worm gonad, it ain't easy.

Tubifex are annelids, part of a large subgroup which includes many terrestrial and freshwater species, including the good old earthworm. Tubifex are freshwater worms. This doesn't mean they live in cool, clear, refreshing water, it just means they don't live in the ocean.

Tubifex live in mud. Also sludge and sewage. They positively thrive in nasty, stinking lakes and rivers across the world. They even look a little red because they have haemoglobin in their body to allow them to survive in oxygen deficient habitats; filth, pollution, that kind of thing.

Like earthworms, Tubifex have little bristles on their sides to provide traction for burrowing into the sediment. With their little red tails all a-flutter as they absorb oxygen, they can stuff their goofy faces with detritus, decay and all the horrible stuff we do our best to avoid.

Image: douneika via Flickr

Truly, they are at one with the filth!

Image: Max Kueng via Flickr

In fact, if there's no slimy and disgusting surface for these worms to cling on to, they'll cling on to each other. They become a great mass of squirming nastiness. And if one worm contracts, it causes all the other worms to do the same. Sling them all down a sewage pipe and it can look...

a bit like colonoscopy.

Despite all that, these worms still manage a bit of romance. Tubifex are hermaphrodite, though the male and female parts come to fruition at different times so they can't fertilise themselves. Eggs are deposited in a cocoon, with the youngsters emerging after two or three weeks.

Despite the squalor of their usual habitat, Tubifex are popular in the aquarium trade. As fish food, I mean. Not decoration or whatever. It's not too difficult to culture them, by the handful even, and fish just love the stuff. Some will chow down until they make themselves sick. It's like hamburgers! Only with less litigation.