The 6-Foot Earthworm That Sounds Like a Draining Bathtub

Giant Gippsland earthworms grow to 6 feet long. Here one does a pretty half-assed impression of the letter M.

They say everything in Australia can kill you: crazy-poisonous eastern brown snakes, enormous saltwater crocodiles, and, until recently, the late ill-tempered supercriminal Mark “Chopper” Read. But the truth is there are plenty of harmless animals and even a handful of harmless humans in Australia.

The continent’s long isolation has given rise to an incredibly unique diversity of life that, yes, includes some extremely lethal critters. But perhaps its most remarkable creature is a gentle, extremely delicate colossus few have had the privilege of glimpsing: the giant Gippsland earthworm, which can grow to some 6 feet long. Give it a stretch–only if it’s already dead, you chucklehead–and it can easily double in length.

These elusive monsters have been known to science only since the late 1800s, when workers unearthed a specimen while surveying a rail line. Mistaking it for a snake, with great care they took it to a professor at the University of Melbourne, who I hope informed them that snakes generally have, you know, teeth and scales and stuff.

This is an extremely vulnerable species, isolated to just 150 square miles at the southeast tip of Australia. Its habitat, once dense forests, has been almost entirely converted to farmland, where tilling and toxins have pushed them to the brink of extinction. But while these worms only surface during heavy rains to avoid drowning in soggy soil, you can actually hear them underfoot.

“Burrows that are occupied by giant Gippsland earthworms have very wet walls,” said biologist Beverley D. Van Praagh, who has studied the creatures for over 20 years, “so when the earthworms move quickly within their burrows, it makes a gurgling sound that is quite loud and can be heard above ground. The sound is a bit like water draining out of a bath and has been known to terrify the uninitiated.”

Life is just one long mud bath for the giant earthworm. The bourgeois lifestyle, though, takes its toll. The worm grows fat and overly content, spending its days sunning and abusing the help before eventually descending into inheritance disputes with its ingrate children.

The giant earthworm burrows through relatively firm soil up to 5 feet deep, using its muscular head to chew through the substrate while ingesting fungi, bacteria, algae, and other microbes. They don’t have teeth, but they do have a gizzard, where small rocks that the worm has eaten help grind up food. (Some birds do this as well, by the way, as did their ancestors the dinosaurs. As do some enterprising human children, though it does them no real good.)

The wastes they expel at the other end are called castings, and the worms actually block their burrows with them, which would seem, well, irresponsible.

“You would think that if they had permanent burrows and block part of their systems with cast that they would run out of room unless they built more burrows,” said Van Praagh. “It does appear that they go back to the same spot and cast in areas where they have already left other cast material, but clearly we do not have the full story on their toilet habitats and burrow building.”

Also still unknown is how they mate in burrows barely wide enough for one. Could they in fact be emerging to mate on the surface?

“Many other species of earthworms mate above ground and don’t have permanent burrows,” said Van Praagh, “but giant Gippsland earthworms are very sluggish on the surface and they would be very vulnerable to desiccation and predators if they stayed above ground for too long.” But they may just have a sexy trick up their sleeves for mating underground. “These worms are fairly flexible, so it’s possible they extend their length to make themselves thinner,” Van Praagh added, “thereby allowing the two worms to couple side by side within their burrows.”

Individuals have both male and female sex organs, and Van Praagh reckons that they align their naughty bits and hand off sperm (here, trade ya!), which is stored in chambers called spermathecae. Van Praagh has found that the worms will store sperm year-round, which means “that they may potentially mate whenever they meet and then store the sperm, ready for producing eggs whenever conditions are favorable. This could be advantageous for worms in low densities and poor dispersal abilities.”

Fertilization actually occurs inside the egg cocoon, which a worm will produce only once a year. When the worms finally decide they’re financially stable and mature enough to have a child, a structure called a clitellum releases an egg case, which slides forward and gathers eggs and sperm. The egg is then laid in a chamber branching off from the burrow, and can take as many as 12 months to hatch.

When it does, at a foot long the baby is already huge (for perspective, that’s as big as a foot-long Subway sandwich … I think). Its growth rate for the rest of its life, though, is slow. And it’s based on this rate that Van Praagh estimates the worm can live as long as 10 years–and probably a lot more.

But this sluggish growth, combined with a tiny distribution and the giant worm’s positively lazy sex life of just one cocoon a year, pose a serious problem for a creature living in the anthropocene–the epoch of devastating human impacts on the planet.

Read more at Wired Science