科学美国人60秒:Hitchhiking Worms Survive Slug Guts Transport

Why did the tiny nematode worm cross the road? Well, for all the usual reasons. But a more interesting question is “how did it make the crossing?” Turns out, it may have hitched a ride—inside a slug, or other invertebrate. That’s according to a study in the journal BMC Ecology. [Carola Petersen et al, Travelling at a slug's pace: invertebrate vectors of Caenorhabditis nematodes, link to come]

Nematodes are about a millimeter long. They’re often found on decomposing fruits or rotting plants, where they feast on the resident bacteria. But when that food source is exhausted, how do these diminutive diners make their way to their next meal, which could be in a mulch pile a major trek of several yards away?

To find out, researchers hit the compost heap, and they collected some 600 slugs and 400 centipedes, spiders, beetles, flies and locusts. And they found that the innards of slugs, centipedes and woodlice are littered with live worms that the larger creepy crawlies accidentally ingested as they snacked.  

But what becomes of these itinerant intestinal interlopers? To solve that mystery, the researchers exposed 79 slugs to more than a million nematodes that had been tagged with a fluorescent marker. And they saw that the worms not only survive a southbound trip through a slug’s guts, they emerge none the worse for where-they’ve-been when their ride takes a bathroom break.

Sure, a chugging slug isn’t exactly high-speed rail. But its bacteria-filled belly means that, for the nematode passengers, the dining car is always open.

—Karen Hopkin