To be able to feed themselves, worms travel great distances, looking for decomposing fruit and plants. To be able to travel great distances, they hitch a ride on slugs.

Researchers at the University of Kiel in Germany observed nematode worms, including Caenorhabditis elegans, and found out how exactly they "board" the slugs and get to their destination to look for food.

The team collected more than 600 slugs, after searching in gardens and compost heaps. They also gathered about 400 other invertebrates, such as flies, beetles, centipedes, spiders and locusts. Through dissection and using microscopic analysis, they tried to locate nematode worms inside the collected animals, which they believed may have been hitching a ride on the invertebrates.

The study discovered 79 slugs were exposed to over a million fluorescently tagged worms.

"Our study reveals a previously unknown nematode lifestyle within the guts of slugs," said lead researcher Dr. Hinrich Schulenburg. He noted that nematode worms are among the most intensively studied creatures; however, not much is really understood about their natural ecology.

Nematode worms are also affected by changes in temperature. Along with the hunt for rotten organisms to feed on, temperature changes make the creatures move around a lot. How and why they are able to do that has not been known until now.

The worms invade the intestines of the slugs and remain there for the rest of the journey, until they are excreted into their destination. According to Schulenburg, the worms seem to have evolved, persisting in the harsh environment inside the intestines of slugs. This makes the worms similar to a symbiont or a parasite.

The researchers further noticed that the worms survived the entire digestive process in slugs. The worms were most probably unintentionally consumed by the slugs, passed through their intestines and excreted alive in feces. While a nematode worm is inside the gut of a slug, it can also reproduce. This process takes place in not more than one day, in time for worms to reach their destination.

During the entire process, the researchers saw that the slugs were not harmed.

Woodlice and centipedes may also serve the purpose of being a transport agent for worms, the scientists said.

Findings of the study were published in BMC Ecology.