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Some mushroom-eating slugs may be important 鈥� if slow 鈥� dispersal vehicles for fungal spores, which the animals spread through their faeces.

The languid molluscs deliver payloads of spores from a wide range of forest fungi, including honey (Armillaria) and rustgill (Gymnopilus) mushrooms, to microhabitats that are perfect for new fungal colonies.

at Kanazawa University in Japan had been studying the potential for fungi to make use of animals as spore dispersers. But she didn鈥檛 think much about slugs in this role, since they 鈥渨ere not very mobile鈥�.

However, when she and a colleague in her lab, , found that faeces from mushroom-eating fly larvae increased fungal colonisation in soil, they took a closer look at the slugs as potential fungi ferries.

Researchers collected mantleslugs (Meghimatium fruhstorferi) in a forest on the Kanazawa University campus, keeping them in captivity for a short time so they could collect droppings. The researchers used microscopes to detect spores in the faeces and DNA analysis to identify which species of fungi the slugs had eaten.

Nearly three-quarters of the slugs from the forest had fungal spores in their droppings, and the researchers detected the DNA of dozens of different fungal species in the faeces of eight individual slugs. Most of the fungi were wood-rotting varieties, but there were also pathogenic species and fungi that form beneficial symbiotic relationships with trees.

Going through the slugs鈥� digestive tracts wasn鈥檛 much of a problem for the spores. Many species鈥� spores didn鈥檛 experience any declines in germination rate after being excreted. In fact, some germinated even more readily, with some spores appearing to start germinating in the slugs鈥� guts. Tuno thinks moisture in the digestive tract and in fresh droppings may speed the process.

Tuno and her team painstakingly tracked the movement of five slugs through their forest habitat at night for several hours, marking the position of each slug every 30 minutes. They found that the molluscs tend to move through leaf litter and wood debris well-suited for new fungal colonies, something made more likely by the vast quantity of spores in slug droppings.

鈥淭he overwhelming number of spores being dispersed in a germinated state鈥� would be an advantage over competing decomposer species, she says.

Tuno likens the role of the slugs to that of elephants, which eat plants and transport seeds across their habitats. She adds that the diversity of wood rot fungi being deposited together may be crucial, since multiple fungi species are required to work together to break down wood.

at the University of California, Riverside, who wasn鈥檛 involved with this research, says that slug dispersal may be a great way for fungi to spread to prime microhabitats in a targeted fashion, rather than relying solely on the wind to blow spores around.

He wonders about the slugs鈥� contribution to where and whether certain fungi grow in the forest: 鈥淲hat if, for some reason, slugs disappear? What is going to happen with the fungal community?鈥�

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