Beautiful snails endemic to the Ryukyu Islands threatened with extinction Parasitic mites confirmed from two species

Two endangered snail species endemic to the Ryukyu Archipelago have been found to be naturally infected with the parasitic mite Riccardoella reaumuri, according to research conducted by Tsukasa Waki, Lecturer at Toho University, Faculty of Science, Yuichi Kameda, Special Researcher at the National Museum of Nature and Science, Takahiro Hirano, Assistant Professor at Tohoku University, and Satoshi Shimano, Professor at Hosei University. The paper was published in the Biological Magazine Okinawa in March.

We had a chance to hear about Dr. Waki’s research. The outline of his research is as follows.

Summary Arboreal Satsuma species, namely “Okinawa-yamataka-maimai”, are beautiful land snails endemic to the Ryukyu Archipelago. All species of the group are currently listed on the Ministry of the Environment’s Red List of Threatened Species II (VU) or higher as they are vulnerable to environmental changes due to habitat shrinkage caused by economic developments. In this study, Waki and his colleagues examined the parasites of arboreal Satsuma land snail species to find that the two species, S. tokunoshimana and S. eucosmia eucosmia, are infected with the snail mite Riccardoella reaumuri . Waki said “All organisms live in relationship with the organisms around them. Especially in the case of endangered species, it is important to understand what kind of organisms they coexist with in order to consider their conservation.” This mite is thought to cause little harm to snails and is not thought to be a parasite of humans.

*Riccardoella reaumuri sampled from the lungs of Satsuma eucosmia eucosmia. scale: 0.1 mm*

Glossary
Snail mites of genus Riccardoella are parasites of land snails and slugs. Waki et al. (2018) found the snail mite Riccardoella reaumuri on the land snail Satsuma mercatoria inhabiting on the ground in Okinawa and reported for the first time in Japan. Subsequent surveys have shown that this mite species is distributed throughout Japan up to Hokkaido (Waki et al., 2019, etc.). Waki and his colleagues thought that snails were infected in the soil, as the mite has been found on terrestrial snails that inhabit on the ground and/or burrow underground during hibernation; however, the mite has also been found in arboreal Satsuma snails which live on trees throughout their lives in the present study, indicating that horizontal infection of the mite can be occurred in dry conditions.

For questions, contact Dr. Tsukasa Waki
Faculty of Science, Toho University
at tsukasa.waki【@】sci.toho-u.ac.jp