[MIS20-P03] Abundant tardigrades found in snow pack in Mt.Gassan in Yamagata Prefecture, Japan
Keywords:Tardigrada, mountain, snow, forest
The fieldworks were carried out on snow packs in the forest located in Mt. Gassan in Yamagata prefecture in Japan. Snow and moss samples were collected in a total of four times from April to October 2018, three times in snow season and once in no snow season. Mt. Gassan is an area with heavy snowfall in winter. Microscopic observation revealed that there were many tardigrades of the genus Hypsibius in surface snow. While only one species of Hypsibius was observed in snow samples, a total of two species including one species of the genus Macrobiotus were observed in moss of trees in the forest, and a total of six species were observed in moss of trees collected in no snow season. The species observed in snow is likely cold-tolerant tardigrade and preferably lives in the snow pack. Population density of tardigrades in snow was exceptionally higher on the green coloured snow due to algal blooming, but was little on white snow without algae. It was an average of 7.1×103 ind L-1 in green snow samples. The body length distribution of tardigrades shows that the their size increased significantly from April to May in the snow pack, and the small sized larvae were observed only in the moss of trees collected in fall. Therefore, they live preferably in snow packs with green snow algae and grow up. When the snow disappears, they move to moss of trees and reproduce there. This life history seems to adapt to the area where heavy snow seasonally covers.