Freshwater snails, genus Semisulcospira, have as high as 15 endemic species to Lake Biwa water system as a result of adaptive radiation along with the lake expansion. Previous studies have shown their different habitat use in association with the sediment type. However, knowledge for their vertical distribution remain fragmented. The purpose of this study is to describe the vertical distribution of the genus in the lake Biwa in different sediment types.
Snails and sediments were collected from different depths at specific study sites. Samples were collected using the quadrat method at 10 m intervals from the coast (at water depths of 0–6 m) in five localities. Then snails were identified morphologically, and the relationships between sediment and species composition were studied.
In total, 848 individuals including six species and two morphotypes were collected. Two morphotypes were each similar to S. habei (S. habei type A) and S. multigranosa (S. multigranosa type B). Semisulcospira rugosa was found only in shallow depth, <1.4 m depth. The distributions of S. habei type A, S. reticulata, and S. multigranosa were restricted in deeper than 3.5 m depth. Semisulcospira habei, S. decipiens, and S. multigranosa type B were collected from almost all depths. This study demonstrate fine vertical distribution of snail genus Semisulcospira in Lake Biwa system.