The first occurrence of a neritopsine gastropod from a phreatic community

摘要

The neritopsine gastropods are a distinct clade that has radiated in a wide range of environments. They occur mainly on intertidal rocky shores and in brackish to freshwater habitats, from tropical to subtropical areas. Many taxa also occur in cryptic environments, such as submarine caves and undersides of boulders, in chemosynthesis-based communities in the deep sea (see below for references) and in some terrestrial habitats. However, no neritopsine species has so far been collected from a purely freshwater underground site that is isolated from the marine environment. In the course of investigations on stygobiont fauna, pale neritimorph gastropods were collected from a well 12 m deep in Ibukicho, Uwajima, Ehime Prefecture, western Japan. The locality is about 1.9 km from the nearest seashore and about 20 m above sea level.4 The well was drilled in October, 1995, and the water is drained by a pump and filtered to remove sedimental7 particles. The filter chamber of the pump has been inspected periodically (about once a week) by the owner, Mitsuhisa Fukuda, to collect various invertebrates.