A new cave-dwelling eyeless spider of the genus Coelotes (Araneae: Amaurobiidae) from Okinawa Island, the Ryukyu Islands, Japan, with notes on possible parthenogenesis

Abstract

A small troglobiontic coelotine spider is described under the name of Coelotes troglocaecus sp. n. found in limestone caves on Okinawa Island, Japan. This is the first record of an eyeless coelotine spider. Morphological description is given in comparison with a sympatric Coelotes okinawensis. Extensive field survey over the Ryukyu Islands showed that the new species is endemic to Okinawa Island, where it has been found rather widely but exclusively in limestone caves. The population density was extremely low, and the facts that only females have been collected and that they have extremely degenerated structures in epigynum projections and degenerated copulatory opening for coupling strongly suggest parth-enogenetic reproduction. It has some additional morphological traits which seem adaptive to the life in the caves. Specialization to cave habitat is discussed in relation to the geological history of the Ryukyu Islands.