カワムラハデミナシ(イモガイ科)の消長と環境変動

概要

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Leptoconus kawamurai Habe, 1962 is a western Pacific conid species closely related to Leptoconus milneedwardsi (Jousseaume, 1894) living in off Mozambique to Mauritius, Arabian Sea and Bay of Bengal. More than 1500 shell specimens of L. kawamurai were obtained from the shallow sea around Amami to Okinawa Islands during the construction of submarine cable around 1989. However, neither living individual nor soft-body material was discoverd from the thanatocoenoses. Moreover, the tented pattern on the shell surface is pale (or yellowish tan in color) compared with that of L. milneedwardsi. A radiocarbon age of a well-preserved dead shell from off Itoman City, Okinawa-jima was measured with a Tandetron accelerator mass spectrometer (AMS) at the Dating and Materials Research Center, Nagoya University. The ^<14>C dating indicates 292±66 yrBP (NUTA-4301). These suggest that a population of L. kawamurai flourished about 300 years ago. In contrast, living individuals of L. kawamurai have been rarely discoverd. A living one was obtained from the Sumiyoh Bay, Amami-ohshima Island in 1989. The shell of the living individual has a higher density than dead shells of the thanatocoenoses around Amami to Okinawa Islands, as confirmed by observation under the X ray. L. kawamurai still now lives in the vicinity of Amami-ohshima Island but the population has maybe declined since Little Ice Age in 16th to 19th century.
日本貝類学会の論文
1997-09-30