著者

川本 信之 三上 進

出版者

日本貝類学会

雑誌

貝類学雑誌 (ISSN:00423580)

巻号頁・発行日

vol.37, no.4, pp.230-239, 1978-11-30 (Released:2018-01-31)

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It is reported that the Nautilus makes a diel vertical migration from a depth of about 500 m up to the near-surface of the sea. However, it is axiomatic that such a long-ranged migration within a short period of the time cannot be managed by only water-jet propulsion through the hyponome. There has been a number of early works for elucidating how the animal is possible to make this migration, but no satisfactory solution has been obtained so far. Through an anatomical observation on muscle part of Nautilus macromphalus, we could speculate that two major retractors, namely, funnel and cephalic, may be involved in downward migration. Our hypothesis is that the contraction of these two retracting muscle will create a pressure in a sea water intaken in the mantle cavity and this pressure may be transmitted (through unknown mechanism) to the siphuncle. If so, the gas contained in other chamber could be compressed and makes the specific gravity of animal increased.

著者

浜田 隆士 奥谷 喬司 棚部 一成 出口 吉昭 福田 芳生 波部 忠重 平野 弘道 蟹江 康光 川本 信之 三上 進 小畠 郁生

出版者

日本貝類学会

雑誌

貝類学雑誌 (ISSN:00423580)

巻号頁・発行日

vol.37, no.3, pp.131-136, 1978

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Progress and some results of the second rearing experiment of Nautilus macromphalus in Tokyo are described. The temperature controlling experiment is still applying to three extant individuals, that were supplied from New Caledonia last year through the courtesy of the ORSTOM in Noumea, and they are surviving for 222 days in captivity (May 14, 1978). Copulating behaviors are observed mostly in the waters of 17-19℃ in temperature but not in the cooler conditions. Shell growth at the apertural periphery was first measured to find that some individuals probably in a gerontic stage show no remarkable increment on one hand, the young specimens show 10-12 mm elongation per 100 days on the other. Recently the JECOLN also takes care of a living Nautilus pompilius that had been floated possibly from the Philippines along the Kuroshio Current over 2, 000 km and was captured by a fishing net set off Kawajiri, Kagoshima Prefecture in Kyushu, Southwest Japan.