Geographic Variation of Nautilus in the Philippines

Research Project

Project/Area Number	04041085
Research Category	Grant-in-Aid for international Scientific Research
Allocation Type	Single-year Grants
Section	Field Research
Research Institution	Kagosihma University
Principal Investigator	HAYASAKA Shozo Kagoshima University, 学長 (20041212)
Co-Investigator(Kenkyū-buntansha)	OROSCO C. University of San Carlos,, 助教授 BATOMALAQUE A. University of San Carlos,, 生物学科長 TANABE Kazushige Geological Institute, Fac. of Sci., Univ. of Tokyo, 理学部, 教授 (20108640) SUZUKI Hiroshi Labo. of Marine Biology, Fac. of Fisheries, Kagoshima Univ., 水産学部, 助手 (30162994) OKI Kimihiko Institute of Earth Science, Faculty of Sci., Kagoshima Univ., 理学部, 助教授 (90041235) SHINOMIYA Akihiko Labo. of Marine Biology, Fac. of Fisheries, Kagoshima Univ., 水産学部, 助教授 (90041722) TSUKAHARA Junzo Department of Biology, Faculty of Science, Kagoshima Univ., 理学部, 教授 (20008923) A.BATOMALAQU University of San Carlos, 生物学科長 E.C.FLORES University of the Phillippines, 教授 A.C.ALCALA Silliman University, 教授
Project Period (FY)	1992 – 1993
Project Status	Completed (Fiscal Year 1993)
Budget Amount *help	¥15,500,000 (Direct Cost: ¥15,500,000) Fiscal Year 1993: ¥9,000,000 (Direct Cost: ¥9,000,000) Fiscal Year 1992: ¥6,500,000 (Direct Cost: ¥6,500,000)
Keywords	Nautilus / Philippines / Geographical Variation / DNA / Habitat Environments
Research Abstract	In 1993, field works on the environmental condition of nautili habitat and for the study of their geographic variation were carried out at the coastal seas on the west and east sides of Cebu Island in summer (from July to early September) and at the Balayan Bay, southern part of Luzon Island in summer (August) and in winter (November). At the areas on both sides of Cebu Island, bottom topography and bottom sediments are different from the ones at the areas west and south of Bohol Island where we made field study last year. Through the survey on sea water characteristics, a thermocline was recognized to exist between 100 and 150m in depth, and the waters of Nautilus habitat deeper than the thermocline were known to be rich in phosphorus, nitrogen and silica. It was also clarified that the temperature of water deeper than 200m is always 3 to 6ﾟC higher in Tanon Strait than in Bohol Strait. During the field work, 45 individuals of Nautilus were caught through 18 trappings. Their sex ratio is … More 2(male) : 1(female), but this female ratio is far higher than those in Fiji and Palau. Last year, we got many immature individuals of Nautilus at the same station in the area southwest of Bohol Island, and this may be a strong clue to infer the site of spawning and hatching. This year, on the contrary, we could catch many individuals of various growth stages (from 45 to 127mm in shell height) at the same station. These are important information to infer spatial relation between the sites of spawning and hatching and of the habitat of adult individuals. Many male and female mature soft bodies were collected for histological and genetic studies. The fauna associated with Nautilus were also collected and compared with those from many other places, such as Fiji, Palau and Papua New Guinea. The field survey in Balayan Bay was carried out in cooperation with the staff from the Philippine National Museum. 56 individuals of Nautilus for the study of geographic variation and 64 individuals for rearing in tank were collected. Among them, 15 individuals were sent to Japan keeping alive, and are now under the scientific observation. On some fresh specimens, DNA analyses are also planned. Less