Geographic Variation of Nautilus in the Philippines

1993年夏季在宿务岛东西两侧近海进行了鹦鹉螺栖息地环境条件和地理变异的野外调查（7月至9月初）和吕宋岛南部的巴拉扬湾（夏季（8月）和冬季（11月）。在宿务岛两侧，海底地形和海底沉积物与我们去年在保霍尔岛西部和南部进行的实地考察不同。通过海水特征调查，温跃层被认为存在于100至150米深处，而鹦鹉螺栖息地的沃茨比温跃层更深，已知富含磷、氮和硅。在野外工作中，通过18个诱捕器共捕获鹦鹉螺45尾，其中18个诱捕器捕获的鹦鹉螺个体数最多，达农海峡200 m以上的水温比保霍尔海峡高3 ~ 6 ℃。他们的性别比例是 关于我们 2（男性）：1（女性），但这一女性比例远远高于斐济和帕劳。去年，我们在保霍尔岛西南部地区的同一站得到了许多鹦鹉螺的未成熟个体，这可能是推断产卵和孵化地点的有力线索。相反，今年我们可以在同一个站点捕获许多不同生长阶段（壳高从45到127毫米）的个体。这些都是推断产卵和孵化地点与成年个体栖息地之间空间关系的重要信息。采集了许多雄性和雌性成熟软体动物进行组织学和遗传学研究。还采集了与鹦鹉螺有关的动物群，并与许多其他地方的动物群进行了比较，例如斐济，帕劳和巴布亚新几内亚：与菲律宾国家博物馆的工作人员合作，对巴拉扬湾进行了实地调查。共采集到56只鹦鹉螺个体用于地理变异研究，64只个体用于池养。其中15只被送往日本，目前正在接受科学观察。还计划对一些新鲜标本进行DNA分析。少

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