Comparison of the Population Density of Oceanic Sea Skater of Halobates (Heteroptera: Gerridae) among Several Areas in the Tropical Pacific Ocean and the Tropical Indian Ocean

大洋性海黽在熱帶西太平洋與熱帶印度洋數個地區的族群密度調查

Tetsuo Harada ； Takero Sekimoto ； Koki Iyota ； Takashi Shiraki ； Shiho Takenaka ； Mitsuru Nakajyo ； Yuki Osumi ； Chihiro Katagiri

《台灣昆蟲》 30卷4期 (2010/12) Pp. 307-316

https://doi.org/10.6661/TESFE.2010023

摘要

全球只有5種大洋性海黽(Halobates)，其中3種分布在西太平洋與印度洋。本研究的目地在了解牠們在熱帶太平洋西部與熱帶印度洋地區的族群密度。調查在「未來」和「白鳳丸」兩艘日本研究船於2006~2008年的四次巡航中進行，以海洋研究所與紐斯頓網兩種浮游生物網取樣。結果顯示在北半球的熱帶西太平洋地區，H. micans與H. germanus密度遠高於H. sericeus。前二者在調查區域西端(0~10°N, 130°E)的密度皆高達57,000隻／km^2，但是在此以東地區密度驟減，並向東遞減，只有13,000~17,000隻／km^2。此密度差異可能是由於西端靠近印尼與菲律賓，有來自溪流入海帶來的豐沛浮游動物或死魚等食物來源。在東經147°以東的調查區域，H. germanus是優勢物種。H. micans在熱帶印度洋上的密度達42,000隻／km^2，約為H. germanus的17倍，而後者僅發現在赤道以北的採樣點。H. sericeus過去僅知分布在13~45°N的西太平洋，本研究則發現牠們也分布在熱帶地區，密度為2,010~7,100隻／km^2。牠們可能是藉由此區域內數個洋流四處轉移或擴張領域。除了三種已知物種外，本研究另外發現兩個分布在熱帶西太平洋的大洋性的未定物種，但是數量只佔所有海黽的少數，牠們的確實身分須經更進一步的研究確認。

關鍵字

大洋性海黽 ； Halobates ； 族群密度 ； 洋流

並列摘要

The purpose of this study was to clarify the population density of oceanic Halobates in the western area of the tropical Pacific Ocean and the Indian Ocean around the equator (10°S-10°N). This study was carried out during 4 cruises (MR-06-05-Leg 3, KH-07-04-Leg 1, MR-08-02 and MR-09-04) by the Research Vessels Mirai and Hakuhomaru. Samplings were performed using Ocean Research Institute (ORI) nets and Neuston nets. Halobates micans showed to have a high population density of 10,000 individuals/km^2 or higher in the western area of the tropical Pacific Ocean at 0-10°N. In the relatively eastern region of this area which is less likely to be affected by freshwater flowing down from rivers of the tropical islands, the population density was around 5,000 individuals/km^2 and split between 147-156°E and 130-135°E. The distribution of H. sericeus has been reported to being limited to 13-45°N in the Pacific Ocean. However, a relatively moderate population density of between 2,010 to 7,100 individuals/km^2 was found in the four areas (including the area around the equator) of the western tropical Pacific Ocean. This species may have been transferred by several different currents including the Kuroshio Current, North Equatorial Current, Mindanao Current and the North Equatorial Counter Current throughout the large area of the western Pacific Ocean. In this study, the high population density of H. germanus was estimated to range between 13,000 and 60,000 individuals/km^2 throughout the longitudinal area of 130-156°E (0-10°N) of the western tropical Pacific Ocean. Halobates princeps (Halobates sp. 1) which has been reported as a shore species inhabiting widely Indonesia and might be a new oceanic specimen, was collected at 2°N, 130°E during the MR-06-05-Leg 3. The body length of males of H. sp. 1 (apical edge of the head to the penis like an arrow) is about 6 mm, and the reach of the mid-legs is 27 mm in a static posture on a flat surface. Individuals of H. sp. 2 were collected in the tropical Pacific Ocean during the three cruises, MR-06-05-Leg 3, MR-08-02, and MR-09-04. Halobates sp. 2 may be another new oceanic species in Halobates. Its size is similar to H. micans, while the body shape (morphometry) and color are very similar to H. sp. 1, which is much larger than that of H. sp. 2.

並列關鍵字

oceanic sea skaters ； Halobates ； population density ； currents