黑潮笠藤壺和美麗笠藤壺之生殖週期在台灣黑潮流域及東海海域的比較研究

Abstract

台灣為橫跨亞熱帶和熱帶的西太平洋大型島嶼，高溫的黑潮沿著台灣東邊往北流經，為整個台灣東部海岸帶來終年溫暖的海溫；位於東海邊緣的東北角海岸在冬天則受到東北季風所帶來的冷水團影響，終年平均海溫明顯較東岸低。潮間帶生物大部分為無脊椎生物，其生殖週期極受溫度差異所影響。在台灣季節性的海溫差異影響下，我們提出了以下假說：位於東北角海岸及東海岸的潮間帶藤壺，其生殖會受到海溫影響而有所不同。 此研究調查了東北角海岸和東海岸中，兩種潮間帶常見的藤壺：黑潮笠藤壺(Tetraclita kuroshioensis)及美麗笠藤壺(Tetraclita japonica formosana)，自2006年到2009年間，其生殖季和性腺發育情形。卵巢、精巢、儲精囊及受精卵根據發育情形，先藉由外觀判定出不同的形態發育階段，再以切片觀察生殖細胞的發育情形定出生理層級的發育階段。 研究結果顯示，從2006到2009年間，精巢和卵巢的發育皆與海溫有顯著的相關。位於東北角的黑潮笠藤壺和美麗笠藤壺，其精巢多成熟於四月到九月；位於東海岸的黑潮笠藤壺和美麗笠藤壺，其精巢多成熟於二月到十一月，有著較長的成熟期。儲精囊內儲藏的成熟精子在東海岸及東北角皆終年存在。卵巢在東北角和東海岸幾乎都是終年成熟 (具有成熟卵母細胞) 的狀態。東海岸的黑潮笠藤壺和美麗笠藤壺每年具有兩到三次產卵發生，為期二月到十月；東北角的黑潮笠藤壺和美麗笠藤壺每年則有一到兩次產卵發生，為期五月到九月。此生殖差異，很有可能是由於東海岸較高的海水溫度影響所致。

Taiwan is a large island located in the subtropical to tropical region of West Pacific Ocean and the hydrography is influenced by different ocean systems. The Kuroshio Current flows along the east side of Taiwan and continues northward, which brings warm water to the East coast throughout the whole year. The Northeast coast adjacent to the East China Sea also experiences the warm water from Kuroshio Current during the summer season, whereas at the winter season, the strong northeasterly monsoon weakens the effect of the Kuroshio current at the Northeast coast by bringing cold water southward and lowering the water temperature. In the intertidal, most of the species are invertebrates and the reproductive cycle is very sensitive to the temperature change. The water temperature difference with the seasonal variation in Taiwan can be suitable to examine the influence of temperature changes to coastal organisms. Under such circumstances, it is hypothesized that the reproductive cycles of intertidal species at the Northeast coast and at the East coast of Taiwan can be different. In this study, we examined the reproductive status and the gonad development of two common barnacles, Tetraclita japonica formosana and Tetraclita kuroshioensis, in the Northeast coast (He-Ping-Dao and Badouzi) and the East coast (Shi-Ti-Ping and Chenggong) in Taiwan from April 2006 to December 2010. The experiment was conducted by macroscopic and histological approaches. The morphological developments of ovaries, testes, seminal vesicles and eggs were first examined and then histologically sectioned to investigate the development of male and female germ cells. The levels of development were classified into ranked categories. The result showed that during 2006 to 2009, the development of male and female gonads was strongly correlated to water temperature. The testes were mature from April to September at the Northeast coast and from February to November at the East coast. The seminal vesicles were all filled with spermatozoa all year round in all sites. At the Northeast coast, the breeding period was shorter, range from May to September and one to two broods produced per year; whereas at the East coast, the breeding period was longer, range from February to October and two to three broods produced per year. The ovaries were almost mature (with mature oocytes) all year round in both Northeast and East coasts, yet revealed better development in T. kuroshioensis at the East coast than the Northeast coast. It is concluded that in T. kuroshioensis and T. j. formosana, the durations of testes maturation and breeding period were longer at the East coast than the Northeast coast as a result of the influence of temperature.