台灣澎湖地區玉柱蟲Ptychodera flava之生殖週期

Abstract

玉柱蟲是屬於半索動物門腸鰓亞綱下的一群蠕蟲狀海洋底棲動物，近年因其演化地位、再生能力與產生特殊生化物質的能力而被研究。本研究以台灣澎湖縣白沙鄉歧頭地區的玉柱蟲Ptychodera flava為對象，觀察其族群與生殖生物學特性，期為該地區玉柱蟲資源狀態與生殖生物學留下初步記錄。於2009年7月、11月、2010年4月、7月、10月測量該地區族群密度，另於2009年7月起至2010年12月，按月採集玉柱蟲標本，並測量其體型大小及觀察其生殖腺組織切片以探討其生殖週期。此外本研究也對生殖翼內碳水化合物及脂質的累積位置以不同組織化學染色進行初探。結果顯示該地區玉柱蟲密度會隨時間變化，2010年2月平均鰓裂長顯著大於2009年9~10月與2010年9月。樣本共計取得1005隻樣本，包含雌蟲140隻、雄蟲207隻及未能確認性別者658隻，經卡方檢定總性比不為1:1且雄性較為優勢。比較不同鰓裂長區間的性比顯示，0~10 mm雄性較為優勢而20~25 mm為雌性較為優勢，顯示雌雄在鰓裂長有不一樣的分佈頻率。雄性最小鰓裂長為2.25 mm而雌性為5.19 mm，指出兩性的最小性成熟體型有所差異。經組織化學染色顯示碳水化合物及脂肪可能累積於生殖腺內的卵黃細胞，此外本研究發現碳水化合物也聚集在1種出現於生殖翼中且雌雄都有的構造內，且有時會與生殖腺邊緣接觸。由於該構造未被文獻描述過，因此本研究暫稱其為碳水化合物體。本研究依據生殖腺發育階段，推測該地區玉柱蟲P. flava於研究期間一年有一次生殖季，期間約為9~12月。

Acorn worm are worm-like benthic marine invertebrate which belong to phylum Hemichordata and Subclass Enteropneusta. This research focused on the population feature and the reproduction biology of the acorn worm Ptychodera flava at Chito, Penghu, Taiwan. I have studied the population densities on July 2009, November 2009, April 2010 and October 2010. I also examined monthly gonad developments by histological section and measured the body size of this species from July 2009 to December 2010. The localization of carbohydrate and lipid in gonad was studied by various histochemical staining methods. My results indicated that the density of population and average gill length changed with time. The total number of specimen collected in entire research period was 1005, include 140 females, 207 males and 658 sex unknown individuals. The total sex ratio of those specimens was different from 1:1, and the number of males specimens were more than females. Furthermore, male was dominant in the group of gill length in 0~10 mm, and female was dominant when gill length is in 20~25 mm, indicate sexual dimorphism in body size. In addition, the minimum gill length of mature male was 2.25 mm, and mature female was 5.19 mm, suggesting the minimum maturation body size was also different between sexes. The results of histochemical staining showed that carbohydrate and lipid may accumulate in the yolk cells in the gonads. I also found that carbohydrate may also accumulate in the structures in the genital wings in both sexes. These structures existed in the periphery of the gonads and attached to the gonads. Because this structures had not been described before, I named it carbohydrate body in this study. In sum, my data of the gonad development stages suggest that there is one annul reproductive period of the acorn worm P. flava at Chito. and the period was around September to December in both two years.