Morphological and Life History Divergence of the Zoanthid, Sphenopus marsupialis off the Taiwanese Coast

臺灣帶狀兔葵在形態及生活史上之分化

宋克義(Ker-Yea Soong) ； 蕭育聖(Yuh-Saint Shiau) ； 陳章波(Chang-Po Chen)

《Zoological Studies》 38卷3期 (1999/07) Pp. 333-343

摘要

本研究比較了單體型式的袋狀兔葵（Sphenopus marsupialis）在臺灣不同海域的形態及生活史上的變異。樣品由1989至1995年間以底拖網採自沿岸水深10－25米的五個地點。由南部二地點（中芸、林邊）採得的體柱長約是其他較北地點（大溪、馬沙溝、茄萣）的2倍。成熟體柱長也是南部的林邊大於北部茄萣的個體。經由卵徑分析，生殖季應以南部（林邊）在八月早於十至十一月間的北部族群。在南部，個體都是雌雄異體，而北部茄萣則有22%的成熟個體為雌雄同體。北部採得的個體中7%有正在進行橫分裂的現象，而南部的個體則全無此現象。進行分裂個體的比例以五至十月時較低，而以其他季較高，分裂後個體比成熟體柱長還小。臺灣南、北採得的袋狀兔葵顯然在外型及生活史多方面都有很大的差別，然而傳統上用作分類、鑑定依據的不同部位刺細胞上卻未見不同。本研究顯示在目前被認為有世界性分布的袋狀兔葵，在臺灣海岸可能已經有分化的現象。

關鍵字

兔葵 ； 體型 ； 生殖 ； 無性生殖 ； 刺細胞

並列摘要

The morphology and life history of the solitary zoanthid, Sphenopus marsupialis, were studied. Individuals were collected by periodic bottom trawling at about 10-25 m depth at 5 localities along the coast of Taiwan from 1989 to 1995. The sizes (column length) of individuals from 2 southern localities were about twice as great as those from 3 relatively more northern localities. The size of mature specimens was also significantly larger at Linbien (south) than at Chadin (relatively north). The sizes of cnidae occurring on tentacles, actinopharynx, mesenterial filaments, and body columns of the zoanthids were not significantly different between the 2 sites. The seasonal change of oocyte diameters revealed that spawning occurred in August at Linbien, but later at Chadin, between October and November. At Linbien, individuals were strictly gonochoristic, whereas 22% of mature individuals were hermaphroditic at Chadin. Transverse division, the first such case reported in Zoanthidea, occurred in about 7% of more than 8000 examined individuals from the 3 relatively northern localities. In contrast, no evidence of asexual division was observed in more than 500 individuals from the 2 southern localities. Asexual division reduced the size of the organisms to below the normal maturation size. The relative frequencies of dividing individuals were lower between May and October, prior to the presumed spawning, than at any other time of the year. The populations from southern and northern localities are obviously different in their reproductive and life history characteristics, although they cannot be separated by cnidom or septa numbers, which have been traditionally used as taxonomic characteristics. These results suggest that what was considered Sphenopus marsupialis, with worldwide distribution, might actually be comprised of 2 sibling species off the Taiwanese coast.

並列關鍵字

Zoanthid ； Size ； Reproduction ； Asexual ； Cnida