カブトガニの適応戦略と種分化

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概要

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• 1) Adaptation : The horseshoe crabs adapt highly to the environment during their life ecologically and physiologically as well as morphologically. For example, the spawning behavior of horseshoe crabs shows a semidiurnal rhythm. As they lay eggs in the sand near the high tide level at high tide twice a day, egg clusters are submerged for a relatively short time and exposed to the air most of the day. This environment is favorable to protect the eggs from enemies, but it is not always adequate for the eggs because of dryness and low or high salinity. As a countermeasure, the horseshoe crab embryo forms a thick and strong membrane, inner egg membrane, under the chorion. The embryo holds seawater in the perivitelline space surrounded by the inner egg membrane and the egg with this membrane is gradually swollen by influx of seawater during embryonic development. The developing embryo is protected in this expanding aquatic space for about 30 days until hatching. 2) Speciation : The American horseshoe crab shows a distant relation to the Asian species at the higher level than at the genus level, judging from the external and internal morphology, artificial crossing experiments among four extant species, biochemical studies of high molecular protein and so on. From the morphological point view, it is reasonable to divide the Asian species into two genera, Tachypleus and Carcinoscorpius. However, from our results of artificial crossing and analyses of proteins, T. tridentatus has rather closer relation to C. rotundicauda than to T. gigas. Thus, we consider that the three Asian species of horseshoe crabs belong to the same genus, Tachypleus.

• 日本古生物学会の論文
• 1994-06-30

著者

• 関口 晃一

  筑波大学

関連論文

• カブトガニの適応戦略と種分化
• 6.インドネシアおよびその周辺のカブトガニの分布について(動物分類学会第17回大会講演要旨)
• カブトガニの生息地の現状--沿岸性節足動物の一例として (特集 検証 生物の減少・絶滅)

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