Thallus reconstruction of nongeniculate coralline algae (Corallinales, Rhodophyta)

研究了非膝状珊瑚藻体的重建。在琉球群岛石垣岛卡比拉湾，人们在白石叶（Lithophyllum pallescens）的枝尖上人工制造了水平和垂直的伤痕，这些伤痕生长到巨石大小的结节。对疤痕恢复过程的时间序列观察揭示了以下几点。(1)在大多数情况下，当形成水平瘢痕时，位于断裂细胞下面几层的细胞变成分生组织细胞，向外产生新的上皮细胞，向内产生新的营养细胞。然后，新生上皮细胞上方的死细胞脱落。瘢痕周围未损伤部位很少产生新组织；随后新组织的横向生长恢复了疤痕。(2)垂直疤痕重建时，疤痕边缘、侧面和底部都形成了新的细胞。新形成的组织在边缘和侧面是二聚体，而底部的组织则是巨大的或二聚体。这些结果表明，尽管上皮细胞被认为是终止细丝的细胞或具有通过脱落去除有害物体（如其他藻孢子）的功能，但它们在珊瑚藻体的死亡部位的脱落中起着积极的作用。

Reconstruction of nongeniculate coralline algal thalli was investigated. Horizontal and vertical scars were artificially given on the branch tips of Lithophyllum pallescens growing as up to boulder-sized nodules in Kabira Cove, Ishigaki-jima, Ryukyu Islands. Time-series observations on the course of the recovery of scars have revealed followings.(1) When the horizontal scars were given, in most cases, those cells located several-cell-layrs beneath the broken cells became meristem cells that produced new epithallial cells outwardly and vegetative cells inwardly. Then the dead cells above the new epithallial cells were sloughed off. Rarely new tissues were generated from undamaged parts encircling the scars ; the scars were recovered by subsequent lateral growths of the new tissues.(2) In the case of the reconstruction of vertical scars, new cells were formed at the edges, sides, and bottoms of scars. Newly-formed tissues are dimerous at the edges and sides, while those at the bottoms are monomerous or dimerous.These results demonstrate that coralline algal thalli possess excellent capability of recovering scars by herbivores and that epithallial cells play positive role for sloughing off dead parts of coralline algal thallus, although they have been regarded as those cells terminating filaments or having a function for removing harmful objects such as other algal spores by sloughing.