日本の紅藻アカバ属

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The red algal genus Neodilsea (Dumontiaceae, Cryptonemiales) includes at present six taxa : N. integra (KJELLM.) A. ZINOVA (1961), N. americana ABBOTT (1968), N. crispata MASUDA (1973a) and N. integra var. longissima MASUDA (1973b). These taxa have been recorded from various localities in temperate to cold zones of the Northern Hemisphere. Among these, the four taxa which are reported from Japan are : N. yendoana, N. tenuipes, N. crispata and N. integra var. longissima. The purpose of the present study is to analyze taxonomic features of each Japanese taxon based on a comparison between field material and cultured plants. Furthermore, the geographic distribution of each taxon in Japan is delineated, using herbarium specimens and the literature. The following features circumscribe the genus as it occurs in Japan : the mode of spore germination, the thallus structure, the occurrence of unicellular colorless hairs, the development of reproductive structures : tetrasporangia, spermatangia, carpogonial branches and auxiliary cell branches, and the development of gonimoblasts. The following taxonomic features are used to characterize each taxon in this paper: the size of spores, the thallus shape, the stipe length, the thallus surface, the thallus margin, the thallus texture, the frequency of hairs, and the form and size of spermatangia. A large number of tetraspores and carpospores were measured (Fig. 1) and their size ranges are definite for each taxon. Tetraspore dimensions are especially different from each other. In N. tenuipes and N. integra var. longissima the tetraspores from both field-collected and cultured plants are similar to each other. The difference in the dimensions of mature tetrasporangia among the four taxa appears to be uniform and within specific ranges, suggesting that the mature tetrasporangium dimension in Neodilsea has taxonomic significance (MASUDA, 1973a). The thallus shape is the most conspicuous feature in differentiating gross morphology (Fig. 3). That of three taxa other than N. yendoana is almost uniform ; N. tenuipes has an elliptical to circular thallus, whereas N. crispata and N. integra var. longissima possess linear to linear-lanceolate thalli. However, the thallus shape of N. yendoana shows a broad range of variation which includes those of the other three taxa, although the most common shape is obovate. The stipe length is of some taxonomic significance. N. yendoana has a short terete stipe usually less than 1 mm in length, whereas the other taxa have more conspicuous stipes of 2-7 mm in length (Fig. 4). The three species other than N. integra var. longissima possess irregularly rough furrows over the thallus surface in the living state, whereas the thallus surface of the latter is smooth. The marginal portion of well grown thalli of N. crispata becomes crispate, but that of the others are entire throughout their life history. The texture of living thalli is soft, except for N. yendoana which has a rather hard texture. The frequency of unicellular colorless hairs is characteristic of each taxon. N. integra var. longissima has numerous hairs throughout its life history. N. crispata has also hairs throughout its life history, but less abundant than those of the former taxon. Young plants less than 1 cm in length of N. yendoana and N. tenuipes bear abundant hairs, but the number decreases with age and in adult plants the hairs are scarce. The size and shape of spermatangia have some taxonomic significance (TAZAWA, 1956). N. yendoana produces large, ellipsoid spermatangia, whereas N. integra var. longissima bears small, almost spherical spermatangia. N. tenuipes and N. crispata bear spermatangia which are intermediate in size and form between those of the former two taxa. N. yendoana is widely distributed along the entire coast of Hokkaido and the Pacific coast of northern Honshu. Its range of distribution extends northward to Paramshir Isl., the northern Kurile Islands, and Sakhalin and westward
日本植物分類学会の論文
1982-04-20

日本の紅藻アカバ属

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