Bibliographic Detail

Ioriya, T., 1986

Reference:
Ioriya, T. (1986). Taxonomic studies of the genus Tribonema (Xanthophyceae, Chrysophyta) from Japan. Journal of the Tokyo University of Fisheries 73(1): 1-48.

Abstract:
On the basis of natural and cultured populations, systematic revision was made of six taxa of Tribonema, T. minus, T. affine, T. aequale, T. yamadanum, T. bombycinum var. bombycinum and T. bombycinum var. vulgare collected from Japan, mainly Hokkaido and southward to the Kanto District. Through this study, the diameter of vegetative cells was found characteristic to species and regarded at one of the most effective taxonomic characters. The diameter in T. bombycinum var. bombycinum showed a peculiar bimodal distribution in the variation of natural and cultured materials obtained from akinetes and that in unialgal cultured materials from a fragmental filament showed a normal distribution. The diameter of the other species examined showed a normal distribution in the natural and cultured materials obtained from fragments and akinetes. The cell length and length/diameter ratio were effective characters for identification of species only when they were used with other characters. Chromatophores in cells were disc-, plate- or band-shaped. The shape of them was specific, though they were somehwat changeable by the effect of light intensity. The number of them in a cell was comparatively definite with species, and was another one of the most effective characters. The cytological observations proved that the chromomome number was 17 in all species examined. Akinetes were formed in the N-free cultures. There were found three types of germination in the mother cell; axial extending, one side swelling and all directions swelling types. Difference in tolerance of akinetes for drying among species was also recognized. Zoospores were formed in the dark culture at low tmeperature (10.degree. C). The size of zoospore and shape and number of chromatophore in zoospores were characteristic to species. Physiological characters, including growth in different temperatures (20.degree. and 8.degree. C) and viability in dark were examined. These observation and experiments allowed to describe six taxa in detail with a variation of quantitative characters. Of these taxa, T. bombycinum var. vulgare was described as a new combination.