Abstract
The freshwater red algal form taxon, Chantransia macrospora Wood, was recently collected at an artificial reservoir pond in Okinawa, Japan. This species is chiefly characterized by a bluish-green thallus and erect filaments irregularly branched with cylindrical to tapered cells and monosporangia on lateral branchlets. Our culture study confirmed that C. macrospora from Okinawa was the ‘chantransia’ sporophyte of Batrachospermum species. The rbcL sequence of C. macrospora from Okinawa was identical to isolate FG15 of this species from French Guiana in South America. The sporophyte Chantransia macrospora as well as the gametophyte B. macrospora Montagne are distributed in North and South America. However, there have been no records of either C. macrospora or B. macrosporum in Japan or in eastern Asia. Therefore, C. macrospora specimens originally from South America may have been introduced to Okinawa, Japan, through the vector such as ornamental macrophytes.
Highlights
Many introduced species of marine macroalgae have been reported worldwide, for example, the green algae Caulerpa taxifolia (Vahl) C
The thallus was composed of a uniseriate erect filament branching with narrow angles (Figure 1A) and well-developed rhizoids
Lateral branches irregularly arose from the axial cell and formed monosporangia (19-23 μm in diameter and 31-39 μm in height) on apices of the ultimate branches
Summary
Many introduced species of marine macroalgae have been reported worldwide, for example, the green algae Caulerpa taxifolia (Vahl) C. Several introduced species of freshwater macroalgae, Bangia Lyngbye, Compsopogon Montagne, Hildenbrandia Nardo, have been found, and the possibility of their introduction was usually reinforced by molecular phylogenetic analyses (Müller et al 1998; Rintoul et al 1999; Sherwood and Sheath 1999)
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