J Integr Plant Biol. ›› 1962, Vol. 10 ›› Issue (2): -.

• Research Articles •    

Studies on Chinese Species of Dictyosphaeria

C. K. Tseng and C. F. Chang   

Abstract: The genus Dictyosphaeria was founded by Decaisne, Valonia favulosa Ag. being chosen as the type. It has become fairly well known through the morphological and systematic studies of Murray (1892), Crosby (1903), Webervan Bosse (1905), Arnoldi (1913), Boergesen (1912, 1913) and Egerod (1952). In all these investigations the genus has been placed in Valoniaceae near Valonia. Dictyosphaeria is a small genus of tropical and subtropical algae now credited with only the following 9 accepted species and 2 varieties. Dictyosphaeria cavernosa (Forssk.) Boerg. (1932), and D. c. var. bullata Boerg. (1952), D. sericea Harv. (1860), D. versluysii Weber-van Bosse (1905), D. intermedia Weber-van Bosse (1905), and D. i. var. solida Nasr (1944), D. van bosseae Boerg. (1912), D. bokotensis Yamada (1925), D. australis Setchell (1926), D. setchellii Boerg. (1940), D. mutica Yamada (1944). Among these plants, Nasr's plant is probably the plant redescribed by Yamada (1944) as D. mutica as pointed out by Dawson (1956:29). The first records of the species of this genus from China were those of D. cavernosa (Forssk.) Boerg. and D. bokotensis Yamada from Taiwan Province by Yamada (1925). Later, the former species was reported by Okamura (1931), Tseng (1936) and Chou (1950) respectively from Kotosho, Taiwan Province, Hainan Island, Kwangtung Province, and Tungshan Island, Fukien Province. Fifteen collections from the various parts of the South China coast have recently been studied by the writers and a detailed study of these materials shows the presence of three more species, including a new one. The following is a description of the new species, Dictyosphaeria spinifera Tseng et C. F. Chang sp. nov.1): Thallus hollow, up to 2 cm. in diameter, obpyriform when young, later becoming irregular in shape (Pl. Ⅰ, fig. 1), attached by rhizoidal cell pro- jections from the ventral surface. Polygonal segments 450–900 μ, up to 1350μ in diameter. Multiplication of the hapteroid cells effected by cell division. The basal portion of each hapteroid cell composed of a great number of very short rhizoid-like lobe. Hapteroid cell square shaped, 45–55μ diameter in lateral view (pl. Ⅰ, fig. 3, upper); round or with slightly triangular shaped, 30–40 μ diameter in dorsal view (Pl. Ⅰ, fig. 3, middle); and rectangular, ca. 45μ in length in ventral view (Pl. Ⅰ, fig. 3, middle). Intercellular spines present at the inner walls of the segments, 37–85 μ long, obtuse at tips and 9–20μ wide at their bases, generally quite straight or sometimes bending a little, with smooth and even or sometimes a little waved surfaces. The hollow frond with spines projecting into the cell cavity is so distinctive as to separate this species readily from all others now recognized in this genus. The type specimen AST 60-2655, was collected from surf-beaten rocks near middle littoral region, Zhelang, Haifeng District, Kwangtung Province on 15, I, 1960 and deposited in the Herbarium of the Institute of Oceanology, Academia Sinica. This species has also been collected many times from the following places: Woody Island, March (58-4020)1), Rocky Island, April (58-4153), May (58-5333), Drummond Island, May (58-4658), all on Paracels Islands. The two species here reported for the first time for China are Dictyosphaeria versluysii and D. intermedia. The former species grows on rocks and dead coral chips in the middle and lower littoral regions. It has been collected from the following places of Hainan Island, Kwangtung Province: Paohujiao, Wenchang District; Sanya (Sama), Dongluo I., Maling and Hongtang, Ya District, and Paracels Islands: Woody I., Rocky I., North I., Observation Bk., Drummond I. and Luodao. A comparative study of D. versluysii with descriptions of three other closely related species, D. van bosseae Boerg., D. australis Setch. and D. setcheUii Boerg., show that they are not separable from each other and the last three species are therefore reduced to the synonymy of D. versluysii, as already suspected by Egerod (1952:355). These species, according to diagnoses, are differentiated only by the size of segments and intercellular spines. Our specimens show great variations of these characteristics even in the same specimen, with the segments varying from 425 to 2000μ in diameter, and intercellular spines from 22 to 150μ long and 7 to 30 μ wide. Thus, the supposed characteristics of the three species falls within the limits of D. versluysii, as revealed by our specimens. Papenfuss and Egcrod (1957:84) have doubted the separability of D. versluysii Weber-van -Bosse from D. bokotensis Yamada. After close examination of our materials, however, the writers have come to conclusion that they are sufficiently different from each other. D. bokotensis may be distinguished from D. versluysii by hollow frond, by simple intercellular hapteroid cells and by small cells of the upper parts of the plant. D. intermedia grows on rocks in the middle and lower littoral regions, often cast shore. It has been collected from Xinyinggang, Chengmai District and Jiaotou, Ya Dis- trict, Hainan Island, Kwangtung Province. D. cavernosa and D: bokotensis have already been recorded from China. The former species grows on rocks, pebbles and dead coral chips in the littoral and upper sublittoral regions. It has been collected from the following places: Dongshan I. of Fukien Province; Naozhoudao and Weizhoudao of Kwangtung Province mailand; Hainan Island: Qinglangang and Fengjiagang, Wenchang District, Xinyinggang, Chenmai District, Yinggehai, Ledung District, Gangbeigang, Wanning District, Xincungang, Lingshui District, Haitangtou, Luhuitou, Yulingang, Sanya, Hongtang and Jiaotou, Ya District of Hainan Island, Kwangtung Province; and Woody I, Rocky I., Middle I., Duncoh I., Drummond I., Observation Bk. and Luodao of the Para,els Islands of Kwangtung Province. The later species grows on dead coral chips in the'upper sublittoral region. It has been collected from Woody I., Paracels Is., Kwangtung Province, and has been recorded from Pcscadores I. and Ryukyusho, Taiwan Province by Yamada (1925; 1950). In the course of our morphological studies of the Chinese species of Dictyosphaeria, it has been found that the characteristics of the intersegmental hapteroid cells are of sufficient value in dividing them into taxonomic groups. Egerod is the first to recognize the value of the characteristics of intersegmental hapteroid cells in separating D. caver- nosa and D. versluysii. We are of the opinion that this characteristics is of sectional value and, therefore propose to divide Dictyosphaeria Decaisne into the following two sections: (1) Section 1. Simplex, sect. nov. Hapteroid cells are simple, unbranched. Typical species: Dictyosphaeria cavernosa (Forssk.) Boergesen. (2) Section 2. Ramifieata, sect. nov. Hapteroid cells are branched, bifurcate or trifurcate. Typical species: Dictyosphaeria versluysii Weber-van Bosse.

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