Caulerpa ambigua Okamura, 1897: 4, pl. I: figs. 3–12 (type locality: Ogasawara-gunto [Bonin Islands], Japan).—Papenfuss, 1952: 167–168.— Isaac, 1956c: 11.— Isaac & Chamberlain, 1958: 127–129.— Pocock, 1958: 24.— Egerod, 1975: 53, fig. 21.— Seagrief, 1980: 20, fig. on pl. 1.— Kalugina-Gutnik, Perestenko, & Titlyanova, 1992: 24 (table 1).— Titlyanova, Perestenko, & Kalugina-Gutnik, 1992: 45.
Caulerpella ambigua (Okamura) Prud'homme van Reine & Lokhorst, 1992: 114.—Wynne, 1995: 331, fig. 85.
Taxonomic synonym:
Caulerpa vickersiae Børgesen, 1911: 129–132, fig. 2 (syntype localities: St. Jan [St. John], Virgin Islands; Barbados).—Børgesen, 1949a: 6–12, figs. 1, 2 ("var. typica'').— Børgesen, 1953: 6–8.— Børgesen, 1954a: 6.— Nizamuddin, 1967: 160, 163–164, figs. 14–17, pl. II.— Hackett, 1977: 23.— Payri, 1985: 640.— Shameel, 1978a: 277–282, tables 1, 2.— Shameel & J. Tanaka, 1992: 28.— Amjad & Shameel, 1993b: 115.
INDIAN OCEAN DISTRIBUTION: Maldives, Mauritius, Mozambique, Pakistan, Réunion, Seychelles (including Mahé Island), South Africa, Thailand.
Note: The conspecificity of Caulerpa ambigua and C. vickersiae was proposed by Eubank (1946: 410–413) but denied by Børgesen (1949a: 6–12; 1953: 6–8). Dawson (1956: 35–36) recognized both species growing together in the Marshall Islands. Egerod (formerly Eubank) (1975: 53, fig. 21), after observing that branching patterns characteristic of each species could be found on one thallus, maintained her original conclusion. Prud'homme van Reine & Lokhorst (1992) also came to this conclusion. In a study of this species from the Cape Verde Islands, those authors found whorls of reproductive structures (possibly gametangiophores) separated from the main axis by a distinct transverse wall. Considering that all instances of reproduction observed in Caulerpa so far have been holocarpic (that is, the gametes are formed throughout the coenocyte), they established the new genus Caulerpella to receive Caulerpa ambigua. Because this species shares the highly specialized trabeculate structure of all other species of Caulerpa, it seems more appropriate to accord infrageneric taxonomic value to the character of non-holocarpic reproduction, assuming that further studies will uphold this distinction.