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Benthic Marine Algae of Rotuma Island 3 89
Halimeda triloba Decaisne 1842: 102.
Halimeda opuntia (Linnaeus) Lamouroux f. triloba (Decaisne) J. Agardh 1887: 84;
Taylor 1960: 176; Verheij and Prud'homme van Reine 1993: 138, pl. 6, fig. 6.
?Halimeda opuntia (Linnaeus) Lamouroux var. macrocarpa Askenasy.
(Fig. 70a-c)
Fijian Records
Askenasy 1888; Chapman 1971: 166; Kasahara 1985: 22, pl. 2, fig. 3; Kasahara 1988;
South 1991: 5; South 1992: 9, figs 26-28; South and Kasahara 1992: 51.
Halimeda opuntia (Linnaeus) Lamouroux var. opuntia Hillis 1959: 360, pl. 2, fig. 8; pl.
5, fig. 3; Chapman 1977: 162; Wynne 1993: 23, fig. 11.
(Figs 70b, 83)
Plants bushy and possessing multiple attachment points; branching dense and irregular to
opposite, in many planes. Clumps to 10 cm in diameter, 6 cm high. Segments 10 mm broad
to 5 mm high, reniform, ribbed and trilobed at base of plant. Colour light to dark green, basal
segments often white. Cortical utricles small, rounded and slightly adhering in surface view
10-12 p,m in diameter. Secondary utricles slender and fork-shaped, arising as dichotomies of
the medullary filaments.
Distribution
Tropical Pacific and Indian Oceans.
Rotuman Distribution
Fapufa (Fl); Hofe'a (H46, H82, H105, H110, 11 1, H200, H202, H206, H219, 220);
Oinafa (015, 023, 036, 37, 040,41, 043, 045, 047, 049, 0531 USP 397, 056, 059, 071,
72,075); Tua'koi (Tll USP 399, T2).
Habitat and Remarks
Most common Halimeda sp. on Rotuman reefs, found at all sites and often in exposed
places (e.g. edge of reef) where its low-profile habit and strong attachment mode offer a
distinct advantage over other species. In sheltered, sandy sites (e.g. Isilepi at Hapmafau) this
species forms large clumps up to 1 m in diameter in shallow water, often in association with
epiphytic Caulerpa racemosa and C, serrulata.
Halimeda opuntzh (Linnaeus) Lamouroux var. hederacea (Barton) Hillis 1959: 360, pl. 2,
fig. 7; pl. 5, fig. 4; Taylor 1950: 81, pl. 40, fig. 1; Dawson 1956: 42; 1957: 109; Payri and
Meinesz 1985a: 509; Lewis 1987: 3 1.
Halimeda opuntia f. hederacea Barton 1901: 21, pl. 2, fig. 23 (type locality: Indonesia).
Halimeda opuntia forma Taylor 1950: 83.
?Halimeda incrassataJ: distorta Yamada 1941: 119, fig. p. 120; Yamada 1944: 28, pl. 4.
(Figs 70c, 84)
Plants bushy and loose in habit, with multiple holdfasts, forming distinctive net-like
complexes. Heavily calcified, light green to white in colour. Does not form clumps, but
rather assumes a creeping or hanging habit. Segments up to 6 mm broad and 5 mm high,
trilobed at base of plant, becoming reniform to oval at outer portions, very slightly ribbed.
Peripheral utricles hexagonal in surface view, 24-27 p.m in diameter.