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Benthic Marine Algae of Rotuma Island 393
Avrainvillea rotumensis N'Yeurt, Littler et Littler 1996 (type locality: Hofka, Rotuma
Island).
(Figs 51a-d, 53,56)
Thalli to 10 cm tall, olive-green, solitary; mature blades peltate, 9 cm in diameter, 4 mm
thick, smooth, concentric zonation faint, blade margins smoothly rounded, not lobed or
ragged, to 2 mm thick; stipe to 6 cm long, 2 cm in diameter, cylindrical, seldom branched;
anchored by bulbous, fibrous rhizoidal system. Medullary siphons of blade 20-40 pm in
diameter, moniliform, weak-walled; surface siphons of blade taper abruptly to 8 pm in
diameter, moniliform to tortuous, dichotomies wide-spreading; apices rounded, hooked or
tortuous, forming loose cortex; siphons of growing margin 30-40 pm in diameter,
moniliform, tapering to 20 ym in diameter; medullary siphons of stipe 50-80 pm in
diameter, moniliform; cortical siphons of stipe tapering to 8-15 ym in diameter, moniliform
to tortuous, often hyaline; rhizoids moniliform, tortuous to cylindrical, 20-50 pm in
diameter tapering to 10 pm in diameter.
Rotuman Distribution
Hof6a (H2301 !USP 615; H2311 USP 622).
(! = type specimen)
Habitat and Remarks
Growing 1.5-3 m depth, at the mouth of a passage on outer reef; anchored in carbonate
sediments. Specimens of this alga were confirmed as representing a new species by D.S., and
M.M. Littler of the Smithsonian Institution, and it is described by N'Yeurt et al. (1996). It is
characterised by being the only truly peltate form of the genus, and hence easily recognisable
in the field).
Chlorodesmis Harvey et Bailey 1851: 373
Key to the Rotuman Species of Chlorodesmis
1. Plants up to 6 cm high; filaments 95-130 pm in diameter ..................... .C. hildebrandtii
1: Plants up to 15 cm high, filaments 140-182 pm in diameter ........................ .C. nzajor
Chlorodesmis hildebrandtii A. Gepp et E.S. Gepp 191 1: 16, pl. 8, figs 74, 75 (lectotype
locality: Johana (Anjouan) Island, Comoro Island,fide Ducker 1967: 165); Weber-van Bosse
1913a: 114; Gilbert 1947: 122; 1961: 442; Egerod 1952: 377, pl. 34a, figs 9a, b, d; Dawson
1954: 394, fig. 1lJ g; Tsuda 1964: 5; Taylor 1966: 352; Ducker 1967: 164, pl. 6, fig. 16;
Trono 1968: 173, pl. 13, figs 1-3; Jaasund 1976: 27, fig. 55; Tsuda and Wray 1977: 95;
Magruder and Hunt 1979: 21; Dong and Tseng 1984: 286, pl. 142, fig. 3; Ngan and Price
1979: 6; Trono 1986: 224, fig. 24; Lewis 1987: 27; Silva et al. 1987: 118; Abbott 1989: 226;
Coppejans and Prud'homme van Reine 1989: 129, pl. 3, figs 5-1 1; 1992a: 177; Verheij and
Prud'homme van Reine 1993: 133, text fig. 4b; Wynne 1993: 22.
(Figs 54, 63)
Thallus light green and fluffy in water, up to 6 cm tall and composed of many free, hair-
like cylindrical filaments 95-130 ym in diameter, with repeated symmetrical dichotomous
(and sometimes trichotomous) branching. Supporting filaments truncated at point of branch
constrictions; the constrictions equal just above dichotomies. Basal translucent rhizoids
irregularly branched, 86-1 15 p,m in diameter.
Distribution
Fiji, Micronesia, Hawaii, northern Australia, Indonesia, Philippines, Vietnam, China,
Maldives.