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Benthic Marine Algae of Rotuma Island
Rotuman Distribution
Lopta (L351 USP 477, *L50/ USP S7: 13).
Habitat and Remarks
Forming dense, compact mats on the outer reef crest in association with Gelidiella
acerosa and Chondria sedifolia. Exposed to considerable wave action.
Laurencia sp.
(Figs 193, 194,201,202)
Plants to 5 cm long and 3 mm in diameter, repent and dorso-ventrally flattened. Colour
dark red to purplish. Side branchlets opposite, up to 3 mm long and terminating in a tuft of
sunken apical trichoblasts. In cross-section, composed of ovoid medullary cells up to 65 ym
in diameter, a cortical layer of inner cells up to 18 pm in diameter, and an outer layer of
subquadrate cells 5-3 ym in diameter. Cortical cells projecting at apex; lenticular thickenings
absent. Secondary pit-connections between outer cortical cells absent. Plants sterile.
Rotuman Distribution
Maka Bay (MAK191 USP 612).
Habitat and Remarks
Mixed with Sargassum polycystum and Coelothrix irregularis within seagrass beds. This
alga was examined by Professor I. A. Abbott at the University of Hawaii, but no match with
any existing species could be obtained. Its status is currently under further investigation.
Polysiphonia Greville 1824: 308
Polysiphonia scopulorum Harvey 1855: 540 (type locality: Rottnest Island, Western
Australia); Womersley and Bailey 1970: 330 (as var. villum (Harvey) Hollenberg); Tsuda
and Wray 1977: 110; Cribb 1983: 132, pl. 70, figs 1-2; Lewis 1984: 55 (as P. scopularum);
Payri and Meinesz 1985~: 514; Millar 1990: 445, figs 65E-G; Price and Scott 1992: 210, fig.
77A-D; Millar and Kraft 1993: 58.
var. scopubmm (Harvey) Hollenberg 1968a: 79, fig. 6F; Trono 1969: 83; Abbott 1989: 23 1.
(Fig. 207a-d)
Plants purplish-red, up to 5 mm high with cells mostly shorter than broad, the prostrate
branches 58-65 ym in diameter with 4 pericentral cells each about 58 X 29 pm around a
central axial cell about 76 X 12 pm. Erect branches up to 115 ym long and 60 ym broad,
arising mostly at 2 or 3 segment intervals along the prostrate branches. The segments of the
median parts of the erect branches mostly shorter than broad; the apical region of the
branches bearing trichoblasts at intervals of 20r 3 segments from the tip of the branch, scar-
cells present on lower parts. Trichoblasts up to 50 pm long and 9 ym in diameter, often
forming lateral whorls; rhizoids up to 35 ym long and 60 pm broad, in open connection with
the pericentral cells and terminated by an inflated portion up to 117 pm in diameter.
Distribution
Fiji, Caroline Islands, Hawaii.
Fijian Records
Kapraun and Bowden 1978: 201 (as P. scopularum), figs 23, 24; South 1992: 9; South
and Kasahara 1992: 67.