Antithamnion antillanum Børgesen

Scientific Description

Habit and structure. Plants with prostrate primary axes 1–1.2 mm long, producing paired laterals in a distichous or slightly decussate pattern, attached by rhizoids arising from the basal cell of whorl branches. Prostrate axes opposite-distichous, with cells to 65 µm in diameter, and L:B = 2, bearing pairs of whorl branches, these dimorphic with one of each pair remaining short, the second becoming upright and to 25 cells and 900 µm long. Upright whorl branches alternate distichous, except for unbranched basal cell; basal cell isodiametric and 20–25 µm in diameter, distal cells of whorls L/B ca. 3, and tapering to a fine point. Gland cells ellipsoid, 16 x 9–12 µm, on the basal cell of branchlets, arising as a curved, oblique division of the apical cell, the subtending cells then dividing further to produce a simple filament 3–6 cells long, the gland cell abutting the bearing cell but most of its length lying confluent with the cell distal to the bearing cell. Gland cells are mostly restricted to the basal cells, but occasionally additional gland cells are formed on more distal cells.

Reproduction. Reproductive structures not observed.

Distribution. Widespread in tropical seas