Dasya kraftii Parsons & Womersley

Scientific Description

Habit and structure. Thallus light to dark red-brown, soft and mucilaginous, 3–20(–45) cm high, with 1–2 corticated axes 1–2 mm in diameter. Main axes profusely and irregularly branched throughout, with lower laterals often as long as the main axes, moderately to heavily covered by basally branched, pigmented, attenuate, monosiphonous filaments. Holdfast small, discoid; epiphytic or on solid substrates. Structure. Pericentral cells 5, formed in circular order, not obvious in transverse sections of older axes, heavily corticated by rhizoidal filaments which occur both internally and externally to the pericentral cells. Pseudolaterals from every segment, 1–2 mm long, basally subdichotomous every 1–2 cells with 3–5 subdichotomies on any filament giving 10–20 ultimate branches, distinctly attenuate from their base to beyond the last subdichotomy and then scarcely attenuate in the ultimate unbranched filament. Adventitious monosiphonous filaments similar to young pseudolaterals, frequent, arising from the upper portion of pericentral cells 1, 3, and 4 (not the smaller 2 and 5), beginning about 12 segments from the apex, and also from later formed cortical cells. Basal cells of pseudolaterals and adventitious filaments 45–65 µm in diameter, L/D 0.7–1; cells after the last subdichotomy 22–23 µm in diameter, L/D 1–2(–3); cells of ultimate filaments 12–22 µm in diameter, L/D (1–)2–9. Intercalary cell divisions occasional in the ultimate branches. Lateral axes usually adventitious, arising from the basal cell of the first branch of a monosiphonous filament. Rhodoplasts discoid to elongate, reticulate in older cells.

Reproduction. Gametophytes dioecious. Procarps borne spirally on a polysiphonous, usually adventitious, axis. Carposporophytes with a moderate basal fusion cell and ovoid to clavate, apical and lateral carposporangia. Cystocarps sessile on lateral axes, urceolate, 400–700 µm in diameter, with a neck (0.2–)0.3–0.5 the diameter of the cystocarp in length; pericarp 3–4 cells thick, outer cells irregularly ovoid. Spermatangial branches sessile or on a 1–2–celled monosiphonous stalk, on the lower branches of both pseudolaterals and adventitious monosiphonous filaments, prominent, ovoid to ellipsoid, 120–250 µm long and 75–100 µm in diameter, with 7–11 fertile segments and a 6–16-celled attenuate apical filament. Stichidia on a 1–2(–3)-celled monosiphonous stalk, on the lower branches of both pseudolateral and adventitious monosiphonous filaments, cylindrical, 100–650 µm long and 100–150 µm in diameter, with 8–15 fertile segments of (4–)5 pericentral cells all of which become fertile. Each tetrasporangium with (2–)3 cover cells which are at first small, rather narrow and irregular in shape, scarcely covering the sporangium, later becoming elongate irregularly upwards and often dividing once.

Distribution. Rottnest I., W. Aust., to Cape Thomas, S. Aust., and Montagu, NW Tas.

Habitat. D. kraftii occurs on fucoids in the sublittoral fringe and in pools, or sublittoral on Osmundaria prolifera, on Posidonia sp. to 10 m deep and on wooden jetty piles to 1–2 m deep.

[After Parsons & Womersley in Womersley, Mar. Benthic Fl. Southern Australia IIIC: 433–436 (1998)]