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Electronic Flora of South Australia Species Fact Sheet
Phylum Rhodophyta – Order Ceramiales – Family Dasyaceae
Thallus (Fig. 216A) dark red-brown, 3–10 cm high, profusely subdichotomously branched throughout with dense, slender, tufted, even-topped, upper branches, becoming denuded on lower axes. Attachment by rhizoids; epiphytic (on Halophila?). Structure. Apices sympodial. Pericentral cells 5. Branches 45–90 µm in diameter and L/D 2–3 (–4) shortly below apices, increasing to 200–450 µm in diameter and L/D (2–) 3–4 in lower parts, ecorticate apart from few longitudinal cortical filaments on oldest parts. Pseudolaterals (1–) 2 axial cells apart (Fig. 216E), 2–4 mm long, with 4–5 basal subdichotomies 2 cells apart and unbranched ends 15–20 cells long; basal cell isodiametric, lower cells 25–60 µm in diameter and L/D 2–4, tapering gradually to upper cells 10–15 µm in diameter and L/D (2–) 5–15. Lateral branches probably arising on basal cell of pseudolaterals. Rhodoplasts discoid to elongate, becoming chained.
Reproduction: Gametophytes probably dioecious. Procarps with a carpogonial branch and probably 2 sterile groups, axial and sterile pericentral cells becoming darkly staining (Fig. 216B). Carposporophytes much branched with terminal clavate to lacrimiform carposporangia (Fig. 216C) 15–20 µm in diameter. Cystocarps ovoid, 350–550 µm in diameter, with only a slight neck; pericarp of 15–20 erect filaments, each cell cutting off 2 pericentral cells outwardly, ecorticate apart from cortical cells on the bearing branch at the base of the cystocarp. Spermatangial branches (Fig. 216D) borne on lower branches of pseudolaterals, with 1–2 pedicels, 300–700 µm long and 45–90 µm in diameter, cylindrical and tapering terminally, with axial cells cutting off 1–2 layers of cells and then surface spermatangia.
Tetrasporangial stichidia (Fig. 216E, F) borne on lower cells of pseudolaterals, with a 1–2-celled pedicel, 500–1500 µm long and 100–220 µm in diameter, lanceoid, with 10–20 fertile segments, 6 pericentral cells and tetrasporangia per segment (sometimes 5 in basal segment), tetrasporangia subspherical, 35–65 µm in diameter, each with 3 obloid cover cells L/D 2–2.5, palisade like, covering only part of each sporangium.
Type from American R. inlet, Kangaroo I., S. Aust., 2–3 m deep in channel opposite Muston (Kraft, 7.iv.1972); holotype and isotype in AD, A42417; isotype in CHR, 316104.
Selected specimens: American R. inlet, Kangaroo I., S. Aust., drift at jetty (Womersley, 25.viii.1963; AD, A27684).
Distribution: Only known from American R. inlet, Kangaroo I., S. Australia.
Taxonomic notes: Dasya tenuis is named for the slender branches of the thallus; it is known from only few specimens from a single locality, but appears to be distinctive in having branching mostly 2 axial cells apart, in being largely ecorticate, in having terminal clavate carposporangia, and in having whorls of 6 tetrasporangia in the stichidia.
References: The Marine Benthic Flora of Southern Australia Part IIIC
Publication:
Womersley, H.B.S. (24 December, 1998)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIC. Ceramiales – Ceramiaceae, Dasyaceae
©State Herbarium of South Australia, Government of South Australia
Illustration in Womersley Part IIIA, 1998: FIG. 216.
Figure 216 enlarge
Fig. 216. Dasya tenuis (AD, A42417). A. Habit, part of holotype sheet. B. Young cystocarp. C. Mature cystocarp, with clavate carposporangia. D. Spermatangial branches. E. Stichidia on pseudolaterals 2 cells apart on an ecorticate branch. F. Stichidium showing 6 tetrasporangia per segment and palisade-like cover cells.
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