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Jania minuta Johansen & Womersley 1994: 613, figs 10–14,27–31.

Phylum Rhodophyta – Class Florideophyceae – Order Corallinales – Family Corallinaceae – Subfamily Corallinoideae – Tribe Janieae

Thallus (Fig. 137A) light grey-red, (1–) 2–6 (–10) mm high, (10–) 20–40 intergenicula long, slender; fronds branching every (3–) 5–10 (–20) intergenicula, open to fastigiate, mostly in one plane. Intergenicula terete to slightly compressed, (40–) 60–100 µm in diameter, (100–) 110–150 (–165) µm long, L/D 1.2–2 (–2.5). Holdfasts thin, crustose, 200–600 µm across, each bearing several erect branches; epiphytic on seagrasses or Myriodesma. Structure. Medullary cells in 1 (–2) tiers (Fig. 137B) per intergeniculum, each tier (30–) 40–60 µm long; cortex one cell thick, organised in two tiers per intergeniculum, the distal of which cuts off apically small cells each of which produces a hair or hair initial. Genicula (35–) 60–80 µm long.

Reproduction: Asexual by propagules (fig. 137B) borne laterally on intergenicula, propagules multicellular, compressed, more or less triangular and becoming bilobed, 120–200 µm long and 140–250 µm across the lobes when well developed, each attached by a pad 5–8 cells across, the lobes potentially developing branch buds which presumably may develop further.

Gametangial thalli monoecious. Female conceptacles (Fig. 137C) non-amphoroid, lying between the diverging arms of furcate intergenicula 200–280 µm long, branchlets containing other conceptacles sometimes growing from the developing arms; externally 280–360 (–400) µm long and 180–240 µm in diameter, chamber diameter 150–200 µm when carposporangial, containing 3–6 subspherical to ovoid carposporangia each 40–100 µm in diameter. Male conceptacles (Fig. 137D, E) terminal on short, simple, branches from the same basal crusts as branches bearing female conceptacles, externally 225–300 (–430) µm long and 100–180 µm in diameter, chambers 70–110 µm in diameter and 425–590 µm high.

Sporangial conceptacles (Fig. 137F, G) between the diverging lobes of furcate intergenicula, the two (occasionally three) arms usually continuing as branchlets; externally 275–370 µm long and 230–270 µm in diameter (excluding arms), chambers 150–230 µm in diameter; each sporangium three-celled, consisting of a large two-nucleate cell and small basal and apical cells containing single nuclei, sporangia (140–) 170–220 µm long and 50–100 µm in diameter.

Type from Barker Rocks, Yorke Pen., S. Aust., on Posidonia sinuosa, drift (Womersley, 17.x.1989); holotype in AD, A59883.

Selected specimens: Albany, W. Aust., on Myriodesma, drift (Burbidge, 24.xi.1935; AD, A4560, with propagules). Point Sinclair, S. Aust., on Heterozostera, uppermost sublittoral (Womersley, 25.i.1951; AD, A13808). Petrel Bay, St Francis I., S. Aust., on Posidonia sinuosa, 3 m deep (Shepherd, 7.i.1971; AD, A38427). Waterloo Bay, S. Aust., on P. sinuosa, 2 m deep (Shepherd, 20.x.1970; AD, A37526). Tiparra reef, S. Aust., on P. sinuosa, 5–6 m deep (Shepherd, 28.i.1971; AD, A37837). Seal Bay, Kangaroo I., S. Aust., on Myriodesma integrifolium, drift (Womersley, 24.i.1957; AD, A20757). West I., S. Aust., on Posidonia, 5 m deep (Shepherd, 18.i.1978; MELU, 22779, 22727). Kitty Miller Bay, Phillip I., Vic., on Amphibolis antarctica, drift (Ducker, 25.v.1977; MELU, 22610).

Distribution map based
on current data relating to
specimens held in the
State Herbarium of SA

Distribution: Albany, W. Aust., to Phillip I., Vic., on Posidonia, Heterozostera and Myriodesma.

Taxonomic notes: Jania minuta is monoecious, has non-amphoroid carposporangial and (tetra)sporangial conceptacles, tetrasporangia replaced by three-celled sporangia, small conceptacle dimensions, and one (or two) tiers of intergenicular medullary cells alternating with genicula. The distinctive propagules in J. minuta are similar to those recorded by Dawson (1953, p. 116, pl. 9 fig. 1) for .1. capillacea Harvey from Baja California, Mexico. In J. minuta, the plants bear either conceptacles or propagules; plants bearing both are unknown.

All asexual conceptacles examined contained the unusual sporangia with four nuclei within three cells, a large, central cell containing two nuclei and smaller uninucleate basal and apical cells.


DAWSON, E.Y. (1953). Marine red algae of Pacific Mexico. Part I. Bangiales to Corallinaceae subf. Corallinoideae. Allan Hancock Pacif. Exped. 17, 1–239.

JOHANSEN, H.W. & WOMERSLEY, H.B.S. (1994). Jania (Corallinales, Rhodophyta) in southern Australia. Aust. Syst. Bot. 7, 605–625.

The Marine Benthic Flora of Southern Australia Part IIIB complete list of references.

Author: H.B.S. Womersley & H.W. Johansen

Publication: Womersley, H.B.S. (28 June, 1996)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIB. Gracilarialse, Rhodymeniales, Corallinales and Bonnemaisoniales
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIB 1996, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

Illustration in Womersley Part IIIA, 1996: FIG. 137.

Figure 137 image

Figure 137   enlarge

Fig. 137. Jania minuta (A, F, G, AD, A59883; B, AD, A4560; C, D, AD, A13808; E, AD, A38427). A. Habit. B. Branches with a propagule. C. Carposporangial conceptacle. D. Male conceptacles. E. Male conceptacle with spermatangia lining the walls. F. Tetrasporangial conceptacles. G. Tetrasporangial conceptacles, upper small cell of tetrasporangia just visible.

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