Electronic Flora of South Australia Species Fact Sheet

Herposiphoniella plurisegmenta Womersley, sp. nov.

Phylum Rhodophyta – Family Rhodomelaceae – Tribe Herposiphonieae

Thallus (Fig. 131A) red-brown, 1–4 cm long, largely free from the host, complanately branched with indeterminate axes irregularly branched and bearing 5–7 (–13) alternate, distichous, simple, determinate laterals 600–800 µm long between short indeterminate laterals (Fig. 131B–D). Attachment of the basal axes by rhizoids; epiphytic on Pterocladia capillacea, Laurencia filiformis and Dictyota. Structure. Apical cells hemispherical to conical, 15–20 µm in diameter, segmenting transversely and the subapical cells obliquely, with each segment bearing an indeterminate or determinate lateral. Axial segments 140–270 µm broad with 11

pericentral cells, L/D (0.3–) 0.5–0.8, ecorticate; segments of determinate laterals 110–140 µm broad basally, tapering gradually, with 8 pericentral cells, L/D 0.5–0.9, basal segment shorter with 4 isodiametric pericentral cells. Lateral axes developed by continued growth of indeterminate laterals. Trichoblasts present near apices of young determinate laterals, 0.5–1.5 mm long, branched, basal cells 20–30 µm in diameter and L/D 1–2. Rhizoids cut off from pericentral cells, unicellular, with digitate haptera. Cells uninucleate, larger cells probably multinucleate; rhodoplasts discoid, ribbon like in larger cells.

Reproduction: Reproduction unknown.

Type from N side Althorpe Is, S. Aust., on Pterocladia capillacea, 10–12 m deep (Baldock, 4.i.1964); holotype and isotype in AD, A27321.

Selected specimens: W. Aust. (Clifton; Herb. Harvey, TCD; AD, A18168). Seamount off Cannon Reefs, S. Aust., on Dictyota, 22–30 m deep (Branden, 22.i.1991; AD, A61204). Masillon I., Isles of St Francis, S. Aust., epiphytic, 13–18 m deep (Shepherd, 5.i.1971; AD, A38022). Pearson I., S. Aust., on Laurencia, 35 m deep (Shepherd, 7.i.1969; AD, A34034). 1.3 km off Cape Northumberland, S. Aust., 15 m deep (Shepherd, 26.xi.1976; AD, A47822).

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

Distribution: Near Fremantle, W. Aust., to Cape Northumberland, S. Australia.

Taxonomic notes: H. plurisegmenta appears to be a deep-water epiphyte on the west coast of Eyre Peninsula and from Cape Northumberland, S. Australia. It is also known from a Clifton collection in Herb. Harvey, probably from near Fremantle, W. Australia.

The species is named for the larger and variable number of determinate laterals between the indeterminate ones.

References: The Marine Benthic Flora of Southern Australia Part IIID

Publication: Womersley, H.B.S. (24 February, 2003)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIID. Ceramiales – Delesseriaceae, Sarcomeniaceae, Rhodomelaceae
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIID 2003, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

Illustration in Womersley Part IIIA, 2003: FIG. 131.

Figure 131   enlarge

Fig. 131. Herposiphoniella plurisegmenta (A, AD, A47822; B–D, AD, A38022). A. Habit. B. Branches with indeterminate laterals separated by usually 5 determinate laterals. C. As for B. D. Branching pattern at higher magnification.

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