About
Contact
Links
Electronic Flora of South Australia
Electronic Flora of South Australia
Census of SA Plants, Algae & Fungi
Identification tools
 

Electronic Flora of South Australia Family Fact Sheet

Tribe HETEROTHAMNIEAE Wollaston 1968: 407

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae

Thallus erect, without or with slight prostrate filaments, erect axes ecorticate, bearing whorls of 2–6 whorl-branchlets from each axial cell, often fewer per whorl on lower axial cells, whorl-branchlets usually branched; attachment by rhizoids; usually epiphytic; gland cells usually present on whorl-branchlet cells, touching the bearing cell and often the next outer cell. Cells mostly uninucleate.

Reproduction: Gametophytes dioecious or monoecious. Procarps on normal or reduced whorl-branchlets (often 2-celled) on 1–3 (–4) axial cells near branch apices, with the basal cell acting as the supporting cell and with 4-celled carpogonial branches; the auxiliary cell cuts off a gonimoblast cell which produces a terminal and then lateral, rounded, gonimolobes, the carposporophyte without a distinct involucre but often partly surrounded by branchlets or branches from lower cells. Spermatangia cut off from terminal cells of whorl-branchlets or on special clusters borne on lower cells of whorl-branchlets.

Tetrasporangia sessile or on special short branches on cells of the whorl-branchlets, tetrahedrally or decussately divided.

Life history triphasic with isomorphic gametophytes and tetrasporophytes.

Taxonomic notes: The Heterothamnieae, based on Heterothamnion J. Agardh and as recognised here, differs from the Antithamnieae in having gland cells on normal whorl-branchlets and not on reduced 2–4-celled branches on the whorl-branchlets.

Athanasiadis (1996) separated from the Heterothamnieae the genera Antithamnionella, Trithamnion and Acrothamniopsis, which he placed in the Dohrnielleae, but without giving a key to the tribes. The Dohrnielleae originally included Dohrniella and Callithamniella, which have alternate branching with a single branchlet per axial cell and tetrasporangia borne on a single pedicel cell directly on the axes. It appears that genera with whorled branchlets and tetrasporangia on normal whorl-branchlet cells are best kept separate, and they are here retained in the Heterothamnieae. The Perithamnieae of Athanasiadis is also not recognised here, since the differences in spermatangial arrangement appear inadequate for tribal separation, and tetrasporangia are essentially similarly situated to other genera. Amoenothamnion and Leptoklonion appear best placed in the Heterothamnieae rather than the Ceramieae with its closely appressed cells derived from periaxial cells.

Relationships between the various genera of the Heterothamnieae need further assessment. The tribe is one of the most complex of the Ceramiaceae, and comprehensive material is need for determination of most species and studies of their variation.

References:

ATHANASIADIS, A. (1996). Morphology and classification of the Ceramioideae (Rhodophyta) based on phylogenetic principles. Opera Botanica No. 128, pp. 1–216.

WOLLASTON, E.M. (1968).Morphology and taxonomy of southern Australian genera of Crouanieae Schmitz (Ceramiaceae, Rhodophyta). Aust. J. Bot. 16, 217–417.

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

Author: H.B.S. Womersley

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

KEY TO GENERA OF HETEROTHAMNIEAE

1. Thalli erect from clumped endophytic basal rhizoids as continuations of axes, epiphytic on Cystophora spp. (or Platythalia)

HETEROTHAMNION

1. Thalli with erect axes usually on prostrate bases, attached by individual rhizoids (clumped in Acrothamniopsis and Trithamnion vulgare) to the host or solid surface or from a rhizoidal holdfast on or only just penetrating the host surface

2

2. Axial cells with whorls of (2–) 3 (–4) whorl-branchlets (5–6 in Antithamnionella multiramosa), not branched from their basal cells (except Scageliopsis and Aa glandifera)

3

2. Axial cells with whorls of 4–6 whorl-branchlets, branched from basal cells (except Acrothamniopsis)

5

3. Whorl-branchlets variable in number, 2–4 (–6) per whorl

ANTITHAMNIONELLA

3. Whorl-branchlets mostly 3 per whorl

4

4. Whorl-branchlets similar in size and form, basal cell branched

SCAGELIOPSIS

4. Whorl-branchlets usually uneven in size, often with one distinctly larger than the other two; basal cell usually unbranched

TRITHAMNION

5. Whorl-branchlets short (less than 150 µm long), simple or usually with a few branches, whorls distinctly separated on axes

6

5. Whorl-branchlets longer (mostly over 150 µm long), branched several times, whorls usually fairly closely adjacent

7

6. Thallus branching essentially subdichotomous, originating close to the apices

AMOENOTHAMNION

6. Thallus branching lateral, replacing whorl-branchlets or originating from the basal cells of whorl-branchlets

LEPTOKLONION

7. Axes with 2 opposite major whorl-branchlets and usually 2 minor whorl-branchlets on each side; rhizoids formed from successive cells of minor whorl-branchlets, with clumped digitate haptera

ACROTHAMNIOPSIS

7. Axes with 4 or 5 whorl-branchlets of similar form (differing in length in Elisiella divan

8

8. Tetrasporangia borne on special branched filaments of short cells on the lower cells of whorl-branchlets

ELISIELLA

8. Tetrasporangia sessile on basal to mid cells of whorl-branchlets

9

9. Spermatangia terminal on further divisions of terminal cells of whorl-branchlets

PERITHAMNION

9. Spermatangia borne on branched clusters adaxial on lower cells of whorl-branchlets

TETRATHAMNION


Disclaimer Copyright Disclaimer Copyright Email Contact:
State Herbarium of South Australia
Government of South Australia Government of South Australia Government of South Australia Department for Environment and Water