Electronic Flora of South Australia Family Fact Sheet

FAMILY NEMASTOMATACEAE Schmitz 1892: 22, nom. cons.

Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales

Thallus erect, simple and foliose to much branched subdichotomously to irregularly with terete to compressed branches, not calcified except for Titanophora. Structure multiaxial with a cortex of subdichotomous branch systems of ovoid to elongate cells, lacking secondary pit-connections between laterally adjacent cells of the cortex; medulla laxly filamentous; rhizoidal filaments occasionally present from cells of inner cortex and outer medulla. Cells uninucleate.

Reproduction: Sexual thalli monoecious or dioecious. Carpogonial branches borne on inner cortical cells, (2–) 3–4 (–5) cells long, outwardly directed with a straight or coiled trichogyne. Auxiliary cells intercalary as inner cortical cells (the adjacent cells bearing small round cellules in Predaea) or near the end of long rhizoidal filaments (in Adelophycus), connecting filaments relatively long. Gonimoblast developing from the auxiliary cell or adjacent connecting filament, with a single initial, usually outwardly (inwardly in Adelophycus), with all cells becoming carposporangia; fusion cell, involucre or pericarp absent, a pore or ostiole between the cortical filaments present or absent. Spermatangia cut off from outer cortical cells.

Tetrasporophytes (where known) isomorphic with gametophytes, with tetrasporangia borne in the outer cortex, cruciately or obliquely divided, or crustose with zonately divided tetrasporangia (in Schizymenia).

Life history triphasic with isomorphic or heteromorphic gametophytes and tetrasporophytes (the latter unknown in many species, and crustose in Schizymenia).

Taxonomic notes: This family has been generally known as the Nemastomataceae Schmitz (1892, p. 22), rather than the Gymnophlaeaceae Kützing (1843, p. 389) and the former has been recommended for conservation (Silva 1993b, p. 708).

A family of 7 genera of which 5 occur on southern Australian coasts. It is characterised by the discrete subdichotomous cortical branch systems, due to lack of secondary pit-connections between cells in adjacent filaments, the non-procarpic sexual reproduction with 3 (–4)-celled outwardly directed carpogonial branches, the outwardly (usually) directed gonimoblast with all cells becoming carposporangia, and the lack of an involucre or pericarp around the carposporophyte.

The Nemastomataceae contains two generic groups. Group 1 is characterised by connecting filaments that issue directly from carpogonia and grow to auxiliary cells (Nemastoma, Adelophycus, Tsengia and Predaea). Tetrasporophytes are either unknown, isomorphic, or more-or-less disorganised minute filaments. Group 2 (Schizymenia, Platoma and Titanophora), has connecting filaments that first fuse with the nutritive auxiliary cells borne immediately on the supporting cell, then give rise to secondary connecting filaments. No member of this group has an isomorphic tetrasporophyte; where known, they seem to be Hematocelis-type crusts.

While Predaea is well characterised by having small nutritive cells on cells adjacent to the auxiliary cells and Adelophycus by habit and anatomical features (e.g. cortical gland cells), Tsengia, Schizymenia and Platoma are not so well defined. Previous discussions by Feldmann (1942), Kraft & John (1976), Kraft (1975; 1981, p. 29), West & Hommersand (1981, p. 167) and others, and study of southern Australian taxa, shows that the family is in urgent need of generic revision.

References:

FELDMANN, J. (1942). Remarques sur les Némastomacées. Bull. Soc. bot. Fr. 89, 104–113.

KÜTZING, F.T. (1843). Phycologia generalis. (Leipzig.)

KRAFT, G.T. & JOHN, D.M. (1976). The morphology and ecology of Nemastoma and Predaea species (Nemastomataceae, Rhodophyta) from Ghana. Br. phycol. J. 11, 331–344.

KRAFT, G.T. (1975). Consideration of the order Cryptonemiales and the families Nemastomataceae and Furcellariaceae (Gigartinales, Rhodophyta) in light of the morphology of Adelophyton corneum (J. Agardh) gen. et comb. nov. from southern Australia. Br. phycol. J. 10, 279–290.

KRAFT, G.T. (1981). Rhodophyta: morphology and classification. In Lobban, C.S. & Wynne, M.J. (Eds), The Biology of Seaweeds, Ch. 1, pp. 6–51. (Bot. Monogr. Vol. 17, Blackwell: Oxford.)

SCHMITZ, F. (1892). Florideae. In Engler, A., Syllabus der Vorlesungen Ober spezielle und medicinisch-pharmaceutische Botanik. Eine Ubersicht fiber das gesammte Pflanzensystem mit Berticksichtigung der Medicinal-und Nutzpflanzen. Grosse Ausgabe. (Berlin.)

SILVA, P.C. (1993b). Report of the Committee for Algae: 1. Taxon 42, 699–710.

WEST, J.A. & HOMMERSAND, M.H. (1981). Rhodophyta: Life Histories. In Lobban, C.S. & Wynne, M.J. (Eds), The Biology of Seaweeds, Ch. 4, pp. 133–193. (Bot. Monogr. Vol. 17, Blackwell: Oxford.)

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (14 January, 1994)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIA, Bangiophyceae and Florideophyceae (to Gigartinales)
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIA 1994, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

KEY TO GENERA OF NEMASTOMATACEAE

1. Thallus firm, drying cartilaginous, subdichotomous with compressed branches 1–2 (–3) mm broad; subspherical to pyriform gland cells present in cortex; auxiliary cells subterminal in a rhizoidal filament, with the gonimoblast developing thallus inwards

ADELOPHYCUS

1. Thallus more or less mucilaginous, foliose or branched with compressed branches; gland cells present and elongate, or absent; inner cortical cells becoming auxiliary cells, with the gonimoblast developing thallus outwards

2

2. Cells adjacent to the auxiliary cells bearing small nutritive cells

PREDAEA

2. Cells adjacent to the auxiliary cells without small nutritive cells

3

3. Thallus subdichotomous or laterally much branched, or with few flat branches; cells adjacent to carpogonial branches not darkly staining; tetrasporophytes isomorphic with gametophytes, tetrasporangia cruciately to obliquely divided

TSENGIA

3. Thallus foliose, simple to marginally lobed; cells adjacent to carpogonial branches darkly staining; tetrasporophytes crustose with zonate tetrasporangia, or unknown

4

4. Gland cells usually (but not always) present in cortex; cortex with a depressed ostiole above each carposporophyte

SCHIZYMENIA

4. Gland cells absent; cortex with only slight pores or gaps above each carposporophyte

PLATOMA


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