Electronic Flora of South Australia Genus Fact Sheet

Genus AHNFELTIOPSIS Silva & DeCew 1992: 576

Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Phyllophoraceae

Thallus erect, much branched more or less complanately, branches terete or compressed, subdichotomous, apices usually rounded, with a crustose holdfast. Structure multiaxial, medulla pseudoparenchymatous with medium to large ovoid to angular cells, and a cortex of 2–3 layers of smaller isodiametric cells in anticlinal rows.

Reproduction: Sexual thalli monoecious or dioecious. Carpogonial branches 2- or 4-celled, supporting cell acting as auxiliary cell with the gonimoblasts developing into immersed carposporophytes with clustered carposporangia, protruding on one or both sides of the branch, with or without carpostomes through the thickened cortex. Spermatangia in superficial sofi.

Free-living tetrasporophytes are known in only a few species, with surface nemathecia of numerous anticlinal catenate rows of cruciately divided tetrasporangia, terminated by one to several sterile cells.

Life history triphasic or diphasic, heteromorphic with erect gametophytes and free-living crustose tetrasporophytes, or apomictic with carpospores from internal carposporophytes developing directly into female gametophytes.

Type species: Ahnfeltiopsis linearis (C. Agardh) Silva & DeCew 1992: 578.

Taxonomic notes: The genus Ahnfeltiopsis was erected by Silva & DeCew (1992) to accommodate species with internal cystocarps and heteromorphic life histories that had previously been assigned to Ahnfeltia. The type species of Ahnfeltia, A. plicata (Hudson) Fries, has compound external carposporophytes and the unique nature of its reproductive development and pit-plug structure led to its transfer from the Phyllophoraceae to its own family and order (Maggs &

Pueschel 1989). Species previously assigned to Gymnogongrus, but with internal cystocarps were also transferred to Ahnfeltiopsis by Silva & DeCew, as the type species of Gymnogongrus, G. griffithsiae (Turner) Martius, forms tetrasporangia in pustules ("tetrasporoblasts") on female plants without the intermediate formation of a cystocarp. Silva & DeCew assigned 15 species to Ahnfeltiopsis and Masuda (1993) a further 9. This number is likely to grow as the life history of the 30 or so species left in Gymnogongrus is elucidated. Masuda (1993) has recently placed 9 Japanese species in Ahnfeltiopsis.

In southern Australia, two of the four species formerly attributed to Gymnogongrus form internal cystocarps and these therefore belong in Ahnfeltiopsis.

References:

MASUDA, M. (1993). Ahnfeltiopsis (Gigartinales, Rhodophyta) in the western Pacific. Jap. J. Phycol. (SOrui) 41, 1–6.

PUESCHEL, C.M. (1989). An expanded survey of the ultrastructure of red algal pit plugs. J. Phycol. 25, 625–636.

SILVA, P.C. & DECEW, T.C. (1992). Ahnfeltiopsis, a new genus in the Phyllophoraceae (Gigartinales, Rhodophyceae). Phycologia 31, 576–580.

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

Author: J.A. Lewis & 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 SPECIES OF AHNFELTIOPSIS

1. Thallus tufted, 1–4 cm high, branches terete to very slightly compressed, (150–) 200–400 (–700) µm broad

A. fastigiata

1. Thallus complanately branched, usually 1–2 (–4) cm high, branched mainly above, branches compressed, (0.5–) 1–1.5 mm broad

A. humilis


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