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Genus ACROTYLUS J. Agardh 1849: 86

Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Acrotylaceae

Thallus erect, subdichotomously and laterally branched, largely complanately, branches 1–3 mm broad, compressed; holdfast crustose. Structure multiaxial, with a broad filamentous medulla and a pseudoparenchymatous cortex.

Reproduction: Sexual thalli monoecious; procarpic; polycarpogonial. Carpogonial branches borne on inner cortical cells, 3-celled, sometimes with a sterile cell on the basal cell, inwardly directed with reflexed trichogynes. Supporting cell acting as auxiliary cell. Gonimoblast initials several, first inwards, with nutritive cells produced by adjacent vegetative cells forming a sheath and the gonimoblast filaments spreading around the cavity formed by breakdown of the diploidized auxiliary cell, becoming centripetal with terminal carposporangia. Cystocarps sunken, with filamentous enveloping tissue, ostiolate. Spermatangia in scattered clusters in the cortex of (usually) marginal, proliferous branchlets.

Tetrasporangia in nemathecia near branch apices and on lower branches, pit-connected basally to mid-cortical cells, zonately divided.

Life history triphasic with isomorphic gametophytes and tetrasporophytes.

Type (and only) species: A. australis J. Agardh 1849: 86.

Taxonomic notes: Acrotylus is closely related to Ranavalona Kraft from Madagascar, and in southern Australia to Hennedya, which differs in its broader thallus, large inner cortical cells, protruding cystocarps and scattered, non-nemathecial tetrasporangia.


AGARDH, J.G. (1849). Algologiska bidrag. Öfvers. K. Svenska Vetensk. Akad. Rh-h. 6(3), 79–89.

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

Author: G.T. Kraft & 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.

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