Electronic Flora of South Australia Genus Fact Sheet

Genus ARTHROCARDIA Decaisne 1842a: 365

Phylum Rhodophyta – Class Florideophyceae – Order Corallinales – Family Corallinaceae – Subfamily Corallinoideae – Tribe Corallineae

Thallus with a crustose base bearing several to numerous erect, sparsely to densely pinnate fronds, largely complanately branched, intergenicula compressed, elongate to cuneate, broader above; holdfast crustose, epilithic. Structure. Intergenicula with 20–40 (–50) tiers of medullary cells, with lateral cell-fusions but without lateral pit-connections. Genicula of a single tier of elongate, thicker walled cells. Cortex present on intergenicula, of splaying then anticlinal filaments, outer cells with 1 (–2) short epithallial cells.

Reproduction: Conceptacles axial and deeply embedded in the apex of intergenicula, swelling the intergenicula only slightly, usually with two surmounting branches. Gametangial thalli dioecious. Carpogonial filaments arising on floor of female conceptacles, carposporangia in 2–4-celled filaments arising from the surface of the fusion cells. Male conceptacles with beaks, with or without branchlets, spermatangia terminating short filaments on the base and sides of the chamber.

Tetrasporangia (or bisporangia) borne on separate thalli, conceptacles usually with surmounting branches, sunken within the upper end of intergenicula, with several to numerous tetra (or bi-) sporangia arising from the chamber floor.

Life history triphasic with isomorphic gametophytes and tetrasporophytes.

Lectotype species: A. corymbosa (Lamarck) Decaisne 1842a: 365 (Manza 1937, p. 48).

Taxonomic notes: Arthrocardia is most closely related to Corallina, both genera having many tiers of medullary cells of similar length per intergeniculum. Arthrocardia has larger numbers of tiers than Corallina, with conceptacles sunken in the apices of intergenicula, carposporangial filaments over the surface of the fusion cells, and usually with branching from the tetra (or bi-) sporangial conceptacles.

References:

DECAISNE, J. (1842a). Essais sur une classification des Algues et des Polypiers calcifères de Lamouroux. Ann. Sci. Nat., 2 Sér. Bot., 17, 297–380, Plates 14–17.

MANZA, A.V. (1937). The genera of articulated corallines. Proc. Nat. Acad. Sci. 23, 44–48,

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

Author: H.B.S. Womersley & H.W. Johansen

Publication: Womersley, H.B.S. (28 June, 1996)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIB. Gracilarialse, Rhodymeniales, Corallinales and Bonnemaisoniales
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIB 1996, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

KEY TO SPECIES OF ARTHROCARDIA

1. Thallus robust, (2–) 5–12 cm high, axial intergenicula 1.4–3.5 mm broad and L/W about 1, branching from most axial intergenicula	A. wardii
1. Thallus slender, 2–4 (–6) cm high, axial intergenicula 0.7–1.4 mm broad, L/W 2–4, branching from about half the axial intergenicula	A. flabellata ssp. australica

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