Seaweeds of the South African South Coast
Order Corallinales
Family Corallinaceae
Sub-Family Corallinoideae
Arthrocardia Decaisne
Thalli of crustose holdfasts bearing erect, articulated, branched fronds; branching dichotomous in fertile parts, pinnate in vegetative parts. Fronds comprising calcified intergenicula (segments) separated by uncalcified genicula. Conceptacles terminal and axial in fertile segments.
Johansen (1984) stated that “Arthrocardia, represented by four species in South Africa, is characterized by Corallina-like pinnate branching in the vegetative axes and a propensity for regularly producing branches on the fertile intergenicula of all reproductive types.” Later, Seagrief (1984) listed 6 species in South Africa.
Recently, a DNA barcoding study by Kogame et al. (2017) recorded 7 distinct clades of Arthrocardia among 63 articulated coralline specimens (all genera) collected along the South African coast. This study, which aimed to “test the morphological classification” of species within the genera, identified seven (species-level) clades of Arthrocardia. All of the five recorded south coast species except A. palmata were identified. However, A. palmata may have been represented by a specimen from Palm Beach in southern KwaZulu-Natal, in a clade called Arthocardia sp. 1.
While many specimens fit the descriptions of the species below, there are also some that do not, or appear intermediate between certain of these species. It is clear that further molecular and morphological studies would be useful.
Key to Arthrocardia species on the south coast
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1a. Branching mostly pinnate |
2 |
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1b. Branching mostly dichotomous, at least in upper parts |
3 |
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2a. Upper segments 3-4 (-6) mm long, often winged, and/or with long (-6 mm), awl-shaped branchlets |
A. duthieae |
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2b. Upper segments 1-.5 – 3 mm long, wedge-shaped, without long branchlets |
A. carinata |
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3a. Branching dichotomous in fertile areas above, irregularly pinnate below; ultimate segments often incised (branched without articulations); males with beaked conceptacles |
A. flabellata |
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3b. Branching mainly dichotomous throughout; incised end-segments absent; male conceptacles not beaked |
4 |
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4a. Adventitious branching present, sometimes from all sides of segments |
A. palmata |
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4b. Adventitious branching absent/rare |
A. corymbosa |
Arthrocardia References
Johansen, HW 1984 The articulated coralline genus Arthrocardia in the southern hemisphere. British Phycological Journal 19: 195 (abstract).
Kogame, K., Uwai, S., Anderson, RJ., Choi, H-G & JJ Bolton. 2017. DNA barcoding of South African geniculate coralline red algae (Corallinales, Rhodophyta). South African Journal of Botany 108: 337-341.
Seagrief, S.C. 1984. A catalogue of South African green, brown and red marine algae. Memoirs of the Botanical Survey of South Africa, 47: 1-72.
Cite this record as:
Anderson RJ, Stegenga H, Bolton JJ. 2016. Seaweeds of the South African South Coast.
World Wide Web electronic publication, University of Cape Town, http://southafrseaweeds.uct.ac.za; Accessed on 19 April 2024.