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SYSTEMATIC ARRANGEMENT OF SPECIES
PHYLUM Cnidaria
CLASS Anthozoa
SUBCLASS Zoantharia
ORDER Scleractinia
SUBORDER Astrocoeniina Vaughan & Wells, 1943
FAMILY Acroporidae Verrill, 1902
GENUS Acropora Oken, 1815
Acropora Oken, 1815 p.66
TYPE SPECIES Millepora muricata Linnaeus, 1758
Genus name and type species officially validated in 1963 (Boschma, 1961; China, 1963). “Acroporidae which are ramose, rarely massive or encrusting, branching with an axial or leading corallite (or corallites) larger than the more numerous radial corallites budded from it (or them); united by light, reticulate, spinose or pseudo-costate or costate coenosteum. Columella and dissepiments absent”. (Description taken from Wallace, 1978 p.277, modified from Wells, 1956 p. F374.)
SUBGENUS Acropora Oken, 1815 p.66
Single axial corallite forms axis of branch, opening at tip. Radial corallites and coenosteum various.
THE Acropora rudis GROUP
Radial corallites rounded tubular; evenly sized; coenosteum throughout includes elaborated spinules; colonies with simple, irregular branching.
The axial corallite makes the major contribution to branch diameter in these thick-branched, simple, sturdy corals. The sturdiness is also reflected in the large number of synapticular rings that make up the walls of the corallites, so that the radial corallite walls are thick and sometimes swollen, with calices relatively small. All species occur subtidally.
With the exception of the widespread Acropora austera, species in this group are restricted to the Indian Ocean or Red Sea.
Acropora (Acropora) rudis (Rehberg, 1892)
(Map 1, Plate 1)
Madrepora rudis Rehberg, 1892 p.41 p1.4 fig.9
Material examined
MNB: 2693 Ceylon (Sri Lanka) Madrepora rudis holotype
MTQ: Seychelles: G51792; Sri Lanka: G55223–4; Bangladesh: G50567; Thailand: G37293, G37302; Indonesia: G47165–6 W. Sumatra
Skeletal characteristics
Corallum. Irregular arborescent with sturdy, erect, tapering branches 12–40 mm diameter and up to 160 mm long; sometimes incipient axial corallites are common, contributing to the irregular branching pattern; growth indeterminate.
Corallites. Axial corallites outer diameter 2.6–4.1 mm, inner diameter 0.6–1.2 mm; primary septa present up to 3/4R, secondary septa to 1/2R; radial corallites evenly sized, touching on branches, rounded tubular or rounded tubular-conical, with round calices, primary septa present up to 1/2R, secondary septa some to all present up to 1/3R.
Coenosteum. A dense arrangement of elaborated spinules throughout.
Field characteristics
The very large corallite size and rounded appearance of radial corallites of this species, as well as the sturdy branches, are distinctive. Colonies are irregular, up to about a metre in diameter, with branches directed upwards or horizontally: in some habitats branches extend horizontally and then turn downwards; known colours a velvety dark green or brown; occurs in rocky fringing reefs, shallow reef edge and submerged reef top habitats.
Other systematic information and remarks
This species is apparently restricted to the Indian Ocean, specimens having been found in Sri Lanka (type locality), Bangladesh, W. Thailand (where it is common), Seychelles and western Sumatra. The fact that these localities are not often sampled may explain the lack of literature records.
Fossil record
None.
Further literature
Taxonomy and distribution: Wallace & Wolstenholme, 1998.
MAP 1 Distribution of Acropora rudis worldwide, taken from literature records (triangles), type localities of senior and junior synonyms (stars) and specimen-based records in Worldwide Acropora Database at MTQ (squares).
PLATE 1 Acropora rudis (A,B) in W. Thailand; (C,E,H,I) G37293 W. Thailand (D,F,G) G37302 W. Thailand; (A,B) live colony (C,D) portion of colony (E,F) portion of branch (G) electron micrograph showing axial and radial corallites (H) electron micrograph showing radial corallites (I) electron micrograph showing coenosteum between radial corallites.
Acropora (Acropora) variolosa (Klunzinger, 1879)
(Map 2, Plate 2)
Madrepora variolosa Klunzinger, 1879 p.8 p1.1 fig.6 p1.4 fig.6 p1.9 fig.3
Madrepora obtusata Klunzinger, 1879 p.7 p1.1 fig.5 p1.8 fig.18a,b p1.9 fig.2
Madrepora klunzingeri Quelch, 1886 p.158; = Madrepora pustulosa Klunzinger, 1879 (non Edwards & Haime) p.8 p1.1 fig.1 p1.4 fig.15 p1.9 fig.4
Material examined
MNB: 2111 Red Sea Madrepora variolosa holotype; 2112 Red Sea Madrepora klunzingeri holotype; 2113 Red Sea Madrepora obtusata holotype
MTQ: Red Sea: G53550 Sudan; G54681, G54683, G54859, G54862, G55184–5, G55235–6 Saudi Arahia
Skeletal characteristics
Corallum. Arborescent, with sturdy, tapering branches 8–30 mm diameter and up to 115 mm long; growth indeterminate, sometimes thickets being formed.
Corallites. Axial corallites outer diameter 2.2–3.8 mm, inner diameter 0.7–l.2 mm; primary septa present up to 2/3R, secondary septa to 1/2R; radial corallites evenly sized, projecting directly outward from branches, not touching, tubular-conical, with round calices, primary septa present up to 2/3R, secondary septa absent or up to all present, up to 1/3R.
Coenosteum. A dense arrangement of elaborated spinules throughout.
Field characteristics
Colonies range from caespitose to irregular arborescent thickets, with distinctive thick branches and obvious large tubular-conical radial corallites; known colour blue or pale brown; occurs in sandy lagoonal situations.
Other systematic information and remarks
Problems with the delimitation of this species stem from confusion with Acropora austera as well as the questionable affinities of A. hemprichii. Authors have variously combined two of the three species. Acropora variolosa appears to be confined to the Red Sea and to be distinguished from other species by its long and distinctly conical radial corallites with their round openings, the most similar species being A. rudis, which is apparently restricted to more easterly Indian Ocean locations. Madrepora klunzingeri Quelch, 1886 was a replacement name for M. pustulosa Klunzinger, 1879, a junior homonym of M. pustulosa Edwards & Haime, 1860.
Fossil record
None.
Further literature
Taxonomy and distribution: Sheppard & Sheppard, 1991 (as Acropora hemprichii). Biology: Antonius & Riegl, 1998 (as A. hemprichi).
MAP 2 Distribution of Acropora variolosa worldwide
PLATE 2 Acropora variolosa (A,B) in Saudi Arabia, Red Sea (M. Pichon); (C,G,I) G54683 Red Sea (D) G54859 Red Sea (E) G54862 Red Sea (F,H) G54681 Red Sea; (A,B) live colony (C,D)...
