Staghorn Corals of the World

A Revision of the Genus Acropora

Carden Wallace

• Publisher: CSIRO PUBLISHING
• Year: 1999
• ISBN:
  9780643102811
• Topic: Biological Sciences
• Subtopic: Marine Biology
• Index: Biological Sciences

Staghorn corals (genus Acropora ) are the most obvious and important corals on coral reefs throughout the world, providing much of the beauty and variety seen on the reefs.

This invaluable reference tool is the first major review of Acropora in over 100 years. It assesses all the known species worldwide, describing each in detail and illustrating the range of variability of form with habitat and geographic location. The classification, evolution and worldwide distribution of all species are reviewed and illustrated with colour plates, full page black and white plates and distribution maps. Details of the general biology of staghorn corals are discussed and illustrated.

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)...

Table of contents

• Cover
• Title
• Copyright
• Dedication
• Foreword
• Abstract
• Acknowledgements
• Contents
• Introduction
• Review of Literature
• Summary of Type Material
• Fossil Record
• Anatomy, Physiology and Biology
• Genetics and Molecular Biology
• Skeletal Morphology
• Methods Used for Revision and Analyses
• Revision of the Biogeography of Acropora
• Revision of the Phylogeny and Classification of Acropora
• Synthesis of Biogeographic, Fossil and Phylogenetic Data
• Systematic Arrangement of Species
• Subgenus Isopora Studer, 1878
• Insertae Sedis Acropora Squamata Latypov, 1992
• References
• Appendix
• Glossary
• Abbreviations
• Index
• Species Index