Genus Millepora Linnaeus, 1758

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Genus Millepora Linnaeus, 1758

Fire Coral, Stinging Corals

Millepora Linnaeus, C. 1758. Systema naturae per regna tria naturae, secundem classes, ordines, genera, species, cum characteribus, differentis, synonymis, locis. Editio decima, reformata. Holmiae : Laurentii Salvii Vol. 1 10, 824 pp. [790].

Introduction

The hydrocoral genus Millepora (commonly called fire coral), is the only genus in the family Milleporidae. There are 15 accepted species in the genus Millepora; at present six species are known from Australia namely:

Millepora exaesa Forsskål, 1775 (LC under IUCN)
Millepora dichotoma Forsskål, 1775 (LC under IUCN)
Millepora foveolata Crossland, 1952 (VU under IUCN)
Millepora intricata Milne Edwards, 1860 (LC under IUCN)
Millepora platyphylla Hemprich & Ehrenberg, 1834 (LC under IUCN)
Millepora tenera Boschma, 1949 (LC under IUCN)

In Australia, Millepora species occur in inshore and coastal (e.g., the Kimberley) or offshore habitats to depths of at least 30 metres. However, the exact status of all Millepora species in Australia is unknown and further research is needed to identify species and population trends.

Threats:

The major threat to milleporid corals, as for most zooxanthallate tropical corals, is climate change, in particular rising temperatures that lead to bleaching events. It has been observed that milleporid corals are often among the first to bleach after warming events, however they can also respond quickly after disturbance and re-establish (Baird & Marshall, 2002). This genus is collected for curio and jewellery trade (CITES, 2016). Crown-of-thorns Starfish are a major threat to corals in Australia generally, however, observations in Fiji, suggest Millepora is not targeted, perhaps due to the presence of stinging cells (hence the common name fire coral) (Kayal et al., 2012). Pollution and habitat loss are also areas of concern, and the combined effect of all these threats is unknown.

Strategy:

Millepora corals are listed under Appendix I and II of CITES, which regulates the trade of endangered species. This listing is important to conservation and for developing fisheries management strategies.
Millepora distributions include areas of the Australian Marine Protected Areas (MPAs). Nevertheless, conservation measures for this species require ongoing research into their taxonomy, population, abundance and trends, ecology and habitat status (Baird & Marshall, 2002), to protect coral habitats from runoff and coastal development and ensure ecosystem persistence.

Distribution

States

Northern Territory, Queensland, Western Australia

Extra Distribution Information

Tropical distribution.

Other Regions

Coral Sea Islands Territory

Ecological Descriptors

Sessile, tropical.

Diagnosis

Diagnosis from the World Register of Marine Species (WoRMS):

"Hydroid colony forming massive, calcareous exoskeleton (= coenosteum) of varied shape; coenosteum with an internal complex network of coenosarcal tubes and covered externally by a thin ectodermal layer, coenosteal surface perforated by pores; margins of pores not protruding from surface of coenosteum; large gastropores surrounded by smaller dactylopores, forming indistinct cyclosystems; no gastrostyles and dactylostyles; polyps polymorphic; gastrozooids relatively short and stout, with an oral whorl of 4 to 7 short capitate tentacles, arising from gastropores; dactylozooids long, slender, mouthless, with scattered capitate tentacles, arising from dactylopores; cnidome with macrobasic mastigophores; gonophores arising from coenosarc within ampullae embedded in the coenosteum.
Gonophores are free swimming eumedusoids with exumbrellar cnidocyst patches, narrow velum, radial and circular canals, ‘gonads’ occupying the place of an indistinct manubrium and without tentacles and sense organs."

ID Keys

Key to the Indonesian species of Millepora taken from Razak & Hoeksema (2003).

Key to Millepora species:

1. Corallum branching ........................................................................................................................2
- Corallum massive and sub-massive ............................................................................................... 3

2. The lower parts never unite into a plate; branches subcylindrical; growing in all
directions; continuously dichotomous; the upper edges with tapering tips .........................M. intricata
- The lower parts unite into a plate; branches flattened; lateral branches radiating from the central point (ogive structure); the upper edges with blunt or rounded tips.........................................................................................4

3. Massive plate, upright and tall, forming a honeycombed or a parallel tier struc- ture; cyclosystem distinct on a flat surface ............................................................................................................................... M. platyphylla
- Submassive short knobbed branches, growing upward; or free-living, encrusted on coral fragments; no cyclosystem arrangement .......................................................................................................................M. exaesa
- Submassive columnar or slender upright plates, irregular in outline; cyclosytem very conspicuous everywhere on the surface below the growing margins ................... ...............................................................M. boschmai

4. Anastomose branches forming a tall and erect reticulate plate, no coalescence between plates
............................................................................................................................................M. dichotoma
- Branchlets arise on the upper edge.................................................................................................5

5. Branchlets finger-like, arranged in hand-shaped cluster......................................M. intricata f. murrayi

- Branchlets fan-shape .......................................................................................................M. tenera