Overview

Brief Summary

The Hawaiian gold coral (Kulamanamana haumeaae) is a deep sea zoanthid coral found on seamounts throughout the Hawaiian archipelago at depths of 343 m - 575 m.  Known mostly because of its beauty and rareness as a gem coral, it has been collected since the 1970s for the jewelry industry (referred to as genus Gerardia, a synonym of Savalia), but was not scientifically described until 2013.  Molecular evidence indicates that Hawaiian gold coral belongs in its own genus. 

Hawaiian gold coral grows in a fan shape, up to 1 meter (3 feet) in height.  Its skeleton ranges between golden yellow and orange in color, with polyp color, when living, bright yellow to orange.  Polyps will flash with bioluminescence and produce copious mucus when disturbed. 

Since 2001, the fishing industry for Hawaiian gold coral has been restricted to a point where it is no longer cost effective to collect it.  The coral, which grows to a large size and in large numbers of individuals, dominates the coral biomass in its depth range and habitat, and is now recognized for its importance in its ecosystem.  Furthermore, recent dating studies show that K. haumeaae is one of the longest-living species on earth, with some individuals determined as 2740 years of age, growing at tremendously slow rates of about 15-45 micrometers in radius/year. 

Hawaiian gold coral, like other corals in its family (Parazoanthidae), is epizoic, specifically associated with bamboo corals (Isididae; Octocorallia).  It is unclear whether K. haumeaae colonizes host skeletons once its host has died, or whether it parasitizes it, competing for resources (as do some closely related Savalia species).  Recent studies suggest that the speciation and radiation of parazoanthid corals is driven by their close host relationships, and the biology behind these host/epizoid interactions are the subject of understanding a newly-discovered diversity of deep-sea octocorals; four other genera of which were collected and described in the same scientific publication as K. haumeaae (Sinniger et al. 2013).

(Sinniger, Ocaña and Baco 2013, and references cited within)

  • Sinniger F, Ocaña OV, Baco AR (2013) Diversity of Zoanthids (Anthozoa: Hexacorallia) on Hawaiian Seamounts: Description of the Hawaiian Gold Coral and Additional Zoanthids. PLoS ONE 8(1): e52607. doi:10.1371/journal.pone.0052607
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Distribution

Distribution: Throughout the Hawaiian Archipelago seamount and island slopes between 343–575 m on hard substrata in low-sediment areas with high relief. Usually one of the most abundant taxa in this depth range and habitat type, often with other corals present. Also observed in Line and Jarvis Islands, Palmyra Atoll and Kingman Reef however at lower densities [3]. Similar specimens with golden or dark brown, almost black axis, also referred as “Gerardia”, were collected in the West Atlantic [16], [17], and in New Zealand [61]. If those zoanthids appear to be closely related enough to be congeneric, species-level relationships require further morphological and molecular analyses.

  • Sinniger F, Ocaña OV, Baco AR (2013) Diversity of Zoanthids (Anthozoa: Hexacorallia) on Hawaiian Seamounts: Description of the Hawaiian Gold Coral and Additional Zoanthids. PLoS ONE 8(1): e52607. doi:10.1371/journal.pone.0052607
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© Sinniger F, Ocaña OV, Baco AR

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Physical Description

Morphology

In preserved specimens, size of contracted and semi-contracted polyps from 1–8 mm length and 2–7 mm diameter. 28–31 pointed tentacles (usually 28). In expanded living polyps, length of the tentacles equivalent to up to three quarters of the diameter of the oral disc. 13–16 bractea (corresponding to capitular ridges on closed polyps) on the edge of the oral disc. Apex of closed polyps flat (but might appear rounded in small or extremely contracted polyps). Column cylindrical, with no incrusted particles. Well developed coenenchyme completely covering the host. Polyp density variable within the colony with coenenchyme barely visible in the most dense regions (usually the smallest branches) and polyps separated by over 1 cm in the less dense area (such as the main stem). In situ characterised by bioluminescence when disturbed. Size of the fan-shaped colonies up to over 2 m diameter and over 1 m height. Golden scleroproteic skeleton, distinct from the black skeleton found in the genus Savalia Nardo 1844 ( = Gerardia L.-D. 1864). In most major parts of the skeleton, host axis can be observed in the centre. Anastomosed branches are frequently observed and the complex branching pattern and larger size of the colonies is clearly distinct from that of the isidids or other octocorals found in the area, suggesting the ability of this zoanthid to build its own branches (fig. 1a). As observed in other epizoic genera (Savalia and Antipathozoanthus particularly) the colony can spread on other substrata at the base of the original host.

Colour: In vivo, polyps, tentacles and coenenchyme bright yellow to dark orange. Upon formalin fixation tissues turns red as observed in several other zoanthid species. Bioluminescence has been observed in situ.

Microanatomy: 25 to 30 mesenteries following macrocnemic arrangement. Most mesenteries fertile, including incomplete mesenteries. Retractor muscle absent, parietobasilar muscle developed and forming visible pennons. Single siphonoglyph prominent. Sphincter endodermal (0.1–0.3 mm), concentrated in the upper part of the column, forming sinus and processes.

Cnidome: spirocysts, spirulae (b-mastigophores, basitrichs), small homotrichs (holotrichs); penicilli A (p-mastigophores A); penicilli E (Homotrichs; Holotrichs, p-mastigophores E) see table 2 and fig. 3.

  • Sinniger F, Ocaña OV, Baco AR (2013) Diversity of Zoanthids (Anthozoa: Hexacorallia) on Hawaiian Seamounts: Description of the Hawaiian Gold Coral and Additional Zoanthids. PLoS ONE 8(1): e52607. doi:10.1371/journal.pone.0052607
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© Sinniger F, Ocaña OV, Baco AR

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Diagnostic Description

Diagnosis: Golden axis, tissue colour ranging from pale yellow to medium orange, secretion of excessive mucus when collected and absence of mineral incrustations are distinctive characters of this species, In terms of cnidome, the main diagnostic characters appear to be the presence of enlarged penicilli A (p-mastogophores A) in tentacles and body wall and penicilli E in all the tissues.

  • Sinniger F, Ocaña OV, Baco AR (2013) Diversity of Zoanthids (Anthozoa: Hexacorallia) on Hawaiian Seamounts: Description of the Hawaiian Gold Coral and Additional Zoanthids. PLoS ONE 8(1): e52607. doi:10.1371/journal.pone.0052607
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© Sinniger F, Ocaña OV, Baco AR

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Ecology

Associations

Biological interactions: This genus appears to colonise primarily isidid octocorals (bamboo coral), [3]. Previous studies observed this species on the skeletons of several living isidids [16] as well as on several primnoids. More investigations are necessary to determine if this species has a host preference. It is also not clear if this species is colonizing branches free of tissue, or if it parasitises or competes with the host tissue as it spreads along the branches. Comparison with the closely related genus Savalia suggests a parasitic/competitive relationship, but further studies are necessary to understand the ecological relations between this zoanthid and the organisms used as host. Occasionally, colonies of Clavularia grandiflora can colonise Ku. haumeaae [3]. As found in the genus Savalia, a parasitic ascothoracic cirriped was found in several polyps. However, the exact nature of the interactions between this zoanthid and the crustacean are not known. Due to the depths at which this species occurs the absence of observation of zooxanthellae in the histological analyses was not surprising, although the recent findings of Symbiodinium in Hawaiian black corals down to 396 m depth [60] indicate we can not exclude the possibility of an extremely low density of symbionts. Attempts to PCR-amplify zooxanthellae using dinoflagellate specific primers and to grow dinoflagellate cultures using fresh material of this species following collections in 2004 were also unsuccessful (A. Baco and R. Gast unpubl data).

  • Sinniger F, Ocaña OV, Baco AR (2013) Diversity of Zoanthids (Anthozoa: Hexacorallia) on Hawaiian Seamounts: Description of the Hawaiian Gold Coral and Additional Zoanthids. PLoS ONE 8(1): e52607. doi:10.1371/journal.pone.0052607
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© Sinniger F, Ocaña OV, Baco AR

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Life History and Behavior

Life Expectancy

The Hawaiian gold coral may also be one of the longest-lived species on earth. The skeleton and commercial interest in this species led to multiple studies attempting to date the age of the colonies. Earlier ageing attempts on the gold coral focused on ring counts [10], [11] and led to a maximal estimated age of 70 years and a radial growth rate (increase in branch diameter) of 1 mm/year. Recent studies on the red coral Corallium rubrum (Linnaeus, 1758) [12] suggested that the rings traditionally observed based on the density of the skeleton may not reflect yearly cycles but much longer time intervals. This is supported for the Hawaiian gold coral by recent studies using radiometric data which suggest colonies of Hawaiian gold coral are as old as 2740 year with a radial growth rate of 15 to 45 µm/year [13], [14], [15]. In the Atlantic a similar zoanthid referred to as “Gerardia” is found and amino acid racemization experiments [16] indicated a maximal age of 250 years while radiocarbon dating estimate the life span of a colony to 1800 years [17].

  • Sinniger F, Ocaña OV, Baco AR (2013) Diversity of Zoanthids (Anthozoa: Hexacorallia) on Hawaiian Seamounts: Description of the Hawaiian Gold Coral and Additional Zoanthids. PLoS ONE 8(1): e52607. doi:10.1371/journal.pone.0052607
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© Sinniger F, Ocaña OV, Baco AR

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Names and Taxonomy

Taxonomy

The feminine name of this genus is derived from the Hawaiian terms Kula (= gold) and manamana (= branch) referring to the particular skeleton of the type species of this genus (Sinniger et al. 2013).

Recently, DNA information has shed light on the phylogenetic relationships among zoanthids and has also helped revise the taxonomy of several groups of zoanthids as well as describe new taxa. However, the sole use of DNA to identify zoanthid species might not be sufficient to distinguish closely related species and it is therefore necessary to integrate not only DNA and morphology but also ecological parameters to identify specimens (Sinniger et al. 2008; 2013)

  • Sinniger F, Ocaña OV, Baco AR (2013) Diversity of Zoanthids (Anthozoa: Hexacorallia) on Hawaiian Seamounts: Description of the Hawaiian Gold Coral and Additional Zoanthids. PLoS ONE 8(1): e52607. doi:10.1371/journal.pone.0052607
  • Sinniger F, Reimer JD, Pawlowski J (2008) Potential of DNA sequences to identify zoanthids (Cnidaria: Zoantharia). Zool Sci 25: 1253–1260. doi: 10.2108/zsj.25.1253
Creative Commons Attribution 3.0 (CC BY 3.0)

© Sinniger F, Ocaña OV, Baco AR

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