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Palythoa

Palythoa is a genus of anthozoans in the order Zoantharia.

Description

The polyps of Palythoa are partially embedded in an encrusting mat of tissue (coenenchyme) covering the substrate on which the colony grows. The individual polyps have flattened oral discs surrounded by a fringe of tentacles. The tentacles' shape and size can vary considerably between species, and even between colonies of the same species. Their colors are also highly variable, with relatively dull shades like cream, coffee, white, brown, or yellow, being the most common. Bright green colonies also exist, but these are more rare.

Palytoxin

Palytoxin is a highly toxic natural product found in many (but not all) members of the genus Palythoa. The substance was first isolated from the seaweed-like "limu-make-o-Hana" ("Seaweed of Death from Hana") in 1971 in Hawaii. Scientific investigation of the seaweed found it to be a colonial cnidarian, which was classified as a zoanthid and named Palythoa toxica.

The presence of this toxin is of significance to aquarists who keep reef aquariums, as Palythoa and related zoanthids are commonly kept as display specimens in marine aquaria. Aquarists have reported symptoms consistent with palytoxin poisoning prior to having exposure to zoanthids suspected to contain the toxin. One report involved an aquarist being accidentally poisoned through skin injuries after handling various zoanthids. Another report involved an aquarium hobbyist in Virginia who experienced a severe respiratory reaction after trying to eradicate colonies of a brown zoanthid (suspected to be Palythoa) from rocks in their aquarium. A 2010 study found that a single specimen of Palythoa from a sample of fifteen colonies purchased from three aquarium stores in the Washington D.C. area contained high levels of palytoxin, indicating that toxic individuals are occasionally present in the captive population.

While poisoning events have occurred, they are exceedingly rare, and many reef hobbyists have kept Palythoa without any adverse reactions.

It is generally recommended to always wear appropriate protective gloves and goggles when maintaining aquaria.

Taxonomy and systematics

The genus Protopalythoa was once thought to be distinct from the genus Palythoa but is now considered to be a synonym.

Species

The following species are recognized in the genus Palythoa:

¹Indicates Species Unreviewed: has not been verified by a taxonomic editor

Taxon inquirendum:

  • Palythoa anduzii <small>(Duchassaing & Michelotti, 1860)</small>
  • Palythoa auricula <small>(Lesueur, 1817)</small>
  • Palythoa brevis <small>Andres, 1883</small>
  • Palythoa casigneta <small>Walsh, 1967</small>
  • Palythoa distans <small>(Duchassaing & Michelotti, 1866)</small>
  • Palythoa dubiae <small>Walsh, 1967</small>
  • Palythoa eupaguri <small>Marion, 1882</small>
  • Palythoa fulva <small>Walsh, 1967</small>
  • Palythoa fulva <small>(Quoy & Gaimard, 1833)</small>
  • Palythoa gigantea <small>Cubit & Williams, 1983</small>
  • Palythoa glomerata <small>Marion, 1882</small>
  • Palythoa lutea <small>(Quoy & Gaimard, 1833)</small>
  • Palythoa mcmurrichi <small>(Haddon & Shackleton, 1891)</small>
  • Palythoa olivascens <small>Brandt, 1835</small>
  • Palythoa plana <small>(Duchassaing & Michelotti, 1860)</small>
  • Palythoa vanikorensis <small>(Quoy & Gaimard, 1833)</small>
  • Palythoa viridifusca <small>(Quoy & Gaimard, 1833)</small>
  • Palythoa viridis <small>(Quoy & Gaimard, 1833)</small>

References