''Palythoa toxica'', also referred to by its Hawaiian common name, limu-make-o-Hana ('seaweed of death from Hana'), is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

zoanthid Zoanthids ( order Zoantharia also called Zoanthidea or Zoanthiniaria) are an order of cnidarians commonly found in coral reefs, the deep sea and many other marine environments around the world. These animals come in a variety of different coloniz ...

native to

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...

. It is notable as the species in which

palytoxin Palytoxin, PTX or PLTX is an intense vasoconstrictor, and is considered to be one of the most poisonous non-protein substances known, second only to maitotoxin in terms of toxicity in mice. Palytoxin is a polyhydroxylated and partially unsaturat ...

was discovered and from which it was first isolated.Clayden, J., Greeves, N. (2000), pages 19–21

Description

''P. toxica'' is an encrusting species with a firm, tough cuticle. The polyps are partially embedded in a cushiony mat of

coenenchyme Coenenchyme is the common tissue that surrounds and links the polyps in octocorals. It consists of mesoglea penetrated by tubes (''solenia'') and canals of the gastrodermis and contains sclerites, microscopic mineralised spicules of silica or of ca ...

which grows across the rock surface, and which incorporates sand grains and fragments of debris. The oral disc of each polyp is broad and has a fringe of tentacles. The polyps can close up and be retracted into the coenenchyme, which then displays a pitted surface. The colour of this species is variable but is usually some shade of cream, grey or pale brown.

History

A Hawaiian legend relates how in a rock pool in the Hana district on the island of

Maui The island of Maui (; Hawaiian: ) is the second-largest of the islands of the state of Hawaii at 727.2 square miles (1,883 km2) and is the 17th largest island in the United States. Maui is the largest of Maui County's four islands, which ...

there was to be found an

alga Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mi ...

known to the locals as "limu-make-o-Hana" ('seaweed of death from Hana'). The exact location of the pool was known to only a few individuals and visiting it was

taboo A taboo or tabu is a social group's ban, prohibition, or avoidance of something (usually an utterance or behavior) based on the group's sense that it is excessively repulsive, sacred, or allowed only for certain persons.''Encyclopædia Britannica ...

. In 1961, intrigued by this, researchers searched for the location and discovered the zoanthid. Although advised by local people not to do so, they took some specimens away with them. On that very day, the laboratories of the Hawaiian Institute of Marine Biology on Coconut Island, Oahu were destroyed by fire. The toxic effects of this species were known to the early inhabitants of Hawaii, and the zoanthids were applied by them to the tips of their weapons, or according to one account, under severe threat, the warriors could overcome the taboo and dip their spear tips into the pool for them to become lethal.

Distribution and habitat

''P. toxica'' was first discovered in the small district of Muolea on the island of Maui in Hawaii. Its habitat was a shallow pool about deep which was subject to inflows of fresh water during periods of heavy rainfall, so it would appear to be a

euryhaline Euryhaline organisms are able to adapt to a wide range of salinities. An example of a euryhaline fish is the molly (''Poecilia sphenops'') which can live in fresh water, brackish water, or salt water. The green crab (''Carcinus maenas'') is an e ...

species. The zoanthid has since been discovered in a few other locations in the Hawaiian islands.

Palytoxin

''P. toxica'' contains

, one of the most poisonous substances known. This zoanthid is not the only member of its genus to contain the toxin; that distinction is shared by '' P. tuberculosa''. The latter species has a seasonal cycle, varying in toxicity at different times of year, whereas ''P. toxica'' is equally toxic all year round. Other species of ''Palythoa'' have also been shown to contain the substance in varying amounts at different times and in different places, and some algae and certain crabs and fish have been found to contain it. It has been suggested that the toxin is actually produced by a

dinoflagellate The dinoflagellates (Greek δῖνος ''dinos'' "whirling" and Latin ''flagellum'' "whip, scourge") are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered algae. Dinoflagellates are ...

, ''

Ostreopsis ''Ostreopsis'' is a genus of free-living dinoflagellates found in marine environments. Some species are benthic; the planktonic species in the genus are known for the toxic algal blooms that they sometimes cause, threatening human and animal hea ...

'' spp., and incorporated into the zoanthid tissues, possibly through a

symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...

relationship similar to that of

zooxanthellae Zooxanthellae is a colloquial term for single-celled dinoflagellates that are able to live in symbiosis with diverse marine invertebrates including demosponges, corals, jellyfish, and nudibranchs. Most known zooxanthellae are in the genus ''Sy ...

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...

In aquaria

Fishkeepers keep ''P. toxica'' and other species of the genus in

reef aquarium A reef aquarium or reef tank is a marine aquarium that prominently displays live corals and other marine invertebrates as well as fish that play a role in maintaining the tropical coral reef environment. A reef aquarium requires appropriately ...

s. This practice has led to poisonings of hobbyists who have carelessly handled the organisms.

References

{{Taxonbar, from=Q20721392 Palythoa Animals described in 1971