''Triactis'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

sea anemone Sea anemones are a group of predation, predatory marine invertebrates of the order (biology), order Actiniaria. Because of their colourful appearance, they are named after the ''Anemone'', a terrestrial flowering plant. Sea anemones are classifi ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Aliciidae Aliciidae is a family of sea anemones, comprising the following genera: * '' Alicia'' Johnson, 1861 * '' Cradactis'' McMurrich, 1893 * '' Lebrunia'' Duchassaing de Fonbressin & Michelotti, 1860 * ''Phyllodiscus ''Phyllodiscus'' is a monotypic ...

. It is

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

, having only one

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 ...

– ''Triactis producta''. This is found in shallow waters in the

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

where it lives on the seabed, rocks and

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 ...

s. It derives much of its energy needs from the symbiotic

algae 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 mic ...

it contains. It also forms a mutualistic relationship with small ''Lybia'' crabs.

Description

''Triactis producta'' is a small,

cryptic Cryptic may refer to: In science: * Cryptic species complex, a group of species that are very difficult to distinguish from one another * Crypsis, the ability of animals to blend in to avoid observation * Cryptic era, earliest period of the Earth ...

, pale brown sea anemone. The base grows to about in diameter and the column tapers slightly and extends to about in height. It is topped by a crown of about 50, relatively long

tentacle In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

s. Halfway up the column there is a ring of branching, pale brown pseudo-tentacles. These are tubular extensions of the wall of the column and on their upper side there are a few semi-spherical bulges known as vesicles. These can be grey, pink or green and are packed with stinging cells called

cnidocyte A cnidocyte (also known as a cnidoblast or nematocyte) is an explosive cell containing one large secretory organelle called a cnidocyst (also known as a cnida () or nematocyst) that can deliver a sting to other organisms. The presence of this ce ...

s.The sea anemone ''Triactis producta'' Klunzinger, 1877 by Andrea L. Crowther
Invertebrate Zoology. Retrieved 2012-02-17.

Distribution and habitat

''Triactis producta'' is found in shallow waters of the tropical Indo-Pacific Ocean, its range extending from the

Red Sea The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; T ...

and

Mozambique Mozambique (), officially the Republic of Mozambique ( pt, Moçambique or , ; ny, Mozambiki; sw, Msumbiji; ts, Muzambhiki), is a country located in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi ...

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 ...

and

French Polynesia )Territorial motto: ( en, "Great Tahiti of the Golden Haze") , anthem = , song_type = Regional anthem , song = " Ia Ora 'O Tahiti Nui" , image_map = French Polynesia on the globe (French Polynesia centered).svg , map_alt = Location of Frenc ...

. It is inconspicuous, often growing in crevices and concealed among the branches of

stony corals Scleractinia, also called stony corals or hard corals, are marine animals in the phylum Cnidaria that build themselves a hard skeleton. The individual animals are known as polyps and have a cylindrical body crowned by an oral disc in which a mo ...

. It often occurs in dense clusters of what are probably

cloned Cloning is the process of producing individual organisms with identical or virtually identical DNA, either by natural or artificial means. In nature, some organisms produce clones through asexual reproduction. In the field of biotechnology, c ...

individuals.

Biology

''Triactis producta'' has two ways of feeding. In the daytime, when the light is bright, it retracts its tentacles and extends its pseudo-tentacles. These are dark brown because of the dense concentration of

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 ...

algae known as

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 ...

that they contain. These produce sugars by

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...

in sunlight which the anemone uses as nourishment. Retracting its tentacles maximises the photosynthetic potential of the anemone. The well-armed vesicles protect the pseudo-tentacles which may appear edible to a potential predator. At night, or when the animal is in a dim light, the crown of tentacles expands and the tentacles search for small invertebrates in the surrounding water, immobilising them with their cnidocytes. Boxer crabs in the

Lybia ''Lybia'' is a genus of small crabs in the family Xanthidae. Their common names include boxer crabs, boxing crabs and pom-pom crabs. They are notable for their mutualism with sea anemones, which they hold in their claws for defense. In retur ...

'' have developed a mutualistic relationship with small sea anemones such as ''Triactis producta''. The crab's front limbs have modified

chelae A chela ()also called a claw, nipper, or pinceris a pincer (biology), pincer-like organ at the end of certain limbs of some arthropods. The name comes from Ancient Greek , through New Latin '. The plural form is chelae. Legs bearing a chela are ...

, each of which can gently grip a sea anemone by its column, and it usually holds one in each claw. The living anemone is brandished like a weapon to keep

predators Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...

away and is also used in ritualistic territorial protection. The sea anemones used are small and seldom exceed a column height of . If it loses one of its anemones, the crab can tear the other one in half, after which each part grows into a new individual. The crab also uses the anemones to immobilise and capture prey on its behalf. The sea anemones seem unharmed by being used in this way.

Interactions with humans

In the Red Sea, ''Triactis producta'' is reported to be one of the most venomous of sea anemones. The symptoms of stings to bare skin include pain and swelling. In one reported case, these lasted for several weeks and were accompanied by a pigmented, blistered lesion and prolonged skin sensitivity. The

toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subst ...

agent was found to be very stable and resistant to chemicals and heat treatment.

References

{{Taxonbar, from=Q922902 Aliciidae Monotypic cnidarian genera Hexacorallia genera Taxa named by Carl Benjamin Klunzinger