''Janaria'' is a genus of commensal

athecate hydroids Anthoathecata, or the athecate hydroids, are an order of hydrozoans belonging to the phylum Cnidaria. A profusion of alternate scientific names exists for this long-known and heavily discussed group. It has also been called Gymnoblastea and (with ...

in the family

Hydractiniidae Hydractiniidae is a cnidarian family (biology), family of athecate hydroids. Genera The World Register of Marine Species includes the following genera in the family: *''Bouillonactinia'' Miglietta, McNally & Cunningham, 2010 *''Clava (cnidarian ...

. It is a

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 "unisp ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

and the only

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

is ''Janaria mirabilis'', commonly known as staghorn hydrocoral. It is a colonial species and lives on a shell occupied by a

hermit crab Hermit crabs are anomuran Decapoda, decapod crustaceans of the superfamily (taxonomy), superfamily Paguroidea that have adapted to occupy empty scavenged mollusc shells to protect their fragile exoskeletons. There are over 800 species of hermit c ...

. It is native to the tropical and semitropical eastern Pacific Ocean.

Description

''Janaria mirabilis'' is similar in appearance to a colonial coral, but comes from a quite separate group of

cnidaria Cnidaria ( ) is a phylum under kingdom Animalia containing over 11,000 species of aquatic invertebrates found both in fresh water, freshwater and marine environments (predominantly the latter), including jellyfish, hydroid (zoology), hydroids, ...

ns. The adult hydrocoral can be up to high and a similar width. It consists of a single horizontal branch and three or four vertical branches. The branches are straight or slightly curved and have blunt tips which are half as wide as the branches, the colour usually being cream or pale tan. The branches are calcified and each bears numerous polyps, the animal having been described as resembling a "fuzzy glove of feeding polyps".

Distribution

This hydrocoral is native to the tropical and semitropical eastern Pacific Ocean, its range extending from

Baja California Sur Baja California Sur, officially the Free and Sovereign State of Baja California Sur, is a state in Mexico. It is the 31st and last state to be admitted, in 1974. It is also the second least populated Mexican state and the ninth-largest state by ...

to Panama, including the

Gulf of California The Gulf of California (), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Vermejo''), is a marginal sea of the Pacific Ocean that separates the Baja California peninsula from ...

. It occurs at depths between .

Ecology

A juvenile ''Janaria mirabilis'' will settle on a mollusc shell occupied by a

in the genus '' Manucomplanus''. Here it buds and grows into a colony, sending out side-branches, and at the same time exuding chemicals which erode the mollusc shell. Eventually the mollusc shell is dissolved away and the hydrocoral takes up residence on the exposed

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

and abdomen of the crab. The association is mutually beneficial as the crab receives protection from predators that are deterred by the hydrocoral's stinging cells, while the hydrocoral benefits from being moved to new feeding areas by the mobile crab. A single hermit crab can carry a mobile home weighing nearly thirty times its own weight. The tissues of the hydrocoral contain

symbiotic Symbiosis (Ancient Greek : living with, companionship < : together; and ''bíōsis'': living) is any type of a close and long-term biolo ...

zooxanthellae Zooxanthellae (; zooxanthella) is a colloquial term for single-celled photosynthetic organisms that are able to live in symbiosis with diverse marine invertebrates including corals, jellyfish, demosponges, and nudibranchs. Most known zooxanthell ...

harboured within which provide additional nutrients for the colony. The hydrocoral often has

epizoic An epibiont (from the Ancient Greek meaning "living on top of") is an organism that lives on the surface of another living organism, called the basibiont ("living underneath"). The interaction between the two organisms is called epibiosis. An ep ...

invertebrates such as

barnacle Barnacles are arthropods of the subclass (taxonomy), subclass Cirripedia in the subphylum Crustacean, Crustacea. They are related to crabs and lobsters, with similar Nauplius (larva), nauplius larvae. Barnacles are exclusively marine invertebra ...

s living on its surface.

Description

Distribution

Ecology

References

Further reading