''Lychnorhiza lucerna'' is a species of jellyfish in the

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

Rhizostomeae. It is found off the Atlantic coasts of South America.

Description

When small, ''Lychnorhiza lucerna'' has a hemispherical bell, but this becomes flattened into a saucer shape as the jellyfish grows. Very large specimens have been known to reach in diameter and are dish-shaped. The upper surface is flexible and thin and is covered in low conical projections. Round the periphery are many small, triangular lappets. Hanging under the bell there are four pairs of oral tentacles, about two thirds as long as the diameter of the bell. The upper halves of these are somewhat flattened and the lower halves divide into three vanes which have multiple, inrolled edges. Among these are suctorial mouthlets leading to the interior of the bell and various thick dangling filaments. There is no central mouth. The stomach occupies most of the interior of the bell and there are a ring of small cream or white

gonad A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gonad, the testicle, produces sper ...

s round its edge. The colouration of this jellyfish varies, but in general, the bell is translucent and colourless or a pale shade of buff, sometimes with irregular streaks of light brown. The dangling lappets round the edge of the bell are darker brown and the lower parts of the oral tentacles may be brown as well, the upper parts being colourless.''Lychnorhiza lucerna''
Marine Species Identification Portal. Retrieved 2012-04-01.

Distribution

''Lychnorhiza lucerna'' is found in tropical waters in the western Atlantic Ocean. Its range extends from French Guiana to

Buenos Aires Province Buenos Aires (), officially the Buenos Aires Province (''Provincia de Buenos Aires'' ), is the largest and most populous Argentine province. It takes its name from the city of Buenos Aires, the capital of the country, which used to be part of th ...

in Argentina. It occurs in shallow coastal habitats and estuaries and is the most abundant jellyfish in its order (Rhizostomeae) in these waters. It often becomes stranded on beaches.

Life history

''Lychnorhiza lucerna'' has a complex life cycle with an alternation of sexual and asexual stages. An adult jellyfish is known as a medusa and is

gonochoristic In biology, gonochorism is a sexual system where there are only two sexes and each individual organism is either male or female. The term gonochorism is usually applied in animal species, the vast majority of which are gonochoric. Gonochorism c ...

, which means that it is either male or female. The fertilized eggs hatch into planula larvae. These soon settle and undergo

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...

into

sessile Sessility, or sessile, may refer to: * Sessility (motility), organisms which are not able to move about * Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant * Sessility (medicine), tumors and polyps that ...

polyps, known as a scyphistomae, with four tentacles. These grow larger, and after a series of moults have twenty-two tentacles. They develop cysts from which new polyps known as ephyrae grow. These develop transverse constrictions and separate from the original polyp by

strobilation Strobilisation or transverse fission is a form of asexual reproduction consisting of the spontaneous transverse segmentation of the body. It is observed in certain cnidarians and helminths. This mode of reproduction is characterized by high offspr ...

. The scyphistomae can strobilate several times and in a study it was estimated that one founder polyp could produce up to sixty ephyrae in a period of four months. Ephyrae develop into juvenile medusae after a further fifteen days or so.

Ecology

''Lychnorhiza lucerna'' has associations with the parasitic flatworm '' Dibothriorhynchus dinoi'', shrimps '' Periclimenes spp'', the Atlantic bumper fish, '' Chloroscombrus chrysurus'' and the bluntnose jack, ''

Hemicaranx amblyrhynchus ''Hemicaranx amblyrhynchus'' (bluntnose jack) is a tropical marine fish in the jack family ( Carangidae). It is found in shallow parts of the western Atlantic Ocean. Description The bluntnose jack is a deep bodied fish with a large, deeply forke ...

''. Young spider crabs, ''

Libinia ferreirae ''Libinia ferreirae'' is a species of tropical spider crab in the family Epialtidae. It is found on the seabed in shallow waters off the Atlantic coast of South America. Description Like other spider crabs, ''Libinia ferreirae'' has a roughly ci ...

'' and '' Libinia spinosa'', use the inside of the bell as a nursery where they are safe from

predation 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 ...

References

{{Taxonbar, from=Q2139538 Lychnorhizidae Animals described in 1880 Taxa named by Ernst Haeckel