''Vallentinia gabriellae'', the hitch-hiking jellyfish, 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 ...

of small, inconspicuous hydrozoan 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 ...

Olindiidae Olindiidae is a family of hydrozoans in the order Limnomedusae. They have a polyp (zoology), polyp phase and a Jellyfish, medusa phase. The polyps are generally small (1 mm) and solitary, but a few species are colonial. They have a varying ...

. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to a few isolated parts of the western Atlantic Ocean. It is elusive in the wild but sometimes makes its appearance unexpectedly in seawater cultures of other organisms in the laboratory.

Synonymy

''Vallentinia gabriellae'' is found in the south west Atlantic. A related species, '' Vallentinia adherens'', is found in the Pacific Ocean and the two are so similar that it has been suggested that they are different populations of the same species.''Vallentinia gabriellae'' (Hitch-hiking Jellyfish)
Smithsonian Marine Station. Retrieved 2011-12-08.

Description

''Vallentinia gabriellae'' can grow to about 12 millimetres (0.5 in) in diameter but is more usually 6 to 8 millimetres across. The dome-shaped bell of the

medusa In Greek mythology, Medusa (; Ancient Greek: Μέδουσα "guardian, protectress"), also called Gorgo, was one of the three monstrous Gorgons, generally described as winged human females with living venomous snakes in place of hair. Those ...

is two thirds as high as it is wide. It is transparent and gelatinous and has 4 radial canals. Alongside their lower ends lie 4 folded, sac-like

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. There are 4 to 8 large tentacles halfway down the outside of the bell located between the radial canals and sometimes 4 more, close to them. These have adhesive pads on their tips which allows the jellyfish to grip hold of objects. There are up to 128 (more usually 64-75) hollow tentacles fringing the margin of the bell. These have several rings of

nematocyst 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 along their length. Between the tentacles are

statocyst The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves, cnidarians, ctenophorans, echinoderms, cephalopods, and crustaceans. A similar structure is also found in ''Xenoturbella''. The statocyst cons ...

s, sensory organs which can detect

gravitational pull In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stron ...

and which help the animal to orient itself correctly. Underneath the bell there is a central

manubrium The sternum or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood vessels from injury. Sha ...

with the mouth at its tip. This connects to the

gastrovascular cavity The gastrovascular cavity is the primary organ of digestion and circulation in two major animal phyla: the Coelenterates or cnidarians (including jellyfish and corals) and Platyhelminthes (flatworms). The cavity may be extensively branched into ...

, the radial canals and the circular marginal canal.

Distribution and habitat

''Vallentinia gabriellae'' is found on the western side of the Atlantic Ocean. It is known from isolated sites in Brazil, the Yucatan Peninsula,

Louisiana Louisiana , group=pronunciation (French: ''La Louisiane'') is a state in the Deep South and South Central regions of the United States. It is the 20th-smallest by area and the 25th most populous of the 50 U.S. states. Louisiana is borde ...

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

and

Bimini Bimini is the westernmost district of the Bahamas and comprises a chain of islands located about due east of Miami. Bimini is the closest point in the Bahamas to the mainland United States and approximately west-northwest of Nassau. The populat ...

in the

Bahamas The Bahamas (), officially the Commonwealth of The Bahamas, is an island country within the Lucayan Archipelago of the West Indies in the Atlantic Ocean, North Atlantic. It takes up 97% of the Lucayan Archipelago's land area and is home to ...

. It lives in shallow water, on or close to the

seabed The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

. In the

Indian River Lagoon The Indian River Lagoon is a grouping of three lagoons: the Mosquito Lagoon, the Banana River, and the Indian River, on the Atlantic Coast of Florida; one of the most biodiverse estuaries in the Northern Hemisphere and is home to more than 4,300 ...

in Florida it was first detected in 1990, in a barrier ditch adjoining

mangrove A mangrove is a shrub or tree that grows in coastal saline water, saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evoluti ...

swamps. In Louisiana it was found in a

seagrass bed A seagrass meadow or seagrass bed is an underwater ecosystem formed by seagrasses. Seagrasses are marine (saltwater) plants found in shallow coastal waters and in the brackish waters of estuaries. Seagrasses are flowering plants with stems and ...

. It has been found experimentally to be tolerant of a wide range of

salinities Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...

and a wide range of temperatures.

Life cycle

Reproduction in ''Vallentinia gabriellae'' has two phases. These are the medusa or jellyfish which reproduces sexually and a polyp that reproduces by

budding Budding or blastogenesis is a type of asexual reproduction in which a new organism develops from an outgrowth or bud due to cell division at one particular site. For example, the small bulb-like projection coming out from the yeast cell is know ...

. The male and female medusae liberate

gamete A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce t ...

s into the

water column A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediment.Munson, B.H., Axler, R., Hagley C., Host G., Merrick G., Richards C. (2004).Glossary. ''Water on the Web''. University of Minnesota-D ...

. After fertilisation, the

eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

develop into

planula A planula is the free-swimming, flattened, ciliated, bilaterally symmetric larval form of various cnidarian species and also in some species of Ctenophores. Some groups of Nemerteans also produce larvae that are very similar to the planula, which ...

larvae which are

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

ic. After some time drifting with the current, they settle onto the seabed, 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 ...

and become sedentary. The smallest polyps that form, under 1 millimetre (0.04 in) long, have 2 tentacles while older, larger ones have 3 to 5. The polyps can

reproduce asexually Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the fu ...

, budding to form either more polyps or free-swimming medusae. A polyp can have several buds forming at any one time. Polyps can also bud to produce

frustule A frustule is the hard and porous cell wall or external layer of diatoms. The frustule is composed almost purely of silica, made from silicic acid, and is coated with a layer of organic substance, which was referred to in the early literature on d ...

s. These are groups of about 4 polyps embedded in mucus and capable of withstanding adverse circumstances. When conditions improve they can develop into new polyps over the course of a few weeks.

Ecology

On several occasions, specimens of ''Vallentinia gabriellae'' have unexpectedly appeared in cultures of other marine organisms in the laboratory. The ease with which they can be cultured (fed on brine shrimps (''

Artemia salina ''Artemia salina'' is a species of brine shrimp – aquatic crustaceans that are more closely related to ''Triops'' and cladocerans than to true shrimp. It belongs to a lineage that does not appear to have changed much in . ''A. salina'' is nati ...

'')) has led to the possibility of their being used for teaching purposes and in medical research. Knowledge of this species mostly comes from observations in the laboratory because they have only infrequently been found in the wild. In a feeding trial, specimens of ''Vallentinia gabriellae'' were deprived of food for 48 hours and then offered a choice of

rotifer The rotifers (, from the Latin , "wheel", and , "bearing"), commonly called wheel animals or wheel animalcules, make up a phylum (Rotifera ) of microscopic and near-microscopic pseudocoelomate animals. They were first described by Rev. John H ...

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...

nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...

crab Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...

zoea Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The ...

l larvae and

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

veliger A veliger is the planktonic larva of many kinds of sea snails and freshwater snails, as well as most bivalve molluscs (clams) and tusk shells. Description The veliger is the characteristic larva of the gastropod, bivalve and scaphopod ...

larvae. They preferred larger items of prey which they immobilised with their nematocysts before ingesting them whole. They continued feeding until replete. Other unfed jellyfish were offered juvenile fish ( mullet) ranging in size from 12 to 15 millimetres in length, larger than the 10 millimetre diameter of the jellyfish. These were entangled and immobilised by the marginal tentacles, eventually being wrapped round and enclosed by the mobile manubrium. Undigested remains were expelled the following day.

References

{{Taxonbar, from=Q2257541 Olindiidae Animals described in 1948