Barreleyes, also known as spookfish (a name also applied several species of chimaera), are small, deep-sea, odd-looking osmeriform fish comprising the family Opisthoproctidae. Found in tropical-to-temperate waters of the Atlantic, Pacific, and Indian Oceans, the family contains 11 species in six genera (four of which are monotypic). Families Callorhynchidae Rhinochimaeridae Chimaeridae Other meanings, based on a fantastic animal, are at Chimera Chimaera is the common name of the species in the families Callorhynchidae, Rhinochimaeridae and Chimaeridae which all are closely related to sharks; they are also called ghost sharks. ... Atlantic herring, Clupea harengus, the most abundant fish species in the world. ... Scientific classification or biological classification refers to how biologists group and categorize extinct and living species of organisms. ... The Atlantic Ocean is Earths second-largest ocean, covering approximately one-fifth of its surface. ... The Pacific Ocean (from the Latin name Mare Pacificum, peaceful sea, bestowed upon it by the Portuguese explorer Ferdinand Magellan) is the worlds largest body of water. ... In biology, a species is a kind of organism. ... See genus (mathematics) for the use of the term in mathematics. ... Monotypic refers to a taxonomic group with only one subgroup at the next (smaller) taxonomic level, for example, a monotypic genus has only one species. ...

These fish are named for their barrel-shaped, tubular eyes which in most species are fixed gazing upwards. The family name Opisthoproctidae is derived from the Greek words opisthe ("behind") and proktos ("anus"). An eye is an organ that detects light. ... Male Anatomy The anus, in anatomy, is the external opening of the rectum. ...

Physical description

The morphology of the Opisthoproctidae varies between three main forms: the stout, deep-bodied barreleyes of the genera Opisthoproctus and Macropinna; the extremely slender and elongate spookfishes of the genera Dolichopteryx and Bathylychnops; and the intermediate fusiform spookfishes of the genera Rhynchohyalus and Winteria. All species have large, telescoping eyes which dominate and protrude from the skull. In all but Winteria, the eyes are fixed gazing upwards; in Winteria, the eyes are directed forwards, but with a slight upward pitch. The opisthoproctid eye has a large lens and a retina with an exceptionally high complement of rod cells and a high density of rhodopsin (the "visual purple" pigment); there are no cone cells. Morphology is the following: In linguistics, morphology is the study of the structure of word forms. ... 50 cm refracting telescope at Nice Observatory. ... A Hippopotamuss skull A skull, or cranium, is a bony structure of vertebrates which serves as the general framework for a head. ... The lens or crystalline lens is a component of the eye. ... Human eye cross-sectional view. ... Normalised absoption spectra of human rod (R) and cone (S,M,L) cells. ... Categories: Biochemistry stubs | G protein coupled receptors | Sensory receptors | Pigments ... Normalised absorption spectra of human cone (S,M,L) and rod (R) cells Cone cells, or cones, are cells in the retina which only function in relatively bright light. ...

To better serve their vision, barreleyes have transparent to translucent heads; this presumably allows the eyes to collect even more incident light. The toothless mouth is small and terminal, ending in a pointed snout. As in related families (e.g. Argentinidae), there is an epibranchial or crumenal organ present behind the fourth gill arch. This organ—analogous to the gizzard—consists of a small diverticulum (pouch) wherein the gill rakers insert and interdigitate for the purpose of grinding up ingested material. In life, the body of most species is a dark brown covered in large, silvery imbricate scales; but these are absent in Dolichopteryx, leaving the body itself a transparent white. In all species a variable number of dark melanophores colour the muzzle, ventral surface, and midline. The gizzard is a very muscular stomach that is found in birds, earthworms, and other animals. ... Diverticula are outpouchings of the intestinal wall. ... In most biological nomenclature, a scale (Greek lepid) is a small rigid plate that grows out of an animals skin to provide protection. ...

The eyes of Winteria telescopa differ slightly from those of other opisthoproctids by their more forward-pointing gaze.

Also present in Dolichopteryx, Opisthoproctus, and Winteria species are a number of luminous organs; in Dolichopteryx there are several along the length of the belly, and in Opisthoproctus there is a single organ in the form of a rectal pouch. These organs glow with a weak light due to the presence of symbiotic bioluminescent bacteria; specifically, Photobacterium phosphoreum (family Vibrionaceae). The ventral surface of Opisthoproctus species is characterised by a flattened and projecting sole; in the mirrorbelly (Opisthoproctus grimaldii) and Opisthoproctus soleatus this sole may act as a reflector, by directing the emitted light downwards. The strains of P. phosphoreum present in the two Opisthoproctus species have been isolated and cultured in the lab. Through restriction fragment length polymorphism analysis, the two strains have been shown to differ only slightly. Common Clownfish (Amphiprion ocellaris) in their magnificent sea anemone (Heteractis magnifica) home. ... Bioluminescence is the production and emission of visible light by a living organism as the result of a chemical reaction during which chemical energy is converted to light energy. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Genera Allomonas Beneckea Enhydrobacter Listionella Lucibacterium Photobacterium Salinivibrio Vibrio The Vibrionaceae are a family of Proteobacteria, given their own order. ... A microbiological culture is a way to determine the cause of infectious disease by letting the agent multiply (reproduce) in predetermined media. ... In molecular biology, the term restriction fragment length polymorphism (or RFLP) is used in two related contexts: as a characteristic of DNA molecules (arising from their differing nucleotide sequences) by which they may be distinguished, and as the laboratory technique which uses this characteristic to compare DNA molecules. ...

In all species the fins are spineless and fairly small; in Dolichopteryx however, the pectoral fins are greatly elongated and wing-like, extending about half the body's length. In all species the pectoral fins are inserted low on the body, and in some the pelvic fins are inserted ventrolaterally rather than strictly ventrally. Several species also possess either a ventral or dorsal adipose fin, and the caudal fin is forked to emarginate. The anal fin is either present or greatly reduced, and may not be externally visible; it is strongly retrorse in Opisthoproctus. There is a single dorsal fin originating slightly before or directly over the anal fin. There is a perceptible hump in the back, beginning just behind the head. The gas bladder is absent in most species, and the lateral line is uninterrupted. The branchiostegal rays number 2–4. The javelin spookfish (Bathylychnops exilis) is by far the largest species at 50 centimetres standard length (SL; a measurement excluding the caudal fin); most other species are under 20 centimetres SL. Raised thorns on the stem of the wait-a-bit climber Thorns on rose stems A spine is a rigid, pointed surface protrubance or needle-like structure on an animal, shell, or plant, presumably serving as a defense against attack by predators. ... Fish anatomy is primarily governed by the physical characteristics of water, which is much denser than air, holds a relatively small amount of dissolved oxygen, and absorbs light more than does air. ... Fish anatomy is primarily governed by the physical characteristics of water, which is much denser than air, holds a relatively small amount of dissolved oxygen, and absorbs light more than does air. ... Fish anatomy is primarily governed by the physical characteristics of water, which is much denser than air, holds a relatively small amount of dissolved oxygen, and absorbs light more than does air. ... Fish anatomy is primarily governed by the physical characteristics of water, which is much denser than air, holds a relatively small amount of dissolved oxygen, and absorbs light more than does air. ... Dorsal Fin of the Orca A dorsal fin is a fin located on the backs of fishes, whales, dolphins and porpoises. ... The gas bladder (also fish maw, less accurately swim bladder or air bladder) is an internal organ that contributes to the ability of a fish to control its buoyancy, and thus to stay at the current water depth, ascend, or descend without having to waste energy in swimming. ... In fish, the lateral line is a sense organ used to detect movement in the surrounding water. ...

Life history

Barreleyes inhabit moderate depths, from the mesopelagic to bathypelagic zone, ca. 400–2,500 metres down. They are presumably solitary and do not undergo diel vertical migrations; instead, barreleyes remain just below the limit of light penetration and use their sensitive, upward-pointing tubular eyes—adapted for enhanced binocular vision at the expense of lateral vision—to survey the waters above. The high number of rods in their eyes' retinae allow barreleyes to resolve the silhouettes of objects overhead in the faintest of ambient light (and to accurately distinguish bioluminescent light from ambient light), and their binocular vision allows the fish to accurately track and home in on small zooplankton such as hydroids, copepods, and other pelagic crustaceans. The distribution of some species coincides with the isohaline and isotherm layers of the ocean; for example, in Opisthoproctus soleatus upper distribution limits coincide with the 400 metre isotherm for 8°C. The pelagic zone is the part of the open sea or ocean comprising the water column, i. ... Diel means in the course of the day. Thus a diel variation is a variation that occurs regularly every day or most days. ... Binocular vision (also referred to as stereoscopic vision) is a type of visual system common in many kinds of animals where both the eyes produce only a single image in the brain. ... Photomontage of plankton organisms Plankton is the aggregate community of weakly swimming but mostly drifting small organisms that inhabit the water column of the ocean, seas, and bodies of freshwater. ... Orders Calanoida Cyclopoida Gelyelloida Harpacticoida Misophrioida Monstrilloida Mormonilloida Platycopioida Poecilostomatoida Siphonostomatoida Copepods are small, aquatic animals living in the sea and nearly every freshwater habitat, a form of plankton, specifically zooplankton, some copepods are parasitic. ... Classes Remipedia Cephalocarida Branchiopoda Ostracoda Maxillopoda Malacostraca The crustaceans (Crustacea) are a large group of arthropods (55,000 species), usually treated as a subphylum. ... An isotherm is a line of equal or constant temperature on a graph, plot, or map; an isopleth of temperature. ...

What little is known of barreleye reproduction indicates they are pelagic spawners; that is, eggs and sperm are released en masse directly into the water. The fertilized eggs are buoyant and planktonic; the larvae and juveniles drift with the currents—likely at much shallwer depths than the adults—and upon metamorphosis into adult form they descent to deeper waters. Dolichopteryx species are noted for their paedomorphic features, the result of neoteny (the retention of larval characteristics). Reproduction is the creation of one thing as a copy of, product of, or replacement for a similar thing, e. ... This article is about biological spawning. ... Wiktionary has a definition of: Egg Egg has multiple meanings. ... Schematic diagram of a sperm cell, showing the (1) acrosome, (2) cell membrane, (3) nucleus, (4) mitochondria, and (5) flagellum (tail) A sperm cell, or spermatozoon ( spermatozoa) (in Greek: sperm = semen and zoon = alive), is the haploid cell that is the male gamete. ... Photomontage of plankton organisms Plankton are the weakly swimming but mostly drifting small organisms that inhabit the water column of the ocean, seas, and bodies of freshwater. ... A larva (Latin; plural larvae) is a juvenile form of animal with indirect development, undergoing metamorphosis (for example, insects or amphibians). ... Metamorphosis in biology is physical development of the individual after birth or hatching involving significant change in form as well as growth and differentiation. ... A paedomorph is an organism that keeps physical and mental characteristics of its childhood in its adulthood. ... Neoteny is a term in developmental biology that describes the retention of juvenile characteristics in the adults of a species and is similar to but not the same as progenesis, which is the attainment of sexual maturity by an organism still in its larval stage, as is found among certain...

The bioluminescent organs of Dolichopteryx and Opisthoproctus, together with the reflective soles of the latter, may serve as camouflage in the form of counterillumination. This predator avoidance strategy involves the use of ventral light to break up the fishes' silhouettes, so that (when viewed from below) they blend in with the ambient light from above. Counterillumination is also seen in several other unrelated deep-sea families, which include the marine hatchetfish (Sternoptychidae). Also found in marine hatchetfish and other unrelated families are tubular eyes; cf. telescopefish, tube-eye. Anolis caroliensis showing blending camouflage and counter-shading. ... Genera  Argyropelecus  Polypipnus  Sternoptyx Marine hatchetfish are small, deep-sea bathypelagic fish of the family Sternoptychidae, together with bottlelights, pearlsides and constellationfish. ...

See also

• List of fish common names
• List of fish families

This is a list of fish common names. ... This is a list of fish families sorted by scientific name. ...

References

• "Opisthoproctidae" (http://www.fishbase.org/Summary/FamilySummary.cfm?Family=Opisthoproctidae). FishBase. Ed. Ranier Froese and Daniel Pauly. February 2005 version. N.p.: FishBase, 2005.
• "Mesopelagic fishes" (http://www.ifm.uib.no/StaffPages/salvanes/Salvane&Krist-encycl-2001.pdf). Encyclopedia of ocean sciences, Vol. 3, 2001. A. G. V. Salvanes and J. B. Kristofersen. February 2005 version. (PDF file.)
• "Restriction Fragment Length Polymorphism Analysis Reveals High Levels of Genetic Divergence Among the Light Organ Symbionts of Flashlight Fish" (http://www.biolbull.org/cgi/reprint/181/1/135.pdf) The Biolological Bulletin. 181: 135-143. (August, 1991). Connie J. Wolfe and Margo G. Haygood. February 2005 version. (PDF file.)
• "Bioluminescent signals and the role of reflectors" (http://www.iop.org/EJ/S/UNREG/AspaB4CD0G1zKhZYnd5CjA/abstract/1464-4258/2/6/202) Journal of Optics A: Pure Applied Optics. 2 R29-R38. Peter J. Herring (2000). February 2005 version.
• Fishes: An introduction to ichthyology. Peter B. Moyle and Joseph J. Cech, Jr; p. 320. Printed in 2004. Prentice-Hall, Inc; Upper Saddle River, NJ. ISBN 0131008471