Meristics is an area of zoology and botany which relates to counting quantitative features of animals and plants, such as the number of fins or scales in fish. A meristic (countable trait) can be used to describe a particular species, or used to identify an unknown species. Meristic traits are often described in a shorthand notation called a meristic formula.
Meristic characters are the countable structures occurring in series (e.g. myomeres, vertebrae, fin rays). These characters are among the characters most commonly used for differentiation of species and populations. In the salmonids, scale counts have been most widely used for the differentiation of populations within species. In rainbow and steelhead trout the most notable differences among populations occur in counts of scales. Meristic comparison is used in phenetic and cladistic analysis.
A meristic study is often a difficult task. For example, counting the features of a fish is not as easy as it may appear. Many meristic analyses are performed on dead fish that have been preserved in alcohol. Meristic traits are less easily observed on living fish, though it is possible. On very small fish, a microscope may be required.
Ichthyologists follow a basic set of rules when performing a meristic analysis, to remove as much ambiguity as possible. The specific practice, however, may vary depending on the type of fish. The methodology for counting meristic traits should be described by the specialist who performs the analysis.
A meristic formula is a shorthand method of describing the way the bones (rays) of a bony fish's fins are arranged. It is comparable to the floral formula for flowers.
Spine counts are given in Roman numerals, e.g. XI-XIV. Ray counts are given in Arabic numerals, e.g. 11–14. [1]
The meristic formula of the dusky spinefoot (Siganus luridus) is: D, XIV+10; A, VII+8-9; P, 16–17; V, I+3+I; GR, 18-22
This means the fish has 14 spiny rays (bones) in the first part of its dorsal fin (D), followed by 10 soft rays. A is the anal fin, P represents the pectoral fins (near the gills and eyes), V represents the ventral or pelvic fins, and C is the caudal fin or tail (not indicated in this example). GR means gill raker count (see below).
The number of bones in the backbone is a feature which can also be used to classify fish species. Usually all the vertebrae are counted. Vertebral counts may be split into abdominal (those associated with the body cavity) and caudal (tail) vertebrae. If there are sutures in the urostyle, components are counted, otherwise the urostyle is usually counted as one vertebra. [2]
The number of gill rakers on the first gill arch can also be used to identify a fish species. Rakers are counted for the upper and lower limbs of the gill arch, and a raker at the joint of the upper and lower limbs is counted as of the lower. Counts for the upper and lower limbs are separated by a + sign and ranges are bracketed, e.g., GR: 3 + (4-5). [3]
Ichthyostega is an extinct genus of limbed tetrapodomorphs from the Late Devonian of what is now Greenland. It was among the earliest four-limbed vertebrates ever in the fossil record and was one of the first with weight-bearing adaptations for terrestrial locomotion. Ichthyostega possessed lungs and limbs that helped it navigate through shallow water in swamps. Although Ichthyostega is often labelled a 'tetrapod' because of its limbs and fingers, it evolved long before true crown group tetrapods and could more accurately be referred to as a stegocephalian or stem tetrapod. Likewise, while undoubtedly of amphibian build and habit, it is not a true member of the group in the narrow sense, as the first modern amphibians appeared in the Triassic Period. Until finds of other early stegocephalians and closely related fishes in the late 20th century, Ichthyostega stood alone as a transitional fossil between fish and tetrapods, combining fish and tetrapod features. Newer research has shown that it had an unusual anatomy, functioning more akin to a seal than a salamander, as previously assumed.
Fish anatomy is the study of the form or morphology of fish. It can be contrasted with fish physiology, which is the study of how the component parts of fish function together in the living fish. In practice, fish anatomy and fish physiology complement each other, the former dealing with the structure of a fish, its organs or component parts and how they are put together, such as might be observed on the dissecting table or under the microscope, and the latter dealing with how those components function together in living fish.
The stream catfishes comprise the family Akysidae of catfishes.
This glossary of ichthyology is a list of definitions of terms and concepts used in ichthyology, the study of fishes.
The Ukrainian stickleback also known as the Caspian ninespine stickleback, southern ninespine stickleback, and Aral ninespine stickleback, is a species of fish in the family Gasterosteidae. It is found in Afghanistan, Bulgaria, Iran, Kazakhstan, Moldova, Romania, Russia, Serbia, Montenegro, and Ukraine.
The Malabar trevally, also known as the Malabar jack, Malabar kingfish or nakedshield kingfish, is a species of large inshore marine fish of the jack family, Carangidae. It is distributed throughout the Indian and west Pacific Oceans from South Africa in the west to Japan and Australia in the east, inhabiting reefs and sandy bays on the continental shelf. The Malabar trevally is similar to many of the other species in the genus Carangoides, with the number of gill rakers and the grey-brown colour of the tongue being the diagnostic features. The Malabar trevally is a predator, taking a variety of small fish, cephalopods and crustaceans. The species is of minor economic importance throughout its range, caught by a variety of net and handline methods.
Dvinosaurus is an extinct genus of amphibious temnospondyls localized to regions of western and central Russia during the middle and late Permian, approximately 265-254 million years ago. Its discovery was first noted in 1921 by Russian paleontologist Vladimir Prokhorovich Amalitskii in a posthumously published paper that documents the findings of a site in Russia's Arkhangelsk District. Its name is derived from the proximity of this site to the Northern Dvina River.
The imposter trevally, also known as the imposter jack or white-tongued trevally, is a species of small coastal marine fish in the jack family Carangidae. The imposter trevally is distributed through the tropical waters of Indian and west Pacific oceans, from the Gulf of Oman in the west to Japan and Australia in the east. The species is quite similar to the Malabar trevally, but can be distinguished by its gill raker count, and is identifiable from other species by having a white to pale grey tongue. It is a relatively small species, growing to a maximum recorded length of 30 cm. The imposter trevally inhabits coastal waters of the continental shelf in depths of up to 140 m, often associating with closely related carangid species. It preys on a range of small fish, crustaceans and cephalopods, but little is known of its reproductive biology. The imposter trevally is of minor importance to fisheries throughout its range, taken by hook and line, bottom trawls and several types of artisanal gear.
Cancelloxus elongatus, the whiteblotched klipfish, is a species of clinid found in subtropical waters of the Atlantic Ocean along the South African coast. It prefers sandy habitats with nearby rocks at depths of from 10 to 25 metres. It can reach a maximum length of 5 centimetres (2.0 in) TL. This species preys primarily on zoobenthos.
Clinus acuminatus, the sad klipfish, is a species of fish in the family Clinidae. It is endemic to Southern Africa, where it occurs along the coast of Namibia and South Africa. It can reach a maximum length of 13 centimetres (5.1 in) TL and is viviparous. The sad klipfish feeds on crustaceans.
Clinus berrisfordi, the Onrust klipfish, is a species of clinid that occurs in subtropical waters of the Atlantic Ocean from False Bay to Skoenmakerskop, South Africa where it prefers marine and brackish habitats with plentiful growth of seaweed. This species can reach a maximum length of 12 centimetres (4.7 in) TL.
Clinus brevicristatus, the Cape klipfish, is a species of clinid that occurs in subtropical waters of the Atlantic Ocean around South Africa where it prefers habitats with plentiful growth of seaweed. This species can reach a maximum length of 12 centimetres (4.7 in) TL.
Clinus venustris, the speckled klipfish, is a species of clinid that occurs in subtropical waters of the Atlantic Ocean from Namibia to South Africa where it is found in the subtidal zone as well as being a denizen of tide pools. This species can reach a maximum length of 12 centimetres (4.7 in) TL. and feeds primarily on amphipods, isopods, mysids, and echinoderms.
Datnioides is a genus of fish known commonly as tigerfish, tiger perch or freshwater tripletails, but all of these common names are also used for other families. It is the only genus in the family Datnioididae. These fish are found in fresh and brackish waters of rivers, estuaries and coastal areas in South and Southeast Asia, and New Guinea.
The vertebral column, also known as the backbone or spine, is the core part of the axial skeleton in vertebrate animals. The vertebral column is the defining characteristic of vertebrate endoskeleton in which the notochord found in all chordates has been replaced by a segmented series of mineralized bone called vertebrae, separated by fibrocartilaginous intervertebral discs. The dorsal portion of the vertebral column houses the spinal canal, a cavity formed by the neural arches that encloses and protects the spinal cord.
Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of Actinopterygii, Dipnomorpha, Actinistia and Chondrichthyes fishes. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as seen in sharks. Apart from the tail or caudal fin, fish fins have no direct connection with the spine and are supported only by muscles. Their principal function is to help the fish swim.
Squalius valentinus, commonly known as the Valencia chub and the Levantine bagra, is a species of freshwater fish in the carp family Cyprinidae. It was first isolated from the Turia River in Valencia, hence its name. It is considered endangered. This species is differentiated from its cogenerates by having eight branched rays in its dorsal fin; eight branched rays in its anal fin; two rows of pharyngeal teeth on both sides possessing 2 and 5 teeth ; a wide caudal peduncle; its number of gill rakers; the number of scales in its lateral line; the number of scale rows above the latter; by possessing three scale rows below it; by having thirty-nine vertebrae ; showing large 4th and 5th infraorbital bones; a maxilla with a very distinct marked anterior process; exhibiting a frontal bone expanded at the middle; a wide neurocranium bone; the lower branch of the pharyngeal bone being robust; a large and narrow urohyal; as well as genetic differences (allozymes).
Hemiramphus far, the halfbeak, black-barred halfbeak, black-barred garfish, barred halfbeak, barred garfish or spotted halfbeak, is a schooling marine fish in the family Hemiramphidae. It has an Indo-Pacific distribution and has invaded the eastern Mediterranean through the Suez Canal.
The broomtail grouper or mangrove grouper is a species of ray-finned fish from the family Serranidae which is found in the eastern Pacific along the western coast of the Americas from California to Peru.
Nansenia oblita, also called the forgotten argentine or the Mediterranean large-eyed argentine, is a species of fish in the pencil smelt family (Microstomatidae).