GLOSSARY OF SCIENTIFIC TERMS
FOR KILLI-HOBBYISTS

 

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Notes (page last update on January 24. 2020):

This glossary is an updated copy of the printed pages in Killi-Data 2007.

"°" means that the word is defined elsewhere in this glossary.


A

A. Anal ray° counts.

acid water. Water with a pH below 7.0. A fairly frequent occurrence in pure rainwater biotope°, and especially black° waters.

aestivation. A condition of torpor or dormancy which allows fish to survive outside water during a while, often on leaves, plants or branches (frequent in oviparous Cyprinodontiformes, notably in genera Rivulus et al., or Kryptolebias, but not reported in viviparous groups (also aestivating).

affinis (aff.). Systematically° or phylogenetically° related to but not identical with (affinity, relationship) ; a Latin word also used to define a population that is not fully identified with certainty and identification is temporarily assigned to a related similar species, e.g. Aphanius aff. dispar ; Latin abbreviation 'cf.' (from 'confer', I attribute to) has a similar meaning of uncertainty but it adds a personal appreciation (less formal, subjective) by the concerned author of the identification.

alkaline water. Water with a pH above 7.0. Such water is just the reverse of being acid; usually water containing dissolved lime, but also brackish° or marine or hypersaline° waters.

allometry. Differential size or growth in 2 or more measurements (e.g., between juvenile and adult stage).

allopatric populations. Populations° living in separate biotopes° or biogeographical areas (Allopatry).

allotype. One of the types° (or not), different by its sex° from the holotype°: usually the female (usage not advised by I.C.Z.N.° today).

Anal fin°. Anal Length (A.L.), from base° to tip°, is measured (in mm or as a % of S.L.°), possibly in view of showing sexual dimorphism°  also measured: Anal Base (A.B.): length between the first and the last ray ; in Killi-Data, by convention, fins are labelled with initial cap letter to differentiate them from region or area of sides.

anal area or zone or region. Part of sides°, situated above the Anal fin°.

annual species. A species of which the free-swimming individuals live for less than one year, the fertile eggs hibernating in the soil during desiccation (when the biotope° is dry and there is no more water)°.

anaerobic. In the absence of oxygen ; black° waters are very poor in dissolved oxygen (opposite: aerobic).

arm. Branch of a chromosome°, fastened to a knot named the centromere ; in metacentric chromosomes, the 2 arms are of equal length, in subtelocentric (or submetacentric) chromosomes, the 2 arms are of not of equal length, one is short, the other is long, in acrocentric (or telocentric) chromosomes, only 1 arm is present.

apomorphic. In cladistics°, defines a derived (i.e. not primitive) character (opposite: plesiomorphic°).

available Name. A name at whatever level (from specific to generic and above) which does fulfil the minimum provisions of the code of rules and recommendations enacted by I.C.Z.N.° (opposite: Nomen nudum or non available or unavailable° name).

 

B

base of fins. Distance between the first and the last ray° of the fin°, measured near the body for Anal, Dorsal and Pectoral fins.

biospecies. A zoological species defined by its reproductive isolation from other biospecies with a similar morph (synonym:  the biological species).

biotope. Place where the fish live and its environment, as defined by type of water body, width, depth, current if any, substratum, presence or not of plants, submersed or terrestrial, physico-chemical characteristics, such as pH°, conductivity°, D.H.°, etc.

black waters. Usually from forest streams with much humic content; high acidity° (low pH°) and low conductivity°.

bootstrap. Statistic tool used to ascertain branches solidity in trees as graphic representation of results of phylogenetic° studies from various methods (morphological°, osteological°, molecular°), processed by phylogenetic computer° programs ; bootstrap values varies between 0% (no putative solidity of branch) to 100% (putative solidity of branch) ; molecular trees are associated with high bootstrap values (more than 95%), but they are often considerably different from morphological or osteological trees, hence the tendency, today infrequent, to use combined characters of molecular (genotypic) and phenotypic° origins with much larger matrixes.

brackish water. Water containing a mixture of fresh and salt waters, such as in estuaries ; water that has more salinity than fresh water, but not as much as seawater (marine water).

branchiostegal rays. Ossified rays, that sustain the lower membrane of the branchial cavity.

 

C

C. Caudal rays are counted, branched or unbranched.

Caudal fin° (or tail). Length (C.L.), from base° to tip°, is measured (in mm or as a % of S.L.), possibly in view of showing sexual dimorphism° ; in Killi-Data, by convention, fins are labelled with initial cap letter to differentiate them from region or area of sides.

caudal length. Easily computed by T.L.° minus S.L.°, in mm or as a % of S.L.

chromosome. In the nucleus, a body carrying the genetic material: made of a centromere (knot) and 1 or 2 arms°.

CIR. Circumpeduncular scales. Count around the narrowest part of Caudal peduncle, in a zig-zag row.

clade. Group of taxa (at species or at generic level) sharing exclusively a common ancestor.

cladistics. Method of taxonomy° (or systematics°) which groups strictly monophyletic° taxa° based on apomorphic° characters, only.

cladogram. Diagrammatic tree showing monophyletic° taxa°, up to their common ancestor.

clearing and staining (c&s). Technique which involves the clearing of muscle tissues and staining of bones; it allows the study of the osteology° (cleared and stained specimen, in short c&s).

Code. List of rules, recommendations, published by the International Commission of Zoological Nomenclature (I.C.Z.N.°), in order to organize and settle the availability° of taxa° (names at species°, genus° and family-group° levels) and publications ; the last edition of the book is published in 1999, for new rules to be starting on January 1. 2000, and since then new provisions, notably for electronic issues are presented on the Internet ; for a given taxon described in a given year, the code pertaining to that year only applies (not subsequent versions).

complex. Group of monophyletic° species; a concept similar to superspecies or to species-group depending on authors°.

computerized systematics. Modern method of systematics using computer programs (e.g., T.N.T, Phylip, PAUP) based on a matrix of component taxa° (e.g., genera°, species°) and of characters coded generally as '0' or '1' in order to a phylogenetic tree, with bootstrap° values.

conductivity of water. An electrical measurement that shows the amount of mineral matter dissolved in water or the salinity of the water. High figures equal much mineral matter. Unit: microSiemens (µS).

congeners. Species belonging to the same genus° (resp. subcongeners for species belonging to the same subgenus°).

conspecific populations. Populations belonging to one and the same species.

convergence. When a given character (pattern, morphology, osteology, genetic sequence) is identical between 2 species° or 2 superspecies (species groups) that has been independently acquired (i.e. by chance or hazard, and not by phylogeny°); frequently color convergence is observed among 2 frontier° species.

cryptic (or kryptic) species°. Allopatric° isomorphic° (bio)species, only distinguished by genetic isolation and color pattern° or other minor external features, from other members of the same superspecies°.

ctenoidy. Usually spine-like structures developing on the edges of scales or at the ends of fin ray segments (rarely, in the middle). Ctenoid spines are more often encountered in old dominant males.

cytology. The study of cells, i.e., sub-branch of biology concerned with the structure and function of cells in living organisms.

 

D

D. Dorsal ray° counts.

D/A (Dorsal over Anal). This count shows the relative posterior (resp. anterior) position of Dorsal fin insertion to Anal fin by counting the number of rays of Anal, up to vertical of the Dorsal origin: e.g., +3 means that the first Dorsal ray is inserted above the third Anal ray; -3 means that the first Dorsal ray is inserted ahead of the first Anal ray and that the third Dorsal ray is above the first Anal ray. It is always interesting for systematic° analysis and assignments to superspecies.

describer(s). Author(s) of the first (original) published description° a new taxon°.

description (original). First published definition or diagnosis of a new taxon° (subsequently: redescription).

desiccation. Period during which certain biotopes° are dried up : the dry season.

D.H. German hardness (degrees). 1 DH = 17.86 ppm (US).

diagnosis. Key elements to define and differentiate a taxon° vs. putatively related taxa°(plural: diagnoses).

diapause. Temporary arrest of the egg development. Up to 3 diapauses have been reported to occur in annual° species (labelled as I, II or III).

dimorphism. Difference in morphology°: may be in terms of sex°, i.e. between male and female, or of age, i.e. between juvenile and adult.

diploid. The normal (somatic) cell containing a diploid (paired) set of homologous chromosomes° from mother and father.

dorsal area or zone or region. Part of sides°, situated below the Dorsal fin°.

Dorsal fin°. Length (D.L.), from base° to tip°, is measured (in mm or as a % of S.L.), possibly in view of showing sexual dimorphism° ; also measured: Dorsal Base (D.B.): length between the first and the last ray ; in Killi-Data, by convention, fins are labelled with initial cap letter to differentiate them from region or area of sides.

 

E

ecological conditions. All external factors influencing the life of the population° in a certain place. Usually climatic conditions, soil type, water type, forest, savannah, altitude, etc.

electrophoresis. Identification technique based on distinction of protein movements (today disused).

embryology. Study of the egg (membrane, development, diapauses°, adhesivity, etc.) ; in Cyprinodontiformes, egg needs a long development time sometimes interrupted by diapause° states and has a thickened chorion to resist to desiccation, with possible filaments or other ornaments on egg surface°.

endemic. Restricted to a usually rather small geographical area (but not always… a species may have a huge endemic range, such as Sahelian areas in Africa, or the Amazon basin).

endangered species. A species that runs the risk of extinction° if appropriate protective measures are not instituted ; thus, included in Appendix II of the Convention of Washington on the International Trade in Endangered Species of Wild Fauna and Flora (C.I.T.E.S.) ; also a status managed I.U.C.N.°, International Union for the Conservation of Nature and Natural Resources as the world's main authority on the conservation status of species.

et al. (et allii). Latin abbreviation to quote shortly a group of authors, e.g. the publication by Agnèse, Zentz, Legros & Sellos, 2006 is abbreviated as Agnèse et al., 2006 ; also used for names, to consider a name and the related names (e.g., Rivulus et al. means Rivulus and related genera, Epiplatys sexfasciatus et al. means sexfasciatus and related species).

Evolutionarily Significant Unit (ESU). A group of populations° in the wild which are somewhat distinctive by some minor stable characters and may deserve a new taxonomic name in the future (or not), either as a molecular° species or as a cryptic° species.

extinct species. A species thought to have definitely disappeared in the wild throughout its geographical range due to competition or biotope destruction, but may be maintained in aquariums or laboratories or in artificial refugia for conservation by dedicated aquarists.

eye diameter. Distance between anterior and posterior orbital walls (in mm or as a % of S.L.).

 

F

F-generation. Characterizes the number of generations obtained by breeding or crossing : F0 means wild strain, F1 first generation from wild parents or obtained in crossings, then F2, F3… fertile F3 generation is necessary to confirm interfertility.

ff-scales. A series of frontal scales that usually bridges the grooves for the lateral line organs of the front°, dividing these grooves into supra-orbital and post-orbital parts.

falaise. The steep slope which separates the inland plateau° (highlands°, above 350 meters high) from the coastal lowlands° (French-derived word in English).

Family-Group Names (F.G.N.). In the pyramidal organisation of nomenclature, levels above the genus° level°, starting from subtribe (always ending by -ina), then upwards followed by tribe (always ending by -ini), then by subfamily (always ending by -inae), then by family (always ending by -idae), then by superfamily (always ending by -oidea), then by suborder (always ending by -oidei), then by order (always ending by -formes).

fins. Organs of motion and equilibrium ; distinguished in unpaired (Caudal° or tail, Dorsal° and Anal°) or paired (Pectorals°, Ventrals° or Pelvics). In Cyprinodontiformes, there is neither Adipose fin (behind the Dorsal) nor double Dorsal fins, but Anal fin is modified into a gonopodium°.

fission. The decomposition of a two-armed chromosome° by acentromeric break.

front. Superior part of head, in between the eyes; a very important part for the Cyprinodontiformes (sensory organs), since most species are near-to-surface dwellers.

frontal squamation (or scalation). Specific arrangement of the scales on the front° ; depending on the scales overlying the others, the arrangement is named "dd, ee, ff, g" or "h", while the "a" scale covers the pineal organ.

frontal neuromasts°. The cephalic neuromasts situated on the front in grooves or below pores. Their taxonomic significance may be important at or above the genus° level (rarely at specific level).

frontier species. A biospecies° with a restricted geographical distribution, living at the border of the range of its superspecies° and thus facing the competitive pressure of the neighboring superspecies°.

fusion. An exchange of arms between two subtelocentric° chromosomes°. See also Robertsonian° fusion.

 

G

genotype. The sum of the genetic characters of the individual (opposite : phenotype°).

genus. In the pyramidal organisation of nomenclature, the first level above species°, itself the basis for taxonomy (above genus level are the family-group° names, below genus level are the subgenus° name and the species name).

gill Rakers. Sort of spines in variable numbers, on the edges of the branchial arches ; those on the first arch (ceratobranchial and epibranchial) are counted for systematic° purpose in osteological° studies.

gonopodium. Modification of male Anal fin into an intromittent reproductive organ for viviparous species° (livebearers) ; its study is a key criterion in systematics° of those fishes ; in Goodeinae, gonopodium is different and a pseudo-gonopodium, technically named andropodium.

 

H

H-scale. Scale, usually rather small, situated in front of the central g-scale and often below that scale.

haploid. Cells having only one set of chromosomes°. Sex° cells are haploid, normal cells are diploid°.

Hd. (Head). Distance from the tip° of the mouth to the back of the fleshy opercle (in mm or as a % of S.L.).

height. Body depth at Anal level, distance between upper and lower part of the body (in mm or as a % of S.L.°). The greatest height, usually at the vent, may be also measured, but it is distorted in pregnant females and overfed aquarium specimens. Height, at Caudal peduncle (dcp), is also measured. Body height is an uncertain criterion, as there may be allometry° in growth: juveniles are more slender.

hemoglobin. The compound that transports the oxygen via the blood stream to different parts of the body and produces the red color of the blood ; the so-called hemoglobin pattern gives indication of phylogeny°.

heteromorphic. With a difference in morphology°. Two superspecies are heteromorphic, as well as two morphospecies (opposite: isomorphic).

highlands. Regions of mountains or inland plateau° (above 350 m altitude), separated from lowlands° by a falaise° ; if steep, then the fauna is distinctive from that of lowlands°.

holotype. A single preserved (fish) specimen for which a certain zoological name has been attached. Today, the designation of the holotype and its deposition in a museum collection is mandatory in order that a described name is considered as available by I.C.Z.N.° code

homoplasy. Parallely acquired character (cladistics°), either by convergence or by reversal to a previous primitive state.

hybrid. An individual artificially produced by the crossing of individuals (parents) from different populations, usually from different biospecies° or morphospecies°  natural hybridization is an extremely rare event among oviparous Cyprinodontiformes but quite significant among viviparous Cyprinodontiformes (and if natural hybrids are recent, then their description as new species is not allowed by I.C.Z.N.° and such names are considered as not available°).

hypersaline. Water with higher salt concentration than sea, as in salt marshes (much greater than 35 parts per thousand or PPT).

 

A

I.C.Z.N. International Commission of Zoological Nomenclature. A commission which enacts the rule of nomenclature° (the Code) and exceptionally settle, on request, debated nomenclatural cases.

inversion. A chromosomal structural change between one extremity and the centromere fastening.

I.O. (Interorbital Space). Distance between the eyes or width at eye level (in mm or as a % of S.L.°).

isomorphic. With the same morphology° or a proportionate equivalent. Components of a superspecies° are isomorphic and then named cryptic° species, when isomorphic° (opposite: heteromorphic).

I.U.C.N. Red List. System dividing threatened species into 7 categories in a scale variation from worse to fine, as extinct (EX), extinct in the wild (EW), critically endangered (CR), endangered (EN), vulnerable (VU), not threatened (NT), and least concern (LC) ; since it concerns all living organisms, Killi-Data adapts those categories and estimates trends based on recent past, from fine to worse, as unknown, widespread, locally endangered, globally endangered (in need of protection), protected (legally), protected (with artificial transplants), extinct (in the wild, but with laboratory or aquarists conservation), extinct (fully).

 

K

karyotype. A schematic figuration of the haploid chromosome° complement (better linguistically: caryotype).

Killi (plural: Killies). Old Dutch name (Kill: creek), first used for some Fundulus species from North America, then by extension for all oviparous° and sometimes viviparous° Cyprinodontiformes, herein equivalent to all Cyprinodontiformes (or Cyprinodonts in short), i.e. including various common names such as splitfins (Goodeinae), toothed minnows, tooth-carps, pupfish, rivulins, lampeyes, panchax, etc.

 

L

lateral line. Sensory organs on mid sides of the fish. Rare in Cyprinodontiformes.

lecithotrophy (yolk feeding, no maternal feeding). The form of internal development for some viviparous° sp. in which the embryo receives no nutrition from mother other than the yolk originally contained within its egg, as true ovoviviparity (adjective : lecithotrophic ; opposite : matrotrophy).

lectotype. A single type specimen designated as such from a series of syntypes° (while the other syntypes become paralectotypes) in order to uniquely exemplify the species (like the holotype°).

L.L. Scale Count on Lateral Line or Series. From the gill opening to the rear end of hypural plate; if counted, those inserted posteriorly on Caudal are separated by a "+".

lowlands. Low altitude regions, mostly near the coast. Its fauna is often distinctive from that of highlands°.

lumpers. Persons who are global and synthetic minded ; they tend to describe fewer taxa (opposite : splitters°).

 

M

matrotrophy (yolk feeding and maternal feeding). The form of internal development for some viviparous° sp. in which the embryo receives nutrition from mother other than the yolk originally contained within its egg, as true viviparity (adjective : matrotrophic ; opposite : lecithotrophy).

meiosis. The type of cell division during which reproductive cells are produced (adjective : meiotic).

meristics. Morphological characters that can be counted (fin rays°, scales°, vertebrae°, gill arches°, branchiostegal rays°, etc.).

metacentric. A two-armed° chromosome° in which the centromere is situated midway along the axis.

micro-morphometrics. Study of minute characters that can be described then classified, such as frontal squamation (or scalation) types, head (or cephalic) neuromasts patterns, etc.

mitosis. The normal cell division (adjective : mitotic).

molecular biology°. The study of gene sequences, either in full or in significant parts, either mitochondrial or nuclear.

molecular species°. A group of populations assigned to a specific° name, distinctive by molecular biology° only (and not distinctive by morphology°, osteology° or live or preserved pattern°).

monophyletic. Which belongs to a single common ancestor (opposite: polyphyletic°).

monotypic. With a single unit; for example, a monotypic genus° encompasses only one species.

morphology. Shape of the fish, in general and all details that are counted (meristics°), measured (morphometrics°) and described (squamation or scalation°, neuromasts°) to form the phenotype (opposite : genotype).

morphospecies. A zoological species defined by the external morphology, including colors.

morphometrics. Study of morphological characters that can be measured in mm, then computed as a % of S.L.° (e.g., P.Do.°, P.A.°, Height°, Hd°, etc.).

 

N

N. The number of specimens, characters (etc.) that are studied.

n. The haploid chromosome number (2n is the diploid° number; A, the number of arms°).

neotype. Subsequently designated type to replace the original description type which is lost or may never have existed in the first place.

neuromast. A sensory organ of the lateral line° or the head°, open in the form of a button or within a pore.

nomenclature. The zoological system of naming, following the code of rules and recommendations enacted by I.C.Z.N.°

nomen nudum. A name at whatever level (from specific to generic and above) which does not fulfil the minimum provisions of the code of rules and recommendations enacted by I.C.Z.N.° (synonym: non available° name).

nominal species. Zoological name at the species level, independent of its validity.

nominate subspecies (or better: nominotypical subspecies). The first-named subspecies, repeating the species name, e.g., Epiplatys fasciolatus fasciolatus.

 

O

ocellus. Dark blotch (often supracaudal), surrounded or not by gold: a female character (not always).

opercle (or Operculum). Gill-cover. Part of skeleton that covers the branchial opening.

opercular (short for pre-opercular) neuromasts. Sensory organs situated in a groove or hidden in a canal in-between the posterior wall of eye and opercle.

osteology. The study of the skeleton, notably of the head° (cephalic bones), the vertebrae°, the fins suspensoriums, the gonopodium° (and alike) for livebearers.

otoliths. Calcareous (calcium carbonate) deposits or bones found in chambers at base of fish skull ; sectioned, these bones often show rings or layers which can be used to determine age and for systematics°.

oversized arms. Chromosome° arms° measuring more than about 6%.

oviparous. Egg-laying. Characterizes Cyprinodontiformes whose eggs are laid and incubated in water (possibly also in dry substratum for annuals°) until full development and birth (opposite live-bearers, as viviparous° or ovoviviparous).

 

P

P. Pectoral ray° counts (rarely counted).

paratypes. The types°, other than the holotype°, when the description° is based on several specimens.

pattern. Color pattern (on live or preserved° specimen) : drawing of colors, especially important for unpaired fins° and sides° and pre- or post-opercular region° for Cyprinodontiformes.

pectoral fin. Length of fin from base° to tip° is measured in mm or as a % of S.L., as a characteristic of some species having extensions ; in Killi-Data, by convention, fins are labelled with initial cap letter to differentiate them from region or area of sides.

pericentric inversion. A chromosomal structural change.

pH. A term that indicates the degree of alkalinity° or acidity° of water. Ex: pH4 (very acid), pH9 (very alkaline).

phenotype. The sum of visible characters of the individual, and by extension, of a population° or a biospecies° (opposite : genotype).

peduncle. Part of the body on which Caudal° fin is attached.

plateau. Regions of hilly highlands (above 350 m altitude), separated from lowlands° by a falaise° ; if steep, then the fauna may be distinctive from that of lowlands° (French-derived word in English).

plesiomorphic. In cladistics°, it defines a primitive or ancestral (i.e., not derived) character (opposite: apomorphic°).

polyphyletic. Which gathers taxa having several ancestors (opposite: monophyletic°).

population. Inhabitants of a biotope for a given species. By extension, the aquarium strain that is developed from the wild specimens brought back alive.

post-opercular blotch. Black marking situated immediately behind Pectoral root and operculum°.

P.A. (Preanal Length). Distance from the tip of the mouth to the first Anal ray (in mm or as a % of S.L.°).

P.Do. (Predorsal Length). Distance from the tip of the mouth to the first Dorsal ray; this is a major diagnostic feature, since it measures the position of that fin; it is recognized in all fishes as an evolutionary mark (in mm or as a % of S.L.°).

pDor (Predorsal Scales counts). Count starts from behind the pineal scale ("a"), up to the scale just in front of Dorsal; this is reasonable since several minute scales nearer the mouth may be wiped out; however, the "a" scale is not always easily located.

preserved specimen. A fish fixed either in formalin or in alcohol (or both sequentially) before it is stored in Museum collections, as a type specimen or not.

preopercle. A disc-like bone just in front of the opercle° and situated below the eye ; also refers to the space between the posterior eye and the opercle.

preorbital. Refers to the space between the eye and the mouth.

P.V. (preventral or prepelvic length). Distance from the tip of the mouth to the first Ventral ray (in mm or as a % of S.L.°).

 

Q

quadrate. A paired, triangular, deep, endochondral bone on which the mandible hinges, connecting lower jaw to palatine and hyoid arches and an important character in osteology° systematics°.

 

R

radio(photo)graph. X-ray photo that shows the bones; particularly useful to fix morphomeristics with certainty (e.g., for old types°, with damaged or folded fins°), to count vertebrae° and to study the osteology°.

ray counts. Counts at Dorsal (D.) and Anal (A.) that include all (even half-) branched and unbranched rays, the last one being counted as 2 if split near to base; the first minute ray can only be seen by experienced researchers or counted on radiophotographs° in many cases (also done, but less frequently, for other fins).

relict. The remaining populations° of a morphospecies° that is supposed to have had a much larger geographical distribution in the past.

Robertsonian fusion. A chromosomal change, which transforms two (sub)telocentric° chromosomes° into a single large metacentric°.

 

S

squamation. Specific organisation of the scales (synonym: scalation); example: frontal scalation or squamation, opercular scalation or squamation, ventral scalation or squamation, fins scalation or squamation (on Dorsal° fin, Anal° fin, Caudal° fin, notably for annuals°).

sensory organs. The fleshy filaments or buds (neuromasts°), groups of sensitive cells with a sensory function; often, they develop around ctenoid (or not) structures.

sex. Male or female ; sexation corresponds to the date when sexes are distinguishable ; sexual maturity (later) to the first date of spawning ; sex ratio to the number of male vs. female in wild collections or in aquarium offspring (e.g. 1:4, if 1 male for 4 females, or 1:1 if equilibrated).

sides. Flanks of the fish with key parts as post opercular°, ventral°, dorsal°, peduncular°, anterior, posterior and mid-sides.

sibling species. Biospecies° that cannot be separated on the basis of their morph. Also called cryptic° species, if allopatric°. Sympatric° biospecies° are extremely rare in Cyprinodontiformes (less so in viviparous groups).

species. The basis for taxonomy°: see variant concepts as biospecies° and morphospecies° and cryptic species° and molecular species° and evolutionarily significant unit (ESU)°.

splitters. Persons who are analytic minded; they tend to describe many taxa and to recognize an excess of taxonomic units previously described by others (opposite: lumpers°).

Standard Length (S.L.). Distance from tip of mouth to rear end of the hypural plate, as ascertained by bending Caudal; this is the basic criterion for morphological proportions or morphometrics° (in %).

subgenus. In the pyramidal organisation of nomenclature, the level between genus° and species°, itself the basis for taxonomy.

subspecies. The lowest taxonomic° unit in zoology. Subspecies differ by their phenotype°, are interfertile, and are allopatric° (especially vicariant°)… a concept of limited utility and declining usage in Cyprinodontiformes because populations are genetically highly differentiated.

superfetation. Simultaneous occurrence of more than one stage of developing offspring in the same female of viviparous° sp. (probably up to 5) ; superfetation is not automatic in viviparous° sp. (for example it does not occur at all in Goodeinae and it is irregular on a species° basis in Poeciliinae) ; superfetation is independent from lecithotrophic°-matrotrophic° characteristics).

superspecies. A morphospecies° composed of several biospecies° or cryptic° species.

subtelocentric. A chromosome° composed of a long and a short arm° (usually shorter than 2%).

sympatry. Living in the same geographical spot or biotope°. Rule: components of distinct superspecies° live in sympatry, whereas components of the same superspecies° are allopatric°. Some authors define sympatry as living in the same region or river basin, and therefore use syntopic in the herein restricted sense.

synapomorphy. Derived character shared by two or more taxa° (cladistics°).

symplesiomorphy. Primitive character shared by two or more taxa° (cladistics°).

synonym. Different names for one and the same genus°, species°, or subspecies°. It is said to be junior if described after and senior if described before the discussed name.

syntypes. Previously, a series of types° was deposited without distinguishing the holotype°, bearing the risk of being composed of several species. To clarify the situation, a lectotype is designated among the syntypes, the remaining specimens being named paralectotypes.

systematics. Pyramidal classification of organisms in various (usual) levels, down from order (ending: -formes), suborder (-oidei), superfamily (-oidea), family (-idae), subfamily (-inae), tribe (-ini), subtribe (-ina), genus°, subgenus°, species° to the lowest unit, the subspecies°.

 

T

taxonomy. The study of names (taxon; plural: taxa). By extension, the classification of organisms, like systematics°.

telocentric. Chromosome° with only one arm° (synonym: acrocentric).

threatened species. Species vulnerable to extinction in the near future (a category officially managed by I.U.C.N.°)

tip. Distal extremity of fin, mouth, etc.

T.L. (Total Length). Distance from tip of mouth to end of longest Caudal ray ; a key criterion when the fin is not damaged and the specimen is adult ; full aquarium size is given in cm for male : this can be up to 30 % more than in nature, where competition, lack of food and predation limit life expectancy and size.

TRAV. (Transverse Series). Count from the first scale° (even halved) in front of Dorsal°, anteriorly downwards to Anal base°.

tree. Graphic representation of results of phylogenetic° studies from various methods (morphological°, osteological°, molecular°), derived from a matrix of component taxa° (e.g., genera°, species°) and of characters, processed by phylogenetic computer° programs ; solidity of tree can be ascertained by various statistic tools, the most used being the bootstrap° value.

triploidy. The normal cells containing not two but three sets of chromosomes (may occur in backcrossings of hybrid females).

trophotaeniae (plural). External, ribbon-like absorptive processes associated with the gut of embryo or, for a short time, newborn of viviparous° sp. (only in Goodeinae).

type° locality (also Terra Typica). Place where the holotype° was collected.

types. Specimens declared as such by the describer, which are deposited in Museum institutions and represent the species.

 

U

univalent. When homologous chromosomes° fail to pair during the first meiotic° division, they segregate at random. Elements shorter than 2% usually occur as univalents and may become lost. Univalents often occur in hybrids°.

 

V

V. Ventral ray° counts.

Ventral or Pelvic fin. Length of fin from base° to tip° is measured in mm or as a % of S.L.°, as a characteristic of some species having extensions ; in male of viviparous Cyprinodontiformes, Ventral fin is modified into a gonopodium°, as an intromittent organ ; in Killi-Data, by convention, fins are labelled with initial cap letter to differentiate them from region or area of sides.

VER. (Vertebrae). From occipital bone to hypural plate; abdominal vertebrae (Ab) are distinguished by having paired ribs, whereas caudal vertebrae (Cd) have caudal arches. Counts are based mainly on radiophotographs°.

vicariant. Living in two neighboring areas. Components of a superspecies°, or if interfertile, subspecies° are vicariant.

viviparous. Livebearing. Characterizes Cyprinodontiformes whose offspring is laid alive while eggs are developed internally (opposite egg-laying, as oviparous) with 2 options, either viviparous or ovoviviparous.

 


 

 

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