Tuesday,23 October 2018, 8 : 26 AM

Taxonomy Of Fish

Etroplus
Etroplus suratensis
Image Credit: Beta M

Introduction



Taxonomy is the practice and science of classification.
It is composed of two greek words, taxis (order, arrangement) and nomos (law or science), hence the word literally means "Science of arrangement".

The first attempts to classify fish began in ancient world, the first recorded work is in Indian text known as "Kautila´s Arthasastra" belonging to period about 321 BC.


Ashoka Edicts

Stone Pillar erected by Emperor Ashoka
Image Credit: Wikipedia



These were very detailed descriptions, like "Pirthuroman"which means a fish with long hairs, i.e barbels near snout.
Around 246 BC King Asoka had pillars erected throughout India, these pillars had vital information inscribed on them.

Many of them had descriptions of various animals including fish.
Some example are:

  • Anathikamacchi- boneless fish (sharks).
  • Vedaveyake- eluding grasp (Eels).
  • Kaphatasayake-sleep feigning fish (puffer fish).

Hippocrates and Aristotle from around 384-322 BC from Greece are two other pioneers who developed animal classification.

There have been changes is the classification system, however the system proposed by Carl Linne (Linnaeus) is followed till today.
He proposed what is called bi nominal nomenclature, naming every living thing with a two part name, the first one based on genus(plural genera) and second part on species (same in singular or plural).

This system again saw a major change with Charles Darwin´s publication "The origin of Life"in 1859.
His theory of evolution meant that species placed together in a genus were assumed to have had a common origin, a concept that underlies all important subsequent classifications of fishes and other organisms Current System.

The current system is based on classifying living beings into separate divisions called "Taxon" or "Taxa"in plural.
Hence the term Taxonomy. Each level of this classification is called a "Rank".

The classification used today must confirm to "International Code of Zoological Nomenclature" which is administered by International Commission on Zoological Nomenclature based at "Natural History Museum" in London.

The highest rank is called "Kingdom".
There are five kingdoms currently recognized, Monera,Protista, Plantae, Fungi, and Animalia.

Kingdoms

Life Classification System
Image Credit: Wikipedia



Classification in Animal Kingdom



All animals are grouped under kingdom Animalia.
The topmost classification is "Kingdom", while lowermost is Species.
In some cases one more rank is used, "Subspecies".
There are other lower categories in case of plants like variants etc, but these are not used in case of animals.



Animal Classification

Animal Classification System
Image Credit: Wikipedia



Species

Species is the keystone of taxonomic study.
This is because it is the only rank that can be collected, observed and studied.
It is always written in two parts, the first part always starts with a capital letter and signifies Genus, while the second part signifies "sepcies" and always start with a letter in small caps.
Both parts are always written in italics.
Thus the name Labidochromis caeruleus, refers to Labidochromis which is the genus and the second part caeruleus,refers to the species.


Subspecies

This "rank" is below the rank of species and is expressed in 3 parts.


Genus

Genus or Genera(plural) is the taxonomic rank just above species.
It might include a single species or group of species presumably of common phylogenetic (sharing a common evolution relationship) origin.
In some case there are sub categories also called sub genus.

Genus forms the first part of name of a species.
It always starts with a capital letter and the first letter is always capitalized.
There might be many species in a genus or there can be a single species also.


Family

Family are a taxonomic rank which comprises many genera.
In some cases even a single genus can form a single family due to its peculiarities.
All families end with words idae.


Order

Order are a taxonomic rank including one or more family.
They may consist of number of similar families in most cases, however sometime a single family can form an order due to its peculiarities like family Amiidae in order Amiiformes.
Sometimes a genus may be placed directly under a order with any family or any other category in between like genus Conorhynchos under order Anguilliformes.
All order end with words formes.


Class

It is a sub divison of Phylum.


Phylum

Phylum is one of the major taxonomic ranks used in classification of animals.


Type Specimens

Species and subspecies are described on the basis of specimens which are called type specimens.
These specimens are stored carefully and so that they can be studied by future generations.

Specimens briefly can be of two types, Primary and secondary.

Primary specimens can be further divided into following categories:

  • Holotypes: When a species is described on the basis of single specimen it is called holotype.
  • Neotype: Sometimes a replacement of primary is permitted only when there is strong evidence that the original primary type specimen was lost or destroyed and when a complex nomenclature problem exists that can only be solved by the selection of a neotype.

Secondary types are Para types, and these are additional specimens which are used in the description of a new species.