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Melanochromis auratus
Melanochromis auratus Photo: Vlad Butsky

Binomial nomenclature

Introduction

What is Binomial nomenclature? Everyone will be familiar with scientific names which are used for all living things. Every species is given two names, the first name is the Genus and the second name is the species. The genus name is written first and begins with a capital letter, all the other letters are lower case. The species name which comes second is always written in lower case only. Both the genus and species names are italicised.

An example for a Guppy, Poecilia reticulata. Where Guppy is the common name, Poecilia is the genus name and reticulata is the species name. The common name is not part of binomial nomenclature and is simply used for the convenience of people who are unfamiliar with scientific names.

In scientific works the authority for the binomial name is usually given at least when it is first mentioned and the date of publication may be mentioned.
An example again using a Guppy,  Poecilia reticulata  Peters, 1859. You will also see this written where the authority is in brackets. Example: Melanochromis auratus  (Boulenger, 1897)  in this case it means that Boulenger was the first scientist to describe the fish but since that first description the name has been changed. The original name given by Boulenger was Pseudotropheus auratus and even though a different scientist may have updated the name it is still Boulenger who is credited with describing the species.

 

Melanochromis auratus

Melanochromis auratus Photo: Vlad Butsky

There are sets of internationally governed  codes and rules governing the use of binomial nomenclature the two most important being the International Code of Zoological Nomenclature (ICZN) for animals and  the International Code of Nomenclature for algae, fungi, and plants (ICN) for plants.

The advantage of using a scientific name is that it is unique to that species and unlike common names or trade names it is the same all over the world.

If only things were so simple

As we are all aware scientific names are forever changing as we learn more about the relationships between the various species. Some species are offered for sale in aquatic stores even before they have been scientifically described and are sold under a trade name which may vary from dealer to dealer. There are also different terms used to describe a collection of species from one genus and so on. All of which can add to the confusion for those (probably the majority of us) who aren’t fully aware of how the system works.

  • Hybrids: In botany plant hybrids are scientifically named and are signified by using an ‘x’ in the name. Animals (including fish) are treated differently and are not given a scientific name.
  • Unnamed species: Are occasionally offered for sale. They are often sold under a trade name which can vary from dealer to dealer. A trade name has no meaning in science. If the unnamed is from a known genus i.e Apistogramma then it should be referred to as Apistogramma sp. for a single species and Apistogramma spp. for multiple species of Apistogramma the abbreviation for species (sp. and spp.). These abbreviations can be used for named species too.
  • Unconfirmed species or species under review: When a species is unconfirmed the abbreviation cf. is used. Example Chaetostoma cf. thomsoni. In this example the cf. which is never italicised indicates that although the fish has been identified as Chaetostoma thomsoni there remains some uncertainty and the fish is under review.
  • Similar or related species: Species affinis (aff.) Indicates that the species is similar to but not identical to the species in the binomial name that is shown. Example Astyanax aff. fasciatus. In this example it means that the fish concerned is very similar to or related to Astyanax fasciatus but it is a distinct species.
  • Extinct species: In some instances the dagger symbol “†” indicates a species is extinct. Example: Acanthobrama hulensis †. The symbol is placed after the scientific name.

Abbreviations

These abbreviations can be italicised but are better not being in order to set them apart from the genus and species names.
sp. and spp. = Species and multiple species of one genus.
cf. = Uncertain ID or a species under review.
aff. = A species which closely resembles but is not identical with or is related to the species in the binomial name shown.
† = Is often used to indicate an extinct species

The ‘Authority’

The authority is the scientist who first described and named a species and not as is sometimes thought the person who discovered the species. Describing a species involves a lot of work where each step of the methods used and results of all measurements taken are published in a paper and open to scrutiny by other scientists (peer review). If the paper is accepted it will be published in a relevant scientific journal once published in this way the scientific community will  formally accept the existence of the new species.

The first step is to determine that the specimen is indeed a new species and not one which has already been described. This involves checking he archives, writing to other experts and visiting museums to examine voucher specimens and even DNA sequencing. Once the specimen is determined as a new species then it has to be given a name following certain Latin grammatical rules although there is a large scope for imagination too. Next the species has to be described in detail including all the body parts and particular mention given to features which are different from other species and define it as a species. The description has to be finely detailed, objective and accurate. This work may take years or in some cases even decades.

References:

About Andy Rapson

I've been interested in fish for about fifty years and I have kept many different species in that time. I have also worked in the fish trade running my own fish shop and I'm a Fishbase collaborator. I'm now mainly interested in fish husbandry, fish health, native marines and fish photography.

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