Cichlid Room Companion

Wonderful cichlids

Cichlid binominal names, how are they chosen?

By , 2019. printer
Last updated on 11-Jul-2019

Juan Miguel Artigas Azas,

Classification: Taxonomy and phylogeny.

" In this article I talk about the principles and rules that have to be followed when applying scientific binomial names to organisms "

In the last installment of this column I have written about cichlid species names and after exposing the reasons concluded with the declaration that for cichlids, the scientific binominal names have to be used over common names to prevent ambiguities. In this occasion I will write about how those binominal names are forged.

The binominal classification system as we know it was first proposed in 1758 in the 10th edition of the book Systema Naturae by the Swedish botanist Carl von Linné, who Latinized his own name as Carolus Linnaeus, as it was common for scientists who published in Latin, which was considered the Lingua Franca of Science. Binominal as a word can be translated from Latin into bi = two + nominal = a noun phrase or adjective meaning relating to or consisting of (a) name(s). The main objective of binominal names is that species in the same kingdom can each have a unique combination of two names which unambiguously label them – e.g. while one of the names can be repeated in different species, both names can’t. Consider for example Oreochromis aureus and Thorichthys aureus: in both binominal names the word aureus is present, but the genus uniquely labels them. The first part of a scientific name is called the generic name; the second part is the specific name.

Scientific names for species don’t start with Linnaeus, even before him they were used, composed by a Latin genus name and a descriptive Latin species name. The latter could be formed by several words in a way that would diagnose the species (tell it apart) from others in the genus. Those names were known as polynomial names, they however turned long and awkward to use. In Carl Linnaeus single word species names, the term does not necessarily has to diagnose the species, think for example of Thorichthys meeki where meeki refers to the American ichthyologist Seth Eugene Meek (1859 - 1914), nothing to do with the differences this species has with others in the genus Thorichthys. Linnaeus binomial names bring an element of economy to the species name: easy to talk about them, easy to remember them. Probably you doubt me now if the Peruvian cichlid Tahuantinsuyoa macantzatza comes to your mind.

Female threatening Thorichthys meeki was named afterthe American ichthyologist Seth Eugene Meek (1859 - 1914). Photo by Juan Miguel Artigas Azas. (29-Apr-2016). determiner Juan Miguel Artigas Azas

The binomial system brought its own problems and need for rules. For example, what happens when two species in different genera hold the same specific name, but then a taxonomist decide to put the two of them in the same genus? It would create a problem of name duplication. Or for example: what happens when once species is described with two (or more) different names?

In 1842 at the instance of the British Association [British Science Association], Hugh Edwin Strickland (1811 - 1853), a British geologist and ornithologist, put together “assisted by many zoologists, British and foreign” (which included among others Charles Darwin) the first comprehensive Rules for Zoological Nomenclature, known as the Stricklandian Code (Strickland, 1842). The rules were first published in the Report of the British Association for 1842 and had as its main feature the formal codification of the “principle of priority”. The Stricklandian Code was translated and circulated widely; it was published in France, Italy and the United States of America and enjoyed great acceptance. Subsequent editions of the code were published posthumously in British Association reports together with proposed alterations, and as a standalone text in 1878.

International Rules for Zoological Nomenclature were seen as necessary in the first (Paris 1889) and second (Moscow 1892) International Zoological Congresses. The aim was a code that could cover fossil and extant species and that would rule names over all disciplines. In the 1889 congress in Paris a group of rules were first adopted and they became official in 1905 as the “Règles internationales de la Nomenclature zoologique”; they were published in French, English and German. Through subsequent zoological congresses, the rules started to suffer modifications, which were published in the reports of such congresses. With time, to obtain and follow updated nomenclature rules became a difficult task.

In the zoological congress taking place in Copenhagen in 1953, a declaration was approved to prepare new rules. In 1958, an editorial committee in London, known as The International Trust for Zoological Nomenclature (appointed by the International Union of Biological Sciences), elaborated a completely new version of the nomenclature rules, which was finally published as the first edition of the International Code of Zoological Nomenclature (ICZN) on 9 November 1961, replacing the Règles in force.

To our days, the ICZN has been replaced three times: 1964, 1985 and 1999, in every occasion incorporating changes but also remaining compatible with the actions taken by zoologists in the past. The ICZN is published in English and French and both versions have equal force. As indicated in the introduction of its fourth edition, the ICZN has one aim “which is to provide the maximum universality and continuity in the scientific names of animals compatible with the freedom of scientists to classify animals according to taxonomic judgments.”

Unlike most laws which cannot be applied retroactively, the ICZN in force (fourth edition) is applied to nomenclature acts that have taken place at any moment in time. Understandably, the ICZN considers different time frames for application of different rules.

The ICZN is guarded by International Commission on Zoological Nomenclature. This commission may amend or add code articles or legally pronounce on any contemplated of non- contemplated controversy, it may also rule exceptions in the strict application of the code if it judges necessary. Anybody can submit a controversy to the commission, the application is then reviewed and if accepted a number is assigned and it is published in the Bulletin of Zoological Nomenclature. The commission then requests for comments and after a minimum period of six months the case is voted and the commission opinion published.

Let’s examine this example: A case proposal was submitted by Jay R. Stauffer, Jr. in 1995 to replace the holotype of the Malawi cichlid species Iodotropheus sprengerae Oliver & Loiselle. 1972. The description of the taxon was based on aquarium-reared, possibly hybridized, specimens, the original brood stock of which was purported to have been collected from Boadzulu Island in the southeast of Lake Malawi, where the species does not occur. The holotype is not within the morphological range of wild specimens. It was proposed that the type material be set aside and a wild-caught specimen from Chinyankwazi Island, where the species is known to occur, be designated as the neotype. The proposal was accepted and the case resolved favorably by the commission.

Male at Chinyamwezi Island The holotype of Iodotropheus sprengerae, a deformed aquarium specimen of dubious provenience was replaced by a wild caught specimen from Chinyankwazi Island in Lake Malawi, now the neotype. Photo by Juan Miguel Artigas Azas. (06-Nov-2008). determiner Ad Konings

The International Code for Zoological Nomenclature is based upon the following principles:

Principles of the ICZN:

Principle of binominal nomenclature

The scientific name of a species is a combination of two names; that of the genus and that of the species. In some occasions, three words are used to denote subspecies but the nominal species name remains to be two words.

Principle of Priority

The name to validly use for a taxon (like a species) is the first it received that complied with the rules of the ICZN, referred to as the first “available name”. Names that do not comply with this set of rules are called “nomen nudum” (naked name from Latin), a term that although is strictly meant for names published without description or diagnosis, is widely used for any kind of unavailable names. This is the most important and widely applied principle of the ICZN. Exceptional cases ruled by the commission could however revert the priority rule.

Principle of Coordination

When a new group name is proposed (i.e. family, genus, species) that name becomes the name that should be used nominally when a different rank is proposed.

For example: when the Lake Tanganyika cichlid Lamprologus leleupi longior was proposed as subspecies of Neolamprologus leleupi by the German ichthyologist Wolfgang Staeck in 1980, the name Neolamprologus leleupi leleupi, with the same original authorship of Neolamprologus leleupi, is automatically created. The name becomes Neolamprologus leleupi leleupi (Poll, 1981).

Principle of the First Reviser

When two names are proposed simultaneously for the same taxon, the first person reviewing the names becomes the person who gets to choose the name to be used.

Principle of Homonymy

The name of a taxon must be unique in the animal kingdom. In the case a name is used twice, the principles of priority or first reviser should be applied to determine which taxon retains it. The other is to be renamed either by revalidation of a junior synonym or proposal of a new replacement name.

For example: Eigenmann & Kennedy (1903) proposed the name Biotoecus for a genus of Amazonian cichlids originally named Saraca by Steindachner, 1875 because the latter name was given earlier to a genus of butterflies (Saraca Walker, 1865).

There are mainly two types of homonymy: primary and secondary:

A primary homonymy happens when a binomial name is originally composed by the same genus and species names. An example of this is Paratilapia ventralis Nichols, 1928, preoccupied by Paratilapia ventralis Boulenger, 1898 (now Ophthalmotilapia ventralis). Paratilapia ventralis Nichols, 1928 had to be replaced with another combination: Pseudocrenilabrus nicholsi. Even if the species is subsequently referred to a different genus it continues to be invalid. Paratilapia ventralis Nichols, 1928 was referred invalidly as Haplochromis ventralis and Pseudocrenilabrus ventralis.

A secondary homonym happens when two species with the same specific epithet but originally in different genera are placed together in the same genus, which produces two identical names. For example: Herichthys underwoodi Regan, 1906 and Tomocichla underwoodi Regan, 1908 became secondary homonyms when both were placed in Cichlasoma by Meek (1914), hence he replaced the latter name by the junior synonym Cichlasoma tuba Meek, 1912. Secondary homonyms remain invalid only when they were replaced before 1961 (hence Tomocichla tuba is the valid name and not T. underwoodi). Mistakes in this respect can cause considerable confusion.

Principle of Typification

Any name down from a family group (family, genus, species) has (or potentially has) a name-bearing type fixed that provides the standard of reference and to which it is permanently attached. In the past, this could be a drawing or even a common agreement about what is the type. Since 1999 however, a name-bearing type fixed is mandatory. For species and subspecies it is a single specimen (holotype) or several specimens (syntypes); for genera and subgenera it is a nominal species (type species); for families it is a nominal genus (type genus). If types are lost, neotypes can be proposed for a species if they become necessary.

Formation of names

A biological name may be a word in or derived from Latin, Greek or any other language (even one with no alphabet), or be formed from such a word. It may be an arbitrary combination of letters providing this is formed to be used as a word. A name can be a noun, adjective, proper, geographic, etc. The only requirement is that the name is spelled only in the 26 letters of the Latin alphabet.

For example: The specific epithets in Aulonocara koningsi Tawil, 2003 and Teleogramma obamaorum Stiassny & Alter, 2015 are given after a person: Ad Konings and Michelle & Barak Obama, respectively. Herichthys tamasopoensis Artigas Azas 1993 after a place: Tamasopo. Cyphotilapia frontosa (Boulenger, 1906) is an adjective: fronto = one with a large forehead (Latin): Rheoheros lentiginosus (Steindachner, 1864) is a descriptive name: lentiginosus = covered with freckles (Latin). Tomocichla asfraci Allgayer, 2002 is an acronym: (As)sociation (Fr)ance (Ci)chlid. Metriaclima pambazuko Stauffer, Black & Konings, 2013 from Swahili, means dawn or sunrise. There is no yet a Cichlasoma abcde but, it could be!

A common source of frustration for many is what it is known as gender agreement. This means that when a species has been moved from one genus to another the specific name has to be adjusted so it now agrees with the gender of the new genus.

For example: Coptodon gutturosus (Stiassny, Schliewen & Dominey, 1992) was described in the genus Tilapia (feminine) as Tilapia gutturosa. With the placement of the species in the new genus Coptodon, (masculine), the species combination should now be Coptodon gutturosus, with the specific name changed from gutturosa (feminine) to gutturosus (masculine) for the gender to agree. This may be pesky sometimes but certainly makes much more intuitive to make this change.

Integrated code

Nowadays, there are separate codes that regulate the nomenclature of animals (ICZN), that of virus and bacteria and also that of plants. It is wished by many that those rules are all integrated into a unified Biocode. Studies and symposia are organized by the International Union of Biological Sciences with this end. Nonetheless, although it is believed that a unified code will one day become a reality, the different codes have diverged so much over the years that at the moment the imposition of such Biocode would create a lot of name instability. Biological naming is a continuous developing process.

The frustration of taxonomic advance

Frustration about taxonomic changes is experienced every time a species is placed in a different genus of that on which we have known it for years. That is quite understandable; as we all like stability, but as many others, Taxonomy is an evolving discipline and we cannot stop its development because of comfort. Every day we are gaining a more solid knowledge of the relationship between living begins and the name alone already may tell us things about the species and its relationship. We should welcome changes but not too enthusiastically, but with a critic view. As much as we should not curse because a species has been reclassified we should not immediately jump on the boat of a new generic classification, at least without understanding the reasons that led to it.

References (5):


Artigas Azas, Juan Miguel. (July 11, 2019). "Cichlid binominal names, how are they chosen?". Cichlid Room Companion. Retrieved on November 28, 2021, from: