International Code for Zoological Nomenclature

What was the need of giving scientific names to the organisms? 

It was the inquisitive nature of the human beings and desire to know more about the objects and organisms around him that lead to naming of the animals. In pre historic times when mode of communications and transport were in the infancy,  when human beings used to live in the isolated places and independent societies, each society had its own language. The name of same organism in different languages was different e.g  peacock is a English name of a bird which is known as Moore in Hindi, Pfau in German, paon in French,  tovus in Uzbek languages and so on, similarly the lion is the English name of an animal which is known as sheer or Singh in Hindi, pinyen in Chinese, raion in Japanese and so on. Now can you imagine a Japanese trying to tell about the lion to an Indian when they hardly know about each other's language. Exactly same problem was started to be felt when the mode of transport evolved and different societies started intermingling and interacting i.e. when whole of the globe became a single society. There arouse the need to have a uniform naming system for organisms, especially among the scientific fraternity for smooth communication and transmission of the knowledge. It is well said that the need is mother of invention;  need of universal, unique and stable names of organisms was felt which led to the evolution of a system of scientific naming of the animals in the form of a book Known as the International code of zoological nomenclature. It consists of three main parts viz code proper,  appendices and glossary. The code proper consists of 90 articles in 18 chapters. Appendices are three in number of which first two are concerned with recommendations and third one includes the constitution of the international commission for Zoological Nomenclature. Glossary includes the explanation of terms used in it. 

Linnaeus was the first to set rules of nomenclature in his books Critica Botanica and Philosophica Botanica in 1737 and 1751 respectively. But it was Professor Blanchard who prepared and presented the set of rules of nomenclature at ist International congress of zoology which was held in 1889 in Paris, but these rules were accepted in 2nd international congress of zoology in 1892 at Moscow and for the first time after some revision these rules were published by International society of zoology in 1961 in the form of book called as International Code of Zoological nomenclature and currently its fourth  addition(1999) is  available. Informally, it is also know as the ICZN Code or simply Code. It is a set of rules which forms the basis of scientific naming of the animals. It maintains the universality, uniqueness and stability of the zoological nomenclature.  It consists of six principles: 1. Principle of binomial nomenclature. 2. Principle of Priority. 3. Principle of Coordination. 4. Principle of first Reviser. 5.Principle of Homonymy. 6. Principle of Typification.

Principle of Binomial nomenclature:  As per this principle;

1. The scientific i.e. zoological name of the animal consists of two words of which first word is generic/Genus and the second word is specific/species. e.g. Homo sapiens where Homo is generic name and sapiens is a specific name where as the subspecies name is trinomial consisting of Genus, species and subspecies however all taxa above species level are uninomial.

2. Generic name should always start with a capital letter and species name must start with a small letter.e.g. Homo sapiens.

3. Scientific name in typed content  must be in italics ( e.g. Homo sapiens) and when handwritten it must be underlined(e.g Homo sapiens), also the underlining must be separate under generic and specific names.

4. Scientific name must be Latin or latinised and easy to pronounce.

5. The minimum and maximum letters in a name must range from 3 to 12.

6. Zoological name when repeated in the same paragraph is written in abbreviated form .e.g Homo sapiens as H. sapiens

 

7.Zoological name must describe some characters of the organisms.

8. Zoological name must be followed by the name of author who published it first and the year of publication of the name,  also, the author name and the year must be separated by a comma (,)e.g Homo sapiens Linnaeus, 1758.

9. In case the species is shifted from one genus to another genus the name of the author who first coined the species name must be written in brackets e.g Hemilea bipars (Walker, 1862) Hardy, 1959 which means bipars is coined by Walker in 1862 and the genus has been assigned by Hardy in 1959.

10. In case of scientific names the second or even the third part (Sub species) can repeat the first name e.g Bufo bufo bufo, Naja naja.

11. If a subgenus taxon is used, it is included within parenthesis in between genus and species part and is not included in binomial and trinominal nomenclature, e.g. Atrina(Servatrina) pectinata pectinata.

12. The names of supra generic taxa such as supra family, family and sub family are derived from generic names by adding suffixes -oidea for superfamily  in vertebrates and -acea for superfamily in invertebrates, -idae for family and -inae for subfamily, to it. e.g, in case of  man genus is Homo which is derived from Hominid whose root is Homin, its supra family, family and subfamily are Hominoidea, Hominidae and Honininae respectively. 

Principle of Priority: This principle governs the uniqueness and stability of the nomenclature. As per this principle, in case of the conflict between two or more zoological names for same species, the older name has precedence and therefore is the valid or correct name i.e. the first properly published name of a species or genus takes precedence over any subsequently published names. But it applies only to the names published after 01.01.1758 and all the names published prior to this date are considered unavailable. e.g. suppose an author X coins a name for a species as Bhi zee in 2010 and another author Y names the same species as Ghee tee in 2011 and when the conflict comes to light, the name Bhi zee which is established earlier will have the precedence and  therefore will be a valid one where as the other name would be regarded as junior synonym.

Principle of Coordination: As per this principle there are three groups of related Taxa viz 1.family group which consists of superfamily, family and sub family. 2. Genus group which consists of Genus and sub genus. 3. Species group which consists of species and sub species and when a scientist establishes the name of a Taxon, the name of other Taxa of that group are automatically established even if the author has never coined them they are supposed to be established by him only . e.g. if a person named as Burington published a new family Ecksidae Burington, 2011, then by the principle of coordination superfamily Ecksoidea, subfamily Ecksinae would be considered to have been created at the same time even if he did not talk about them.

Principle of First Reviser: This principle suppliments the principle of Priority. It comes into play when the date of establishment of the different names for same species or date of establishment of same name for different taxa is same. In such a conflict first author who belives that the two or more names are synonyms, has the discretion to choose a valid name, such author is called as the first Reviser. e.g 

Linnaeus in 1758 established two different  species of owls and named them as Strix scandiaca and Strix noctua but latter on in 1931 Lonnberg found that both the species were in fact the two different stages of same species, the snowy owl. Thus two names turned out to be synonyms. Lonnberg acted as first Reviser and selected Strix scandiaca to have the precedence over Strix noctua. 

Principle of Homonymy:  Homonymy is a phenomenon of having same names for different Taxa and different species of animals.  Homonyms are words which have same spelling and pronunciation  but different meanings. As per this principle the name of each animal must be unique i.e.one name must be given to only one animal taxa and two different taxa must not be given same name. There must be a difference of atleast one letter between the two names. In case the names of an animal taxon and plant taxon are identical, they are not treated as homonym. In case there exist many Homonyms only the senior Homonym is regarded as valid name as per the principle of Priority. e.g, Genus Echidna was proposed by Forster in 1777 for a fish commonly called as Morey eel where as Cuvier in 1797 used Echidna for the genus of spiny ant-eater. When the conflict came into the light the law of priorty overruled the use of Echidna for the spiny ant-eater which has now bee named as Tachyglossus by Illiger in 1811.

Principle of Typification:  students find this principle very difficult to understand but I have tried to give a simple explanation to this principle. 

Taxonomists collect specimen during their field visits which may include the whole organism, the parts of the body of the organism or even photographs of the organisms. These specimens are preserved and studied by author for  establishing the names of its taxonomic categories such as genus , species, family and order etc. The specimen so collected by the author are called as type specimen and categorizing these type specimen into different types is called typification. The Zoological Code recognizes only a few terms/ types like;

 Holotype: It is the Single specimen selected by the author from  a collection of specimens for establishing names.

Paratype: It includes all specimens collected by the author excluding holotype. 

Syntype: It includes the selection of more than one specimen by the author from the whole collection of specimens. In simple terms it is selection of more than one holotypes.

Lectotype: it is the the single specimen selected by the Reviser from the syntype.

 Neotype: If the type specimen is lost under certain conditions then the reviser can select another specimen and it is called neotype.

DRAWBACKS OF ICZN 

As we came across  a large number  of merits of following the zoological nomenclature such as universality, stability, uniqueness and many more, still there are so many drawbacks in this system of naming. A few important drawbacks are as under:

 1. In earlier times i.e. during linnaean period the number of genera were surround 300 where as further advancement in the TAXONOMY the number of genera has increased many times as today around 50 thousand genera have been established which has added to confusion and difficulties in remembering them. 

2. The species name in isolation has no meaning and hence no significance. 

3 . This system does not depict the evolutionary history i.e. phylogeny of the organisms.  Therefore there is still a great scope of improvement in it.

Regards

Dr Rahul Kait 

Assistant Professor in Zoology 

GGM SC COLLEGE JAMMU.