Although I am no longer a professional taxonomist I spent twenty years working on fish classification at the Natural History Museum (London) and in that time have come across most taxonomic problems, so I will do my best to explain in as few words as possible just what these problems are.
As you know, in order to communicate about any organism, plant, animal, virus etc. it is essential that everyone knows that they are talking about the same thing. So the agreed system based on that of Carl Linne (or Linnaeus) of 1758 is a two-name (binominal) system.
This is a genus name, always spelt with a capital letter, eg. Barbus and a species name, having a lower case initial letter, e.g. pallidus. The names are derived from Latin or Greek terms and are printed in italic script or underlined to make them stand out in a text.
In the combination Barbus pallidus the name means that the species pallidus is a unique entity but it shares all the features of other species which unite them into the genus Barbus. So in effect the name does more than just identify the fish, it is a statement about the genetic relationship of the species.
It is important to know the difference between identification and classification. Identification means just that, giving a name to the fish whereas classification is concerned with placing the species into a scheme of relationships.
Here, I am only going to deal with the problems surrounding Identification.
The subject of classification will have to wait for another time
When a zoologist identifies a fish he/she checks out various manuals and cross-matches with previous identified specimens until a "best fit" is found.
Nine times out of ten the fish will already have been described (named) and it is simply a case of diligently searching the literature. If no identification is possible then the specimen may represent a "new species", ie, one unknown to science. If this is so then the fish has to be described in an acceptable Zoological journal and the specimens deposited in an "available" museum collection.
There are routine procedures for such descriptions which should include photographs and drawings of the specimens. In these descriptions you will come across words such as 'holotype,' 'paratype' etc which are categories of the specimens, and I shall explain what I they mean.
Suppose a new species is described on the basis of 20 specimens, then one of these - a "typical" specimen will be selected as the TYPE or HOLOTYPE, the remaining 19 are then known as the PARATYPES.
In earlier times, the type concept was not so rigid as it is today and a species may have been described from several different specimens, from different localities collected at different times! In these cases they are know as SYNTYPES.
Often, nowadays when a researcher looks over a number of syntypes they realise they don't all belong to the same species and that perhaps out of say, 6 syntypes only 4 are the species so named.
In this case the researcher (reviser) will nominate one of these syntypes as the holotype but because it is done retroactively the nominated specimen is called a LECTOTYPE, the others becoming PARALECTOTYPES.
Let's suppose somebody describes a species on the basis of a single specimen, a practise frowned upon nowadays but common in the past. Then suppose that specimen gets lost; it is then extremely difficult, if the description is poor, to determine exactly what the species is!
In this case a researcher will select will select a type of what they think was the species described and this is then called a NEOTYPE.
However this can lead to all sorts of problems.
In one case a worker nominated a neotype for a characid species and then later the original was found and the neotype turned out to have been wrongly determined and itself represented another species!
Synonyms and Name Changes
A synonym is another name for the species. Often in taxonomic works one sees a whole list of synonyms under a species name. Why is this?
Supposing somebody names a species Barbus hunteri then later somebody else names a species Barbus browni. Then along comes a third worker and realises that the author of Barbus browni had failed to spot the original description of Barbus hunteri and, in fact both are the same species.
Because Barbus hunteri was the first to be described (however badly) it takes priority and so Barbus browni is know as a JUNIOR SYNONYM.
This is the most frequent cause of species synonym.
When a researcher "revises" a group of species he/she will almost find errors of identification during literature searching.
In some cases, workers may have independently described the same species under different names!
In other cases it is simply our improved knowledge of species variability that makes us realise what were original described as two species are just population variants.
Generic synonyms arise through rather different causes but can upset a lot of people. I will give one example that has caused havoc.
Several species of Salmon formerly included in the genus Salmo have now been referred to the genus Oncorhynchus. Biologically and anatomically this makes perfect sense: all Oncorhynchus now occur on the western seaboard of North America and all Salmo on the Atlantic side and around Europe.
There is excellent biological and biochemical evidence to support this generic arrangement, arrived at by independent researchers.
The trouble is that some so-called Trout are now regarded as Salmon and this has caused such problems with the fish marketing industry, that a court case was brought concerning the proper trade description of Rainbow Trout - whose generic name has changed from Salmo to Oncorhynchus (biological evidence) - and whose species name has changed from clarkii to matsou on grounds of name priority!
When a well known generic name is found to be the junior synonym of an obscure name which everyone has overlooked it is possible to make a special case to conserve the original name. The rules for naming animals scientifically are drawn up and administered by the International Commission for Zoological Nomenclature (ICZN) whose offices are in the Natural History Museum, London. In such cases as the conservation of a name then the ICZN Council make a ruling their decision being published as an opinion in the ICZN Bulletin.
Some problems can be difficult to resolve.
For example, several species of Amazonian fishes described in the early 1800's by Spix and by Castelnau are know only from the illustrations they published.
In such cases the "type" being an illustration is called ICONTYPE, but has a debatable standing. It is now almost impossible to match these "icontypes" with any known species possibly because the artist enbellished or neglected certain features.
In such circumstances a case can be made to declare the species name a NOMEN DUBIUM and to place it on a "black list" of names which can no longer be used.
Sometimes (this has occurred in aquarist literature) a "new species" appears just as a name without any formal description. This is referred to NOMEN NUDUM. If the species does eventually turn out to be a “new" one then a formal description is required to validate the species.
Yet one other reason why name changes occur is that a generic name may have been PREOCCUPIED elsewhere in the animal kingdom.
No two animal species can bear the same binomen.
Sometimes one finds that a generic name is already in use, say for an insect, so a new name NOMEN NOVUM must be given to replace it.
Sometimes a name may be too close in spelling to another, eg, Cyprinus and Cyprinis in which case the Junior name is rejected on the grounds of HOMONYMY.
I have set out an hypothetical example of typical synonymy which incorporates some of the problems given above.
Example of a Synonymy
Barbus hunteri (Gray) 1820
Genus Species Author's Date
When the authors name is in brackets it indicates that
the species was originally placed in another genus.
Cyprinus hunteri Gray 1820 Rec. Ind Mus. 20: 1-10
Journal name abbreviated with
volume number and page numbers.
Capoeta dubia Buchanan 1830 Put into synonymy because Buchanan
described it without realising Gray's
species was identical
Barbus hunteri Day 1840 (part, Indus) This entry means that only the Indus
river specimens belong to Barbus hunteri,
the remainder of B.browni is still a valid
Barbus hunteri, Davis 1920 The comma after the species name means
Davis was the first author to put hunteri
into the genus Barbus.
?Barbus grayi Johnson 1990 The query mark means this is possibly the
same species but the description is too
poor to tell.
I must emphasise that name changes are made only with good reason and not just for the sake of it and are usually the outcome of much research which leads to a more stable taxonomy.
I hope these few examples give some idea of the problems surrounding the naming of fishes.
Last updated February 2005