The Nature of Names, the Names of Nature | Details | Articles

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Issue: July 2007

Author: David E. Boruchowitz

Common names are used quite often in the hobby, but it’s important for aquarists to understand the importance of using scientific names for identifying fish.

Before we begin, take this little quiz. Go ahead, circle your answers right here on the page. I’ll wait while you get a pen.


1. A goldfish is a barb.     True False

2. A piranha is a tetra.     True False

3. There are three species of blue tangs.            True False

4. The Honduran redpoint is not really a convict cichlid. True False

5. The neon goby has a blue stripe.      True False


Okay, how’d you do?

What do you mean, I didn’t give the answers yet? It doesn’t matter. You can answer true or false to any of them. That’s because all five are interpretations, not statements of fact. Specifically, they use common names, and common names have no fixed association with any particular species. They also have absolutely no authority. This isn’t a minor matter. If you believe that any of them are necessarily right or wrong, you don’t understand the difference between common names and scientific names…and you aren’t alone!

Many hobbyists don’t like scientific names. They complain they are unwieldy and too technical. The truth, however, is that they are often necessary and always helpful. Among aquarists who truly know a group of fishes, say cichlididiots or killie nuts, you will find they regularly use scientific names and never use common names. This choice is not based on ease of use or pronounceability; it’s based on need.

Percula Clown—True or False?

You’ve certainly seen statements like “The true green terror is ‘Aequidensrivulatus,” “Amphiprion ocellatus is the false percula clown,” or “The correct scientific name for the port cichlid is Cichlasoma portalegrense.” Such statements are all based on an extremely widespread but also extremely unfounded belief that there is a one-to-one match between scientific names and common names and on the corollary that common names are somehow regulated or supervised. At best, this error is misleading and confusing. It can, however, also lead to some significant problems, since a given species can have several common names, and a given common name can apply to several species. The irony is that many people argue in favor of common names because scientific names are too confusing. Confusing? Absolutely nothing is more confusing than the actual use of common names!

A few saltwater surgeonfishes will serve as illustrative examples. The three species Acanthurus coeruleus, A. leucosternon, and Paracanthurus hepatus are all called blue tangs. In addition, the first is called the Atlantic blue tang, the yellow tang, and the Atlantic yellow tang. Of course, Zebrasoma flavescens is also called the yellow tang, as well as the Hawai‘ian yellow tang. A. leucosternon is also called the powder blue tang, and P. hepatus is also called the hippo, palette, regal, or yellowtail blue tang.

A. japonicus is known as the gold rim, Japanese, powder black, powder brown, white cheek, white face, or white nose tang. A. nigricans is also called both the powder brown tang and the gold rim tang, as well as the brown, velvet, white cheek, powder grey, and yellow fin tang. Two other species are also called brown tangs—A. nigrofuscus and Zebrasoma scopas.

Confused yet? Confusion isn’t the only cost, however. A. japonicus and A. nigricans are both routinely called the gold rim, powder brown, and white cheek tang. There will be some people who object, saying, “No, no, no! That one is the powder brown, not the gold rim!” The problem is that different people will select different species. People will speak of “the real powder brown,” or “the real white cheek”—only they will have different species in mind! This situation becomes more serious when you factor in that while A. japonicus can make a good aquarium specimen, A. nigricans almost never survives in captivity. Thus, misidentification can result in tragedy.

While researching the actual use of various common names for these fish, I did come across one source that called both of them white faced powder brown tangs and stressed correct identification by scientific names due to the vast difference in survivability between the species. Most sources, however, picked a common name for one and another common name for the other, then went on to describe the fish’s appearance and husbandry. Of course, the names chosen varied from source to source. What amazes me is that people are trying to reinvent the wheel. By defining a common name as belonging to just one species, they recognize how important it is for each species to have a unique name—but while their attempt to restrict just one of many shared common names to just one certain species is doomed to failure, each species already has a unique name: its scientific name! The obstinate insistence that a particular species is a particular common name would be much better channeled into the proper use of scientific names.

There are no safe common names. Even such regulars as “guppy,” “neon tetra,” and “tiger barb” do not always refer to the same species. Sometimes the use of common names is peculiar, even idiosyncratic. Several times I have heard an aquarist use a common name that I was certain was universally accepted for a certain species—only the aquarist used it for a different species. In some cases these aquarists were retailers, meaning that they propagated their idiosyncratic usage each time a customer took note of it.

For decades I have seen the name “porthole cat” applied to the callichthyid cats of the genus Dianema. One day I saw some in a dealer’s tank, and sure enough, the sign on the tank listed porthole cats among the inhabitants. When I said I wanted some, the dealer told me to go ahead and net them out. So, I did. As I was sealing the bag he came over, looked at it, and said, “Those aren’t porthole cats!”

I told him that they were what I knew as porthole cats and asked what he thought they were. He pointed to the tank, at the mochokid Synodontis notatus in it. “See,” he explained, “they have big round spots like portholes along their sides.” Well, I couldn’t argue with that, and I have no idea why the Dianema are called porthole cats, but it was a first for me. Even if the retailer was the first person to use the name this way, the usage has certainly spread in the hobby via his customers.

Dynamic Uniqueness

I often hear the argument that there’s no use learning scientific names, when they’re always changing. This is a non-argument, for three reasons. First, all names aren’t always changing. Consider the lungfish Protopterus aethiopicus, whose name is unchanged since Heckel gave it to the fish in 1851, or the cuckoo wrasse, named Labrus mixtus by Linnaeus himself back in 1758, or the common carp Cyprinus carpio, also named in 1758 by Linnaeus.

Second, often when a name changes, it doesn’t keep changing. Perhaps the most famous example is the krib, at first called Pelmatochromis kribensis and later (and still) called Pelvicachromis pulcher. It is true that certain groups of fishes are undergoing massive taxonomic reform, and their names change rather frequently, but even this is insignificant when you consider the third response to the specious argument about learning scientific names: uniqueness.

Even when scientific names change, no name is ever assigned to two different species. This means that all scientific names, whether old and invalid or brand new, are unique in their application. If you use an earlier, now invalid name, you may be out of date, but you will still be referencing the same species as someone who uses the new name. The name you use will never be used to refer to some other species. This is important enough to restate: An older name may be out of date, but it will never refer to a different species.

Someone might object here and cite one of the uncommon examples of misidentified fish that were known for some time in the hobby by the wrong scientific name, which was later sorted out and applied to the correct species. This, however, is not a fault of scientific naming—it’s an error on the part of hobbyists. And, it’s demonstrably wrong, unlike common name usage, which can be neither right nor wrong. We can correct mistakes in using scientific names because every species has a unique name; if we misapply them, we can discover our mistake and correct it. If necessary, we can go back to the original description, or even to the preserved holotype. There is no parallel with common names.

Geographical Uniqueness

Common names often change as you move from one region to the next, and they always change when you move from one language to another. Even when you take translation into account, common names are typically different in different languages. On the other hand, scientific names do not change. In fact, they do not even change when you move from one writing system to another. Thus, you will see pages written in Chinese or Hebrew or Russian punctuated with scientific names, which are always written in the Roman alphabet.

I found a Russian aquarium webpage that spoke of a fish called крылаткаполосатая (krylatka polosataya), meaning roughly “striped wing nut.” Since I had no idea what that fish was, I was very glad to see that the scientific name was also included: Pterois volitans. It is also easy to imagine that a Russian aquarist visiting an English site that spoke of the red lionfish, turkey fish, firefish, or dragon fish would be happy to find the scientific name Pterois volitans included.

More than an ID

Using scientific names has further usefulness than just an exact identification—though that is a major benefit in itself! Taxonomic nomenclature is based on relationships among the species, so it helps us to learn about the fish we keep. Knowing that two fish are in the same genus enables us to make educated guesses about their behavior and their proper husbandry. As we go further up a taxonomy, from genus to family to order, the group gets bigger and the relationships become attenuated.

Consider the common names for two groups of fishes, cichlids and catfish. Both are large groups, with more than 2000 species each. Cichlids, however, are a family (Cichlidae), while catfish are an order (Siluriformes) with about 35 families in it. The most distantly related cichlids are much more closely related to each other than many catfishes are to each other. The explosive radiation of cichlids relative to that of catfish has many consequences for us as aquarists, as does the suborder (Labroidei) relationship of cichlids (Cichlidae) and damselfish (Pomacentridae). Often by learning a little bit about taxonomy we can learn a great deal about our favorite fishes. We can also learn a lot from the fact that some fish have no scientific name.

No Name?

I’m not talking about yet-undescribed species—there are many popular aquarium fish that are hybrids of two or more species. There is a way to indicate a hybrid with scientific names, but that refers only to the F1 generation, in other words, one species crossed with another. Domesticated varieties like swordtails or mollies breed true but are genetic mixtures of three or more species. Flowerhorn cichlids are hybrids of a variety of species, and two flowerhorns may have very different parentage. None of these are naturally occurring (Sorry, Wayne, no Lago de las Ilusiones), and they cannot have scientific names, at least not species names. We sometimes show parentage when both species are in the same genus, as in Xiphophorus sp. “domesticated.” The problem with notations like that is the parallel with names like Xiphophorus sp. “Rio Pequeño.” In this case we are dealing with a natural species, but we aren’t sure whether it is one that has already been described or a new one needing description. Such is not the case with the domesticated strain, which is not a domesticated species, but a domesticated mongrel of various species.

You might think that at least these fish will have definite common names. Unfortunately, they don’t. In fact, the common names for domesticated hybrid strains seem to be even less uniform than usual. Almost all dealers and distributors have their own names for the same fish, and you may find several strains called by the same name.

Your Responsibility

Are you starting to think that maybe using scientific names is a good idea? Good! But it is important that you understand that using them carries with it a responsibility to use them correctly. Of course you have to use the right name for a particular fish, but that’s not what I’m talking about here. You must also take care that you do not corrupt the chain of custody of the name.

What you call the fish in your collection doesn’t really matter much. Whether you use scientific names, usual common names, made-up common names, or proper names like “Sam” and “Lucy” has little consequence, at least for other people. As soon as you interact with other aquarists, however, it matters a great deal. If you identify fish for another hobbyist, sell or trade your fry, or in any other way link a name to one of your fish, you must act responsibly. This applies to three stages in your custody of the fish and their name:

If you obtain fish under a scientific name, you should ascertain whether or not you can trust the name. In most cases a retailer cannot tell you where fish came from or who identified them. There are two concerns here: are the fish a pure species or a hybrid, and if pure, were they correctly identified?

Purity of Strain

It is very important to maintain correctly identified fish so that they will not hybridize in your tanks. Although hybrids are usually unlikely when males and females of both species are present, they can result whenever related species are housed together. In addition, uncovered tanks near each other can experience “migrations” that create unintentional hybrids. Aquarists are also increasingly concerned about breeding different populations together. The frequency with which subspecies become species and vice versa is a strong argument for keeping original breeding populations reproductively isolated from other populations.

Passing on Fish

If you pass along fish with a scientific name, you should be certain that it is appropriate. Otherwise, you should explain your reservations to the new owners.

Hopefully you now have a better idea of why scientific names are important and how to use them. Common names certainly have their place in the hobby, but they are of almost no use for identification, and breeders and other serious hobbyists will have little patience with them.


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