Binomial Nomenclature - What's In A Name?

Scientific literacy sounds like a public broadcast afternoon special to nap through, but we all need to understand the world around us better. Biology (for better or for worse) has a long history of naming creatures to set each one into a specific group to help us better understand their roles in larger eco-systems; often this results in names the vast majority of the public can't pronounce and don't understand and terms like “eco-systems” that result in further confusion. So, to help you, the proud aquarium geeks you are, or would like to be, we want to dive a little bit into a topic called binomial nomenclature (or literally translated = two-part name.)

We digress. If you've spent any time at your local fish store, or online researching fish or invertebrates, or plants for your aquarium, or chatting about this stuff in forums, you've come across people using what is widely referred to as a “scientific name.” They are always at least two words; for example, we will pick on a fish you all likely know called a “Betta” or the “Siamese Fighting Fish.” The scientific name (binomial nomenclature) of this fish is Betta splendens. The Betta part of this name is the fishes genus, and splendens is the species.

There are actually many more parts to this name, in fact, “Betta splendens” is just the last two words in a name that is much longer. All classification or organisms starts with what “kingdom” they are in, and for everything animal, this classification is “animalia.” Kingdom is is then divided into separate “phylum” and because fish have a nervous system that runs down their back, they are classified as “Chordata.”

Kingdom: Animalia Phylum: Chordata

Phylum gets subdivided a couple times, and when we divide phylum, we do it into groups intuitively called “subphylum.” Bettas belong in the subphylum “vertebrata” because they have an advanced nervous system (with brain!), internal skeleton / spine, blood that circulates through a vessel systems. Subphylums are then divided into a more tightly defined group, called an “infraphylum” and fish belong to the infraphylum “gnathostomata” and the category here is defined by things that have a jaw.

Subphylum: Vertebrata Infraphylum: Gnathostomata

The next major subdivision is one called “class.” Bettas belong to the group called “osteichthyes” or “bony fishes.” There are other classes that fish can fit into, jawless fishes (agnatha,) and cartilaginous fishes (chondrichthyes), and a couple more, but they are infrequently used and somewhat more confusing (lampreys and hagfish). Classes also have subdivisions and our example belongs to a “gigaclass” called “actinopterygii” which is more commonly described as the “ray finned fishes.” There are more subclasses here (big surprise) and the subclass for Bettas is “Teleosti” which indicates the presence of a swim bladder.

Class: Osteichthyes Gigaclass: Actinopterygii Subclass: Teleosti

We think by this point you've sensed a theme and yes, there are more divisions coming. Classes get divided into “Orders” and our little buddy Betta Fish belongs to an order called “Perciformes.” Perciformes is a huge order, containing the vast majority of fish, fish in it are defined by having two dorsal fins. Fish that have a labyrinth organ (a primitive organ that allows the fish to breath atmospheric oxygen) are given a suborder called “anabantiformes” and if you guessed our Betta fish fell into this category, you are right.

Order: Perciformes Suborder: Anabantiformes

We divide classes into families, and here is where the tree gets very diverse. Family is a confusing classification because people commonly say that fish are in the same “family” but what they really mean is the next classification down which is genus. Really oversimplified, when you think of families, think of it as all of the people at your family reunion; there is a ton of people there you've never seen before and don't know from Adam (nice guy btw). When you think of genus, its more like all the siblings and first cousins you grew up with and frequently look like. Our Betta fish is in the family “osphronemidae” which is more widely known as the “Guaramis.”

Family: Osphronemidae

Genus is a group of fish that is much more tightly similar, and as we've referenced before, our example fish has a common name that is actually its genus, “Betta.” These organisms will all share many if not most of their physical, and physiological traits (look similar and have similar biology requirements.) Species are the individual fish within a genus that have enough genetic difference to be considered a separate organism but still capable of interbreeding and sharing genes, though not of producing fertile offspring. However there are exceptions to this rule, because, as Ian Malcom so famously said, “life finds a way.” The species for the Betta, is splendens, and at the time of this writing, there were at least 75 other species in the Betta genus, a number which is sure to grow with time (unless some of them get reclassified and a new genus created, which does happen.

Genus: Betta Species: splendens

The most complete way to describe a fish with its scientific name, is to use all these names, but that results in a name that looks like: Vertebrata Gnathostomata Osteichthyes Actinopterygii Teleosti Perciformes Anabantiformes Osphronemidae Betta splendens. It's a lot. The average person likes to shorten Betta Splendens down to just Betta, so it's no surprise that as scientists, we generally refer to individual species by just the genus and species. Will you ever need to know all this? Unless you are writing your doctorate on Vertebrata Gnathostomata Osteichthyes Actinopterygii Teleosti Perciformes Anabantiformes Osphronemidae Betta splendens, probably not, but it doesn't hurt to know the what and why of how we got here.

As a side note, the correct term here is “fishes” as we are talking about multiple different kinds of fish. The plural of fish is still fish, and this is acceptable no matter how many species you are talking about, but if you are talking about multiple groupings of fish, especially in scientific reference, then the plural is “fishes.” Another side note is that when you write down the binomial nomenclature of any organism, the genus is always capitalized and the species is always lower case. Hundreds of years of work have gone into the classification systems we've developed, and there is much work left to do. If this topic has peaked any interest in you at all, then it's possible you may be a budding taxonomist as well!