What’s in a Name?
Classification:
Domain: Eukarya
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Anguilliformes
Family: Anguillidae
Genus: Anguilla
Species: Anguilla japonica
So, where does the Japanese eel fall in the grand scheme of things?
Hungry for More?
For more taxonomical information, visit the World Register of Marine Species.
A photo of a Japanese Eel swimming along a river bottom.
The Japanese eel contains complex cells including a nucleus and other membrane-bound organelles, earning it a seat in the Domain Eukarya.
It takes many of these cells organized into complex tissues to make an eel. Also, the organism is heterotrophic, meaning it cannot create its own food. A lack of cell walls and the organisms ability to move make it a sound choice for the Kingdom Animalia.
During development, the eel features a notochord, dorsal nerve chord, pharyngeal pouches, an endostyle, and a post-anal tail. These are the tell-tale signs of a member of the Phylum Chordata.
An eel’s fin consists of webs of skin stretched over bony projections, placing it into the Class Actinopterygii.
The Order Anguilliformes consists of all the true eels. These are fish with elongated bodies that lack pelvic fins. The dorsal, anal, and caudal fins have merged into one fin running along the entire back. This description matches the Japanese eel’s morphology to a ‘T’.
Strangely, the Family Anguillidae and the Genus Anguilla are one and the same. The family, and genus, includes all of the “freshwater” eels that are actually catadromous.
The name Anguilla japonica, like all scientific names, is Latin. Interestingly, when translated to English, it is exactly the same as the common name, Japanese eel.
Interesting....but what makes you say that?
This is a phylogenetic tree of 5 of the Anguilla species most closely related to the Japanese eel based solely on morphological characteristics. This means that it was created using only what we could see on the organisms, without utilizing any of our modern tools. According to this, A. japonica is most closely related to either A. anguilla or A. rostrata, the European and American eels, respectively. These two species are more closely related to each other, but they are the closest relative that the Japanese eel has. This tree indicates that this section of eels is a monophyletic group. In reality, the entire Family is monophyletic. Every member of the genus can be traced back to a common ancestor, shared by all.
So how do the species of Anguilla relate to one another?
Image courtesy of Taiwanese Government.
This is a broad-scale phylogenetic tree based upon information from the Tree of Life Web Project, found at www.tolweb.org. This is based upon molecular data, rather than simply morphological characteristics. Most of the data compiled was from 18s rRNA sequences. The incorporation of molecular data makes the tree much more accurate, and shows some surprising results. For example, the tree shows that the Japanese eel shares a more recent common ancestor to the terrestrial vertebrates, including us humans, than with the Lamprey eel. Morphologically, these species are similar enough to share the eel namesake. However, when you consider the importance of the evolution of a jaw, its not surprising that the two are so distantly related. In fact, there are numerous “eel” species from many different genera that are very distantly related to the true eels. These are known as “false eels”.
To learn more about a “false” eel, check out this page on the Gulper eel.
For a great blog series on the different families of eels and nearly-eels, including the true freshwater eels, stop in to this site!
So how do the species of Anguilla relate to other species?
