Bony-eared assfish – who thought of this name? How come this is an official name of the species?

Bony-eared assfish – that is not a beginning of an article you probably expected to see, but it is just a name of a fish. In fact, it is an official name of the species Acanthonus armatus. Bony-eared assfish is a cusk-eel found in tropical and sub-tropical oceans. It lives quite deep – at around 1,171-4,415 metres below the surface. However, probably you are more intrigued by its name than anything.

Acanthonus armatus, better known as the bony-eared assfish, a record holder for the smallest brain-to-body weight ratio of all vertebrates. Image credit: R. Mintern via Wikimedia

It is ok to laugh at bony-eared assfish’s name. It is quite funny or unusual at best. Profanity is not really your friend when you are trying to think of a nice name to describe a newly discovered species. And it is certainly not what happened. Scientific name of the species, Acanthonus armatus, was provided to the assfish by German ichthyologist Albert Günther back in 1887. Günther was particularly interested in the assfish, its living environment and bizarre looks. And yet bony-eared assfish looks nothing like the human buttocks.

You may know that a word “ass” has several meanings and one of them is a donkey. Where does a donkey come into play? Well, let’s take a look at the name Acanthonus armatus. Armatus in Latin means “armed”. Assfish has spikes on its nose and gills, which explains why Günther chose that part of the name. Meanwhile Akanthos is Greek for “prickly” and onus means denotes a hake – a relative of cod. Put it all together and you get an armed prickly hake. Not that close to the bony-eared assfish, is it? But English names for species are rarely literal. These spikes on the head of the assfish could be considered bones, which would make this fish “bony-eared”. If you choose to note those spikes, this part of the name is not that strange. However, even though onus means hake, it also means a donkey. So sometime along the line someone decided to name it a “donkey-fish” or simply an assfish.

Funny thing is that bony-eared assfish is really sloppy. It is difficult to grow substantial bones at such a depth where food is scarce. Which is why the assfish is flabby and its skeleton is light. It grows to a length of 37.5 centimetres and is quite light. These fishes are not very common, but currently there is no danger for them to go extinct. Living so deep they avoid fishing nets and other potential dangers. In fact, they avoid so many things that they don’t even need a large brain – bony-eared assfish has the smallest brain-to-body weight ratio of all vertebrates.

But you have to be nice to the bony-eared assfish. Yes, it has a funny name. And yes, it is quite ugly and has a small brain. But all animals are beautiful in their own ways in their natural environment. At least unusual name helps the bony-eared assfish to be more well-known to the general public.


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