Saltwater Fish Without a Tail

Jellyfish are the most common saltwater fish that don't have tails.

There is an old riddle meant to be clever asking, "What's the one saltwater fish without a tail?" The only problem is, there is technically more than one. Between eels, jellyfish, and knife fish, one can argue there are three saltwater fish species that don't have tails. This is definitely an unusual trait, and one that piques the interest.

Jellyfish

Jellyfish are the obvious answer to the riddle, since these animals don't have any type of tail. The jellyfish, known for their stingers, can cause great harm to people who step on them, or get caught up in a group while diving or swimming. The Portuguese Man of War, known for its large size and very long tentacles, is one of the largest and most intimidating of all the jellyfish species.

Eels

Saltwater eels are another example of a saltwater fish that don't appear to have a tail. These long snake-like fish are throughout the oceans and can be very aggressive. Moray eels are territorial. The Yellow Canary Eel, sometimes referred to as the "banana eel" due to its color, is one of the rarest (or at least hardest to find) saltwater fish without a tail.

Saltwater Knife Fish

The saltwater knife fish is a strange case, as some people would argue that it has a tail, but this fish does not have the distinctive back fin the way other species do. There is a long fin on the underbelly that stretches all the way to the back, and helps to propel the knife fish, but there is no distinctive tail on this species.

Why So Few?

There are very few saltwater fish without tails because, evolutionarily speaking, fins make sense. Fish without fins don't make as much sense. Eels can move very quickly and to fit into small holes or underwater caves for protection. Jellyfish are heavily poisonous, allowing them to make up for it. But for most fish, it makes a lot more sense to have tails.

Odd Tails

There are also fish that have tails, but not in the normal way. Seahorses and stingrays are two examples. These fish technically have tails, but they do not function the same way as for other fish. The stingray's tail is actually for self defense or hunting, as movement is primary from its wings, or flaps. Seahorses are also an example of an odd fish that doesn't have a normal tail.

References

• DNR Sea Science: Jellyfish
• The Marine Center: Yellow Canary Eel
• Aqua-Fish: Jack-Knifefish
• National Geographic: Stingrays
• Seahorse.org: News