Last Reviewed and Updated on February 4, 2023
There is much diversity when it comes to eels; with about 800 different species, these animals come in many sizes, shapes, and unique quirks. Dive deep and learn all the basics about this group of animals and some of the most interesting facts about eels, from their life cycle to how they can be team players.
About True Eels
Eels are a group of slender ray-finned fish in the order Anguilliformes. There are eight suborders with 19 families and 111 genera; all in all, there are about 800 different species of true eels.
These fish can be found all around the globe, both in saltwater and freshwater habitats. Most species can be found in the shallow waters of oceans. They are mainly nocturnal animals.
Eels are mostly slender, elongated fish without pelvic fins (and some without pectoral fins). Their tail, dorsal and anal fin are fused together and form a single long fin that runs along most of the length of their bodies.
Eels are mainly nocturnal animals.
They are primarily carnivorous, preying on smaller fish, invertebrates, crustaceans, shrimp…
Facts About Eels
Ready to learn more about these fascinating fish? Read on and learn some of the facts about eels that make this group of animals out of this world.
1. Eels swim by moving their bodies like a wave
Eels use a pretty unique method of swimming called undulation. This is a wavelike motion of the body which they use to propel themself forward and backward.
2. One-jawed eel is the smallest, and slender giant moray is the largest eel
One-jawed eel (Monognathus ahlstromi) is the smallest known eel species; it measured 2 inches / 5 centimeters in length. The slender giant moray (Strophidon sathete) is the longest known eel species, with the longest specimen recorded measuring almost 13 feet / 4 meters in length.
3. Some eels are catadromus
Some eels are catadromous, meaning they migrate from freshwater into the sea to spawn.
These eels spend most of their lives in freshwater but migrate to saltwater to breed.
One such species is the American eel.
4. Eels use their sense of smell and not sight to hunt
Eels have poor eyesight but a great sense of smell. Most eels hunt by night, and the low visibility works as an advantage for them. They lie in wait, ambushing the unsuspecting prey.
5. They have an interesting life cycle
After they emerge from the eggs, eels begin their lives as flat and transparent larvae (called leptocephali). These larvae metamorphose into glass eels (transparent juvenile eels), which become elvers before moving to their juvenile (and adult) habitats.
Adult eels mate/spawn only once, and adults die after.
6. Moray eels have a “second ” jaw.”
Pharyngeal jaws are a “second” set” of jaws in an animal’s throat or pharynx. This is even more fascinating because Moray eels, unlike other species of fish with second jaws, have extendable second jaws.
Moray eels capture their prey with their first set of jaws, the second set of jaws are then brought forward, biting and gripping the prey, and then the second jaw is retracted, pulling the prey, essentially swallowing it.
7. Moray eels can team up with other fish
The roving coral grouper has been observed recruiting giant morays to hunt together. The roving coral grouper initiates the hunt by head shaking, and morays flush prey from niches that aren’t accessiaren’t groupers.
8. Garden eels resemble plants in the garden
Garden eels got their name because of their living habits; they often live in larger groups and with their bodies buried in the sand, with only their heads and part of the body sticking out, resembling a garden.
9. The coloration of ribbon eel depends on their age and sex
Ribbon eels (Rhinomuraena quaesita) have a unique coloration as far as eels go. Juvenile eels are black with a yellow dorsal fin. Adult males are blue with a yellow dorsal fin, and adult females are entirely yellow (or have some blue on the posterior).
10. Mouth of the pelican eel is larger than its body
Pelican eels got their name because their large mouth resembles a pelican’s beak. Their mouth is larger than the rest of their body.
11. All ribbon eels are born male
All ribbon eels are born male; as they age, they transition to a female, developing female reproductive organs.
12. Some eels excrete toxins
All eels have blood that is poisonous to humans and other mammals. In addition, some Moray eels secrete protective mucous over their skin containing toxins.
13. Eels can get stuck in seal’s noses
Endangered Hawaiian monk seals have a peculiar problem. They sometimes get eels lodged up in their nostrils. Why this happens remains a mystery, but one possible explanation is that seals disturb the eels when they are nosing around for food, and the eels are trying to defend themselves or run into the “crevice” (seal’s nose).”
14. Moray eels can hunt on land
Moray eels have been recorded hunting on the land.
15. Not all animals named eels are true eels
Some animals resemble eels but aren’t true eels even closely related to them.
These include; electric eels, spiny eels, swamp eels, and deep-sea spiny eels. These animals developed their eel-like shapes independently.