Pufferfish are well-known for their ability to “puff up” into a round, sometimes spiky ball. Some people also know them for the poison their bodies hold. These unique fish are usually found in shallow ocean water, but a few species are found in freshwater. Here’s what you need to know about these inflatable fish, especially the freshwater species.
What Are Pufferfish?
Pufferfish are a type of fish known for blowing their body up like a balloon. They can range in size from one inch to two feet long. There are about 120 species of pufferfish worldwide, and they’re divided into two families: Tetraodontidae and Diodontidae.
Tetraodontidae pufferfish. Pufferfish in the family Tetraodontidae are sometimes called smooth pufferfish. They don’t have scales or spines but may have small, prickly bumps on their short, round bodies. These fish have two fused teeth on both the top and bottom that act a bit like a beak. They use these teeth to crush or scrape their prey. There are 191 species of Tetraodontidae pufferfish.
Diodontidae pufferfish. These spiny pufferfish, also called porcupine fishes, have large, pointy scales that act like spines. These spines lie flat against the body most of the time but stick out when the fish inflates. Spiny pufferfish have large eyes to help them see in the dark, and their mouths contain two heavy plates that help them crush the shells of their prey. There are 18 species of Diodontidae pufferfish.
Pufferfish have some distinctive features. They can close their eyes by sinking their eyes into their sockets and puckering the surrounding skin. They also have a mating ritual that involves the males digging complex shapes and patterns into the seafloor.
How Do Pufferfish Inflate?
Pufferfish are named for their ability to “puff up.” This is a defense mechanism they use. Pufferfish are agile swimmers, but they’re slow. They can’t easily outswim predators, so instead, they puff up, making them more difficult to eat.
Pufferfish inflate by gulping water into a special sack near their bellies. If they’re outside the water, they may gulp in air instead.
Diodontidae pufferfish also have an added layer of protection thanks to their spiky scales. Many pufferfish also contain a toxin that not only tastes terrible to predators but can kill them.
In the wild, pufferfish live in the tropics and subtropics. Most pufferfish live in the oceans near the shore and in shallow water. Some species of pufferfish live in fresh water or in brackish water, where fresh water from lakes and rivers meets ocean salt water.
Freshwater pufferfish. While freshwater pufferfish are less common than those that live in the oceans, there are many interesting species. These include:
- Arrowhead pufferfish (Pao suvattii): Arrowhead pufferfishes are a Tetraodontidae species that grow to be about four inches long.
- Dwarf pufferfish (Carinotetraodon travancoricus): These tiny Tetraodontidae pufferfish are only about an inch long, making them the smallest species of pufferfish. They’re found in lakes and rivers in southwest India.
- Mbu pufferfish (Tetraodon mbu): Sometimes called the freshwater pufferfish or giant pufferfish, these Tetraodontidae family fish are the largest species of pufferfish, often growing over two feet long. They're found in Africa, most commonly in the Congo River basin and Lake Tanganyika, especially at the mouth of the Malagarasi River in Tanzania.
- Nile pufferfish (Tetraodon lineatus): As their name suggests, the Nile pufferfish are found in the Nile River in Egypt. Another species of fish from the Tetraodontidae family, they’re usually eight to nine inches long.
- Spotted Congo puffer (Tetraodon schoutedeni): The spotted Congo puffer does indeed have spots, and it is indeed found in the Congo river basin, especially in Pool Malebo in the Democratic Republic of Congo. They’re part of the Tetraodontidae family and grow to about four inches long.
Most species of pufferfish feed on mollusks, a type of invertebrate that often has outer shells. They’ll also eat other types of invertebrates like sea sponges and coral.
Smooth pufferfish hunt near the reef during the day, looking for prey that dwells along the seafloor like brittle stars, coral, sea squirts, and sea urchins. They then rest in caves or crevices at night
Spiky pufferfish prefer a nocturnal schedule. They hunt at night, using the hard plates in their mouth to crush prey like hermit crabs, sea urchins, and snails. They rest during the day in caves or under ledges.
The lifespan of a pufferfish can range from three to 20 years, with an average of 10 years. Their lifespan can depend on many things, including the species and their environment.
Pufferfish are very sensitive to their environments and can become easily stressed. This stress can make them sick and shorten their lifespan. In captivity, pufferfish need quality water and food and enough room to swim. Freshwater pufferfish are often easier to keep as pets because they are more adaptable.
As a method of defense, most pufferfish have sacs in their bodies filled with a poison called tetrodotoxin. Scientists think pufferfish create the poison from bacteria in their diets. Tetrodotoxin is about 1,200 times more poisonous than cyanide, and one pufferfish can have enough tetrodotoxin to kill about 30 people.