Pufferfish are a weird group of fish with a reduced skeleton, beak-like dentition and “spines” – spiky skin structures – in certain patches around their bodies. But how and why these oddities developed remains a mystery.
Pufferfish also have a unique ability to inflate their bodies when threatened or trying to fend off predators. This increase in size (almost double vertically) reduces their range of potential threats and provides a second defense: sharp spines that radiate outward from the body when it’s puffed up.
Spines
Puffer fish are some of the most bizarre animals in the ocean. Their body is shaped like a balloon, and they have spiky skin spikes called spines that stick out of the surface of their bodies.
When threatened, pufferfish inflate their bodies by pumping water into their stomachs, which then expands and unfolds to fill gaps beneath their head, dorsal fins, anal fins, and caudal peduncles, and even their mouths! This unusual behavior has helped these fish survive in many environments.
Researchers have recently studied the development of spines in pufferfish and discovered that these spikey skin structures are derived from a single collection of genes, just like feathers and hair. This discovery is an important breakthrough for scientists working on ways to help animals survive in the face of climate change and other threats, says Gareth Fraser, the lead author on the study published July 25 in iScience.
In addition, he notes that the diversity of spine layout and morphology observed throughout this group of teleosts is a unique feature of their skin ornamentation. This morphological variation may have arisen through adaptation to different ecological pressures, or it could simply be a result of the natural selection of different morphologies in this highly derived order.
To understand the evolutionary origins of these spiky skin structures, the research team examined the development of spines in pufferfish embryos. They found that the spines formed independently of scales and were developmentally unique from them.
The researchers used this discovery as a jumping-off point for further investigation into how skin appendages are developed in other vertebrate species, such as zebrafish, mouse hair, and chicken feathers. They also showed that a similar genetic network triggered the development of these spikey skin structures in these animals as well, confirming recent findings from other studies that this set of genes is responsible for all animal skin appendages.
In addition to demonstrating that the same genetic network is responsible for all animal skin appendages, the study also found that this same gene set can be manipulated to reduce the number of spines on an individual pufferfish. This is the first time that this has been done in a non-human animal, and it suggests that these morphologically diverse ornamentations are based on a simple evolutionarily adaptive mechanism.
Bones
The skeleton of a puffer fish is quite unusual. It is a reduced skeleton, with beak-like dentition and spiky skin structures called spines in certain patches around the body (see the image below).
Pufferfish have a strange ability to inflate their bodies, which can increase them several times their original size. This is a defense mechanism that allows the fish to deter predators and avoid predation when it is in its inflated state.
When the fish inflates, it essentially absorbs air from its surroundings and expands by pumping water into its stomach. This expansion is a natural process, which requires an extremely elastic stomach and special muscles to move the water in and out of it.
However, the tetrodotoxin that makes up most of the body of a pufferfish is deadly to both humans and other marine creatures. When swallowed, it can cause death in an instant, even when there is no visible signs of inflation.
The toxins are found in the ovaries, roe, and liver, and in smaller amounts in the skin and intestines. Concentrations are higher in females and peak during spawning season.
TTX production is thought to be the result of a bacterial symbiont that lives in the intestines of tetrodotoxin bearing animals. Various bacterial strains are known to produce the toxin, but it is most commonly detected in shellfish and puffer fish species.
Researchers have recently discovered that the spiky spines of pufferfish are not simply an evolution of scales, but actually developed as an anti-predator defense. The researchers found that pufferfish spines are developed using the same genetic network that gives birds their feathers and other animals hair.
In addition, they were able to pinpoint the genes that give pufferfish their spines, which is an interesting discovery for evolutionary biologists. They were able to trace the genetic history of the spines from their development in embryos to their appearance on adult pufferfish.
The research is very exciting because it is shedding light on an intriguing piece of animal anatomy that has baffled scientists for years. While a pufferfish’s unique behavior may have originated by chance, the evolution of its bones and other features is actually pretty neat.
Teeth
The skeleton of puffer fish is composed of a series of bones and a few organs that help them survive in their environment. Among these are the lungs, which allow them to breathe and store oxygen; the stomach, which is responsible for their puffed-up appearance (when they gulp water or air); and the mouth, which allows them to open their mouth and eat.
The mouth of a puffer fish is made up of a unique beak that is used for eating soft-shelled invertebrates, like mollusks, crustaceans, and insects. The beak is formed by a stack of elongated teeth that are cemented together in a matrix of hard tissue.
In this way, the beak can be adjusted to suit different tasks. For example, the upper teeth may be positioned for crushing shelled prey, while the lower teeth are suited to eating smaller invertebrates.
A beak is also important for protecting a puffer fish from predators. It is strong enough to break the skin of an intruder and pierce through its body.
Teeth are also an important part of the skeleton because they help the fish keep food in its system. In fact, they can be shaped to help a fish swallow hard-shelled prey, and they may even have a special notch that helps them bite harder than their neighbors.
Puffer fish teeth grow very fast, so it’s important to give them a good diet to avoid problems with their teeth. This can be done by giving them whole, unshelled food items that are crunchy.
These include clams, snails, mussels, shrimp, prawns, woodlice, crayfish and small crabs. For this reason, it’s important to make sure that you choose the right type of puffer fish for your aquarium so that it can properly eat its food.
In addition, a healthy, balanced diet can prevent overgrowth of the teeth and help them look their best. Overgrown teeth make a puffer fish appear bucktoothed, and they can cause the fish to have trouble opening and closing its mouth.
Skin
The skin of a puffer fish skeleton is made up of collagen fibers that are arranged in more or less ordered arrays. This allows the skin to provide a rigid framework that can support the body’s contents and a flexible covering that can be altered in order for the puffer fish to inflate.
These skin structures are referred to as spines, and they can vary in coverage from a single spine to many throughout the fish’s body. This variation in the number of spines is largely due to a genetic mechanism that makes it possible for pufferfish to adapt to different ecological niches, according to new research from scientists at the University of Florida.
Fraser’s research team identified a set of genes that regulate the development of the spines in the puffer fish. By manipulating these genes with CRISPR-Cas9 and small molecule inhibition, the researchers were able to reduce the number of spines on the puffer fish and loosen restrictions that normally govern where they appear.
This is similar to how birds grow feathers or other animals develop hair. The genetic code involved in the development of spines is identical between puffer fish and other species, including birds and mammals, enabling the researchers to study how these spiky, dermal skin structures are formed.
When the researchers examined the skeleton of the Hawaiian pufferfish (Tetraodontidae), they found that this family of fish has an unusually diverse array of dermal ornamentations. These can range from one caltrop-like dermal spine to several that cover the entire fish.
The morphology of these spines is also unique in that they are not always visible until the fish inflates, so they don’t have to make an appearance at all during normal movement. This allows the fish to be able to hide from predators while resting on a coral reef or other rocky surface, where they can then camouflage themselves by changing colors of their skin.
The morphology of the spines also allows this fish to be a good prey fish for other marine life, especially in areas where predators are abundant. Some species of puffer fish can eat plankton and other small invertebrates, but they are best known for their ability to feed on larger, more dangerous invertebrates such as mollusks, crustaceans, crabs and worms.