There are many different types of fish, but some of the most interesting skeletons come from teleosts, including pufferfish (Tetraodontiformes). These fish can be found in brackish water and freshwater, with their flesh being eaten by people worldwide.
In addition to their striking appearance, these fish also have an impressive arsenal of defenses. One of the most notable is their ability to expand themselves to over three times their original size.
Puffer fish have a strange skeleton, similar to those of birds, in which the skin forms spines instead of scales. These spiky skin ornaments are unique to puffers, and their appearance has long puzzled researchers.
Spines in puffer fish are used for two different functions: protecting the fish from predators and delivering a message that warns of the blowfish’s lethal toxicity. These warnings can range from colorful patterns and wild markings on larger species to more muted or cryptic coloration on smaller ones.
The puffer fish skeleton has a number of spines that can vary in size and shape, and they can be restricted to specific ventral or dorsal areas, depending on the species. Some species have spines that form a complete coverage of the entire body, while others only become visible when the fish inflates its stomach.
These spines are designed to protect the puffer fish from predators that might not notice them until the pufferfish has inflated its stomach. When a pufferfish swallows water or air, it inflates its extremely elastic stomach into a ball that can be almost double vertically in diameter.
When this happens, the spines radiate outward, forming a warning to any predator that might be near by. These sharp spines can choking or suffocating any predator that might try to swallow the puffer fish.
According to Gareth Fraser, a professor at the University of Florida, the pufferfish’s ability to inflate its stomach is an important secondary defense mechanism. This allows the pufferfish to reduce its range of potential predators, and this is a big help when it comes to defending against aggressive, large-mouthed prey such as sharks or crocodiles.
While the exact process of how pufferfish get their spiky spines has remained mysterious, researchers have recently identified a number of genes that are responsible for the development of these spiky skin ornaments. These genes are similar to those that give feathers and hair to birds, which could explain why the puffer fish has these special skin features.
Using genetic techniques, the researchers blocked certain genes that are classic markers of skin appendage development to see what would happen. They found that by blocking these genes, they could reduce the number of spines on the puffer fish and loosen the restriction where these spines appear.
Puffer fish, also called blowfish, get their common name because of the way they inflate, blowing up several times their size to help protect them from predators. They are tropical and warm-temperate-dwelling fish, found in oceans worldwide, but a few species live in freshwater.
Most pufferfish are small and slow swimmers, and they often use their inflated appearance as an effective camouflage against predators. They are also poisonous and can kill a human with a single bite. Many pufferfish are now threatened by overfishing for resale to the tourist industry, which often catches them in their inflated form.
During inflation, pufferfish ingest excessive amounts of water, which allows them to expand more than three times their normal size. The pufferfish’s stomach contains accordion-like folds that allow it to pump the water in and seal it off. Special muscles in the mouth and esophagus then push all the water back out to deflate the fish again.
Aside from their unique ability to inflate, pufferfish are a fascinating example of how strange anatomical adaptations evolved. They are part of an order of tropical fish known as Tetraodontidae (or “piddlefish”), and they belong to the same family as the porcupine fish and sun fish.
The skeletal system of a pufferfish is fairly simple, consisting of the head and torso, as well as some ribs and vertebrae. Their skeletons are made up of nanocrystalline hydroxyapatite, protein (collagen), and water, just like the scales of other fish.
These bones are covered with spines, which are made up of a combination of the same materials as scales. These spines evolved to defend the fish from predators.
They are also used to help keep the fish stable during the inflation process. The spines help the pufferfish remain stable while it gulps water to inflate, and they also help the pufferfish breathe.
To understand how the spines evolved, Fraser and his team studied the skeletal structure of one of the most common puffer fish species, Takifugu niphobles (Tetraodontiformes). They blocked particular genes that are classic markers of skin appendage development, which reduced the number of spines that appeared on the pufferfish.
The skeleton of puffer fish is unique in its lack of ribs and pelvic fins, but it is packed with interesting adaptations that protect these predators from attack. These include puffed-up bodies, armored scales or spines, and powerful toxins.
One of the most renowned features of a puffer fish skeleton is its ability to inflate up to three times its normal size when threatened. The swell, which is a remarkable feat of biomechanics, occurs when the puffer inhales water and pumps it into its stomach.
It’s the same process that triggerfishes Balistes capriscus use to shoot jets of water at spiny sea urchins, causing them to roll over and expose their unprotected belly. Like spiny puffers, triggerfishes are Tetraodontiformes and share many similar morphological characteristics.
But while other members of the family have a spine covering their entire body, such as the gar fish, the spines of pufferfishes vary in pattern and coverage. They range from being completely overlapping (seen in Carinotetraodon; Britz et al., 2012) to being restricted to specific ventral or dorsal regions in the Japanese pufferfish Takifugu niphobles (fugu).
In general, puffer fishes have relatively broad variations in spine coverage that provide adaptive benefits for their ecology. This diversification in spine coverage is driven by modifications in genetic signaling. These changes are facilitated by CRISPR-Cas9 and small molecule inhibition.
A study published in the journal Marine Biology and Evolution reveals how this variation in spine coverage evolved over time. It found that the spines of pufferfishes were initially developed as a defense mechanism, but later evolved into an ornamentation for the skin.
This morphological diversity has enabled the pufferfish family to adapt to a wide variety of ecological niches by allowing it to exploit diverse prey resources. As a result, there is a large variety of different species in the family.
Among these are the tripod fish, which perches over the seafloor of deep ocean waters using three elongated projections from their modified fins. These fish can be found in the Atlantic, Pacific and Indian Oceans.
When puffer fish feel threatened, they inflate their skeletons to fend off predators. The skin is adapted for this, and it expands by 40% of its original size.
When they are inflated, their bodies become a rigid, ball-shaped structure covered with spines that stick out of the surface of the skin. This spiky armor makes them unappealing to potential predators, and if they are attacked, the spines are highly toxic.
They also have some spines that are visible even when they are not inflated. These spines are caltrop-like, and are embedded in connective tissue pockets within the thick dermis layer of their skin.
These pockets are filled with an amorphous, acellular, PAS positive material, which is richly supplied with fine blood capillaries. This amorphous tissue is thought to be a product of CRISPR-Cas9 gene editing.
The skeletal system of puffer fishes is unique. It lacks ribs, but it has fused bones in the cranium and jaw. It is not very complex, but it has evolved a number of characteristics that make it a good swimmer and help it survive in the oceans.
Despite their slow speed, puffer fish are very maneuverable and able to swim in a series of different movements. They do this by using their pectoral, dorsal, anal, and caudal fins. These movements give them an evasive burst of speed that can deter predators and give them an advantage over them.
Pufferfishes are members of the Tetraodontidae family, which also includes triggerfish and tripodfish. They are found throughout the world in a variety of habitats, including tropical and subtropical waters.
They are primarily carnivorous, and their main prey is mollusks, but they also eat a variety of algae. They can be found in fresh and saltwater, though they prefer the warmer waters of the southern hemisphere.
When puffer fish are threatened, they inflate their skeletons by taking in water and expanding their stomachs. This is a very unusual physiology, and it helps the fish fend off predators.
In addition to the lungs, puffer fish have special muscles that allow them to inhale water and pump it into their stomachs. This pumping allows them to inflate their bodies to three times their normal size without breaking their ribs or pelvic fins.