Order Tetraodontiformes ( Tetraodontiformes )
Family Tetraodontidae ( Tetraodontidae )
Genus Tetraodon — Tetraodon.
Representatives of the genus live in tropical seas, as well as in African and Indian rivers. They eat everything alive, including algae, pieces of coral, tunicates, and sea sponges. Some species spawn near the coast in the surf zone. Some species inhabit brackish and fresh waters. They are characterized by strong jaws with four robust bone plates. Unlike most fish, the main propulsion for pufferfish is provided by the pectoral fins and, partly, the dorsal and anal fins.
The fan-shaped dorsal fin is shifted backward. Pelvic fins are completely absent. The tail is usually tightly compressed and slightly turned to the side. It is used for swift and powerful dashes. With the help of strong pectoral fins, the fish can abruptly change their direction of movement, including moving backward, or hover in one place.
Despite their apparent clumsiness, they are very agile and maneuverable. Their movements resemble a bee rapidly fluttering its wings, frozen in the air near a flower. Their ability to inflate like a ball is widely known, and this is done not only in direct danger, but also without visible external stimuli.
The ability to turn into a hard, spiky ball is a good defense against birds and other numerous enemies lying in wait for this fish. A cavity extends from the stomach, which fills with water or air when frightened, giving the fish a deterrent spherical shape.
Predatory fish, aggressive towards each other and fish of other species. They do not eat dry food, feeding exclusively on meat diet. Fish can only be transported in hard containers, as they can puncture or bite through the wall of a plastic bag. By reproduction type, pufferfish are divided into two groups: some lay eggs on a substrate which is then guarded by the male, while others spawn in the water column, and the eggs sink to the bottom or float. Under normal conditions, secondary sexual characteristics in pufferfish are absent, so it is impossible to reliably distinguish males from females.
I. Parshkov proposed an original method for determining sex. It consists of the following. Two fish are placed in a spacious aquarium, preferably a meter long, and their behavior is observed. If an irrepressible fight begins and both fish attack each other, this means that the individuals are most likely males. In the case of placing two females, they “sink” to the bottom without showing excessive aggressiveness, while at the same time preventing another individual from entering the occupied territory.
If a pair has formed, the male attacks the female, and she moderately fights back, allowing him to nip her. The dorsal and pectoral fins suffer the most. The tail is bitten last. To prevent the fish from accidentally killing each other through oversight, males and females are separated by a sturdy mesh that allows them to see each other and sense chemical signals—pheromones.
— Figure Eight Puffer — Tetraodon biocellatus [Tirant, 1885]. Synonym: Tetraodon steindachneri, Chelonodon biocellatus. (English: Eye Spot Pufferfish, Figure Eight Puffer, Palembang Pufferfish, Sumatra Puffer). Thailand, Malaysia, Sumatra, Borneo. 9 cm. Coloration varies depending on age and habitat. Each fish has its own unique pattern. The body is brownish or black, with bright yellow dots and meandering lines. The belly is white in juveniles, but mottled brown in adults.
Below the dorsal fin, at the base of the caudal fin, and on the back, black oval spots with a yellow border stand out. Looking at the fish from above, it is easy to notice two distinct eye-spots on the body behind the dorsal fin, for which the species got its name — biocellatus (eye-spot). Females are slightly larger than males. Unlike other pufferfish species, color brightness does not fade with age. Fins are rounded.
The fish are very aggressive, starting fatal fights with representatives of other species, even larger ones. Aggressive towards smaller fish. Large females also constantly drive conspecifics away from food. Older ones become territorial and aggressive. Young individuals are usually peaceful.
It is best to keep a pair of puffers in a separate medium-sized aquarium. They occupy the middle layers of water. Representatives of this species are sluggish and spend most of the day in shelters. Lighting in the aquarium is diffused. The aquarium needs to be well planted with plants along the sides. The plants used must be hard-leaved and tolerate brackish water.
They feed on all large types of animal foods, small fish, and are very fond of mollusk meat, the shells of which they crush with their powerful teeth. Brackish water is essential for a healthy and long life. The water needs to be hard, pH 7-8, with the addition of salt at the rate of 1 tablespoon per 10 liters; they get sick in freshwater. The tanks must have good filters, water changes are performed weekly, as pufferfish easily go into shock with sudden changes in conditions.
Reproduction is possible at the end of the first year of life. Spawning and fry care in this species resemble the corresponding behavior of cichlids. The pair lays eggs on a flat stone. The male guards the clutch. They live up to 18 years. pH 6.5-8.0; dH 7-16°; T 22-27°C.
Identification: Figure Eight Puffer — Tetraodon biocellatus.
Tetraodon cutcutia, fluviatilis, lineatus.
Colomesus asellus, Colomesus psittacus. 
