The family of puffer fish (Tetraodontidae) belongs to the suborder of puffer fish-like (Tetraodontoidei).
It consists of two subfamilies, the round-headed puffers (Tetraodontinae) and the sharp-headed puffers (Canthigasterinae). The latter consists of only one genus namely Canthigaster. About 200 species are currently known.
Most species are found in salt water, coastal areas and coral reefs. Some species live in fresh or brackish water.
Puffer fish got their name because of their body shape. They have a rounded, squat shape and thus differ significantly from the body shape of other coral fish.
The head and eyes are strongly developed in comparison to the body.
Locomotion is mainly through the pectoral fins. The dorsal fin and the anal fin are only supportive and the caudal fin serves as a rudder. They have no pelvic fins. Although puffer fish are not very fast, they are extremely agile in all directions.
Their body length varies between 2 cm (Carinotetraodon travancoricus) and 120 cm in the case of the giant puffer (Arothron stellatus), which is also sold in the aquarium trade and is maintained. It goes without saying, however, that such an animal cannot be kept in a normal home aquarium.
In case of danger, puffer fish can inflate themselves to appear much larger to attackers. Often this does not succeed in catching the now much larger animal.
They have a leathery, poisonous and scaleless skin with short spines that serve as barbs when they inflate. It is hardly possible for predatory fish to devour the puffer fish. However, this inflation should not be forced by the keeper, because it means pure stress for the animal.
Its own, beak-like mouth consists of teeth that have grown together to form an upper and a lower row of teeth. This makes it one of the highly developed bony fish, which are scientifically referred to as Tetraodontidae = four-toothed.
A matter that should not be underestimated is the right food. Puffer fish must be observed as closely as possible with regard to their nutritional status and, above all, the food they accept must be offered. If possible, they should be provided with smaller food (shrimps, mussels, snails). Puffers are quite prone to begging, which can tempt the keeper to overfeed. In general, puffer fish are not easy to socialize in the aquarium and are therefore more for the experienced aquarist.
Last but not least, we think it is important to point out that in such tanks, glass heaters, thermometers and cables must be well protected because the animals would also like to bite into them.
An interesting paper by Michael Megerle on toxicity.
Tetrodotoxin - The poison of the puffer fish.
According to a Jewish diet, the toxicity of puffer fish has been known for a long time. Quote: "You must not eat this of the things that live in the water: you can eat anything that has fins and scales. But you must not eat anything that does not have fins and scales. It shall count as unclean for you” (Deuteronomy 14).
The most well-known representative among the puffer fish is the fugu. In Japan it is valued as a culinary specialty, although (or perhaps because?) it is poisonous. In Japan, anyone involved in catching, trading or preparing fugu must have a special license lasting years. Despite this, people still die from eating it. In Germany, the import and preparation of fugu as food is prohibited by law.
Other known marine organisms that also contain tetrodotoxin include the blue-ringed octopus, the parrotfish, certain starfish, some species of crab, certain sea snails, and some species of algae. The dwarf puffer (Carinotetraodon travancoricus), popular with aquarists, is poisonous, like the majority of all representatives of this species.
The Deadly Poison
The venom content of a puffer fish is very dependent on geographical occurrence and seasonal criteria, such as the spawning season. The poison can be ingested through skin contact, ingested, or inhaled as a powder. The main component of puffer fish venom is tetrodotoxin (TXX), which is primarily formed in the skin, liver, gallbladder, intestine, gonads and eggs of the fish. Tetrodotoxin is one of the most potent known non-proteinaceous toxins. The lethal dose for an adult human is 1-2 mg. Only 16 millionths of a gram for a 20 gram mouse. TXX is 1000 times more toxic than cyanide and 10-100 times more toxic than black widow venom. Tetrodotoxin is water soluble and heat stable.
The neurotoxin does not affect the cranial nerves, only the peripheral nerves. Here TXX inhibits the transmission of nerve stimuli by blocking the transport of sodium ions through the cell membranes. A single molecule per channel is sufficient for no more action potentials to be triggered. The consequences are motor and sensory paralysis.
The irritability of the skeletal muscles and the ability of the heart muscle to contract are reduced. The effects of the poison then lead to complete paralysis if the person is fully conscious. Death then occurs from respiratory paralysis or cardiac arrest. If the poisoning is detected early, there is a chance of stabilizing the body's circulation and breathing. In rare cases, the effects of the poison can wear off within 24 hours without leaving any permanent damage to the victim.
There is evidence that tetrodotoxin is not produced directly by the marine organisms named above, but by protozoa (bacteria) with which they live in symbiosis.
For example, the amphibians and fish mentioned above do not produce TXX in isolation in breeding stations. However, if they are fed with tissue material from toxin-producing conspecifics or released into the wild, toxin production begins.
Tetrodotoxin is used in conventional medicine alongside morphine in malignant diseases as a pain and cramp-relieving drug.
The mode of action of the poison in its purest form
The symptoms of poisoning appear at a rapid pace. The first symptoms appear after just 5 to 30 minutes. These include numbness (first in the mouth area after consumption), tingling sensations in the face and limbs, weakness, dizziness, coordination difficulties, unsteady gait, muscle cramps, nausea and vomiting. When the numbness has spread throughout the body, a floating sensation is common. Then paralysis sets in and spreads to the heart muscle and respiratory tract. Circulatory disorders, tachycardia or bradycardia, cyanosis, and chest pain occur. Due to the paralysis, the victim is usually no longer able to communicate. Death occurs with full consciousness from respiratory paralysis or circulatory failure. The time from poisoning to death can be very short. The death of a victim within 17 minutes is documented.
There is no antidote yet, poisoning is always life-threatening!!
(Source: http://homeda.wordpress.com)
