4 Things About Pufferfish

4 Things About Pufferfish

Tetrodotoxin (TTX)

Most pufferfish are carriers of lethal TTX produced from marine bacteria through diet - previously accumulated through the food chain. It implies that non-toxic puffers in bacteria-free environments can get turned toxic with supplementation (except being genetically immune to it themselves). It's found primarily in the liver and gonads, with lesser amounts in the intestines + skin from exocrine gland secretions, alongside trace amounts in muscles.

Vulnerable larvae have most of the toxin on the skin - acquired maternally before birth for protection until obtained via diet - predators spit them out (expectedly tastes horrible).

They are the most poisonous fish, including the second-most of all vertebrates after the golden poison frog. TTX is ~1200x more potent than cyanide to humans and has an overall kill percentage of ~60%. There's no current antidote, and one puffer can kill ~30 average-sized adults if left untreated.

If intoxicated, the neurotoxin blocks your sodium channels, impeding nervous system function and causing a paralysing/numbing effect. Other symptoms involve dizziness, vomiting, lowered blood pressure, rapid heart rate and 'prickling' sensations over the body. The most dangerous aspect will be paralysis of the diaphragm - preventing breathing and going comatose. Treatment entails intestinal decontamination and life support until the toxin gets broken down.

Dolphins have gotten observed playing 'pass the puffer' to get high off the supply - they chew on, knock and throw them about but don't eat. The dolphins are usually left unharmed, only getting tranced from inhaling the chemicals emitted, which are like narcotics to them.

Anti-Predator Adaptations

Pufferfish are typically slow and clumsy; instead, maybe having to hide or deter predators since they're unlikely to escape by speed. However, they have good sight - in addition to independent eye movement for early detection and can use a burst of energy to nimbly shoot away, just with poor precision, even with their tailfin.

Some have subtle colouration to blend in with their surroundings, which could be a size factor - often found in less threatening smaller ones that're better at hiding. Others have a display of vibrant colour known as aposematism - a warning of their toxicity - this could perhaps be more prevalent in bigger ones with more potential to stand up to and fend off predators.

Technically, their teeth could be an anti-predator adaptation because they eat robust shellfish, molluscs, and crustaceans. Puffers have a 'beak' comprised of four teeth at the front and can deliver a strong, concentrated bite.

Otherwise, as a last resort to threats, they have their infamous ability to take in water/air to puff up. They quickly inflate into a ball shape, facilitated by their highly elastic stomach and rib-free pectoral muscles - enlarging to roughly double or even triple their original size, except reducing speed and making themselves helpless until expulsion.

The process makes them unpalatable, which, combined with their spines/quills on the skin instead of scales, makes them really difficult to eat and could lead to jamming the predator's throat and locking the jaw open. It can inflict asphyxiation, protrusive damage and death. Even if they get eaten, they get revenge kills due to TTX.

Some sharks, however, can eat them and not get afflicted by poison because they're immune to the bacteria; also, having so much mass relative to the amount of toxin (some weigh over a tonne) - so they can break it down more efficiently than other creatures.

Counter Current System (CCS)

Fish exchange gases by pulling oxygenated water through their mouths and pumping it over their gills. The CCS enables oxygen extraction that's 3x the rate of a human due to the water arrangement flowing past the gills in the opposite direction of the blood (hence 'counter').

As the flow involves the blood next to the water travelling in opposite directions, the oxygen from the water molecules transfers by diffusion and gets absorbed into the blood - so the oxygen saturation percentage increases.

Importance of Nitrogen Cycle

Fish produce organic waste in the form of poisonous ammonia, contaminating the water they live in - however, there's a natural nitrogen cycle that breaks down the harmful compounds due to biological bacteria (though it's still more efficient to have filters). An insufficient bacteria population equivalates to higher toxin levels that kill fish by burning their gills.

First, ammonia gets broken down and converted into less poisonous 'nitrites' by 'nitrosomonas' bacteria, and then nitrites are converted to even less harmful 'nitrates' by 'nitrobacter' bacteria. Ammonia and nitrites need to be kept at zero, while nitrates must be kept as low as possible (a small reading for the nitrate colour indicator via a test kit monitor).

Pufferfish, in particular, have no scale protection, meaning they're more receptive to disease, pollution and sudden changes in water states.

Ensure nitrates don't build up to a toxic level by changing ~30% of the tank water fortnightly. Equipment should be cleaned using waste tank water but never tap water, as chlorine kills bacteria essential for the cycle, alongside destroying a fish's natural protective mucous membranes. A dechlorinator can be used for tap water; or it can get left to sit for 24 hours so the chlorine naturally dissipates.