Camouflage is used by prey to avoid detection by predators. Using camouflage is obviously in many cases a great idea, but it also has a number of costs, one of which is that the camouflaged prey lives life in the slow lane. Movements will have to be avoided as much as possible in order not to alert predators despite the camouflage. Aposematic coloured prey, that is prey using clear and contrasting colours, informing potential predators that the aposematic coloured prey is unprofitable, can move more or less freely relying on its bright colours to warn of predators. Examples of aposematic coloured prey that are poisonous are poison arrow frogs,
many nudibranchs , lionfish and a host of other species. Note that aposematic colouring is of advantage to both prey and predator, as prey are not harmed unnecessarily, and predators avoid getting poisoned. Thus, there should be a high pressure for evolution to favour aposematic colouring.
The production and storage of poison is highly likely to be costly. Many poisons are proteins, and proteins need nitrogen, which is in short supply in many if not all ecosystems. Thus, highly poisonous animals are expected to be clearly marked, warning of predators of making a costly mistake for both prey and predator.
Tetrodotoxin (anhydrotetrodotoxin 4-epitetrodotoxin, tetrodonic acid) is a highly potent neurotoxin. It kills animals by blocking nerves from firing, which essentially will lead to a shutdown of body functions. It is found in a number of animals, such as newts, snails, bluering octopus and others, most of which are clearly aposematic coloured. However, there is a major group of animals that have high levels of tetrodoxontin, but are more or less camouflage coloured.
The puffers, including porcupinefish and burrfish are all, to my knowledge, coloured in order to blend in in the background of their habitat.
This makes no sense at all. Puffers and their relatives should be brightly coloured in red, black, yellow or white, preferably with a contrasting pattern as well, in order to inform puffer predators about their imminent death if ingesting a puffer.
Porcupinefish and burrfish even have spines in order to defend themselves. Why haven´t evolution taken care of these fish and got them an outfit more representative of something really poisonous? Well, to be perfectly honest, I do not have the slightest idea!