Whilst drifting through my usual random searches to find something interesting, I stumbled across an article on the box fish. I had never come across such a thing, and after reading the article I don’t think I ever will, but understanding some of it’s attributes led me straight into a chemistry lesson.
I’ll link to the article on box fish at the end – apologies to younger readers as the author was fairly foul-mouthed but undoubtably humorous.
The box fish is a small fish that feeds on algae and crustaceans in coral reefs mainly in Australia and Asia. Their recognisable shape is given by a fused skeleton, but this also handicaps the box fish by restricting any and all movement as its body cannot twist or turn. Nevertheless, the adaptations of the box fish are intriguing.
Firstly, compared to the tiny, agile fish of shallow waters, the box fish surely has no place. You could quickly assume that it would have died off thousands of years ago – or is at least on the endangered species list. However, because most of its body is encased within the skeleton, the box fish isn’t the most appealing fish to any nearby predators. And, even if singled out, the box fish sports impressive manoeuvrability when needed.
Its other adaptation that fascinated me was its penchant for poisons. As many marine biologists will tell you, putting these fish in a tank with others is a bad idea. When frightened or threatened, the box fish excretes a toxic goo from cells all over its body. This is notably different from most other fish using toxins as it is not concentrated in the box fish’s tissues. The chemistry of this fascinates me as – previously unknown to me – the ostracitoxin given off is from the same category of chemical compound (surfactants) as things like soap (which slightly worried me at first). At a basic level, surfactants disperse through water very well and, in essence, make things that don’t dissolve in water do just that (especially fats and oils). It was thought that the cells were directly attacked by these surfactants (as they are made from some form of lipid – containing fats). Yet, it has been found that ostracitoxin targets red blood cells specifically so the attacker (or the unlucky tank-mate) cannot get enough oxygen and dies of asphyxiation.
After reading all of this article, the only thing left to do was to research more. A prettily bound book (or at least that is what is appeared to be on the pdf) held some answers about the effects of certain surfactants on humans and mammals. You are, of course, more than welcome to research further and have a look at this and I will link it below. However, I would recommend not doing so unless you have copious amounts of spare time and interest in the subject. All in all, the 24 pages show that the common surfactants that we absorb when washing up or when cleaning our teeth are at such low concentrations that human health is not affected by them (in terms of infections, cancer, and numerous other medical aspects). Nevertheless, one surfactant (Polysorbate 80) is being used in some vaccines to weaken the blood-brain barrier and allow drugs to reach the brain when necessary. One article argued that there was too little evidence of its safety to be put in a vaccine, but then proceeded to provide a very one-sided argument so their points should be taken with a pinch of salt. Despite the fact that Polysorbate 80 has been recognised to cause cancer and other illnesses in rats, there is no evidence of the same result in humans and neither is there a record in that article of the doses needed to achieve that.
The concentration of ostracitoxin excreted by the box fish is much higher than a human’s daily intake of numerous surfactants so its effects on predators is wildly disproportionate to what we could expect to see in our lives. It seems, to me at least, that surfactants are safe in our houses (but less so in our aquariums).