Friday, 28 March 2008

Occy Health & Safety

I used to have a pet southern blue-ringed octopus (Hapalochlaena maculosa). Well, it wasn't exclusively mine. It was a shared responsibility for those of us who used the aquarium room. We looked after it for a few weeks before it went on public display. That was more than enough time to develop an affection for the lively character.

Southern blue-rings are cute little things. Not that you'd want to pick one up and pat it … That's a mistake you'd only make once. A blue-ring's body is packed with tetrodotoxin (TTX), a fast-acting toxin produced by bacteria living within the octopus' tissues. Not only does TTX occur in the salivary glands, from where it is injected into prey and predator, but it's also found in the arms. No wonder our blue-ring had attitude. What we'd interpreted as an outgoing personality was really the cephalopod version of 'Dirty' Harry Callaghan. (When we fed it, our octopus would flash its peacock blue markings. We thought it was happy with the table service but it seems that our colourful friend was looking at its pallid providers and asking the question 'Feeling lucky, pink?'*)

Blue-ring envenomation affects the mammalian nervous system, especially the somatic system. The result is paralysis of voluntary muscle, including muscles involved in respiration. And that's the lethal impact of a blue-ring — not enough oxygen. There's no direct effect on the heart or brain but once breathing stops, they succumb to hypoxia.

Bad, huh? Well, it gets worse.

In their review of molluscan toxins, John Williamson and Jacquie Rifkin note:
The absence of direct brain effects of TTX and TTX-like substances can result in an apparently dead patient who is receiving skilled resuscitation listening helplessly in a paralysed state to everything that is said and done.

So take my advice. Don't get bitten.

Although they get all the publicity, blue-ringed octopuses aren't the only molluscs to harbour TTX-manufacturing bacteria. Microscopic toxin factories occur in at least eleven snails families, including Nassariidae, Olividae, Naticidae and Muricidae. These snails are unlikely to take down a human with a radula scrape but may cause problems if served up on a seafood platter. There is a well-established precedent among the backboned animals.

There’s got to be something I haven’t tried. Huh? Hey, hey, what’s this? Fugu!

It is a blowfish, sir. But I should warn you that one—

Come on, pal. Fugu me!

So respect the molluscs. (And avoid the blowfish while you're at it.)


* Sorry