That's just a note to myself; I'm getting the impression that everything in Australia is somehow lethally poisonous. I was just reading this paper about octopus caught off the northwest coast of Australia (for me, reading about obscure cephalopods combines scientific curiousity, the erotic appeal of the exotic, and a little gustatory anticipation), and I'm looking at the pretty picture and thinking "yum," as I'm sure you all are, too, and then I notice the alarming message: these guys are loaded with saxitoxin. Saxitoxin is a potent alkaloid neurotoxin—it binds to and blocks sodium channels, which means the poison basically kills all axon conduction in your nervous system. A good dose has detectable effects within minutes to hours, causing flaccid paralysis, respiratory failure, and death. It's only occasionally fatal, since recovery is possible if artificial respiration is provided, but still—who wants to visit Australia and end up limp and unconscious with a tube down your throat?

The LD50 is approximately 8 µg/kg, and these octopuses carry about 2500 µg/kg in their tissues. The toxin is widespread, unlike the tetrodotoxin found in blue-ringed octopuses, which is concentrated in their salivary glands. While not as concentrated as is sometimes found in shellfish tainted with saxitoxin produced by dinoflagellates, it's still high enough to be a health risk, especially if the consumer is someone willing to gorge themselves on mass quantities of invertebrate flesh. Like me.

I wonder if Australians imported sheep, rabbits, and cane toads just so there'd be a few animals around who aren't threatening to creep up on them and kill them.

Robertson A, Stirling D, Robillot C, Llewellyn L, Negri A (2004) First report of saxitoxin in octopi. Toxicon 44(7):765-771.