CREATURE FEATURE: Ninja of Death!!!

Hapalochlaena maculosa on the prowl!

 One blue-ringed octopus (Hapalochlaena) weighing 25 grams possesses enough poison to fatally paralyze ten adult humans (source) Found in tide pools in the warm Pacific waters and with a body only five centimeters wide and an arm span of only ten centimeters, the blue-ringed octopus secretes a metabolic toxin called tetrodotoxin (source), abbreviated as TTX in its saliva. By sequestering this bacterially produced TTX in its tissues (source), the blue-ringed octopus manages to retain this deadly toxin in its tiny, molluscan body without harming itself.

Map of the Pacific Ocean- home to the BRO

One milligram of TTX is potent enough to kill a full grown human (source), a very adequate defense to overcompensate for its vulnerable size—nevertheless, the blue-ringed octopus is not the only animal able to isolate this toxin. TTX has been isolated in not only the blue-ringed octopus, but in some species of the pufferfish, Californian newt, parrotfish, frogs of the genus Atelopus, sea stars, angelfish, and the xanthid crab (source). Creating a symbiotic relationship with the common marine bacteria called Pseudoalteromonas haloplanktis tetraodonis (source), the blue-ringed octopus obtains this potent neurotoxin by creating ideal living conditions for the bacteria (source). TTX works by “blocking channels that control the movement of sodium ions across nerve and muscle cell membranes, halting their electrical activity;" (source) thus, the victim experiences overall numbness and paraesthesia before paralysis sets in and convulsions, mental impairment, and cardiac arrhythmia occur.

Death usually occurs anywhere between 20 minutes to eight hours after the victim has come into contact with the neurotoxin (source). With such extreme effects, the blue octopus’s ability to secrete this powerful toxin has scientists wondering why these animals are not affected by the toxin themselves. The most probable theory is simple: evolution. Upon examining these highly dangerous animals in more detail, it became apparent that their sodium channels had evolved to resist the dangers of the toxin. Whereas the pufferfish simply developed eight different versions of sodium channels, the blue-ringed octopus had developed a “slightly different sodium channel receptor" (source) which made it immune to the paralyzing effects of the TTX. These mutations make the blue-ringed octopus capable of withstanding roughly 500 to 1,000 times the concentration of TTX in comparison to these other non-toxic fish (source). 

Blue-Ringed Octopus's body in partial defense mode.

However, these creatures are not the only ones that have adapted to the toxin, and predators such as garter snakes in the western United States have similarly evolved resistance to TTX and can feast on highly toxic newts (source); natural selection at its best. No longer affected by the poisonous newts, these snakes have been found to have “independently evolved TTX-resistant sodium channels… and are so resistant that the dose of toxin needed to immobilize them is sufficient enough to kill over 900 people" (source).  Does this mean that the predators of the blue-ringed octopus have the potential to have a symbiotic relationship with the TTX-producing bacteria? Only time will tell. For the mean time, watch out when you go in a tide pool!

Alisha and Ashley; OUT.