The only lethal octopus is this creature found in the waters around Australia. Hapaloclaena maculosa is a small 20 cm octopus , dark brown to dark yellow in color, but with brilliant blue rings that "glow" when it is angry. It is this glowing of the blue that makes it so dangerous, particularly to children who are fatally attracted to it by the rings.
It is found in shallow coral and rock pools , particularly after storms, digging around for crabs. The octopus has a small beak at the junction of its eight arms, and rather than manufacturing ink, it makes poison in its salivary glands. The toxin closely resembles tetradotoxin (TTX) and its bite can produce a flaccid paralysis much quicker than eating puffer fish.
The bite may be almost imperceptible, and many victims notice only a tiny drop of blood at the site. Bites are nearly always associated with handling the creature, as in draping it over the arm, hand or shoulder. The poison is neuromuscular and produces a muscular weakness and eventually respiratory paralysis. Children should be warned t leave them alone, irresistible as they may seem due to the glowing blue circles.