The blue-ringed octopus (Hapalochlaena) is one of the world's most venomous marine animals, although docile and small, they contain a venomous neurotoxin - tetrodotoxin is powerful enough to kill several humans. When the octopus is agitated, iridescent blue rings appear and pulsate within the maculae. This little guy was nearly eaten by striped eel-tail catfishes (Plotosidae). Seen at Malapascua, Philippines, Feb 2017
