Hapalochlaena maculosa—the southern blue‑ringed octopus—is a small, highly venomous octopus (family Octopodidae). When threatened it displays brilliant blue rings as an aposematic signal. Salivary glands contain tetrodotoxin (TTX), a potent neurotoxin causing rapid paralysis.
Ecology & Biology
Diet: small crustaceans and fishes subdued with the beak and venom.
Reproduction: females brood eggs in crevices and are semelparous, dying after hatching.
Behaviour: crevice‑dwelling and camouflaging by day; more active at night.
Identification
Mantle length ~3–6 cm; rings brighten from faint to vivid blue on a yellow‑brown background when aroused. Large eyes; relatively short arms with fine, dense suckers.
Size & Longevity
Length: mantle 3–6 cm; arm span ~12–20 cm.
Weight: generally<100 g.
Life: ~1–2 years.
Range & Habitat
Southern Australia; intertidal to shallow subtidal (~0–20+ m), favouring rocky reefs, seagrass, rubble and harbour pilings.
Venom & Risk
Toxin: TTX blocks voltage‑gated sodium channels.
Hazard: bites are potentially fatal; symptoms can include numbness, slurred speech and respiratory compromise.
First‑aid (educational): call emergency services; apply a pressure‑immobilization bandage; provide assisted ventilation.
IUCN: marked here as Not Evaluated (NE).
