Today I will talk about a fantastic little creature called the blue-ringed octopus (Hapalochlaena lunulata). This is yet another venomous animal that haunts the waters of Australia as well as the Pacific and Indian Oceans. There are several species within the Hapalachlaena genus and I will be writing about that, as all species share the same general characteristics.
Though it is very small and vulnerable, the blue-ringed octopus is fairly docile unless provoked. It likes to hunt in tide pools and shallow reef waters where it scrounges out small crabs and shrimp that are killed quickly with its powerful venom. It is diurnal, so it mainly only comes out to hunt during the daytime. When it catches a prey item such as a small crab, it uses its sharp beak to break open the shell and eat out the insides.
When disturbed, the blue-ringed octopus will show the elaborate coloration that it is named for. Chromatophores in cephalopods such as octopuses, squid, and cuttlefish, are units of neuron controlled glial, muscle, and sheath cells. These are contained in an elastic sac that can expand and contract to change the opacity and translucency of the pigment within. The blue-ringed octopus is unusual in that it does not have chromatophores over its rings, but only surrounding them and underneath them. The iridescent, electric blue pigments in its skin are always present, yet only visible when it wishes them to be. Certain muscles above the iridophores, specialized light reflecting organelles within the cells, hide the blue-green light reflectors until they are contracted and expose the bright color. This is a very quick and highly controlled method of display that is not seen in other species of octopus.
A blue-ringed octopus may only be from five to eight inches in length, but it packs potent enough toxins to kill an adult human in a matter of minutes. It has special salivary glands behind its beak containing bacteria that produce the deadly cocktail it delivers. An envenomation from one of these octopuses starts out with nausea and quickly progresses to numbness, difficulty swallowing, visual abnormalities, and eventually motor and respiratory arrest. Because there is little to no effect on cardiac muscles, a victim’s heart may continue to beat until asphyxia sets in and the central nervous system is deprived of oxygen completely. The bite itself may be painless and show only vague evidence of wound infliction. What makes the venom so deadly is the tetrodotoxin (TTX). This is the same toxin found in pufferfish and is designed to block sodium channels on neuron cell membranes, which in turn causes total paralysis throughout most vital areas of the body (minus the circulatory system). There is currently no quick fix in existence for blue-ringed octopus envenomation, so treatment is limited to life support measures, such as artificial respiration, until the effects of the venom wear off. Sometimes victims may be fully conscious and aware of their surroundings, but unable to move or speak due to the paralysis. Those who survive the first twenty four hours will typically make a full recovery.
Blue-ringed octopuses might be scary, but they are tender love-makers just like we imagine ourselves to be. A male blue-ring will court the female of his choice by approaching her and gently caressing her with his modified arm used for delivering sperm. He will then pull her close to him by grasping her mantle and use this arm to deposit packets of sperm inside her mantle cavity again and again until she is decides she is done. Sometimes the male has to be removed by force because he wants to keep going. Male blue-rings aren’t picky about who they court and will often attempt to mount other males of their own species. However, these interactions are usually much shorter lived and result in both males withdrawing, possibly in embarrassment, without a struggle or exchange of sperm. A little while after a female has been fertilized, she lays a single clutch of about fifty eggs and incubates them with her arms for up to six months. As with all octopuses, she does not eat during this time and dies shortly after her babies emerge from their eggs.
Unfortunately for such a pretty and intelligent animal, the maximum lifespan for a blue-ringed octopus is only two years. But hopefully it is two years well spent hunting, fascinating curious humans, and making sweet, sweet octopus love.
1. Mäthger, Lydia M., et al. “How does the blue-ringed octopus (Hapalochlaena lunulata) flash its blue rings?.” The Journal of experimental biology 215.21 (2012): 3752-3757.
2. Yotsu-Yamashita, Mari, Dietrich Mebs, and Wolfgang Flachsenberger. “Distribution of tetrodotoxin in the body of the blue-ringed octopus (Hapalochlaena maculosa).” Toxicon 49.3 (2007): 410-412.
3. “Australian Marine Envenomations.” Marine Envenomation. University of Sydney, n.d. Web. 23 June 2015. <http://sydney.edu.au/medicine/anaesthesia/resources/venom/marine_enven.html#bluering>.
4. Cheng, Mary W., and Roy L. Caldwell. “Sex identification and mating in the blue-ringed octopus, Hapalochlaena lunulata.” Animal behaviour 60.1 (2000): 27-33.