Blue-ringed octopus

Blue-ringed octopuses
Greater Blue-ringed Octopus (Hapalochlaena lunulata)
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Order:	Octopoda
Family:	Octopodidae
Subfamily:	Octopodinae
Genus:	Hapalochlaena Robson, 1929
Species
See text.

The blue-ringed octopuses (genus Hapalochlaena) are three (or perhaps four) octopus species that live in tide pools in the Pacific Ocean, from Japan to Australia (mainly around southern New South Wales and South Australia^[1]). They are currently recognized as one of the world's most venomous marine animals.^[2] Despite their small size and relatively docile nature, they can prove a danger to humans. They can be recognized by their characteristic blue and black rings and yellowish skin. When the octopus is agitated, the brown patches darken dramatically, and iridescent blue rings or clumps of rings appear and pulsate within the maculae. Typically 50-60 blue rings cover the dorsal and lateral surfaces of the mantle. They hunt small crabs, hermit crabs, and shrimp, and may bite attackers, including humans, if provoked.

Classification

The genus was described by British zoologist Guy Coburn Robson in 1929. There are three confirmed species of Hapalochlaena, and a fourth is still being researched:

• Greater Blue-ringed Octopus (Hapalochlaena lunulata)
• Southern Blue-ringed Octopus or Lesser Blue-ringed Octopus (Hapalochlaena maculosa)
• Blue-lined Octopus (Hapalochlaena fasciata)
• Hapalochlaena nierstraszi - described in 1938 from a single specimen from the Bay of Bengal; the validity of this taxon has been questioned.^{[citation needed]}

Behaviour

An individual blue-ringed octopus tends to use its dermal chromatophore cells to camouflage itself until provoked, at which point it quickly changes colour, becoming bright yellow with blue rings or lines.

Feeding

Their diet typically consists of small crab and shrimp, but they may also feed on fish if they can catch them. They pounce on their prey, paralyze them with venom and use their beaks to tear off pieces. They then suck out the flesh from the crustacean's exoskeleton.^{[citation needed]}

Reproduction

The mating ritual for the blue-ringed octopus begins when a male approaches a female and begins to caress her with his modified arm, the hectocotylus. A male mates with a female by grabbing her mantle, which sometimes completely obscures the female's vision, then transferring sperm packets by inserting his hectocotylus into her mantle cavity repeatedly. Mating continues until the female has had enough, and in at least one species the female has to remove the over-enthusiastic male by force. Males will attempt copulation with members of their own species regardless of sex or size, however interactions between males are most often shorter in duration and end with the mounting octopus withdrawing the hectocotylus without packet insertion or struggle.^[3]

Blue-ringed octopus females lay only one clutch of about fifty eggs in their lifetime towards the end of autumn. Eggs are laid then incubated underneath the female's arms for approximately six months, and during this process she does not eat. After the eggs hatch, the female dies, and the new offspring will reach maturity and be able to mate by the next year.

Venom

Blue-ringed octopus from New South Wales, Australia

The blue-ringed octopus is 12 to 20 cm (5 to 8 inches), but its venom is powerful enough to kill humans. There is no blue-ringed octopus antivenom available.

The octopus produces venom that contains tetrodotoxin, 5-hydroxytryptamine, hyaluronidase, tyramine, histamine, tryptamine, octopamine, taurine, acetylcholine, and dopamine. The major neurotoxin component of blue-ringed octopus venom was originally known as maculotoxin but was later found to be identical to tetrodotoxin,^[4] a neurotoxin which is also found in pufferfish and cone snails that is 10,000 times more toxic than cyanide.^[5] Tetrodotoxin blocks sodium channels, causing motor paralysis and respiratory arrest within minutes of exposure, leading to cardiac arrest due to a lack of oxygen. The toxin is produced by bacteria in the salivary glands of the octopus.^[6]

Treatment

First aid treatment is pressure on the wound and artificial respiration once the paralysis has disabled the victim's respiratory muscles, which often occurs within minutes of being bitten. Tetrodotoxin causes severe and often total body paralysis; the victim remains conscious and alert in a manner similar to curare or pancuronium bromide. This effect, however, is temporary and will fade over a period of hours as the tetrodotoxin is metabolized and excreted by the body. It is thus essential that rescue breathing be continued without pause until the paralysis subsides and the victim regains the ability to breathe on their own. This is a daunting physical prospect for a single individual, but use of a bag valve mask respirator reduces fatigue to sustainable levels until help can arrive.

Definitive hospital treatment involves placing the patient on a medical ventilator until the toxin is neutralized by the body. The symptoms vary in severity, with children being the most at risk because of their small body size. Because the venom primarily kills through paralysis, victims are frequently saved if artificial respiration is started and maintained before marked cyanosis and hypotension develop. Victims who live through the first 24 hours generally go on to make a complete recovery.^[7]

It is essential that efforts continue even if the victim appears not to be responding. Tetrodotoxin poisoning can result in the victim being fully aware of his surroundings but unable to breathe. Because of the paralysis that occurs they have no way of signaling for help or any way of indicating distress. Respiratory support, together with reassurance, until medical assistance arrives ensures that the victim will generally recover well.

The blue-ringed octopus, despite its small size, carries enough venom to kill 26 adult humans within minutes. Furthermore, their bites are tiny and often painless, with many victims not realizing they have been envenomated until respiratory depression and paralysis start to set in.^[8]

References

1. ^ Surf Lifesaving Training Manual, 32nd edition
2. ^ Discovery.com
3. ^ Cheng, M.W. & R.L. Caldwell 2000. Sex identification and mating in the blue-ringed octopus, Hapalochlaena lunulata. Anim Behav. 60(1): 27-33.
4. ^ Sheumack DD, Howden ME, Spence I, Quinn RJ (1978). "Maculotoxin: a neurotoxin from the venom glands of the octopus Hapalochlaena maculosa identified as tetrodotoxin". Science 199 (4325): 188–9. doi:10.1126/science.619451. PMID 619451. 
5. ^ Furlow, Bryant. "Tetrodotoxin and the Life Tree". http://dhushara.freehosting.net/book/upd/jun01/20101/tetro.htm. Retrieved 2011-04-22. 
6. ^ Caldwell, Roy, Dr (1996–2000). "What makes blue-rings so deadly?". http://www.thecephalopodpage.org/bluering2.php. Retrieved 2007-03-19. 
7. ^ Lippmann, John and Bugg, Stan, "DAN S.E. Asia-Pacific Diving First Aid Manual", J.L. Publications, Australia, May 2004. ISBN 0-646-23183-9
8. ^ "Dangers on the Barrier Reef". Archived from the original on 2006-12-05. http://web.archive.org/web/20061205092145/http://www.barrierreefaustralia.com/the-great-barrier-reef/blueringedoctopus.htm. Retrieved 2006-12-06. 

External links

• CephBase: Hapalochlaena

• Blue Ring Octopuses (Hapalochlaena spec.)
• Life In The Fast Lane - Toxicology Conundrum #011