409 Dive Log Australasia December 24

Octopus do not have a complex vocal system like mammals. Instead they communicate using vis ual signals such as colour patterns and body pos tures. They will also use their highly developed arms for tactile communication. Octopus are also sensitive to sound. Noise pollu tion in the oceans is a huge problem for many dif ferent species and can cause things like disorientation. However, for the octopus, it has been found that long periods of low intensity noise damage, such as human made noise in the ocean, can damage the octopus’s inner ear and cause issues for their health and populations. So in order to be able to get cozy, octopus need it to be a quiet and calm environment. Female octopus are usually the larger of a pair and so, she is usually in charge of the mating rit ual. The male will communicate his intentions through colour changes and chemical cues and try to get close to the female. Quite often, the fe male will be uninterested and so will chase him away or even kill him! Possibly a little bit of an overreaction, the males do try their best to be polite about it all. If the female is interested, the male will stretch out one of his arms towards the female. This arm is a modified arm called a hectocotylus and is specialised to store and transfer spermatophores (the packages of sperm that invertebrates carry). If given the all clear, the male will continue his arm quest and the female will pull the male closer. Once the sperm packet has been de posited, things can get a little nasty. The female

Smaller individuals of the common blanket octo pus will carry tentacles of the bluebottle jellyfish (Portuguese man of war) as a weapon to defend themselves from predators. The tentacles are ex tremely painful but the octopus is immune to the venom. Instead they can use the stinging ten tacles to ward off potential predators with a nasty sting if they get too close. Sharks are one of the main predators of octopus around the world. In South Africa, octopus have been seen collecting shells and other debris from the seabed to build themselves camouflaged dens that protect them from the inquisitive senses of the pyjama sharks. And of course, if all else fails, octopus have ink that they can release from special glands. If squirted towards a pred ators eyes, a special compound in the ink will cause a blinding irritation and dramatically con fuse and reduce the predators sense of smell and taste. The perfect last resort! Now that our reef octopus has matured a little, learnt how to catch food and how to ensure that it does not become food itself, it is time to think about passing on her genes. Time to find a mate. Getting your ideas and point across is quite im portant when looking for a mate. If they misread your intentions, it may end up with disastrous consequences. Octopus have been known to be cannibalistic from time to time! Communication is key to any good relationship.

Coconut Octopus in the sand

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DIVE LOG Australasia #409 - December ‘24