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World’s smallest cephalopod gets set to fertilise her own eggs

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Tony Wu/naturepl.com

Photographer Tony Wu

Agency Naturepl.com

THIS dramatic image of a female northern pygmy squid (Idiosepius paradoxus) may make it look like a formidable ocean dweller, but it is in fact a close-up of the world’s smallest cephalopod, a minuscule member of a class of molluscs that includes octopuses and cuttlefish.

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Measuring between just 5 and 20 millimetres across, these squid are so tiny they can fit on a human thumbnail. This female, seen off the coast of Yamaguchi prefecture in southern Japan, is laying her eggs, a process that can take anywhere between a few minutes and an hour, says photographer Tony Wu.

The eggs, however, get fertilised in a rather unusual way. Instead of reproducing by copulation, male pygmy squid attach bundles of sperm called spermatophores onto the bodies of females. The sperm then makes its way to a receptacle in the female’s mouth when she is ready to inseminate her eggs, allowing her to inject a small amount of this through a hole she bites in each egg.

Here, the pygmy squid can be seen delicately preparing to lay another egg on a blade of eelgrass before she starts the process of insemination.

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