https://www.newscientist.com/article/2521744-male-octopuses-have-a-favourite-arm-that-they-mostly-use-for-sex/

Despite the fact that I am evolutionarily quite distant from octopuses, I also have a most precious arm which I endeavour to keep safe and to prevent it from getting damaged or bitten off by a predator.

Male octopuses have a favourite arm that they mostly use for sex

The third right arm of male octopuses has a specialised role in mating, and the creatures take extra care to avoid damaging it or losing it to a predator

New Scientist
@Spoon I'm reading Adrian Tchaikovsky's Children of Ruin, one of tha major themes of which is the accelerated and manipulated evolution of octopuses on an otherwise empty planet with no local predators. It's pretty fascinating stuff.
@jonlawrence @Spoon The Mountain in the Sea" (Ray Nayler) is also a good read. #goodread https://en.wikipedia.org/wiki/The_Mountain_in_the_Sea
The Mountain in the Sea - Wikipedia

@dharmadan @Spoon ooh, that looks great. thanks!