This “case” features the giant nudibranch (Dendronotus iris) and the tube-dwelling anemone (Pachycerianthus fimbriatus).
The giant nudibranch’s favourite snack is the tube-dwelling anemone. Anemones’ stinging cells (nematocysts) serve as a good defence to most predators but not to the giant nudibranch. Nudibranchs that feed on animals with stinging cells actually incorporate the stinging cells and use them as their own defence! They “steal” the anemone’s weapons.
This anemone species is therefore adapted to also withdraw into a tube to get away from the predator sea slug.
And the battle is on! The giant nudibranch patrols the sandy ocean plains “looking” for the tube-dwelling anemone. When it finds one, it rears up and pounces, mouth parts extended in the hopes of grabbing onto the anemone. When the anemone senses the nudibranch’s attack, it withdraws into its tube.
Wait till you see what happens to the giant nudibranch!
See below for a short clip of such an attack.
But that’s not all, this nudibranch species also swims. By lifting off, it may land somewhere with better chances for feeding and mating.
See video below.