I’ve shared some photos of Hooded Nudibranchs before, and I’m sure if you’ve watched my dive compilation videos you’ve seen clips of other nudibranchs… but Hooded Nudibranchs are really unique. I mean really unique – and honestly a bit weird.
Let’s start with the obvious – that giant hooded “face”. While most nudibranchs have a pair of oral tentacles that they use to sense food near their relatively small mouth that they move towards and then eat, the Hooded Nudibranch has just decided it is easier to basically make their whole head a giant expandable bag that they can hold up in the water currents to catch any tasty bits floating by. You can think of this like a more active jellyfish kind of feeding without the stinging tentacles… or kind of like how a whale feeds you know except tiny… or as you’ll see in the video – it almost reminds me of a mobile slow motion venus fly trap with the way it uses its many oral tentacles surrounding the hood to close it up to trap the food inside.
Then there are the Hooded Nudibranch’s rhinophores – while most nudis have a pair of conical shaped rhinophores, the Hoodies have these two paddle shaped rhinophores that basically make it look like it decided it wanted a pair of Mickey Mouse ears. Rhinophores are usually considered the equivalent of a nose on other animals – each one being the separate nostrils – helping nudibranchs to sense their environment and smell out food or danger… I do wonder if all nudibranchs use their rhinophores to also feel water currents and this is why the Hooded Nudibranchs opt for these big flat paddles to help them even more in this regard. Either way, they are unique rhinophores.
And finally their cerata… Not all nudis have cerata – the appendages lining their back – but in those that do, they’re usually also conical or a branching shape. Cerata act as gills as well as a spot for digestive organs as well as in some species to store stinging cell nemacysts that they have stolen from their food sources. But again, the Hoodies have opted for large, flat paddle-like versions. But they also opted for semi-transparent option that makes all of the normal internal stuff much more visible.
Weird. Unique. Cool.