Who’s Eating Who?
Giant Nudibranch on the prowl for Tube-Dwelling Anemones. This species of nudibranch has great variation in colour. See photos at end of blog. ©Jackie Hildering
This “case” features the Giant Nudibranch (Dendronotus iris to 30 cm long) and the Tube-Dwelling Anemone (Pachycerianthus fimbriatus).
The Giant Nudibranch’s favourite snack is this anemone species. It is not impacted by the anemone’s stinging cells (nematocysts).
Giant Nudibranch launching into a Tube-Dwelling Anemone. © Jackie Hildering
The Tube-Dwelling Anemone is therefore adapted to be able to withdraw into its tube (which can be up to 1 m long) in an attempt 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.
As is also generally the way with sea slugs, they also lay their eggs on their prey.
And oh the diversity in colour among Giant Nudibranchs. See photos below.
Interspecies interaction: When this Giant Nudibranch touched the Leather Star, it touched it again and then recoiling with an acute change in direction. The diet of Leather Stars (Dermasterias imbricata) is omnivorous. From Neil McDaniel: “Eats a wide variety of prey, depending on the locale. On the open coast it consumes plumose anemones and tunicates; in sheltered areas it eats orange sea pens, sea vase tunicates, encrusting sponges and bryozoans.” So, Leather Stars are not likely to eat a Giant Nudibranch, especially because Leather Stars are not particularly fast sea stars (15 cm/min) and Giant Nudibranchs can swim away (yes, that’s right they swim). Leather Stars’ skin is known to contain a unique chemical “imbricatine” that does elicit an escape response form Swimming Anemones so . . . whether the Leather Star felt or “tasted” odd to the Giant Anemone, it did “decide” that distancing was the better way to go.
Note: Dendonotids are not known to utilize the stinging cells (nematocysts) of their prey. From the Sea Slug Forum “There has been some confusion in the literature concerning the presence of branches of the gut in the ‘gills’ or ‘cerata’ of species of Dendronotus. Firstly there is no evidence to suggest that any species of Dendronotus has cnidosacs at the tip of its dorsal processes in which to store nematocysts. In fact there is no evidence that they store nematocysts from their prey anemones in any part of their body.“
The Marine Detective 
9 Responses to “Who’s Eating Who?”
Amazing and so beautiful – what an incredible world!
I love that I can share our underwater world with someone whose art I so admire; who is able to create such beauty from the inspiration around her.
Oh Jackie! What a beautiful thing to say! It doesn’t show I ever responded. Thank you for this uplifting comment!
Absolutely fascinating takes of these animals we barely know they exist! Thanks for publishing, great joy and wonder to watch.
I really appreciate the feedback. Thank you!
Beautiful. Haawa from Haida Gwaii.
Thank you so much. Lovely to know this is reaching you there in paradise.
I enjoy the descriptions and videos . thak you.
Allen
Really appreciate the feedback Allen.