Wow… another new discovery from Seraya's Secret, that does not appear in any of the new three big monographs on Indo-Pacific Nudibranchs. Christiane, you've done it again.
This aeolid is typically cuthonid in all features. The long orange body is like no other Cuthona I am aware of. Head tentacles are white and the head and rhinophores orange. The cerata are situated on arches. The color of these is complex, light green basally, with a sub-apical band of blue, followed by a whitish-pink cnidosac, carrying nematocysts. There is also a small, interesting purple-blue batch adjacent to the base of the rhinophores. Amazing little critter.
It appears to be crawling on a hydroid, upon which it likely feeds. Aside from that we know nothing about this beauty.
Hopefully we'll see it again in July, during one of my three workshops at the Villa Markisa dive resort in Tulamben, Indonesia!