Trinchesiidae Nudibranchs are brightly coloured aeolid nudibranchs, and in keeping with other members of this group, Trinchesiidae species have many tapered blood-filled tubes called 'cerata' growing on both the back and side areas of the body.
The cerata are thin-walled, blood-filled tubes which perform several functions, as part of the digestive system and also a gill-like function. The diet can influence the colour of the cerata and as such, members of this family can have varying colours, depending on the diet.
The Siboga Cuthona is a medium sized nudibranch with a pale lilac to purple body and numerous cerata arranged in clusters along the body. The cerata have yellow tapered tips, with a purplish ring below. The cerata on the side of the body having little or no purplish ring.
The rhinophores and moustache-like oral tentacles are also a dark purplish colour.
Siboga Cuthona grows up to 3.5 cm and is often found feeding on hydroids (as pictured here).