Nudibranch - Phyllodesmium rudmani

This solar-powered aeolid is a remarkable mimic of the Xenia colonies on which it feeds, often nestling in cavities it has burrowed out in the base of the colony.

The body and smooth rhinophores are a translucent white with some white dusting especially near the tips of the rhinophores and oral tentacles. The cerata have a cylindrical trunk which widens out at the tip to form a swollen region with longitudinal ridges and deep grooves. Each ceras mimics the shape of a Xenia polyp with retracted tentacles. The ceratal trunk is translucent white except at the swollen tip where the ridges are white and the grooves are green or brown, apparently depending on the colour of the Xenia being eaten. The green and brown colour is from the symbiotic zooxanthellae being which are kept in terminal sacs of the digestive gland, which occur only at the tips of the cerata.

No branches of the digestive gland are found in the body wall or in the trunk region of the cerata. A single digestive gland duct runs up the centre of the trunk region, only branching when it reaches the swollen tip.

For a 'clearer' view of the Nudibranch :