Phyllodesmium hyalinum Ehrenberg, 1831

Phyllodesmium hyalinum is known from the Marshalls by about 10 specimens from Enewetak and one from Kwajalein Atoll. All were found on Xenia soft coral (see bottom photos). The nudibranchs are known to pick up symbiotic zooxanthellae from the soft coral and retain them in their cerata. The zooxanthellae, unicellular algae, use light to perform photosynthesis and produce food which can then be used by the nudibranch. Apparently, the individual zooxanthellae do not last long in these nudibranchs, but they can be continually replenished from the soft coral prey.

Unlike many eolids, Phyllodesmium hyalinum does not retain the nematocyst stinging cells of its soft coral prey, so it apparently relies on camouflage to keep from being eaten. The nudibranch is difficult to distinguish on the Xenia colony below.

This is a colony of Xenia, the soft coral prey of Phyllodesmium hyalinum. When undisturbed, the polyps continually open and close. This "grasping" might be used for capturing planktonic food.

Created 8 January 2007