Sacoproteus smaragdinus

Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Order: Sacoglossa
Family: Limapontiidae
Genus: Sacoproteus
Species: Sacoproteus smaragdinus

Sacoproteus smaragdinus is a small green sacoglossan with swollen, bubble-like cerata. Its rounded outline can make it difficult to separate from the algae around it, so look for the head and the arrangement of the cerata rather than colour alone.

Sacoglossans are sap-sucking sea slugs. They pierce algal cells and draw out their contents, unlike the animal-eating nudibranchs with which they are often grouped in dive guides. The exact food alga should not be assumed from this photograph.

For divers exploring the Philippines, this is a reminder that an unremarkable patch of algae can hold an interesting subject. Inspect it without pulling or turning it over.

Use a macro lens and gentle lighting. A side view can reveal the head while keeping the rounded cerata separate from the background.

It appears on page 336 of Nudibranchs of the Philippines.

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