Costasiella sp. 1

Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Order: Sacoglossa
Family: Costasiellidae
Genus: Costasiella
Species: Costasiella sp. 1

Costasiella sp. 1 is one of a few different leaf sheep found in the Philippines. Leaf sheep are tiny sap-sucking slugs (Sacoglossa), not true nudibranchs, and this one has not yet been formally described.

They get their nickname because they look like tiny sheep and live their whole lives on leaves on the sea floor. These are not actually leaves but Avrainvillea, a fuzzy, felty algae found in sandy areas. They mate, lay eggs, eat and live right on it.

This species stands out with rows of cerata banded in yellow and blue, a dark head with two rhinophores, and small dark eyes.

Leaf sheep make good ambassadors for muck dives. Look closely at patches of Avrainvillea on sandy slopes, and bring a macro lens or diopter, as they are only a few millimetres long.

It appears on page 342 of Nudibranchs of the Philippines.

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