Nembrotha is a genus of sea slugs, nudibranchs, marine gastropod molluscs in the family Polyceridae. Berghia is a genus of sea slugs, aeolid nudibranchs. The latter include the giant clam and various nudibranchs and cone snails. "Chromodoris lochi", like many other dorid nudibranchs, feeds on sponges. "Chromodoris willani", like many other nudibranchs, feeds on sponges. In some nudibranchs, cerata are used as decoy tactics. Lateral outgrowths on the body of nudibranchs are called cerata. Australian underwater photographer Neville Coleman has photographed various nudibranchs at Lord Howe Island. In many aeolid nudibranchs, the digestive system extends into the cerata. These small nudibranchs float upside down on the surface tension in temperate and tropical seas. Currently, about 3,000 valid species of nudibranchs are known. The exact systematics of nudibranchs are a topic of recent revision. These spines make it difficult for the nudibranchs to access the polypide of the zooid. The dorsal surface of the body of nudibranchs is known as the notum. The neurogenesis of "Berghia stephanieae" is similar to that of other nudibranchs.