Tiger Butterfly Sea Slug

Cyerce nigra

The Tiger Butterfly Sea Slug (Cyerce nigra) is a remarkable sacoglossan sea slug belonging to the family Caliphyllidae. Found in the tropical western Pacific, it is widely admired by underwater macro photographers for its elaborate leaf-like structures, bold black-and-yellow patterns and butterfly-like appearance. Appearance and Identification The most striking feature of Cyerce nigra is the series of large, flattened, leaf-like cerata arranged along both sides of its body. These delicate structures overlap like the petals of a flower or the folds of an intricately patterned dress. The two surfaces of each ceras display contrasting designs. One side bears scattered orange-yellow spots against a dark background, while the opposite surface features distinctive transverse black stripes. Yellow-orange margins and fine pale markings add further detail to the overall pattern. As the animal moves and its cerata change position, different surfaces become visible, creating an extraordinary display of alternating spots and stripes. The head and rhinophores also carry distinctive dark and yellow-orange markings. Together, these features provide important clues for distinguishing Cyerce nigra from closely related species. Feeding Ecology and Habitat Unlike sea slugs that feed on sponges or corals, Cyerce nigra is associated with green algae. Scientific studies have documented feeding on algae of the genus Udotea, including Udotea geppiorum. Researchers have also suggested that its actual range of algal hosts may be broader than currently confirmed. Understanding these algal associations is important for studying the species' ecology and habitat preferences. For underwater naturalists, recording the surrounding algae, substrate and environmental conditions can provide valuable infor