Featured on PDR in the collection Kumataro Ito’s Illustrations of Nudibranchs from the USS Albatross’ Philippine Expedition (ca. 1908)

If you ask people what the most spectacular creatures on Earth are some might say the flamingos of the Andes, the birds-of-paradise of Papua New Guinea, or the tropical fish of the Galapagos. How many would say sea slugs? Yet the roughly 3,000 species in the family nudibranchia are legitimate contenders, coming as they do in a delightful, dizzying array of shapes, patterns and colours. Though most abundant in shallow and warm waters, nudibranchs can be found from the Arctic to the Antarctic, down to a depth of 2,500 metres. The barely believable forms of these horned marine wonders have been captured by modern divers and their underwater cameras. A century ago, only a skilled on-site artist stood any chance of doing a nudibranch aesthetic…