The Spongy Atagema (Atagema spongiosa) is a large nudibranch species that belongs to the family Dorididae. It was previously scientifically classified as Trippa spongiosa until a review of the genus by Valdés, A. & Gosliner, T. M. (2001): Systematics and phylogeny of the caryophyllidia-bearing dorids (Mollusca, Nudibranchia), with the description of a new genus and four new species from Indo-Pacific deep waters. Zoological Journal of the Linnean Society, 133: 103-198. Hence the species is no longer referred to as Trippa spongiosa and is known as Atagema spongiosa.
The Atagema spongiosa nudibranch is distributed throughout the tropical waters of the Indo-Western Pacific region. In Australia it has been recorded along the Great Barrier Reef, in New South Wales and in the waters of Christmas and Lord Howe Islands. This species is often overlooked by divers because of its sponge like appearance that helps it blend in with sponge and coral habitats.
This species is easily identified by its size, spongy mantle and the mantle underside is coloured purple. Its upper mantle is generally white or grey in colour and it is known to feed on sponges. The Spongy Atagema (Atagema spongiosa) grows to a maximum length or approximately 13cm.