Distribution: Possibly common in the Solitary Islands Marine Park. Distributed throughout the Indo-Pacific region, from India to the Pacific coast of Mexico, north to Japan, south to Australia. In Australia recorded from Heron Island on the Great Barrier Reef and in northern New South Wales.
Ecological Notes: Inhabits intertidal and shallow subtidal areas, feeds exclusively on Halimeda sp. algae.
Additional Notes: A small camouflaged species not often seen due to its preferred habitat and flattened cryptic appearance. They tend to adopt the body shape best related to the shape of the food source, flattened parapodia on those with flattened segments, while adopting a more rounded shape on the cylindrical segments. Feeds by piercing the cell walls of its algal food source, mouthparts then sucking out the contained fluids. Believed to concentrate toxic metabolites from its food source and when irritated secretes large amounts of mucus containing this toxic substance as an effective defense mechanism. Studies have also found this substance in egg masses of E. pusilla. Grows to at least 32 mm.
References: Gary Cobb, David Mullins, Nudibranchs Encyclopedia, 2nd Edition, 2015. Publishers Thomas Slone, Masalai Press and Tim Hochgrebe, Underwater Australasia. p.70.
Australian Museum, Sea Slug Forum. http://www.seaslugforum.net/find/elyspus1. Accessed 03/08/18.