A distinctive, truly pelagic silvery blue mollusc, up to 6 cm long, with three pairs of arms. Floats upside-down just under the sea surface, feeding on the colonial hydroids Physalia, Porpita and Velella. Habitat: offshore. Distribution: pantropical. N.B. must be handled with care as it can give an extremely painful sting, due to the nematocysts taken from the prey species Physalia, which itself gives a nasty sting.
- Richmond, M. (Ed.) (1997). A guide to the seashores of Eastern Africa and the Western Indian Ocean islands. Sida/Department for Research Cooperation, SAREC: Stockholm, Sweden. ISBN 91-630-4594-X. 448 pp. http://www.marinespecies.org/aphia.php?p=sourcedetails&id=6066