Western Atlantic from Brazil to North Carolina, USA. Also reported from the western Mediterranean (Schmekel, 1979) and from Cape Verde, eastern Atlantic (Valdes & Ortea, 1995)
Upper right: 3mm. Dredged from sand and scattered grass in 2.5m, lee side of Whale Cay. June 28, 1997. Lower right: 4mm. On Sargassum attached to the substrate in 1m, Guana Cay. August 12, 2003. Both locations in Abaco, Bahamas. Photos: Colin Redfern.
Animal translucent with opaque white and brown patching all over body. Usually a large reticulate brown patch behind the rhinophores. It is characterised by four long tapering tentacular papillae at the anterior end around the mantle edge - almost polycerid like - and a series of five or six lateral mantle papillae down each side on the mantle edge. These papillae have a characteristic swelling in the upper third of their length giving them a spindle like appearance, quite different from that of the anterior 4 papillae. It grows to approx 8 mm long alive.
The radula is typical for the goniodorids with a formula of 18.104.22.168.1. The small outer teeth have 3 long pointed cusps.
Marcus, E. (1957) On Opisthobranchia from Brazil (2). Zoological Journal of the Linnean Society, 43(292), 390-486.
Redfern. C., (2001) Bahamian Seashells: a Thousand Species from Abaco, Bahamas. Bahamianseashells.com Inc: Boca Raton. 1-280.
Schmekel, L. (1979) First record of Okenia impexa Marcus, 1957 from the Western Atlantic in the Mediterranean. The Veliger 21: 355-360.
Valdés, Á. & Ortea, J. (1995) Revised taxonomy of some species of the genus Okenia Menke, 1830 (Mollusca: Nudibrancia) from the Atlantic Ocean, with the description of a new species. The Veliger, 38(3), 223-234.
Rudman, W.B., 2004 (December 22) Okenia impexa Marcus, 1957. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/okenimpe