About Berthella medietas Burn, 1962
Berthella medietas is a species of pleurobranchid sea slug first described by Burn in 1962. This species has a small internal shell, with a distinctive orange to bronze body coloration, and can reach a maximum length of approximately 30 mm. Its gill is relatively small, bearing 18–23 pinnate branches, is covered by the mantle, and is partially attached to the body wall. The rhinophores are long, enrolled, and pale yellow to orange, fused at their base and positioned above a broad oral veil. The oral veil is large and triangular, with grooves along its lateral edges and a deep notch at its anterior end. The foot is unspotted dirty yellow-orange, and has a darker anterior mucous groove. A triangular off-center pedal gland is present on the foot sole. Berthella medietas closely resembles the widely distributed species Berthella stellata, but differs externally by lacking the characteristic white cross-like mantle pattern found on B. stellata. The species name has sometimes been incorrectly written as "Berthella mediatas" due to a typographical error from inconsistent spelling of the species epithet in the original 1962 description, even though the correct spelling appeared elsewhere in the same publication. Willan (1987) confirmed that Berthella medietas is the correct, currently accepted name for this species. This species is native to southern Australia and New Zealand. It lives on partially sheltered and open rocky shorelines, typically at depths of up to 10 meters, and has been recorded in low numbers in intertidal and shallow sublittoral zones. Observations recorded by Goddard show that B. medietas feeds on plakinid sponges of the genus Oscarella.
