Discodoris evelinae Marcus, 1955
The end of this month, 30 June, marks the 30th anniversary of the death of Professor Ernst Marcus in 1968. He is remembered for his voluminous publications on opisthobranch molluscs, and his signifcant contribution to revitalizing the study of sea slugs during the 1950s and 1960s. Most of his later publications were written with his wife, Eveline du Bois- Reymond Marcus. This week's Nudibranch of the Week, Discodoris evelinae, was one of the first species of nudibranchs that Ernst Marcus named; fittingly, he named it in honor of his wife.
This species can grow to about 9 cm in total length, although specimens in the 40-60 mm range are more common. The dorsal surface is olivaceous brown with darker blotches; the foot is lighter with large dark spots. The brownish gills are tinged with white, as are also the rhinophores. The illustration shows the ability of this species to autotomize portions of the notal margin.
I described the tooth morphology and meristic characters of its radula in my paper on intraspecific and ontogenetic radular variation (Bertsch, 1976). Newly forming teeth have a different morphology than fully formed teeth, visible with either the scanning electron or light microscopes. The young teeth are weak, thinner, and more transparent than the strong, heavier, darker older teeth. The erect hook of the tooth forms first, as a long, sharp, narrow point, projecting closely along the plane of the radular surface. The basal portion grows later, becoming distinctly angled to the hook as the diameter of the tooth more than triples. The basal portion parallels the plane of the radula, with the hooks projecting outward at about a 60 angle. These thickened, erect teeth can thus effectively rasp and gouge bits from the prey during the radular feeding stroke.
This species occurs widely throughout the tropical western Atlantic (including Gulf of Mexico and Caribbean Sea), having been reported from Brazil, Panama, Texas, Florida, and Puerto Rico. Discodoris hedgpethi Marcus, 1959, is a junior synonym of this species.
Photo of Eveline Marcus taken at Point Loma (San Diego) in August 1969. She has Aplysia californica in one hand and Aplysia vaccaria in the other.