Elysia patina Ev. Marcus, 1980
Original Description: "Except for the patina color no indications of the living slug were noted during the sorting of the day's collection. The preserved animal measured 8 by 7 mm with spread parapodia. It resembles the Pacific E. lobata. Head and neck are short; the anterior part of the foot is delimited by a deep furrow from the posterior one. The rhinophores are short, evidently contracted. The parapodia are joined in a little pointed tail. Their edges bear irregular braching papillae (Fig. 41). A part of the left one is damaged. The color of the animal fixed in Bouin and preserved in alcohol is greyish with a loose network of darker grey spots. The ciliated sole (Fig. 43c) is lighter. It is as broad as each of the parapodia and provided with many basophilous glands. The round eyes are very big, 0.12 mm in diameter. The renopericardiac prominence (Fig. 41) is little less than half the length of the parapodia. Seven vessels enter on the right, six on the left side; only three of the right side are branched, the corresponding ones on the left side are damaged. Between the two hindmost vessels there is a salient, globular thickening on either side, in sections a vesicle (Fig. 43, x), probably functioning as gametolytic vesicles. The male aperture lies in the groove separating the head and right parapodium. The single female pore opens immediately behind the anal opening. The pharynx is about 0.4 mm long. It is muscular but has no ingluvies. The smooth teeth (Fig. 42) are very slender. There is a muscular pouch on the esophagus (Fig. 36). The penial papilla (Fig. 57) is about 0.47 mm long and 0.3 mm wide. The winding efferent duct widens from 0.035 to 0.12 mm in the middle of the papilla and narrows suddenly towards the tip, which is provided with a very delicate cuticular tube of 0.06 mm length. The prostatic and albumen glands are ramified through the whole body. Both extend forward to the anterior border of the parapodia. The farther dorsal and ventral ones have only basophil granuals, 2-3 μm in diameter. They reach farther backwards than the more central ones. The latter have homogeneous acidophil contents around their ducts, farther outwards the longer cells each contain a large vacuole filled with granules 5 μm in diameter, staining weakly. This type of gland eand near the end of teh eminence, together with the hindmost ovotestes.
Though the living animal was not observed, the branching of the dorsal vessels is so far different from all other known Atlantic species, that it is easily recognized as a new species. Also the papillate margin of the parapodia is a good character.
From Prof. Brattström, Bergen, I received one specimen from the Bahamas (39-67-C) taken in 1967. It is similar to the present one of patina, but without the marginal papillae and with different eyes and dorsal vessels (Figs. 59, 60). It measures 4.5 by 4 mm preserved. I do not want to give a name to this second species, but with more material the species with two gametolytic vesicles should be separated from the large genus Elysia, together with E. ornata (Swainson) (Fig. 3) and E. grandifolia Kelaart (Fig. 5).
In the meantime I obtained one more specimen from Florida, a juvenile, without the paired gametolytic vesicles and without marginal papillae. Its dorsal vessels are like those in Brattström's animal " (Marcus, 1980).
Ecology and Distribution
The type locality is the Florida Keys.
Like all sacoglossans, this species is a simultaneous hermaphrodite. Copulation occurs by hypodermic insemination and the secondary copulation bursae (gametolytic vesicles) connect to the “fertilization region” (Jensen, 1999).