Some years back I had the pleasure of diving the waters of southern Belize, Central America with friend Jeff Hamann of El Cajon, California. The trip was amazing and we were able to collect and document a good number of opisthobranchs. Interestingly, many of our finds were species of sacoglossids. One of the most interesting to me was Oxynoe antillarum. As seen in Jeff great photo here like other saco's the species is green. It has translucent white spots all over and characteristic pattern of mottled white pigmentation. The rhinophores are mottled white and there is a band of this color extending along each side of the head from the base of each rhinophore. A similar colored band runs around the edge of the parapodia, and along the edge of the foot. This species has retained an internal shell. Like most sacoglossigs, if you irritate them they will exude a thick milky white secretion from their body. This substance contains unpleasant chemicals to fend off predators. These chemical are thought to be derived from the algae they feed on.
Like other species of Sacoglossid also, this slug incorporates photosynthetic pigments it gets for the algae, in this case Caulerpa seen here in Jeff's photo, into its mantle tissue. This provides a double benefit to the slug who first got nutrients by eating the algae and then receives nutrition from the photosynthetic pigments, which in the presence of sunlight, continue to carry out photosynthesis secreting by-products directly into the slugs tissue.
This specimen was collected at Laughing Bird Cay. Dozens of specimens were observed merrily sucking to sap from the grape shaped branches of Caulerpa. The species is known to occur in the tropical and subtropical west Atlantic from Florida to northern Brazil.
Morch, O.A.L. 1863. Revision des especes du genre Oxynoe Rafinesque, et Lobiger Krohn. Journal de Conchyliologie, 11: 43-48.
David W. Behrens
Pacific Coast Nudibranchs
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