Family Oxynoidae

Animal to 30 Shell bulloid, covering middle body, partly covered by parapodia. Aperture large, upper part of lip overlapping last whorl. Rhinophores ear-shaped. Eyes prominent behind rhinophores. Neck short, thick. Tail long, slender. Parapodia small, originating from ventral part of animal sides, with small papillae. Body green with bluish or whitish-gray spots. Species with planktotrophic development. Lives on and feed on green algae in the genus Caulerpa. The specimen in the main photo (by Ángel Valdés), from Sarasota Bay, was crawling atop the Green Feather Alga Caulerpa sertularioides. The one in the supplementary image was found in 2020 by Amy Tripp Buckner off Marco Island, and photographed by José H. Leal. This species had been previously identified in this guide as Oxynoe antillarum Mörch, 1863.

This sea slug reaches about 15 mm (0.6 inch). Its cap-like, open-coiled, translucent shell is very thin, covers only the central-dorsal part of the animal, and is flanked by the four parapodial lobes that are typical of the genus Lobiger. Most likely, the lobes act to increase the apparent size of the animal. That, combined with production of a sticky substance, probably acts to intimidate potential predators. The Souverbie Lobiger can be very difficult to observe alive, as it displays cryptic coloration, i.e., the green color of the animal mirrors the color of its habitat and preferred food, green algae in the genus Caulerpa. The shell illustrated here was collected in January 2019 by Ann Palmer, at Cayo Costa. The photo of the live sea slug was taken by Anne DuPont at Lake Worth Lagoon, Palm Beach County.