We report 37 species of heterobranch sea slugs from the National Park Alacranes reef, located in the Campeche Bank, at the south-eastern Gulf of Mexico, of which 18 species are reported for the first time in this reef. With this contribution, the species richness in this national park increases to up to 67. The species Nakamigawaia felis, Petaliferasp., Elysia flava, Elysia pratensis and Bulbaeolidia sp. are reported in the Gulf of Mexico for the first time.

 

The geographical distribution ranges for Oxynoe azuropunctata, Elysia ornata, Placida kingstoni, Aphelodoris antillensis and Tritonia hamnerorum are extended westward. Those for Elysia flava, Pleurobranchus areolatus and Felimare ruthae are extended both northward and westward.