Resumo
Heterobranch sea slugs (Gastropoda) present reduction, internalization, or absence of shell, and include more than 6,000 described species. Approximately 250 species are recorded from Brazil but only 14 had been previously recorded from Rio Grande do Norte, on the Brazilian northeastern coast. As a result of different expeditions conducted between 2008 and 2020, species were collected and identified. Among them, five species were recorded for the first time from the South Atlantic Ocean: Chelidonura hirundinina (Quoy & Gaimard, 1833); Sclerodoris prea (Ev. Marcus & Er. Marcus, 1967); Thuridilla malaquita Ortea & Buske, 2014; Berthella nebula Ghanimi, Schrödl, Goddard, Ballesteros, Gosliner & Valdés, 2020 and Berthella vialactea Ghanimi, Schrödl, Goddard, Ballesteros, Gosliner & Valdés, 2020. Thirty-six species are recorded for the first time from Rio Grande do Norte. The present survey expands the knowledge of the diversity of sea slugs from Brazil and supports the hypothesis of similarity between the heterobranch sea slug fauna from the northeastern Brazil and the Caribbean Sea.(AU)