New Contributions to the Euthyneura Biodiversity of Colombia’s Pacific and Caribbean Coasts

The infraclass Euthyneura (Mollusca, Heterobranchia) exhibits significant diversity in morphology, size, life habits, and color. Several species are important for research in evolution, ecology, chemistry, and pharmacology. Despite Colombia’s expansive Pacific and Caribbean coasts, which host ecosystems such as rocky shores and coral reefs, key habitats for sea slugs and sea hares, the biodiversity of Euthyneura remains largely understudied. This study aims to expand the inventory of Euthyneura diversity in intertidal and shallow subtidal rocky and coral reef environments in Colombia’s Pacific (Uramba Bahía Málaga National Natural Park) and Caribbean (Seaflower Biosphere Reserve) areas. Rapid biodiversity assessments using snorkeling and errant scuba diving at depths of 1–40 m resulted in the documentation of 31 species (14 in Caribbean coral reefs and 17 in Pacific intertidal and shallow subtidal rocky shores and reefs). Eleven species were new records. The family Aplysiidae was the richest with five species, followed by Facelinidae with four, and Aeolidiidae, Discodorididae, Chromodorididae, and Plakobranchidae with three each. Given the limited sampling effort (~40 h in the Caribbean and ~20 h in the Pacific) and the substantial new data collected, it is evident that there is still much to learn about this group in these areas. Increased efforts, combined with detailed morphological and molecular techniques, will enhance our understanding and documentation of Euthyneura diversity in Colombia.