Malformations in animals have long been known. In gastropod, natural and induced malformations are mentioned in different systems and in ocular tentacles, mainly linked to cases of parasitism and exposure to pollutants (molluscicides and chemicals). In this study we present a new malformation not documented in the ocular tentacles of slug Deroceras reticulatum that could be due to the action of pesticides. This malformation in D. reticulatum is the first malformation to be mentioned for South America in nursery gardens.Facultad de Ciencias Naturales y Museo