Tritonicula wellsi, the sea whip slug, is a species of nudibranch, a shell-less marine gastropod mollusc in the family Tritoniidae.

[3] A number of Caribbean and western Pacific species of Tritonia were moved to a new genus Tritonicula in 2020 as a result of an integrative taxonomic study of the family Tritoniidae.

The head bears a pair of rhinophores (sensory organs) each with a sheath at its base.

The body has two longitudinal rows of arborescent (tree-like) gills which resemble the polyps of the whip corals on which it lives and feeds.

[5] Tritonicula wellsi is found wherever its host occurs, on the western fringes of the Atlantic Ocean, from North Carolina and Florida south to Belize, Honduras, Costa Rica, the Virgin Islands and Brazil.