Abstract
<jats:p>Dendrodoris arborescens (Mollusca: Gastropoda) is a dorid nudibranch species for which internal anatomical details have remained undocumented. In September 2024, a total of 20 specimens were collected from the low intertidal zone at Heishijiao, Dalian, Liaoning, China (38.865°N, 121.548°E), representing the first record of this species from the area. Here we present a comprehensive description of both external mor-phology and internal anatomy, based on external observation, anatomical dissection, histological sectioning, and scanning electron microscopy (SEM). The body is elon-gate-elliptical and uniformly black; the mantle surface is smooth without tubercles, bordered by a narrow orange-red marginal band. The rhinophores are clavate, bearing densely arranged, obliquely oriented lamellae on their surface. The branchial plumes are dendritic and encircle the anus. The digestive system features a suctorial oral ap-paratus lacking radula. The reproductive system exhibits a tri-duct hermaphroditic configuration, with the hermaphroditic gonad embedded within the digestive gland. These findings provide foundational morphological data for understanding the repro-ductive biology of Dendrodoris and offer a reference baseline for future studies on spe-cies identification and cultivation of this genus.</jats:p>