A New Panther Worm Spotted in Japan, Hofstenia sugashimaensis sp. nov. (Xenacoelomorpha: Acoela)

Hofstenia Bock, 1923, the type genus of Hofsteniidae, was originally established for H. atroviridis Bock, 1923, from Misaki, Kanagawa Prefecture, Japan. This study describes Hofstenia sugashimaensis sp. nov., discovered in water tanks at the Sugashima Marine Biological Laboratory (Nagoya University) and Toba Aquarium, both situated at the mouth of Ise Bay in Mie Prefecture, along the Pacific coast of central Japan. Morphologically, it resembles H. miamia Corrêa, 1960 (commonly known as the “three-banded panther worm”) but is distinguished by two transverse bands and dorsal midline markings based on intra- and interspecific comparisons. Phylogenetic analysis of partial sequences of the cytochrome c oxidase subunit I, 18S rRNA, and 28S rRNA supports its genetic distinction from H. miamia.