Nymphozoon cinderella sp. nov. (Platyhelminthes: Polycladida: Pseudocerotidae), a new species of marine flatworm from Japan

Marine flatworms in Pseudocerotidae Lang, 1884 are known as one of the most abundant groups among polyclads so far. To date, there have been specimen-based records of 36 named species in 5 genera in this family from Japan. The species of Nymphozoon Hyman, 1959 (Polycladida, Pseudocerotidae) are widely distributed in the Indo-Pacific Ocean, but the only known report of the genus in Japan is based on a photo of Nymphozoon orsaki (Newman & Cannon, 1996) taken in the Okinawa Islands. In this paper, we describe a new species from Japanese shallow waters, Nymphozoon cinderella sp. nov., which is characterized by having (1) square-shaped pseudotentacles with broad, black-colored edges and white tips, (2) dull grayish or brownish dorsal coloration, (3) a narrow brown-to-black line encircling the body periphery, and (4) a wide grayish dorsal middle band fringed with a brown-to-black line. Despite the observed color pattern clearly distinguishes the new species from N. orsaki collected in Papua New Guinea, the p-distance based on partial (942 bp) 28S rDNA gene sequences (1.27%) was comparable to the intraspecific range for pseudocerotids. Further analyses based on more rapidly evolving genetic markers such as cytochrome c oxidase subunit I would probably be required to provide enough support to the molecular distinction between these two species having obviously different body color patterns.