Doris lacera Cuvier, 1804

Tibiriçá, Yara, Pola, Marta, Pittman, Cory, Gosliner, Terrence M., Malaquias, Manuel A. & Cervera, Juan Lucas, 2023, A Spanish dancer? No! A troupe of dancers: a review of the family Hexabranchidae Bergh, 1891 (Gastropoda, Heterobranchia, Nudibranchia), Organisms Diversity & Evolution (New York, N. Y.) 23 (4), pp. 697-742 : 726-727

Doris lacera Cuvier, 1804 (Fig. 26A)

Description notes Described from preserved specimens; no notes on living animals; detailed internal morphology: size 90 mm; body relatively flattened; mantle slightly wider than a foot with a lacinate margin; large vesicles on notum; fleshy, slightly serrated oral tentacles; eight to ten gill leaves arranged separately around the anus; penis surrounded by a fleshy envelope; penial bulb colloidal; vas deferent long, thin, with several folds.

Own conclusion/opinion on its taxonomic status Bergh (1900) investigated several preserved specimens of Hexabranchus spp. and concluded that 17 were synonyms of Hexabranchus lacer . Such material deposited in the Muséum National d’Histoire Naturelle (Paris), was later examined by Pruvot-Fol (1934), but she could not conclude whether the material represented one or more species and which species it represented. Baba (1988) stated that the lack of information about the coloration of the living organism and the potential distortion caused by preservation made the correct identification of H. lacer difficult and later authors preferred not to use this name (e.g., Edmunds (1971), Bergh (1905)). Since then, the name H. lacer has been largely ignored. Valdés (2002) examined the syntypes of Doris lacera and concluded that they belong to the genus Hexabranchus . Nevertheless, he declared Doris lacera “ nomen oblitum ” based on Article 23.9.1 of the International Code of Zoological Nomenclature (2000), which states that “if a senior synonym has not been used as a valid name after 1899 and its junior synonym has been used for the same species in at least 25 papers, published by at least 10 authors in the immediately preceding 50 years and encompassing a span not less than 10 years, the usage of the junior synonym must be maintained” However, Valdés (2002) missed Bergh (1900) ’s reference and at least three others: Schauinsland (1899), Eliot (1904b) and Haas (1920). In addition, Valdés (2002) concluded that only one species was valid for the Indo-Pacific, and applying the principle of priority, he claimed Hexabranchus sanguineus to be nomem protectum. On the contrary, our results show that more than one species is present in the Indo-Pacific and that H. lacer and H. sanguineus are distinct species.

Specifically, at least three species are present in the Indonesian region: H. lacer , H. sanguineus and H. giganteus . Despite lacking color details, Cuvier’s (1804) description is sufficiently detailed to confidently attribute this name to a Hexabranchus species widely distributed in the Indo-Pacific. This decision is based on the integration of location, internal morphology, and general appearance. Cuvier’s (1804) drawing clearly shows a very long and coiled penis and deferent duct, excluding the possibility of it being H. sanguineus or H. giganteus . Furthermore, Doris lacera was described presenting nine to ten gill branches, while H. sanguineus typically has six. Cuvier’s (1804) drawing shows incongruent vesicles on the dorsum, but we noted that vesicles may or may not be formed (in multiple species) due to preservation. We find it unlikely that H. lacer represents H. giganteus sp. nov., as the latter is mostly found at depths greater than 30 m and a specimen measuring 90 mm (preserved) would be immature. As a result, we resurrect H. lacer .