Dermatobranchus semilunus, Gosliner & Fahey, 2011

Gosliner, Terrence M. & Fahey, Shireen J., 2011, Previously undocumented diversity and abundance of cryptic species: a phylogenetic analysis of Indo-Pacific Arminidae Rafinesque, 1814 (Mollusca: Nudibranchia) with descriptions of 20 new species of Dermatobranchus, Zoological Journal of the Linnean Society 161 (2), pp. 245-356 : 336-339

publication ID	https://doi.org/ 10.1111/j.1096-3642.2010.00649.x
persistent identifier	https://treatment.plazi.org/id/761B2D60-482D-E20F-0AC7-F926FA423B9D
treatment provided by	Valdenar
scientific name	Dermatobranchus semilunus
status	sp. nov.

Treatment

DERMATOBRANCHUS SEMILUNUS View in CoL SP. NOV.

( FIGS 74C–E View Figure 74 , 78–81 View Figure 78 View Figure 79 View Figure 80 View Figure 81 )

Dermatobranchus sp. 7 Gosliner, Behrens & Valdés, 2008: 311, top three photos.

Type material: Holotype: CASIZ 073045 , dissected, 5 mm preserved, north end Kranket Island , Madang, Papua New Guinea, 11 m depth, collected 1.x.1986 by T. Gosliner . Paratypes: CASIZ 086679 , one specimen, dissected, 12 mm alive, Wair Mitak , Flores, Indonesia, 5 m depth, collected 25.iv.1992 by P. Fiene . CASIZ 110407 , one specimen, dissected, north-west end of Cabilao Island , Bohol Strait, Bohol, Philippines, 30 m depth, collected 28.iv.1997 by T. M. Gosliner . CASIZ 174141 , one specimen, dissected, Pulau Chimbe , off Tioman, Malaysia, collected 5.x.2007 by T. Gosliner . CASIZ 174142 , four specimens, one dissected, Pulau Varella , Malaysia, 15 m depth, collected 1.x.2007 by T. Gosliner . CASIZ 178236 , one specimen, sampled for DNA, Pulau Varella , Malaysia, 15 m depth, collected 1.x.2007 by T. Gosliner . CASIZ, 178239, piece of specimen CASIZ 174141 , sampled for DNA, Pulau Chimbe , off Tioman, Malaysia, collected 5.x.2007 by T. Gosliner .

rhinophore stalk is white and the club is dark. The oral veil is opaque white with some dark irregular spots.

Geographical distribution: This species is known only from Papua New Guinea, Indonesia, eastern Malaysia, and the Philippines (present study).

Etymology: The specific name semilunus is from the combined Latin words meaning half-moon, in reference to the dark, semi-lunar shaped marking on the anterior third of the dorsum of this species.

External morphology: The body shape of the living animal ( Fig. 74C–E View Figure 74 ) is elongate, flattened, and narrows at the posterior end. The foot does not project beyond the distinct mantle margin. There is a series of 10–14 low longitudinal dorsal ridges. The oral veil extends forward and has blunt extensions at the corners. The widely spaced rhinophores are behind the oral veil. They have a series of longitudinal lamellae on the rounded club. The stalk does not narrow noticeably. Marginal sacs are visible along the mantle edge. There are no branchial or hyponotal lamellae. The genital opening is in the anterior quarter of the body wall on the right side. The anus is situated approximately half of the way to the posterior end of the body.

The ground colour of the dorsum, the oral veil, and the foot is opaque white. The depressions between the dorsal ridges are light grey with dark dots. There is a single dark U-shaped band of pigment at the anterior third of the notum. Along the mantle edge are evenly spaced, dark ocellated spots of pigment. The posterior edge of the mantle has a yellowish or tan hue. The Buccal armature: The jaws are large and thickly cuticularized ( Figs 78A View Figure 78 , 79A View Figure 79 , 80A View Figure 80 ), with a thick masticatory margin and multiple rows of long, pointed denticles ( Figs 78B View Figure 78 , 79B View Figure 79 , 80B View Figure 80 ). The radula is wide ( Figs 79C View Figure 79 , 80C View Figure 80 ). The radular formula of the holotype ( CASIZ 073045) is 24 ¥ 33.1.1.1.33 ( Fig. 78 View Figure 78 ). Four paratypes have a radular formula of 23 ¥ 33.1.1.1.33 ( CASIZ 086679), 23 ¥ 29.1.1.129 ( CASIZ 110407), 29 ¥ 40.1.1.1.40 ( CASIZ 174142), and 35 ¥ 73.1.1.1.73 ( CASIZ 174141), respectively. The rachidian teeth ( Figs 78C View Figure 78 , 79D View Figure 79 , 80D View Figure 80 ) have a narrow base with a large, projecting, pointed central cusp that has one to eight pointed, flanking denticles on each side. There is a narrow posterior notch on the top of each rachidian tooth. The inner lateral tooth ( Figs 78C View Figure 78 , 79D View Figure 79 , 80D View Figure 80 ) has a flat base with a large hook-shaped first denticle with one to six much shorter and narrower, pointed denticles. The next five lateral teeth are long pointed hooks with up to 14–15 pointed denticles on the outer side or they may be entirely devoid of denticles. The remaining 17–70 lateral teeth ( Figs 78D, E View Figure 78 , 79E, F View Figure 79 , 80E, F View Figure 80 ) are long hooks lacking denticles, with the outermost teeth being less arched and more elongate than the others.

Reproductive system: The arrangement of the reproductive organs is androdiaulic. The hermaphroditic duct leads into the elongate, tubular ampulla ( Fig. 81 View Figure 81 ). The ampulla bifurcates neat the centre of the female gland mass and into a short oviduct and the very short prostate. The prostate expands into the wide, s-shaped penial sheath. From the small, round bursa copulatrix the narrow vaginal duct extends and then narrows further before expanding into the long, wider vagina. The vagina exits into the genital aperture next to the penial sheath.

Remarks: Externally D. semilunus looks most similar to D. rodmani , D. tuberculatus , and D. fasciatus . All four species have a basically white ground colour, a noticeable dark brown band or bands of pigment crossing the dorsum and darker coloured rhinophore clubs. Of these, D. rodmani and D. tuberculatus lack numerous prominent longitudinal ridges found in D. fasciatus and D. semilunus . For a more complete comparison of D. fasciatus and D. semilunus , see the Remarks section for D. fasciatus .