Dermatobranchus fasciatus, 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 : 307-311

publication ID	https://doi.org/ 10.1111/j.1096-3642.2010.00649.x
persistent identifier	https://treatment.plazi.org/id/761B2D60-4848-E213-0AD6-FC9DFDF43D39
treatment provided by	Valdenar
scientific name	Dermatobranchus fasciatus
status	sp. nov.

Treatment

DERMATOBRANCHUS FASCIATUS View in CoL SP. NOV.

( FIGS 42D View Figure 42 , 50–53 View Figure 50 View Figure 51 View Figure 52 View Figure 53 )

Dermatobranchus sp. 6 Gosliner, Behrens & Valdés, 2008: 310, bottom photo.

Type material: Holotype: CASIZ 174140 , 5 mm preserved, Pamilacan Island off Bohol Island, Panglao, Philippine Islands (9°29.4′N, 123°56.0′E), coral plateau with fine sand, 6–8 m depth, collected 14.vi.2004 by T. Gosliner, Y. Camacho, J. Templado, M. Malaquias, M. Poddubetskaia GoogleMaps . Paratypes: CASIZ 171384 , three specimens, 5–6 mm, two specimens, both 6 mm, dissected, Pamilacan Island off Bohol Island, Panglao, Philippine Islands (9°29.4′N, 123°56.0′E), coral plateau with fine sand, 6–8 m depth, collected 14.vi.2004 by GoogleMaps T. Gosliner , Y. Camacho, J. Templado, M. Malaquias, M. Poddubetskaia . CASIZ 171387 , two specimens, 7–15 mm preserved, one dissected, Pamilacan Island , off Bohol Island, Panglao, Philippine Islands (9°29.4′N, 123°56.0′E), coral plateau with fine sand, 6–14 m depth, collected 11.vi.2004 by GoogleMaps T. Gosliner , Y. Camacho, J. Templado, M. Malaquias, M. Poddubetskaia . CASIZ 073049 , one specimen, 10 mm preserved, Daphne’s Reef , north coast of Madang, Papua New Guinea, 13 m depth, collected 7.x.1986 by T. Gosliner .

Geographical distribution: This species is known from the Philippine Islands and Papua New Guinea (present study).

Etymology: The specific name fasciatus is a noun in apposition, from the Latin word meaning ‘band’. This is in reference to the distinguishing dark band across the notum of this species.

External morphology: The body shape of the living animal ( Fig. 42D View Figure 42 ) is elongate, flattened, and narrows at the posterior end. The foot does not project beyond the distinct mantle margin. There is a series of low longitudinal dorsal ridges. The oral veil extends forward and the corners protrude slightly. The rhinophores are situated behind the oral veil. They have a series of longitudinal lamellae on the rounded club. The stalk does not narrow noticeably. No marginal sacs were visible. There are no branchial or hyponotal lamellae under the mantle margin. The genital opening is situated about one-quarter of the distance along the anterior body side. The anus is situated approximately half of the way to the posterior end of the body. The ground colour of the dorsum and the foot is opaque white with dark spots scattered randomly. Both the mantle and foot have a pink edge. On the mantle, there are two transverse bands of tan coloration with darker spots scattered randomly within the bands. The bands of dark colour divide the dorsum into approximate thirds. The dorsal ridges are the same white as the ground colour and the depressions between the ridges are grey. The rhinophore stalk is white with some random dark spots and the club is dark brown to black with opaque white spots. The oral veil is opaque white with dark spots and a pink margin.

Buccal armature: The buccal mass is thick and muscular. The jaws are large and thickly cuticularized ( Figs 50A View Figure 50 , 51A View Figure 51 ), with a thick masticatory margin and five to six rows of long, pointed denticles ( Figs 50B View Figure 50 , 51B View Figure 51 ). The radular formula of the holotype (CASIZ 171384) is 26 ¥ 18.1.1.1.18 ( Fig. 52C View Figure 52 ), whereas in two paratypes the formulae are (CASIZ 073049) 21 ¥ 18.1.1.18 ( Fig. 51C View Figure 51 ) and (CASIZ 171387) 26 ¥ 23.1.1.1.23 ( Fig. 52A View Figure 52 ).

The rachidian teeth ( Figs 50D View Figure 50 , 51D View Figure 51 , 52B View Figure 52 ) are broad with a large, pointed central cusp that is twice as long and wide as the 11–14 flanking denticles on each side. The outer edge of each rachidian tooth is rounded with a wide notch near its centre. The inner lateral tooth ( Figs 50D View Figure 50 , 51D View Figure 51 , 52B View Figure 52 ) has a broad base and 11 pointed denticles that are equal in length. The next 18 lateral teeth have a comb-like appearance with a broad base and a projecting hook with 15–16 denticles ( Figs 50E View Figure 50 , 51E View Figure 51 , 52C View Figure 52 ). The outermost one to three teeth are curved, acutely pointed, and lack denticles ( Figs 50F View Figure 50 , 51F View Figure 51 , 52D View Figure 52 ).

Reproductive system: The reproductive organ arrangement is androdiaulic. It was examined in two specimens ( CASIZ 171384 and 171387) ( Fig. 53 View Figure 53 ). The latter specimen is larger, more mature, and is illustrated. The former had the same general morphology but had a less well-developed female gland mass and a less convoluted prostate. In the more mature specimen, the hermaphroditic duct leads into the long, curved, ovoid ampulla. The ampulla bifurcates into the female gland mass via a short oviduct and into the thick, tubular prostate, which forms one complete loop before it enters the wide elongate penial sheath. The round bursa copulatrix is larger than the ampulla. From the bursa, the long, narrow vaginal duct extends into an even narrower vagina, which exits into the genital atrium next to the penial sheath.

Remarks: Externally, D. fasciatus ( Fig. 42D View Figure 42 ) most closely resembles D. semilunus ( Fig. 74C–E View Figure 74 ) from the western Pacific. Both species have an opaque white ground colour with a band of tan or white across the dorsum. Dermatobranchus semilunus has a single u-shaped brown marking whereas D. fasciatus has two broader bands of brown. The rhinophores of D. fasciatus are dark brown to black with opaque white spots, whereas those of D. semilunus have white lines along each vertical lamella.

The radular morphology of D. fasciatus and D. semilunus is markedly different. Dermatobranchus fasciatus ( Figs 50–52 View Figure 50 View Figure 51 View Figure 52 ) has fewer radular teeth per half row (18–23) than does D. semilunus (29–73; Figs 78–80 View Figure 78 View Figure 79 View Figure 80 ). The rachidian tooth of D. fasciatus is wide with a wide central cusp and 11–14 denticles on either side. The rachidian of D. semilunus is much narrower with up to six on either side. The inner lateral teeth of D. fasciatus are broad and laterally directed with a series of denticles above a triangular cusp whereas in D. semilunus , there are three to four denticles on the outer side of an elongate central cusp. In D. fasciatus , the majority of teeth are denticulate, whereas in D. semilunus all of the remaining teeth other than the rachidian and first lateral teeth are smooth.

The reproductive system of these two species has some similarities such as the tubular ampulla and a thickened prostate. However, the prostate of D. fasciatus ( Fig. 53 View Figure 53 ) is more elongate and convoluted than that of D. semilunus ( Fig. 81 View Figure 81 ). Additionally, the vagina of D. semilunus widens near the genital aperture, whereas that of D. fasciatus is narrow near the aperture.

Dermatobranchus fasciatus also bears an external and internal resemblance to some specimens of D. tuberculatus . Both species have a whitish body with some transverse brown areas on the notum. Dermatobranchus tuberculatus has irregular tubercles on the notum, but lacks distinct longitudinal ridges. The rhinophores are lighter in colour in D. tuberculatus ( Fig. 74F–H View Figure 74 ) than in D. fasciatus and lack the opaque spots on the upper surface of the rhinophore club that are present in D. fasciatus . The radula of D. fasciatus is also similar in morphology to that of D. tuberculatus . Both species have a rachidian tooth with long lateral denticles. The central cusp of D. fasciatus has a much wider base than that found in D. tuberculatus . The rachidian tooth of D. tuberculatus ( Figs 82D View Figure 82 , 83E View Figure 83 , 84D View Figure 84 ) is narrower than that of D. fasciatus and Dermatobranchus sp. Coleman, 2008: 122 , as purple spots Dermatobranchus .

Dermatobranchus sp. Coleman, 2008: 123 , as Milne Bay Dermatobranchus . has six to ten denticles, whereas there are 14–18 denticles in D. fasciatus . Similarly, the posterior notch of D. tuberculatus is much narrower that that of D. fasciatus . The inner lateral teeth of D. tuberculatus are broad with a distinct prominent cusp at the same height as the adjacent denticles. In D. fasciatus , the cusp is located separately, below the level of the adjacent denticles. The second lateral tooth of D. tuberculatus has 5–11 denticles whereas that of D. fasciatus has 15–17 denticles. In D. tuberculatus the outer three to four teeth lack denticles whereas in D. fasciatus only the outer one to three teeth are smooth.

The reproductive system of D. fasciatus ( Fig. 53 View Figure 53 ) differs from that of D. tuberculatus ( Fig. 85 View Figure 85 ). In D. fasciatus , the vagina is straight and narrow and nears further near the genital aperture. In D. tuberculatus , the vagina is convoluted and has a thicker basal portion and a thinner distal portion that connects to the bursa copulatrix. Additionally, the prostate of D. tuberculatus is longer and more highly convoluted than that of D. fasciatus .