Dermatobranchus diagonalis, 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 : 302-303

publication ID	https://doi.org/ 10.1111/j.1096-3642.2010.00649.x
persistent identifier	https://treatment.plazi.org/id/761B2D60-484F-E26D-0969-FD9BFC043A51
treatment provided by	Valdenar
scientific name	Dermatobranchus diagonalis
status	sp. nov.

Treatment

DERMATOBRANCHUS DIAGONALIS View in CoL SP. NOV.

( FIGS 42B View Figure 42 , 45–47 View Figure 45 View Figure 46 View Figure 47 )

Dermatobranchus sp.1 Ono, 1999:149 , no. 249. Dermatobranchus sp. 3 Gosliner, Behrens & Valdés,

2008: 308, bottom photo.

( Fig. 43C View Figure 43 ) is entirely smooth with no trace of denticles. The rachidian and inner lateral teeth of D. striatus are highly denticulate ( Fig. 28 View Figure 28 ) whereas in D. dendronephthyphagus ( Fig. 43 View Figure 43 ) both the rachidian and inner lateral teeth entirely lack denticles. The reproductive systems of these species also differ. In D. striatus , the penial sheath is bulbous ( Fig. 29 View Figure 29 ) and the vaginal duct gradually narrows distally. In D. dendronephthyphagus ( Fig. 44 View Figure 44 ), the penis is cylindrical and the vaginal duct is wide basally with an abrupt narrowing more distally.

Rudman (2005) depicted an animal from New South Wales, Australia, which he identified as D. nigropunctatus . However, the specimen differs externally in many respects from D. nigropunctatus . Dermatobranchus nigropunctatus has white longitudinal lines on the notum with black spots and orange rhinophores whereas D. dendronephthyphagus has black lines on a white notum and has white rhinophores with black on the lamellae. Internally, D. nigropunctatus ( Baba, 1949: fig. 89) has a rachidian and inner lateral tooth with multiple denticles whereas in D. dendronephthyphagus these teeth lack denticles. It is likely, based on an identical colour pattern, that Rudman’s specimen is identifiable with D. dendronephthyphagus .

Similarly, D. tongshanensis , D. multistriatus , and D. leoni have some similarities in colour pattern, but each with different combinations of orange, white, Type material: Holotype: CASIZ 174167, Rempi Lagoon, 25 km north of Madang, Papua New Guinea, collected 8.viii.1989 by T. M. Gosliner. Paratypes: CASIZ 068708, three specimens, one dissected, Rempi Lagoon, 25 km north of Madang, Papua New Guinea, 15 m depth, collected 8.viii.1989 by T. M. Gosliner. CASIZ 144082, three specimens, one dissected, south-west side Zamami Island, Kerama Islands, Japan, 5 m depth, collected 30.i.2000 by Atsushi Ono.

Geographical distribution: This species is known only from Papua New Guinea and the Kerama Islands of Japan (present study).

Etymology: The specific name diagonalis refers to the numerous diagonal ridges found on the surface of the notum and is a Latinized noun in apposition.

External morphology: The body shape of the living animal ( Fig. 42B View Figure 42 ) is elongate, flattened, and narrows at the posterior end. The foot does not project beyond the mantle margin. There is a series of about 30 shallow dorsal ridges diagonal to the mantle edge, giving the dorsum a distinct leaf-like appearance. Many of these ridges bifurcate along their length. The oral veil extends forward and has rounded corners. The narrow, widely spaced rhinophores are behind the oral veil and are almost cylindrical rather than bulbous. 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. Hyponotal and branchial lamellae are absent. The genital opening is on the right side of the body, near the anterior quarter of the body. The anus is situated approximately one - third of the way from the posterior end of the body.

The ground colour of the dorsum, the oral veil, and the foot is brown and is much darker along the medial portion of the notum. There are opaque white speckles and spots of various sizes scattered randomly on the dorsum. There is a pale yellow band present along the margin of the notum. The rhinophore stalk is white basally with a brown club with opaque white on the lamellae. Some orange pigment is present just below the opaque white apex. The oral veil is opaque white with a pale orange pigment band along the anterior margin. The dorsal surface of the foot margin is covered with dense reddish brown speckles.

Buccal armature: The jaws are large and thickly cuticularized ( Figs 45A View Figure 45 , 46A View Figure 46 ), with a thin masticatory margin that has denticles along the lower third of the jaw. Up to nine rows of pointed denticles are largely unifid, with a few bifid ones ( Figs 45B View Figure 45 , 46B View Figure 46 ). The entire radula is wider than it is long ( Fig. 45C View Figure 45 ). The radular formula of a paratype (CASIZ 068708) is 22 ¥ 11.1.1.1.11., whereas in a second paratype (CASIZ 144082) it is 21 ¥ 9.1.1.1.9 ( Fig. 46C View Figure 46 ). The rachidian teeth ( Figs 45D View Figure 45 , 46D View Figure 46 ) are broad with a large, pointed central cusp, 13–14 elongate flanking denticles on each side. The inner lateral tooth ( Figs 45D, E View Figure 45 , 46D–F View Figure 46 ) is a narrow comb with a pointed this group is similar anatomically. The reproductive system of D. diagonalis ( Fig. 47 View Figure 47 ) is virtually identical to that of D. striatus ( Fig. 29 View Figure 29 ), where both species have a short, curved prostate and short, wide conical penial sheath.