Dermatobranchus cymatilis, 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 : 296-299

publication ID	https://doi.org/ 10.1111/j.1096-3642.2010.00649.x
persistent identifier	https://treatment.plazi.org/id/761B2D60-4845-E267-0963-FAD6FE15389C
treatment provided by	Valdenar
scientific name	Dermatobranchus cymatilis
status	sp. nov.

Treatment

DERMATOBRANCHUS CYMATILIS View in CoL SP. NOV.

( FIGS 30G View Figure 30 , 40 View Figure 40 , 41 View Figure 41 )

Dermatobranchus sp. 10 Gosliner, Behrens & Valdés, 2008: 312, top photo.

Type material: Holotype: CASIZ 074694 , 17 mm preserved, dissected, Horseshoe Cliffs , west-north-west of Onna Village, Okinawa, Ryukyu Islands, Japan, 60 m depth, collected 27.ix.1989 by R. Bolland . Paratype: CASIZ 104706 , one specimen , 12 mm preserved, dissected. Horseshoe Cliffs , Okinawa, Ryukyu Islands, Japan, 53 m depth, collected 20.vii.1994 by R. Bolland ( RFB3286 -A) .

Geographical distribution: This species is only known from Okinawa (present study).

Etymology: The specific name cymatilis is from the Latin adjective meaning ‘sea-coloured or blue’ to describe the deep blue foot margin on this species.

Buccal armature: The jaws are large and thickly cuticularized ( Fig. 40A View Figure 40 ), with a thick masticatory margin and multiple rows of long, pointed denticles ( Fig. 40B View Figure 40 ). The radular formula of the holotype is 27 ¥ 66.1.1.1.66 ( Fig. 40C View Figure 40 ). The rachidian teeth ( Fig. 40D View Figure 40 ) have a narrower base than most Dermatobranchus , with a large, thick, and very long central cusp that is substantially wider than the up to seven flanking denticles on each side. The inner lateral teeth ( Fig. 40D View Figure 40 ) each have a triangular base with a very prominent, long first denticle with four, much shorter and narrower, pointed denticles. The next 66 lateral teeth are long hooks without denticles ( Fig. 40E, F View Figure 40 ).

External morphology: The body shape of the living animal ( Fig. 30G View Figure 30 ) is broad, flattened, and narrows at the posterior end. The foot does not project beyond the distinct mantle margin. There is a series of longitudinal dorsal ridges. The oral veil extends forward and has blunt extensions at the corners. The wide-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. Approximately onequarter of the way down on the right side of the body is the genital opening. The anus is situated approximately one-third of the way from the posterior end of the body.

The ground colour of the dorsum and foot is opaque white, although the foot has a blue margin. There is a pinkish-orange patch about midway on the dorsum that extends the width of the dorsum. Along the mantle margin and perpendicular to the edge, there are dark rays of colour that extend both downward onto the foot and upward into dark patches along the mantle edge. The dark patches extend up and across the dorsum as broken, dark bands. The dorsal ridges have dark crests, although the colour is broken along the length of the ridges. The rhinophore stalk is white and the club is dark. The oral veil is opaque white with dark perpendicular rays. There is an orange margin along a dark patch on the posterior side of the veil, close to the body.

Reproductive system: The reproductive organ arrangement is androdiaulic. The hermaphroditic duct leads into the wide tubular ampulla ( Fig. 41 View Figure 41 ). The ampulla bifurcates into the female gland mass via a short oviduct and into the short, narrow prostate. The prostate curves once then expands into the bulbous penial sheath. The round bursa copulatrix is smaller than the ampulla and much larger than the penial sheath. From the bursa, the very narrow vaginal duct extends into the equally narrow vagina, which exits into the genital atrium alongside the penial sheath.

Remarks: There are several Dermatobranchus species with white ground colour and dark crested dorsal ridges [ D. striatus Hasselt, 1824 ( Fig. 15I View Figure 15 ), D. dendronephthyphagus ( Figs 30H View Figure 30 , 42A View Figure 42 ), and D. semistriatus ( Baba, 1949: pl. 30, fig. 111)]. Dermatobranchus cymatilis has dark patches and ‘rays’ of dark coloration along the mantle edge and dark perpendicular lines along the foot edge. These rays of dark colour are absent in D. striatus , D. semistriatus , and D. dendronephthyphagus . The yellow coloration on the posterior portion of the oral veil of D. cymatilis differs from the fine orange margin of the veil found in D. semistriatus , D. striatus , and D. dendronephthyphagus . In addition, D. semistriatus has scattered small black spots on the notum, oral veil, and foot that are absent in D. cymatilus . Although the two species have a similar radular formula, D. cymatilus has much longer cusps on the radular teeth with fewer denticles on the teeth. The only other species with blue and yellow or orange colour on the oral veil is D. caeruleomaculatus . In this species, the blue spots are on the oral veil and the mantle margin, whereas in D. cymatilus the blue pigment is on the foot margin. The two differ internally as well. In D. caeruloemaculatus , the jaws have a smooth masticatory margin whereas those of D. cymatilus are denticulate. Additionally, the inner lateral tooth of D. caeruleomaculatus is smooth whereas that of D. cymatilus is denticulate.

The radular morphology of D. cymatilis differs from all the externally similar species, but is similar to that of D. semilunus . Both D. cymatilus ( Fig. 40 View Figure 40 ) and D. semilunus have a broad radula, but D. cymatilus has many more teeth per half row (67) than does D. semilunus (30–34) ( Figs 78–80 View Figure 78 View Figure 79 View Figure 80 ). In both of these species, the rachidian tooth has a much narrower base and a very prominent central cusp that is much longer than the central cusp of the rachidian tooth. In both species the inner lateral teeth have an elongate central cusp that is much longer than the adjacent denticles and the remaining teeth are devoid of denticles. In D. cymatilus , the outermost teeth are elongate but sharply curved whereas in D. semilunus they are straighter and more acutely pointed. The rachidian tooth of D. primus Baba, 1976 is also narrower than most other Dermatobranchus and it has a long, pointed median cusp. However, the first lateral tooth is not denticulate as found in D. cymatilis .

The reproductive system is also similar between D. cymatilus ( Fig. 41 View Figure 41 ) and D. semilunus ( Fig. 81 View Figure 81 ). In D. cymatilus the penial sheath and vagina are far narrower than in D. semilunus .