Dermatobranchus kokonas, 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 : 319-321

publication ID	https://doi.org/ 10.1111/j.1096-3642.2010.00649.x
persistent identifier	https://treatment.plazi.org/id/761B2D60-483C-E21D-0ACF-F9E8FEE13F97
treatment provided by	Valdenar
scientific name	Dermatobranchus kokonas
status	sp. nov.

Treatment

DERMATOBRANCHUS KOKONAS View in CoL SP. NOV.

( FIGS 58B View Figure 58 , 61–62 View Figure 61 View Figure 62 )

Dermatobranchus sp. 14 Gosliner, Behrens & Valdés, 2008: 313, below top photo.

Type material: Holotype: CASIZ 075272 , one specimen, dissected, Christmas Bay , Bagabag Island, Madang, Papua New Guinea (4°49.15416′S, 146°13.98558′E), 20 m depth, collected 26.xi.1990 by T. M. Gosliner. GoogleMaps

External morphology: The body shape of the living animal ( Fig. 58B View Figure 58 ) is slender, elongate, flattened, and narrows to the rounded posterior end. The foot does not project beyond the distinct mantle margin. Its mantle is devoid of longitudinal ridges and small, low, randomly distributed conical tubercles are present on the surface. The oral veil extends forward and is rounded at the corners. The rhinophores are situated behind the oral veil. They have a series of longitudinal lamellae on the rounded club with a short extension apically. The stalk narrows slightly. There are marginal sacs on the underside of the mantle edge. The genital opening is about halfway along the body on the right side. The anus is situated approximately half of the way towards the posterior end of the body. There are no branchial or hyponotal lamellae under the mantle margin.

The ground colour of the dorsum, foot and oral veil is opaque white as are the tubercles. A few brown spots are present on the notum. The rhinophore stalk is white and the club is brown. The oral veil is opaque white with a bright orange margin.

Buccal armature: The cuticular jaws ( Fig. 61A View Figure 61 ) are thin and elongate with one to two rows of highly divided denticles ( Fig. 61B View Figure 61 ) along the lower third of the jaw. The radular formula of the holotype ( CASIZ 075272) is 28 ¥ 9.1.1.1.9 ( Fig. 61C View Figure 61 ). The rachidian teeth ( Fig. 61D View Figure 61 ) are broad with a broad base and an elongate, wide central cusp. The cusp is flanked by seven to eight elongate denticles on either side. The inner lateral tooth is broad with five to seven elongate denticles on the outer side of the central cusp. The next five laterals bear one to seven denticles on the outer side of the sharp cusp. The outer two teeth lack denticles ( Fig. 61C View Figure 61 ).

Reproductive system: The reproductive organs are androdiaulic ( Fig. 62 View Figure 62 ). The ampulla is curved and saccate, branching to the female gland mass via a short oviduct and as a narrow, elongate convoluted vas deferens that terminates in a large, broad penial sheath. The penial papilla has an acutely pointed apex. The well-developed female gland mass is well differentiated into a large mucous gland and smaller albumen and membrane glands. Adjacent to the penis is a thin convoluted vagina that leads to a relatively small bursa copulatrix inside the folds of the female glands.

Remarks: Externally, this species is similar to white forms of D. albus , with an opaque white notum and an orange line on the edge of the oral veil. However, D. kokonas lacks longitudinal ridges and lacks the orange pigment on the apices of the rhinophores and along the notal margin. Internally, the two species differ in the dentition of the jaws. Both have elongate jaws with denticles near the basal portion opposite the hinged junction of the jaws. In D. albus , there are six to seven rows of acutely pointed denticles ( Figs 8B View Figure 8 , 10A View Figure 10 ), whereas in D. kokonas there are two rows with multifid apices ( Fig. 61A, B View Figure 61 ). Both species have a narrow radula with a multidenticulate rachidian and a broad, denticulate inner lateral. In D. albus , the remaining laterals are all hammate without denticles, whereas in D. kokonas , the first six laterals are denticulate with only the outer two being smooth. The penial sheath is proportionately much longer in D. kononas than in D. albus , as is the prostate.

The jaws and radula of D. kokonas have distinctive characteristics in common with several other species of Dermatobranchus : D. fortunatus , D. earlei , D. rodmani , D. piperoides , and D. microphallus . The jaws of all of these species have one or two rows of masticatory denticles with divided apices. Additionally, all of these species have an elongate radula with a wide inner lateral tooth. Two of these species, D. earlei and D. microphallus , have prominent longitudinal ridges, whereas the other species lack ridges. Dermatobranchus rodmani may have three low ridges that are not always evident. Of the species without ridges, D. kokonas is the only species with a uniformly white body colour. The only other white species is D. piperoides , which also has black spots on the body and black apices on the orange rhinophores, whereas D. kokonas has brown rhinophores. The oral veil of D. kokonas has a fine orange marginal line whereas in D. piperoides there is an orange spot over much of the anterior portion of the veil. The radular configuration also differs between the two species. In D. kokonas ( Fig. 61 View Figure 61 ) there are nine outer lateral teeth per side whereas in D. piperoides ( Fig. 69 View Figure 69 ) there are five to six teeth per side. The inner lateral teeth of D. kokonas have five to seven denticles, whereas there are 14–15 denticles on those of D. piperoides . Differences in the reproductive system also separate these two species. In D. kokonas , the prostate is narrow and elongate, whereas in D. piperoides it is shorter and thicker. The penial papilla of D. kokonas is elongate and conical whereas it is shorter and blunter in D. piperoides .