Dermatobranchus earlei, 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 : 305-307

DERMATOBRANCHUS EARLEI SP. NOV.

( FIGS 42C , 48 , 49 )

Type material: Holotype: CASIZ 097441 , one specimen, dissected, 10 mm preserved, Makhallah Bay , Arabian Sea, Oman, 10 m depth, collected 30.x.1993 by J. Earle.

central cusp with nine to ten pointed denticles. The remaining 11 lateral teeth are hook-shaped without any denticles ( Figs 45E, F , 46E, F ).

Reproductive system: The reproductive organs are androdiaulic ( Fig. 47 ). The hermaphroditic preampullary duct exits from the ovotestis and widens into the ampulla. The entire ampulla is curved and enveloped by the female glands. A short vas deferens widens into a curved prostatic section. The penial sheath is short and conical. Adjacent to the penial sheath is a thin vagina that leads to a relatively small bursa copulatrix inside the folds of the female glands.

Remarks: The numerous diagonal ridges of D. diagonalis are distinctive and are not found in any other species of Dermatobranchus . The colour pattern is most similar to D. phyllodes , but that species has short ridges and the ridges are situated perpendicular to the longitudinal body axis. These two species have major differences in radular morphology (see Remarks for D. phyllodes ).

The radular morphology of D. diagonalis is similar to other taxa that have a broad rachidian tooth, and comb-shaped inner lateral teeth and the remaining teeth devoid of denticles ( D. striatus , D. albus , D. otome , and D. oculus ). Members of this group also have numerous rows of acutely pointed denticles on the posterior base of the jaws. None of these species has a colour pattern similar to D. diagonalis and they all have longitudinal rather than diagonally radiating notal ridges. The reproductive system of members of Geographical distribution: This species is only known from Oman (present study).

Etymology: The specific name earlei is named for John Earle, who provided the type specimen of this species from the Arabian Sea.

External morphology: The body shape of the living animal ( Fig. 42C ) is wedge-shaped (wide anteriorly and gradually narrowing at the posterior end, similar in body shape to that of most species of Armina ). The foot does not project beyond the distinct mantle margin. The dorsum has very low, broken ridges that angle from along the midline to the mantle margin. The oral veil projects only slightly at the anterior end. 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 and the club has a small projecting tip. Marginal sacs are visible along the mantle edge.

There are no longitudinal hyponotal or branchial lamellae under the mantle margin. The genital opening is situated at the anterior quarter of the body 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 and the foot is pale blue. On the mantle, there are several distinct areas of brown pigment. The dorsal ridge crests are tan. The mantle margin is pale white. The rhinophore stalk is pale white with tan pigment. The club is black. The tip of the rhinophores is white. The oral veil is pale white with an orange margin.

Buccal armature: The jaws are large and thickly cuticularized ( Fig. 48A ), with a thick masticatory margin and a row of irregular denticles ( Fig. 48B ). The radular formula of the holotype is 4.5.1.1.1.5.4. The entire radula was not observed; thus, the number of rows of teeth could not be determined. The rachidian teeth ( Fig. 48C ) are broad with a large, spearshaped central cusp and ten flanking denticles on each side. The base of each rachidian has two humps, one on either side at the upper edge. The first lateral tooth ( Fig. 48C ) is a broad comb with a blunt pointed base and 9–12 pointed denticles. The next four to five lateral teeth are comb-shaped with a longer, pointed first denticle and up to 4–11 long pointed denticles ( Fig. 48D ). The last four lateral teeth are hooks without denticles.

Reproductive system: The reproductive organ arrangement is androdiaulic. The elongate hermaphroditic duct leads into the wide, tubular ampulla ( Fig. 49 ). The ampulla bifurcates into the female gland mass via a short oviduct, and into the short, curved prostate. The prostate expands into the wide, bulbous penial sheath. From the large, round bursa copulatrix the short, narrow vaginal duct leads to the slightly wider vagina. The vagina exits into the genital atrium next to the penial sheath.

Remarks: Externally, D. earlei most closely resembles D. caesitius from South Africa. See the Remarks section of D. caestitius for comparison of these taxa.

Dermatobranchus earlei is internally similar to other species with an elongate radula, which has relatively few teeth per row. These taxa include D. substriatus Baba, 1949 , D. striatellus Baba, 1949 , D. fortunatus , D. microphallus sp. nov., D. funiculus sp. nov., D. rodmani sp. nov., D. piperoides sp. nov., and D. kokonas sp. nov. None of these species has a bluish colour pattern as in D. earlei . Of these species, D. fortunatus , D. piperoides , and D. kokonas lack prominent dorsal ridges that are evident in D. earlei and the remaining taxa. Both D. microphallus and D. rodmani have less prominent ridges than those of D. earlei . In D. substriatus , D. striatellus , and D. funiculus , the ridges are less crowded, wider, and continuous rather than interrupted, whereas in D. earlei they are narrow, congested, and frequently interrupted.

Figures

Figure 42. Living animals. A, Dermatobranchus dendronephthyphagus sp. nov., living animal on prey, Okinawa, Ryukyu Islands, photo by Bob Bolland. B, Dermatobranchus diagonalis sp. nov., CASIZ 068708, Rempi Lagoon, Papua New Guinea, photo T. M. Gosliner. C, Dermatobranchus earlei sp. nov., photo by John Earle. D, Dermatobranchus fasciatus sp. nov., Panglao, Bohol, Philippines, photo by Marina Poddubetskaia. E, F, Dermatobranchus funiculus sp. nov. living animals, Okinawa, Ryukyu Islands, photos by Bob Bolland. G, H, Dermatobranchus funiculus sp. nov. living animals, Maricaban Island, Luzon, Philippines, photos by T. Gosliner.

Figure 45. Dermatobranchus diagonalis sp. nov. Buccal armature, CASIZ 070451, Rempi Lagoon, Madang, Papua New Guinea. A, jaw; B, masticatory margin; C, entire radula; D, central portion of radula; E, middle lateral teeth; F, outer lateral teeth.

Figure 46. Dermatobranchus diagonalis sp. nov. Buccal armature, CASIZ 144082, Kerama Islands, Japan. A, jaws; B, masticatory margin; C, entire radula; D, central portion of radula; E, half-row of radular teeth; F, outer lateral teeth.

Figure 47. Dermatobranchus diagonalis sp. nov. Reproductive system, CASIZ 070451, Rempi Lagoon, Madang, Papua New Guinea. a, ampulla; bc, bursa copulatrix; fg, female gland mass; pr, prostate; ps, penial sheath; v, vagina; vd, vaginal duct. Scale bar = 0.5 mm.

Figure 48. Dermatobranchus earlei sp. nov. Buccal armature, CASIZ 097441, Oman. A, jaws; B, masticatory margin; C, central portion of the radula; D, middle and outer lateral teeth.

Figure 49. Dermatobranchus earlei sp. nov. Reproductive system. CASIZ 097441, Oman. a, ampulla; bc, bursa copulatrix; fg, female gland mass; pr, prostate; ps, penial sheath; v, vagina; vd, vaginal duct. Scale bar = 0.35 mm.