Trapania stegodon, Smirnoff & Donohoo & Gosliner, 2022

Smirnoff, Dimitri S., Donohoo, Samantha A. & Gosliner, Terrence M., 2022, Extra-branchial processes manifest extra diversity: systematics of the genus Trapania (Nudibranchia: Goniodorididae) and nine new species descriptions, Zoological Journal of the Linnean Society 196, pp. 270-313 : 297-300

TRAPANIA STEGODON SP. NOV.

( FIGS 4J , 12B , 14 )

Z o o b a n k r e g i s t r a t i o n: u r n: l s i d: z o o b a n k. org:act: A5044129-BF78-4375-9F4D-2A941FD13AF6.

Trapania sp. 3 Debelius & Kuiter, 2007: 18, middleright photograph.

Trapania sp. 10 Gosliner et al., 2015: 142, middle-left photograph.

Trapania sp. 11 Gosliner et al., 2018: 62, top-right photograph.

Type material: Holotype: NMP 041332 , originally CASIZ 186206 , one specimen, dissected and sequenced, Anilao Harbor (13.75993° N 120.92617°E), Balayan Bay, Batangas Province, Luzon Island, Philippines, 04 May 2011, collected by Alexis Principe.

Ty p e l o c a l i t y: A n i l a o H a r b o r (1 3.7 5 9 9 3° N 120.92617°E), Balayan Bay , Batangas Province, Luzon Island, the Philippines .

Geographic distribution: Known from the Philippines (present study) and Indonesia ( Debelius & Kuiter, 2007).

Etymology: This species is named for Stegodon luzonensis von Koenigwald 1956, a Pleistocene megafauna with ivory tusks that roamed Luzon, Mindanao and other Philippine islands. It refers to the white-tipped extra-rhinophoral and extrabranchial appendages. It is a noun in apposition.

External morphology: Living animal ( Fig. 12B ) 15 mm. It has an opaque grey body covered dorsally with speckled red-brown colour characterized by small and large blotches of missing pigmentation. Notable blotches reside laterally below the rhinophores, below the gill plume and at the posterior portion of the foot. Extra-rhinophoral and extra-brachial appendages have red brown at base but are light yellow to the tip. Rhinophores, eight to ten lamellae and a pointed tip, are uniformly wide along their length and the same colour as the red-brown body, except for the grey tip. Oral tentacles are coloured at their base and opaque grey at the tip. Similarly, the anterior margins of the foot, which extend laterally as elongate appendages, are coloured at their base and opaque grey at their tip. The gill plume is composed of three large and highly branched elements that are the same colour as the body.

Buccal mass: The buccal mass is muscular with a moderately enlarged buccal pump on the dorsal surface. Inside the anterior portion of the mass is a pair of well-developed jaws. The jaws contain several rows of acutely pointed and stubby jaw elements of various sizes that are tightly packed together with a few gaps between them ( Fig. 14A ). The radular formula of the holotype is 44–45 × 1.0.1 ( Fig.14B ). The older teeth ( Fig. 14C ) are much smaller than the newer ones ( Fig. 14D ) and the radula widens gradually towards the more newly developed teeth. The teeth bear numerous denticles of irregular length, but with the smallest ones being found on the inner edge of the tooth. There are approximately nine to 16 denticles on the inner side of the much larger, narrow primary cusp, and one to two small denticles on the outer side of the cusp. The older teeth have fewer denticles than the more recently developed ones.

Reproductive system: The mature reproductive system is triaulic ( Fig. 4J ). The narrow pre-ampullary duct enters the saccate ampulla near the middle of its length. The ampulla narrows again at the postampullary duct and divides into the short narrow oviduct, which enters the female gland mass, and the vas deferens. The vas deferens gradually widens into the thick prostatic portion. At its proximal end, the vas deferens abruptly narrows into a short, thin, curved ejaculatory segment, which again widens into the relatively short, bulbous penial sac. The penial sac terminates adjacent to the vagina. The vagina is relatively short and wide throughout its entire length and enters the base of the large, spherical bursa copulatrix adjacent to the receptaculum duct. The receptaculum duct curves and enters the base of the smaller, spherical receptaculum seminis. The uterine duct emerges from the receptaculum duct near the base of the receptaculum and enters the female gland mass. The female gland mass is composed of the large mucous gland and the smaller albumen and membrane glands.

Remarks: This species is compared to the four other members of its species complex below in the remarks following Trapania kamagong .

Figures

Figure 4. Reproductive systems. A, Trapania japonica (Baba, 1935), CASIZ 221116, scale = 0.50 mm. B, Trapania tatsulok sp. nov., holotype, NMP 041333 (formerly CASIZ 200530), scale = 0.33 mm. C, Trapania kahel sp. nov., holotype, NMP 041330 (formerly CASIZ 186131), scale = 0.28 mm. D, Trapania lemanioides sp. nov., holotype, NMP 041335 (formerly

Figure 14. Trapania stegodon sp. nov. Scanning electron micrographs of buccal armature of holotype NMP 041332, (formerly CASIZ 186206). A, jaw. B, entire radula. C, older radular teeth. D, newly formed radular teeth.

Figure12. Living animals.A, Trapaniatamaraw sp.nov.,holotype,NMP 041334(formerly CASIZ 208391)PuertoGalera,Mindoro Oriental. B, Trapania stegodon sp. nov., holotype NMP 041332 (formerly CASIZ 186206), Anilao Harbor, Batangas, Philippines. C, Trapania sp. ‘Anilao’, preserved specimen, NMP 041329 (formerly CASIZ 182904), Anilao Harbor, Batangas, Philippines. D, Trapania kamagong sp. nov., holotype, NMP 041336 (formerly CASIZ 208585A), Puerto Galera, Mindoro Oriental, Philippines. E, upper photo Trapania kanaloa sp. nov., holotype CASIZ 189444, lower photo, Trapania sp. cf. kanaloa, CASIZ 199250, Koloa Landing, Kaua’i, Hawai’i, photo by Cory Pittman. F, Trapania undulata sp. nov., holotype, NMP 041331 (formerly CASIZ 186132), Ligpo Island, Bauan, Batangas, Philippines.