Trapania kahel, 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 : 286-288

TRAPANIA KAHEL SP. NOV.

( FIGS 1C , 4C , 6 )

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: DEBA67C6-F65D-418D-8AE6-40063C09F594.

Trapania sp. 8 Gosliner et al., 2015: 143, bottom-right photograph.

Trapania sp. 9 Gosliner et al., 2018: 61, bottom-left photograph.

Type material: Holotype: NMP 041330 , originally CASIZ 186131 , one specimen, dissected, Matotonngil Point (13.75528°N 120.90672°E), Mabini, Batangas Province, Luzon Island, Philippines, 3 May 2011, collected by Alicia Hermosillo. Paratype: CASIZ 186133 , one specimen, dissected and sequenced, Matotonngil Point (13.75528°N 120.90672°E), Mabini, Batangas Province, Luzon Island, Philippines, 8 March 2011, collected by Alicia Hermosillo and Peri Paleracio.

Type locality: Matotonngil Point (13.75528°N 120.90672°E), Mabini , Batangas Province, Luzon Island, the Philippines .

Geographical distribution: Known only from Matotongil Point, the Philippines.

Natural history: Feeds on an orange, encrusting bryozoan on small rocks surrounded by coarse sandy areas.

Etymology: Kahel is theTagalog word for orange and refers to the encrusting, orange bryozoan on which this species has been observed feeding. It is a noun in apposition.

External morphology: Living specimens are 5–6 mm ( Fig. 2C ). They have an elongated body typical of Trapania , with an orange-red body coloration. Foot has a dorsal ridge coloured a dark brown/black running all the way to the posterior tip. The same intensity of dark pigmentation covers the three gill branches, the oral tentacles and the top two-thirds of the rhinophores, each with seven lamellae. The extra-branchial and extra-rhinophoral appendages have a slight curve typical of Trapania and are both coloured a bright opaque white. While the mantle between the extra-branchial appendages is the same orange-brown as the rest of the body, a continuous band of bright solid white runs tip-to-tip between the extra-rhinophoral appendages, creating the appearance of a white ribbon. The same white coloration extends up the first third of the rhinophores. Rhinophores are spearshaped with about ten lamellae and a pointed tip. The basal half of the rhinophores is white with a dark-brown to black apex. The oral tentacles are thin and elongate covered with black pigment along their entire length. The anterior margins of the foot extend laterally as elongate appendages are more colourless and are more translucent than the rest of the body.

Buccal mass: The buccal mass is muscular with a moderately developed buccal pump on the dorsal surface. Inside the anterior portion of the mass is a pair of weakly developed jaws. The jaws contain weakly developed triangular elements and have less cuticularization compared to other Trapania ( Fig. 6A ). In the image, a membrane partially covers the elements, but the shape of the thin triangular elements is still visible. The radular formula of the holotype is 16 × 1.0.1 ( Fig. 6B ). The teeth are all highly arched. The newer teeth ( Fig. 6C ) are slightly larger than the older teeth ( Fig. 6D ) and the radula widens somewhat towards the more newly developed teeth. The teeth bear numerous denticles with the smallest ones being found on the inner edge of the tooth. There are approximately six to seven denticles on the inner side of the much larger primary cusp and one to three denticles on the outer side of the cusp. All of the denticles other than primary cusp are similar in size. The older teeth have a more pronounced primary cusp, but the smaller denticles are consistent in size across all teeth.

Reproductive system: The mature reproductive system is triaulic ( Fig. 4C ). The narrow pre-ampullary duct enters the saccate ampulla at its base, adjacent to the post-ampullary duct. The post-ampullary duct divides into the short oviduct and elongate vas deferens. The oviduct enters the female gland mass. The vas deferens is equally sized throughout its length and forms a loop that continues into a convoluted, glandular prostatic portion. This gradually transitions into the slightly wider, muscular ejaculatory portion that is continuous with the wide penial sac. The penial sac terminates at the gonopore adjacent to the vagina. The short vagina is uniformly narrow throughout its length and joins the large, spherical bursa copulatrix and short narrow receptaculum duct. The receptaculum duct joins the pyriform receptaculum seminis near the division of the short uterine duct, which enters the female gland mass. The female gland mass is composed of the large mucous gland and the smaller albumen and membrane glands.

Remarks: In our molecular phylogeny, Trapania kahel is moderately supported as sister to T. japonica ( PP = 0.94, BS = 54) in a clade composed of T. scurra , T. palmula , T. japonica and T. tatsulok . The ABGD analysis and the bPTP analysis reveal a strong genetic divergence of 14.9% in the COI gene and 13.4−13.9% in the 16S gene between T. kahel and T. scurra and 15.1%/13.7−14.0% between T. kahel and T. palmula ( Tables 3 , 4 ). The bright orange colour with white extra-branchial and extra-rhinophoral appendages also help distinguish this species from all described members of Trapania . No members of this clade have an orange body colour. Internally, T. kahel is similar to other members of the clade that have jaws with acutely pointed jaw elements but differs from T. tatsulok , which has jaw elements with numerous pointed spikes. As in T. scurra , T. palmula and T. japonica , the radular teeth have only a single prominent denticle, but have narrower teeth with fewer, coarser denticles. The vagina of T. kahel is much shorter than in other members of the clade and the male duct is elongate with little distinction or narrowing between the prostatic and ejaculatory portions of the duct. The other members of this clade have a distinctly narrower portion of the ejaculatory duct.

Figures

Figure 1. Bayesian inference and maximum likelihood phylogeny of Trapania estimated from the (16S + COI + 18S + H3) concatenated dataset. Values above branches refer to posterior probabilities (PP) and values below branches refer to bootstrapping values (BS). Dashes indicate relationships not recovered during the maximum likelihood analysis. To the right are the results of the ABGD analysis (oval) and the bPTP analysis (square).

Figure 2. Living animals. A, Trapania japonica (Baba, 1935), CASIZ 221116, Mabini, Batangas, Philippines, photo by Peri Paleracio. B, Trapania tatsulok sp. nov., holotype, NMP 041333 (formerly CASIZ 200530), Calatagan, Batangas, Philippines. C, Trapania kahel sp. nov., holotype, NMP 041330 (formerly CASIZ 186131), Mabini, Batangas, Philippines. D, Trapania lemanioides sp. nov., holotype, NMP 041335 (formerly CASIZ 208433), Puerto Galera, Mindoro Oriental, Philippines. E, Trapania lemanioides sp. nov., paratype, CASIZ 221979, Romblon, Philippines. F, Trapania aurata Rudman, 1987, CASIZ 186205, Mabini, Batangas, Philippines. G, Trapania reticulata Rudman, 1987, CASIZ 191431, Madang, Papua New Guinea, photo by Vanessa Knutson. H, Trapania tigger sp. nov., holotype, NMP 041328 (formerly CASIZ 180412), Mabini, Batangas, Philippines, photo by Alicia McKowen. Photo by T. Gosliner unless indicated.

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 6. Trapania kahel sp. nov. Scanning electron micrographs of buccal armature of holotype NMP 041330 (formerly CASIZ 200530). A, jaws. B, entire radular ribbon. C, newly formed radular teeth. D, oldest radular teeth.