Trapania undulata, 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 : 306-307

TRAPANIA UNDULATA SP. NOV.

( FIGS 12F , 16D , 19 )

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: 9A854BA0-0AEA-4D98-9B38-A7ABD853AE90.

Trapania sp. 1 Gosliner et al., 2015: 141, top-left photograph. Gosliner et al., 2018: 58, bottom-left photograph.

Type material: Holotype: NMP 041331 , originally CASIZ 186132 , one specimen, dissected and sequenced, Ligpo Island , Balayan Bay, Batangas Province, Luzon Island, Philippines, 22 May 2011, collected by Peri Paleracio.

Type locality: Ligpo Island , Balayan Bay, Batangas Province, Luzon Island, the Philippines .

Geographical distribution: Known only from Lipgo Island, Philippines.

Etymology: From Latin word undulata , small wave, referring the notable undulating mantle margin of this species.

External morphology: Living specimen 7 mm ( Fig. 12F ). It has an elongated body typical of Trapania with a creamy white body throughout, including the extra-branchial and extra-rhinophoral appendages. Rhinophores are club-shaped with about nine lamellae and a pointed tip. Gill has a central, branching stalk flanked by two smaller branches. Both rhinophores and gills are reddish orange/brown becoming darker at the edges. The rhinophores are reddish orange basally and on the club the reddish orange is only found along the edges of the lamellae; the remainder of the rhinophores is the same colour as the body. Two black ridges run along the edge of the notal margin, approximately from the base of the rhinophores until just before the beginning of the extra-branchial appendages. The notal edge is thicker than the remainder of the body and varies in its width, creating the appearance of having an undulating margin. The anterior margins of the foot extend laterally as elongate appendages and are a more translucent white than the rest of the body. The oral tentacles are a more intense orange version of the rhinophore and gill coloration. The colour becomes lighter and more yellowish towards the tip, and darker and more dark-orange and black towards the base. This coloration continues across the oral veil creating a continuous mask that is mostly black with some reddish colour in the centre. The grey posterior foot had a dorsal indentation along its length creating two ridges along the lateral length. Slight bluish tint adorns the most posterior portion of foot.

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 well-developed jaws. The jaws contain several rows of acutely pointed, cylindrical jaw elements that are tightly packed together with a few gaps between them ( Fig. 19A ). The radular formula of the holotype is 22 × 1.0.1 ( Fig. 19B ). The older teeth ( Fig. 19C ) are much smaller than the newer ones ( Fig. 19D ) and the radula widens towards the more newly developed teeth. The teeth bear numerous evenly graded denticles with the smallest ones being found on the inner edge of the tooth and the longest ones adjacent to the primary cusp. There are approximately seven to 17 denticles on the inner side of the much larger, thick primary cusp, and one to three much smaller 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. 16D ). The pre-ampullary duct is short and enters the ampulla at its proximal end. The elongate, cylindrical ampulla is narrow at the distal end where it connects to the ovotestis. From there it widens and narrows again to the point where it divides into the short oviduct and long vas deferens. The oviduct enters the female gland mass. The vas deferens is initially narrow and widens into a convoluted, glandular prostatic portion and gradually transitions into the wide, muscular ejaculatory portion that is continuous with the wide penial sac. The penial sac terminates at the gonopore adjacent to the vagina. The vagina is widest at its basal opening and narrows abruptly as a short region prior to its junction with 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: Our molecular phylogeny, the ABGD analyses and the bPTP analysis successfully separates Trapania undulata from its similarly coloured sister-species T. gibbera . Furthermore, these two species are separated by a strong genetic divergence of 11.5–12.9% in the COI gene and 9.6−9.8% in the 16S gene ( Tables 3 , 4 ). Both species have a white body colour and have red markings on the oral tentacles, rhinophores and gill branches and a black line on the anterior margin of the head. In T. undulata , the notal margin undulates and has a black marginal line, whereas T. gibbera (see: Gosliner & Fahey, 2008: fig 1F) does not have a distinct notal margin and also lacks any lateral lines along the lateral edge of the notum. Another species with a similar colour pattern is Trapania caerulea Gosliner & Fahey, 2008 . It also has a white body colour and has red markings on the oral tentacles, rhinophores and gill branches and a black line on the anterior margin of the head. In T. caerulea , there are black lines that extend posteriorly from the rhinophores to the lateral margins of the body near the extrabranchial appendages, whereas T. undulata has black lines along the notal margin. The notal margin of T. caerulea is indistinct. Additionally, T. caerulea has a blue Y-shaped marking on the notum between the rhinophores and gill and a second blue line posterior to the gill, running to the posterior end of the foot. In T. undulata , there is only a small blue patch at the posterior end of the foot. Unfortunately, no specimens of T. caerulea are available for genetic comparison. Internally, all three species have similar radular teeth but in T. caerulea , the denticles on the inside of the primary cusp seem to alternate between small and large denticles, whereas they are less regular in T. undulata and T. gibbera . All three species have a wide distal portion of the vagina. In T. caerulea and T. gibbera , there are two distinct vaginal widenings, whereas in T. undulata there is only one. Both T. caerulea and T. gibbera have a long vagina, whereas T. undulata has a short vagina.

Figures

Figure 16. Reproductive systems. A, Trapania sp. ‘Anilao’, NMP 041329 (formerly CASIZ 182904), scale = 0.38 mm. B, Trapania kamagong sp. nov., holotype NMP 041336 (formerly 208585A), scale = 0.25 mm. C, Trapania kanaloa sp. nov., holotype CASIZ 189444, scale = 0.17 mm. D, Trapania undulata sp. nov., holotype NMP 041331 (formerly CASIZ 186132), scale = 0.16 mm. Abbreviations: am, ampulla; bc, bursa copulatrix; fgm, female gland mass; p, penial sac; pr, prostatic portion of vas deferens; rs, receptaculum seminis; ud, uterine duct; v, vagina.

Figure 19. Trapania undulata sp. nov., Scanning electron micrographs of buccal armature of holotype NMP 041331 (formerly CASIZ 186132). 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.