Trapania tatsulok, 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 : 283-286

publication ID	https://doi.org/ 10.1093/zoolinnean/zlac009
publication LSID	lsid:zoobank.org:pub:C288BAB2-A92C-4F13-B04D-D6D4510461F5
DOI	https://doi.org/10.5281/zenodo.7043800
persistent identifier	https://treatment.plazi.org/id/9DF25EE2-655D-485B-92A7-45B7D23B188D
taxon LSID	lsid:zoobank.org:act:9DF25EE2-655D-485B-92A7-45B7D23B188D
treatment provided by	Plazi
scientific name	Trapania tatsulok
status	sp. nov.

Treatment

TRAPANIA TATSULOK View in CoL SP. NOV.

( FIGS 2B View Figure 2 , 4B View Figure 4 , 5 View Figure 5 )

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. o r g: a c t: 9 D F 2 5 E E 2 - 6 5 5 D - 4 8 5 B - 9 2 A 7 - 45B7D23B188D.

Trapania sp. 15 Gosliner et al., 2015: 145, middle-right photograph.

Trapania sp. 17 Gosliner et al., 2018: 63, bottom-left photograph.

Typematerial: Holotype: NMP041333 View Materials ,originallyCASIZ 200530, one specimen, dissected and sequenced, Verde Island Passage (13.92816°N 120.6109°E), Calatagan, Batangas Province, Luzon Island, Philippines, 19 May 2014, collected by Shayle Matstuda. GoogleMaps

Type locality: Verde Island Passage (13.92816ºN 120.6109°E), Calatagan, Batangas Province, Luzon Island, Philippines GoogleMaps .

G e o g r a p h i c a l d i s t r i b u t i o n: K n o w n o n l y f r o m Calatagan, the Philippines.

Etymology: Tatsulok is the Tagalog word for triangle and it refers to the black equilateral triangle found on the dorsum of this species. It is a noun in apposition.

External morphology: The living animal ( Fig. 2B View Figure 2 ) is 5 mm. The body coloration is opaque white with dark orange pigmentation on the outer three quarters of the extra-rhinophoral and extra-branchial appendages. There is a gradation of colour such that the basal portion is more yellow orange. The extra-rhinophoral and extra-branchial appendages are somewhat curved and cylindrical with a uniform diameter throughout. The conical, perfoliate rhinophores have five to six lamellae and are dark maroon/brown except for an opaque-white base. The oral tentacles are identical to the rhinophore coloration, with black spanning between the oral tentacles colouring the anterior margin of the head with a semicircle protruding posteriorly at the medial line. The anterior margins of the foot extend laterally as elongate appendages and are more translucent than the rest of the body. This specimen has a distinct black, equilateral triangle on its dorsum centred on the body midline, midway between the gill plume and rhinophores, with its tip pointing anteriorly. There are three other black markings adorning each side of the lateral flanks, starting at the middle of the body and extending to the posterior extension of the foot. There is another black spot situated medially, posterior to the gill plume.

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 ( Fig. 5A View Figure 5 ). The jaw surface is covered with small semi-spheres, each covered with numerous short and blunt spikes resembling a medieval flail or mace ( Fig. 5B View Figure 5 ). The radular formula of the holotype is 25 × 1.0.1 ( Fig. 5C View Figure 5 ) in the specimen examined and the radula was fragmented into three pieces. The older teeth are much smaller than the newer ones and lack denticles on the outer side of the radular tooth ( Fig. 5C View Figure 5 ). The teeth bear numerous denticles with the smallest ones being found on the inner edge of the tooth. In the newer, larger teeth, which were separated from the main part of the radula during preparation, there are approximately five to seven denticles on the inner side of the larger primary cusp with the ones nearest the primary cusp being the largest (almost the same size as the primary cusp) and a variable number of denticles on the outer side of the cusp with some teeth entirely lacking an outer denticle. There may be as few as three larger denticles or as many as eight smaller denticles, depending on the tooth ( Fig. 5D View Figure 5 ).

Reproductive system: The mature reproductive system is triaulic ( Fig. 4B View Figure 4 ). The pre-ampullary is narrow at the distal end where it connects to the ovotestis. It then enters the saccate, elongate ampulla near its distal end. The ampulla narrows to the point where it divides into the short oviduct and the elongate vas deferens. The oviduct enters the female gland mass. The vas deferens widens into a curved prostatic portion that narrows into a short ejaculatory segment that is contiguous with the relatively narrow penial sac.The penial sac exits adjacent to the narrow vagina. The vagina is narrow throughout its length and joins the almost spherical bursa copulatrix adjacent to the long, narrow receptaculum duct. The receptaculum duct joins the spherical receptaculum seminist adjacent to the moderately long uterine duct, which enters the female gland mass. The bursa and receptaculum are roughly the same size. The female gland mass is composed of the large mucous gland and the smaller albumen and membrane glands.

Remarks: Our molecular phylogeny, the 16S ABGD analysis and the bPTP analysis reveal that Trapania tatsulok is a distinct species of Trapania and can be distinguished by its unique colour pattern of white pigment on the body with black pigment on the oral tentacles, anterior margin of the head, on the rhinophores, medially in front and behind the gill and laterally on the sides of the body. This species is a member of a clade that includes T. scurra , T. palmula , T. japonica and T. kahel (see Remarks section below). Both T. scurra and T. palmula have a stout body with proportionately thicker extra-rhinophoral and extra-branchial processes, whereas T. japonica has a more delicate, elongate body with thin, elongate extra-rhinophoral and extra-branchial as in T. tatsulok . These last two species also have a similar colour pattern of a white body with dark brown to black markings. In T. japonica , the extra-rhinophoral and extra-branchial process are yellow, while in T. tatsulok they are orange. The dark markings of T. japonica are rounded spots, whereas they are irregular in shape in T. tatsulok , with the exception of the triangular marking anterior to the gill. The gill is white in T. tatsulok , whereas the outer portions of the gill branches are black in T. japonica .

Internally, T. tatsulok has several features that clearly distinguish it from other members of the clade of which it is a member. The jaw elements of T. tatsulok contain numerous minute spikes resembling a flail, while T. scurra , T. palmula and T. japonica have simple, acutely pointed jaw elements ( Gosliner & Fahey, 2008, fig. 8a, fig. 10a; Fig. 5B View Figure 5 ). The radular teeth of T. tatsulok have one or two large denticles on the inner side of the primary cusp and numerous smaller denticles, whereas the teeth of T. scurra , T. palmula and T. japonica all have a single prominent cusp and numerous smaller denticles ( Gosliner & Fahey, 2008: fig. 8b–d, fig. 10b–d; Fig. 5D View Figure 5 ). The reproductive system of T. tatsulok is similar to that of T. palmula , with a relatively elongate vagina and ejaculatory portion of the vas deferens, but in T. palmula ( Gosliner & Fahey, 2008: fig. 9) both the vagina and ejaculatory duct are more elongate than in T. tatsulok . In T. scurra ( Gosliner & Fahey, 2008: fig. 11) and T. japonica ( Fig. 4A View Figure 4 ) the vagina and ejaculatory portion of the vas deferens are much shorter than in T. tatsulok .

Three other described species of Trapania from the eastern Pacific have similar colour patterns to T. tatsulok . Trapania velox , T. goslineri Millen & Bertsch, 2000 and T. darwini Gosliner & Fahey, 2008 , all have white body pigment with brown or black markings and orange pigment, but differ in the pattern and distribution of these pigments. In these three species, there is both brown and orange pigment on the extra-rhinophoral and extrabranchial processes, while in T. tatsulok there is only orange. These three species also have orange rhinophores, while in T. tatsulok the rhinophores are dark brown to black. In T. velox , the translucent, white body has darkbrown longitudinal lines, while T. goslineri has brown spots. In T. darwini there is a series of longitudinal brown markings interrupted by white spots. Bhave (2010) posted a photo of another species from India that has yet another

CASIZ 208433 ), scale = 0.33 mm. E, Trapania aurata Rudman, 1987 , CASIZ 186205 , scale = 0.46 mm. F, Trapania reticulata Rudman, 1987 , CASIZ 191431 , scale = 0.50 mm. G, Trapania darvelli Rudman, 1987 , CASIZ 222004 , scale = 0.4 mm. H, Trapania tigger sp. nov., holotype , NMP 041328 View Materials (formerly CASIZ 180412 ), scale = 1.0 mm. I, Trapania tamaraw sp. nov ., NMP 041334 View Materials (formerly CASIZ 208391 ), scale = 0.50 mm. J, Trapania stegodon sp. nov., holotype NMP 041332 View Materials (formerly CASIZ 186206 ), scale = 0.50 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 .

286 D. S. SMIRNOFF ET AL.

combination of white, orange and brown markings and differs from the species discussed above. Rudman (2010) suggested that this specimen may be T. goslineri and that T. darwini may also be the same species as T. goslineri , despite the morphological distinctions clearly noted by Gosliner & Fahey (2008). Another feature clearly distinguishes the specimen photographed by Bhave. In this specimen from India, the base of the rhinophore club is broad and bulbous with an abruptly narrow apex. All of the other species of Trapania with similar colour patterns have narrow, evenly graded rhinophores and it is likely that the specimen from India represents another distinct, undescribed species.