Pannychia nagasakimaruae, Ogawa & Kobayashi & Kohtsuka & Fujita, 2023

Ogawa, Akito, Kobayashi, Itaru, Kohtsuka, Hisanori & Fujita, Toshihiko, 2023, Two new species of the bathyal holothurian genus Pannychia (Elasipodida, Laetmogonidae) from Japanese waters, Zootaxa 5323 (1), pp. 105-125 : 110-115

publication ID	https://doi.org/ 10.11646/zootaxa.5323.1.6
publication LSID	lsid:zoobank.org:pub:4F1F4092-5A70-4BE7-B361-C4978C847899
DOI	https://doi.org/10.5281/zenodo.8203974
persistent identifier	https://treatment.plazi.org/id/D2570167-CA69-FFC1-FF33-FD7DD0FDF831
treatment provided by	Plazi
scientific name	Pannychia nagasakimaruae
status	sp. nov.

Treatment

Pannychia nagasakimaruae View in CoL sp. nov.

( Figs. 2–5 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 )

[New Japanese name: Nagasaki-hage-namako]

Type material. Holotype. NSMT E-13401( INSD accession number LC750304, 600 bps), East of Sanpo-Sone Ridge , off Goto Islands , East China Sea, Japan, 32°13.548′–32˚12.389′N 129°12.561′–129˚13.691′E, depth 436–453 m, T / V Nagasaki-maru N 297 cruise St. A 4.5, 6 Mar. 2010 (n 1 in Fig. 1 View FIGURE 1 ) . Paratypes. NSMT E-9442 (1 specimen) and E-9443 (2 specimens, INSD accession number LC750303, 655 bps) , Southeast of Naka-Kasayama Bank , off Goto Islands , East China Sea, Japan, 32°12.013′N 128°54.825′E, depth 403–413 m GoogleMaps , T / V Nagasaki-maru N 343 cruise St. C 4-1, 3 Mar. 2012 (n 2 in Fig. 1 View FIGURE 1 ) .

Description of holotype. Body cylindrical, 88 mm long, 21 mm wide ( Fig. 2 View FIGURE 2 ). Body wall thin, soft, fragile, easily damaged and detached during the sampling process. Mouth subventral. Anus at posterior end of the body. Dorsal papillae conical, up to 13 mm long, distributed in both sides of ventral-lateral and dorsal radii. Ventral-lateral papillae 23–37, arranged in a single row with intervals. Dorsal radius of papillae counted 58–63, arranged in crowded double rows. Tube feet cylindrical, easily damaged and detached during the sampling process. Ventral-lateral tube feet 37–38, arranged on single zigzag row on each radius. Mid-ventral tube feet 58, arranged on double rows, lacked from anterior quarter of holotype by sampling damages. Tentacles 18, fragile, easily damaged and detached during the sampling process, with cylindrical stems, and shape of terminal disc unknown. Papillae, tube feet, and tentacles nonretractile.

Calcareous ring ( Fig. 3A View FIGURE 3 ), rudimentary fragile continuous ring, consists of 5 radial and 5 interradial elements, surrounding pharynx. Each element of calcareous ring incompletely calcified, tilted so that the anterior opens outward. Radial elements (R in Fig. 3A View FIGURE 3 ) with 3 short anterior processes (Rap in Fig. 3A View FIGURE 3 ) and a deep indentation (Rdn in Fig. 3A View FIGURE 3 ) in posterior edge. Interradial elements (IR in Fig. 3A View FIGURE 3 ) with single anterior process (IRap in Fig. 3A View FIGURE 3 ). Neither element having any opening nor posterior process. Gonad white paired tuft, comprising multi-branched genital vesicles, connected into a central genital duct opened at anterior dorsum. Polian vesicle single, elongate, 20 mm long, white. Stone canal single, along with the mid dorsal mesentery to opening at anterior dorsal body wall.

Body skin transparent white on dorsal and ventral in alcohol ( Fig. 2A, 2B View FIGURE 2 ). Whole of tube feet and stems of tentacles also transparent white in alcohol.

Ossicles. On dorsal body wall three forms of wheel ossicles: large wheels having both triangular rim teeth and calcareous membrane; mid-sized wheels, having triangular rim teeth, but calcareous membrane incompletely covering the nave; small wheels lacking both of them ( Fig. 4 View FIGURE 4 ). Large wheels ( Fig. 4A View FIGURE 4 ) 131–253 µm in diameter (mean 220 µm, N = 26), with 12–14, rarely 16 spokes (N = 26), 4 or 5 central rays (N = 15), thin calcareous membrane covering or narrowing the nave, and triangular rim teeth 19–45 µm high (mean 35 µm, N = 26). Mid-sized wheels ( Fig. 4B View FIGURE 4 ) 56–104 µm in diameter (mean 83 µm, N = 14), with 8–11 spokes (N = 14), 3 or 5 central rays (N = 14), calcareous membrane incompletely covering concave side of the nave, sometimes having bar shaped processes derived inwardly from inner edge of the connecting central portion and narrowing the nave, and having rounded triangular rim teeth 8–16 µm long (mean 11 µm, N = 14). Small wheels ( Fig. 4C View FIGURE 4 ) 42–66 µm in diameter (mean 53 µm, N = 26), with 9–12 spokes (N= 26), usually 4, rarely 3 or 5 central rays (N = 26), without rim teeth and calcareous membrane, rarely having small additional irregular holes on the rim (N = 2, Fig. 4C View FIGURE 4 2 View FIGURE 2 ). Wheel ossicles are distributed high densely, omnipresently in dorsal body wall.

Ossicles in ventral body wall also four forms of wheels, large wheels, mid-sized wheels, small wheels, and perforated wheels ( Fig. 5 View FIGURE 5 ). Large wheels ( Fig. 5A View FIGURE 5 ) 125–205 µm in diameter (mean 175 µm, N = 15), with 12–15 spokes (N = 15), usually 4, occasionally 5 central rays (N = 10), thin calcareous membrane covering or narrowing the nave, and triangular brim teeth 12–32 µm high (mean 27 µm, N = 14). Mid-sized wheels ( Fig. 5B View FIGURE 5 ) 74–122 µm in diameter (mean 95 µm, N = 5), with 10 or 11 spokes (N = 5), usually 4 central rays (N = 5), calcareous membrane incompletely covering concave side of the nave, sometimes having bar shaped processes derived inwardly from inner edge of the connecting central portion and narrowing the nave, and rounded triangular rim teeth 9–15 µm long (mean 11 µm, N = 5). Small wheels ( Fig. 5C View FIGURE 5 ) 35–58 µm in diameter (mean 43 µm, N = 41), with 8–11, usually 10 spokes (N = 41), usually 4 central rays (N = 41), without rim teeth and calcareous membrane, rarely having small additional holes on the rim (N = 2, Fig. 5C View FIGURE 5 2 View FIGURE 2 ). Perforated wheels ( Fig. 5D View FIGURE 5 ), without rim teeth and calcareous membrane, having 31 irregular arranged perforations, rarely present in ventral body wall (N= 1, 39 µm in diameter). Wheel ossicles distributed high densely, omnipresently in ventral body wall.

Ossicles in tentacles are only rod ossicles ( Fig. 3B View FIGURE 3 ). Rod ossicles slightly arched, 212–406 µm long (mean 302 µm, N = 9), 11–19 µm wide (mean 15 µm, N = 9), with sometimes obtuse minute spines scattered on whole ossicles.

Variations of paratypes. Body sizes of the three paratypes range between 61–78 mm in length and 11–15 mm in width, so they are smaller than holotype. All paratype specimens were in poor condition because they are damaged during sampling ( Fig. 2C View FIGURE 2 ), so the arrangement of dorsal papillae was not observed. Ventral-lateral and dorsal papillae of paratypes are mostly broken off, making it difficult to count. One of the paratypes (NSMT E-9443), however, clearly shows a smaller number of tube feet than holotype: 15–27 in ventral-lateral radii and 29 in midventral radius. Oral parts of the paratypes are damaged, and the tentacle numbers are unknown.

Body skin is transparent white on dorsal and ventral sides in unpreserved specimens ( Fig. 2C View FIGURE 2 ). Whole of tube feet and stems of tentacle are also transparent white in living specimens.

Ossicles. Ossicles in the dorsal body wall of holotype consisting of only three types of wheels (large wheels, mid-sized wheels and small wheels), and one paratype (NSMT E-9443) additionally possesses perforated wheels ( Fig. 4D View FIGURE 4 ). Large wheels of a paratype NSMT E-9443 are smaller than of holotype 78–146 µm in diameter (mean 107 µm, N = 13), with 12–14 spokes, and a number of central rays show a larger variation range (4–6 central rays, N = 6), but the length of triangular rim teeth is smaller than of holotype (12–25 µm high, mean 16 µm, N = 39 in NSMT E-9443). Mid-sized wheels of the paratype NSMT E-9443 ranged 49–80 µm in diameter (mean 67 µm, N = 12), with 9–17 spokes (N = 12), 3 or 4 central rays (N = 12), and having rounded triangular rim teeth 4–18 µm high (mean 8 µm, N = 12). Small wheels of the paratype NSMT E-9443 were 38–66 µm in diameter (mean 46 µm, N = 29), with 9–12 spokes (N = 29), usually 4 central rays (N = 29), without rim teeth and calcareous membrane, sometimes having small additional holes on the rim (N = 2). Perforated wheels were rarely present in dorsal body wall (N = 1, with 49 µm in diameter, 27 perforations, Fig. 4D View FIGURE 4 ). Ossicles of the paratypes are also distributed in high density and are omnipresent in the dorsal body wall.

Ossicle composition in ventral body wall also varies between holotype and one paratype (NSMT E-9443). Holotype comprises four types of wheels in the ventral body wall, but one paratype (NSMT E-9443) only possesses small wheels and perforated wheels. The size of the small wheels is slightly smaller than in the paratype NSMT E-9443: small wheels 35–58 µm in diameter (mean 43 µm, N = 77 from 2 individuals), with 8–11. Perforated wheels rarely present in dorsal body wall (N= 1, 51 µm in diameter with 32 holes, from 2 individuals).

Distribution. Known only from two nearby sites on the upper continental slope in the northern part of the East China Sea. Off Goto Islands, Japan, 403–453 m deep (open rhombuses in Fig. 1 View FIGURE 1 , present study).

Etymology. The species is named after the T/V Nagasaki-maru which collected all type specimens.

Remarks. Pannychia nagasakimaruae sp. nov. is distinguished from congeners by the following 6 morphological characters ( Table 1 View TABLE 1 ): i) dorsal and ventral body walls transparent white, ii) dorsal papillae arranged in two rows on each radius, iii) ventral papillae absent, iv) mid-sized wheel ossicles present in dorsal and ventral body walls, v) small wheels in dorsal and ventral body walls lacking rim teeth, and vi) perforated wheels present in dorsal and ventral body walls.

The present species, P. nagasakimaruae sp. nov., shows different morphological characteristics compared to all the eight nominal species/subspecies of Pannychia . This species differs from P. henrici , P. virgulifera , and P. moseleyi mollis in the arrangement of the dorsal papillae in double rows on each radius and in the absence of rod ossicles in the dorsal and ventral body walls. In contrast to P. taylorae and P. multiradiata , this new species differs in the maximum diameter of large wheel ossicles in dorsal body walls not exceeding 300 µm, and is distinguished by the presence of mid-sized wheel ossicles and perforated wheel ossicles in dorsal/ventral body walls of P. moseleyi and P. pallida , and by the absence of ventral papillae from L. fecundum . In particular, the presence of mid-sized wheels and perforated wheels are unique morphological characters among the so far known species of Pannychia including all the synonymous taxa of P. moseleyi and P. virgulifera . Our molecular phylogenetic analysis ( Fig. 9 View FIGURE 9 ) showed genetic differences between the present species and congeners that support this morphological character reflecting interspecific differences between the present species and congeners.