Gymnoscalpellum indopacificum, Chan, Benny K. K., Corbari, Laure, Rodriguez Moreno, Paula A. & Jones, Diana S., 2014

Chan, Benny K. K., Corbari, Laure, Rodriguez Moreno, Paula A. & Jones, Diana S., 2014, Two new deep-sea stalked barnacles, Arcoscalpellum epeeum sp. nov. and Gymnoscalpellum indopacificum sp. nov., from the Coral Sea, with descriptions of the penis in Gymnoscalpellum dwarf males, Zootaxa 3866 (2), pp. 261-276 : 270-275

Gymnoscalpellum indopacificum sp. nov.

( Figs 7–10 )

Material examined. Holotype: MNHN-IU-2013-7435, 1 specimen, BOA1 Stn. CP2422 ( Vanuatu, Big Bay, 14°55’10”S, 166°55’40”E, 6 Sept. 2005, depth: 667–750 m), CL 23.4 mm, CW 14.1 mm, PL 21.4 mm. Paratypes: MNHN-IU-2013-7437, 1 specimen, SALOMON 1 Stn. CP1751 ( Solomon Islands, 9°10’4”S, 159°53’E, 25 Sep. 2001, depth: 749–799 m), CL 17 mm, CW 9.1 mm, PL 10.1 mm; MNHN-IU-2013-7436, 1 specimen. BIOPAPUA Stn. CP3648 ( Papua New Guinea, Huon Gulf, 06°48'S, 147°14'E, 25 Aug 2010, 682– 1012 m), CL 10.9 mm, CW 6.1 mm, PL 5.6 mm.

Diagnosis. Capitulum with 14 partially calcified capitular plates; tergum and upper latus V-shaped, umbos apical; inframedian latus small, triangular, umbo apical.

Description. Capitulum subtriangular, pale yellow, with 14 partially calcified plates ( Fig. 7 A, B). Tergum inverted V-shape, carinal branch about 1.5 times longer than occludent branch, umbo apical ( Fig. 7 A, B). Scutum quadrangular, umbo apical, occludent margin convex, upper latus margin concave ( Fig. 7 A, B), tergal margin shortest; basal margin about 3 times longer than tergal margin ( Fig. 7 A, B). Upper latus inverted V-shape, with two branches similar length ( Fig. 7 A, B). Rostrolatus narrow, quadrangular, wider than high ( Fig. 7 A, B). Inframedian latus small, located at margin of peduncle and capitulum, triangular, umbo apical ( Fig. 7 A, B). Carinolatus inverted V-shape, umbo at basi-carinal angle, angle not extending beyond carina. Carina convex, umbo apical ( Fig. 7 A, B).

Maxilla subtriangular with long maxillary lobe, dense setae along entire margin ( Fig. 8 A). Maxillule not notched, cutting edge short, with 10 large setae ( Fig. 8 B, C). Mandible with 5 teeth excluding inferior angle ( Fig. 8 D), first tooth separated from remainder, fourth tooth smallest, lower margin straight, short, without setae, inferior angle sharp, without setae ( Fig. 8 D). Mandibular palp elongated, dense setae apically ( Fig. 8 E), inferior margin naked, superior margin with few setae ( Fig. 8 F). Labrum bullate, cutting edge smooth, concave.

Cirrus I located close to cirri II–VI; rami unequal ( Fig. 9 A), anterior ramus flattened, 7-segmented, posterior ramus longer, slender, 10-segmented, segments with serrulate setae ( Fig. 9 B). Cirrus II, anterior ramus 15- segmented, posterior ramus 16-segmented ( Fig. 9 C), lesser curvature of intermediate segments of both rami with 5–7 long, serrulate setae, greater curvature with scattered long, serrulate setae ( Fig. 9 D). Cirrus III, anterior ramus 27-segmented, posterior ramus 28-segmented ( Fig. 9 E), lesser curvature of intermediate segments of both rami with 4 or 5 long, serrulate setae, greater curvature with scattered long, serrulate setae ( Fig. 9 F). Cirrus IV, anterior ramus 22-segmented, posterior ramus 22-segmented ( Fig. 9 G), lesser curvature of intermediate segments of both rami with 5 or 6 long, serrulate setae, greater curvature with scattered long, serrulate setae ( Fig. 9 H). Cirrus V and VI similar in morphology ( Fig. 10 A-F). Cirrus V, anterior ramus 27-segmented, posterior ramus 26-segmented ( Fig. 10 A). Cirrus VI, anterior ramus 29-segmented, posterior ramus 27-segmented ( Fig. 10 D), lesser curvature of intermediate segments of both rami in cirri V and VI with 5 or 6 long, serrulate setae ( Fig. 10 B, E), greater curvature with short spines or short, robust setae ( Fig. 10 C, F). Caudal appendages short, 4-segmented, length less than height of basal segment of pedicle of cirrus VI ( Fig. 10 G).

Dwarf males housed in symmetrically paired, oval-shaped receptacles located at upper part and inside margins of scutal plates ( Fig. 11 A–C), each receptacle housing 5–11 dwarf males ( Fig. 11 C). Males elongated oval shape, four reduced shell plates in apical region ( Fig. 11 C, D), surface covered by denticles arranged in fan-shaped pattern, ( Fig. 11 E); apical region distally with aperture, from which penis extends ( Fig. 11 C), penis reaching about 0.8 times total body length of male ( Fig. 11 D), 5 side branches along length of penis, tip of penis with array of dense setae ( Fig 11 D).

Distribution. Coral Sea, Solomon Sea, off Papua New Guinea, Solomon Islands and Vanuatu.

Etymology. The name denotes the first discovery of a species of Gymnoscalpellum in the Indo-Pacific region.

Remarks. Newman & Ross (1971) erected the genus Gymnoscalpellum to accommodate species with 14 reduced calcified plates, an inverted V-shaped tergum, a small triangular inframedian latus and multi-segmented caudal appendages. Currently, there are six described species in Gymnoscalpellum : G. tarasovi Newman & Ross, 1971 , G. l a r v a l e ( Pilsbry, 1907), G. i n s i g n e ( Hoek, 1883), G. leoni ( Zevina, 1968) , G. ku rc h a t o v i ( Zevina, 1972) and G. klepalae Federrspel & Hoffer, 1997 . Of these, only G. tarasovi has a branched upper latus. The remaining species have the upper latus banana-shaped (see Newman & Ross, 1971; Zevina, 1981) or non-branched. In the present study, G. indopacificum sp. nov. has a branched upper latus, similar to G. tarasovi . However, differing from G. tarasovi , the scutum of G. indopacificum sp. nov. has no apicolateral arm and the inframedian latus is relatively larger. The caudal appendages of G. tarasovi are long, having 6 segments, and their height is extended beyond the first segment of the pedicel of cirrus VI ( Newman & Ross 1971). In the present study, the caudal appendages of G. indopacificum sp. nov. are short, with the total height less than that of the first segment of the pedicel of cirrus VI.

Of the previously described Gymnoscalpellum species, G. tarasovi , G. l e o n i and G. klepalae are recorded from Antarctic waters, G. insigne from the Azores, G. l a r va l e from the deep-sea off San Diego, USA and G. kurchatovi from Chile. The present study denotes the first discovery of Gymnoscalpellum in the Indo-Pacific region.

Dwarf males of G. indopacificum sp. nov. have 4 shell plates, similar to the males reported for G. t a r a s o v i. The present study represents the second report of detailed observations on the penis of scalpellid dwarf males, following the first description of the penis of Verum brachiumcancri by Buhl-Mortensen & Høeg (2013). The penis of V. brachiumcancri and G. indopacificum sp. nov. have an array of side branches. However, in contrast to V. brachiumcanri , the number of side branches in G. indopacificum sp. nov. is fewer and they are not arranged in a paired manner.

Figures

FIGURE 7. Gymnoscalpellum indopacificum sp. nov. Holotype (MNHN-IU- 2013 - 7435). A, External lateral view of capitulum, showing partially calcified capitular plates. B, Schematic drawing of lateral view of capitulum. Morphological terms of capitular plates, refer to Fig. 2.

FIGURE 8. Gymnoscalpellum indopacificum sp. nov. Holotype. (MNHN-IU- 2013 - 7435). A, Maxilla. B, Maxillule. C, Magnified view of cutting edge of maxillule. D, Mandible. E, Mandibulatory palp. F, Magnified view of mandibulatory palp. Scale bars in µm.

FIGURE 9. Gymnoscalpellum indopacificum sp. nov. Holotype. (MNHN-IU- 2013 - 7435). A, Cirrus I. B, Serrulate setae on posterior ramus of cirrus I. C, Cirrus II. D, Intermediate segment of anterior ramus of cirrus II. E, Cirrus III. F, Intermediate segment of anterior ramus of cirrus III. G, Cirrus IV. H, Intermediate segment of anterior ramus of cirrus IV. Scale bars in µm, except A, C, E, G, in mm.

FIGURE 10. Gymnoscalpellum indopacificum sp. nov. Holotype. (MNHN-IU- 2013 - 7435). A, Cirrus V. B, Lesser curvature of anterior ramus of cirrus V. C, Greater curvature of anterior ramus of cirrus V showing spines. D, Cirrus VI. E, Lesser curvature of anterior ramus of cirrus V. F, Greater curvature of anterior ramus of cirrus. G, Caudal appendages. Scale bars in µm, except A, D in mm.

FIGURE 11. Gymnoscalpellum indopacificum sp. nov. Holotype. (MNHN-IU- 2013 - 7435). Dwarf males. A, Rostral view of capitulum showing paired receptacles (circled), located on inner edge of scutum. B, Lateral view, somatic body and adductor muscle removed, showing receptacles. C, Magnified view of receptacle, showing embedded dwarf males. Note dwarf males with 4 shell plates, surrounding central aperture. D, Dwarf male observed using compound light microscope, showing extended penis. E, External surface of dwarf males, showing fan-shaped denticles. Scale bars in µm, except A – C in mm. Pl - shell plates, ap - aperture.