Samariscus hexaradiatus, Diaz De Astarloa & Causse & Pruvost, 2013

Díaz de Astarloa, Juan M., Causse, Romain & Pruvost, Patrice, 2013, New dextral flounder Samariscus hexaradiatus sp. nov. (Samaridae, Pleuronectiformes) from the Solomon Islands, South-West Pacific Ocean, Cybium 37 (4), pp. 241-246 : 243-246

Samariscus hexaradiatus n. sp.

( Fig. 1 , Tab. I)

Holotype. - MNHN 2002-3655 , Solomon Islands, Pacific Ocean , 10°12’0’’S, 161°19’1’’E; 135-325 m, Salomon 1 cruise, Sta. cp1831; 5 Oct. 2001, 100.3 mm SL.

Paratype. - MNHN 2002-3761 , Solomon Islands, Pacific Ocean , Salomon 1 cruise, Sta. cp1831; 5 Oct. 2001, 80.9 mm SL .

Diagnosis

A species of Samariscus with the following combination of characteristics: six pectoral- fin rays, 82 dorsal-fin rays, 60 to 62 anal-fin rays, 74 to 75 lateral-line scales, and 9 abdominal and 32 caudal vertebrae.

Description

Both measurements and meristics of the holotype are listed first, followed by those of the paratype placed within parentheses.

Head small, length 21.5 (21.9); body laterally compressed, elliptical, deepest near midpoint, depth 31.0 (34.4); snout short, length 18.5 (19.2) in HL, smaller than eye diameters; upper eye diameter 33.3 (32.2); lower-eye diameter 34.2 (32.7); orbital length 35.2 (34.4); interorbital width 3.2 (3.4); upper-jaw length on ocular side 30.1 (25.4), on blind side 27.8 (24.8); lower-jaw length on ocular side 47.2 (46.9), on blind side 44.9 (41.8); caudal peduncle depth 13.3 (11.5); length of longest pectoral fin ray 26.9 (28.1); length of longest pelvic fin ray on ocular side 19.6 (15.9), on blind side 9.6 (9.0).

Dorsal-fin rays 82 (82); anal-fin rays 60 (62); ocular-side pectoral-fin rays 6 (6); pectoral fin absent on blind side; pelvic-fin rays 5 (5) on both ocular-side and blind-side fins; caudal-fin rays 16 (16); lateral-line scales 74 (75); abdominal vertebrae 9 (9), caudal vertebrae 32 (32); total vertebrae 41 (41).

Nostrils of blind side higher than those on ocular side. Both anterior nostrils with flap of skin covering the opening. Ocular-side anterior nostril tubular. The posterior nostril also tubular and placed ventrally relative to anterior nostril. Eyes dextral, separated by a narrow fully scaled bony ridge. Lower eye slightly anterior to upper eye. Ventral margin of upper eye and upper margin of lower eye covered with ctenoid scales. Mouth oblique. Ocular-side upper jaw reaching a vertical through anterior one-fourth of lower eye. Premaxillae and dentaries with three bands of viliform teeth (four in the dentary of the Paratype). Gill rakers on first branchi- al arch of both sides with rudimentary stout gill rakers on lower limb, 5 (6) on the ocular side and 3 (5) on the blind side. Ocular-side lateral line almost straight, curving slightly upward at half- length of pectoral fin. No lateral line on blind side. Small ctenoid scales on both sides of head and body, except for snout which is scaleless. Dorsal-fin origin on blind side of head, anterior to upper eye. Anal-fin origin just posterior to anus. Dorsal- and anal-fin rays unbranched. Pectoral fin on ocular side longer than head 1.25 (1.3) in HL, with all rays unbranched. Pectoral fin on blind side absent. Pelvic fins subsymmetrical, ocular-side fin 2.0 (1.8) longer than that on blind side. Length of ocular-side pelvic fin 0.9 (0.7) times in HL, length of blind-side pelvic fin 0.4 (0.4) times in HL. Origin of ocular-side fin slightly anterior to that of blind side. Blind-side pelvic-fin origin at level of sec- ond ray of ocular side pelvic fin. Dorsal, anal, pectoral, and pelvic fins scaleless. Caudal fin rounded with 16 rays with twelve medial rays branched and uppermost and lowermost two rays unbranched. Anus on midventral line. Cone-shaped urinary papilla on ocular side placed anterior to anal-fin origin.

Colour in alcohol

Ocular side of body light brown with four and three distinguishable horseshoe-shaped spots along margins of both dorsal and ventral profiles, respectively. With two ill-defined dusky blotches on lateral line, one situated under the last one-third of the pectoral fin when flattened posteriorly, the other placed near the last one-third of the body. Two other darkly pigmented distinct spots on upper and lower margins of caudal peduncle just after the posterior end the unpaired fins. Pectoral fin darkly pigmented. Dorsal- and anal-fins rays dusky brown on their proximal and distal regions and with series of small dusky spots on the medial regions.

Distribution

Known only from the Solomon Islands, in the South-West Pacific Ocean, at depths of 135-325 m.

Etymology

The specific name refers to the six pectoral fin rays, derived from the Greek word hexa (meaning six) and Latin radius (rays).

Comparisons

The new species described herein Samariscus hexaradiatus is unique and easily distinguished from congeners in having six ocular-side pectoral fin rays. All other species of Samariscus have either four ( S. asanoi , S. corallinus , S. desoutterae , S. luzonensis , S. macrognathus , S. nielseni and S. xenicus ) or five pectoral-fin rays ( S. filipectoralis , S. huysmani , S. inornatus , S. japonicus , S. latus , S. leopardus , S. longimanus , S. maculatus , S. multiradiatus , S. neocaledonia , S. sunieri and S. triocellatus ( Norman, 1934; Matsubara and Takamuki, 1951; Quéro et al., 1989; Alfonso, 2001; Kawai et al., 2008, 2011; present study).

The number of dorsal fin rays (82) and anal fin rays (60-62) in S. hexaradiatus distinguishes this species from S. asanoi (71 and 54: Ochiai and Amaoka, 1962), S. corallinus (75-77 and 63-65: Gilbert, 1905), S. filipectoralis (71- 77 and 53-58: Shen, 1982, Tab. I), S. huysmani (75-80 and 59-60: Tab. I), S. inornatus (61-70 and 48-53: Lloyd, 1909), S. japonicus (62-73 and 47-57: Kamohara, 1936), S. latus (66-74 and 49-57: Matsubara and Takamuki, 1951; Shen, 1982; Tab. I), S. leopardus (72 and 59: Voronina, 2009), S. longimanus (66-71 and 50-54: Norman, 1927), S. luzonensis (68 and 54: Fowler, 1934), S. macrognathus (71-73 and 56-58: Tab. I), S. maculatus (73 and 57: Günther, 1880), S. multiradiatus (85-89 and 69-72: Tab. I), S. nielseni (70 and 55-56: Quéro et al., 1989, Tab. I), S. sunieri (72-85 and 55-66: Tab. I), S. triocellatus (65-71 and 51-57: Tab. I) and S. xenicus (62-70 and 46-53: Ochiai and Amaoka, 1962). Furthermore, the presence of ctenoid scales on the interorbital space and the higher number of lateral line scales distinguishes the new species from S. neocaledonia ( Tab. I). In addition, 9 abdominal vertebrae in the new species is lower than 10 in S. huysmani , S. latus , S. neocaledonia ( Tab. I) and S. japonicus ( Kamohara, 1936; Shen, 1982), and 32 caudal vertebrae in the new species is higher than 28 in S. inornatus ( Lloyd, 1909) , 29 in S. filipectoralis , S. nielseni , S. macrognathus ( Tab. I), S. japonicus ( Kawai et al., 2008) , 29-31 in S. huysmani ( Tab. I), 29-30 in S. latus ( Tab. I) and 31 in S. sunieri and some specimens of S. latus ( Tab. I). Although the new species here described has the same number of caudal vertebrae (32) than S. triocellatus , the latter could be easily distinguished from S. hexaradiatus n. sp. by the presence of three distinct round dark-brown-edged ocelli in a line along the middle of ocular side ( Tab. I).

The present species, on the other hand, differs from other species of Samariscus in having longer both pelvic fins on ocular and blind sides. It resembles S. filipectoralis in having a short snout, but differs from the latter, S. latus , S. macrognathus , S. neocaledonia , S. nielseni and S. unieri in having a much shorter pectoral-fin length ( Tab. I).

Additional material examined

All measurements in standard length.

Samariscus multiradiatus . - Holotype: MNHN 2006-1758 . New Caledonia. R / V Vauban, cruise MUSORSTOM 4, Stn. CP 213, 22°51’0”S, 167°12 0”E, 405-430 m depth, 28 Sep. 1985, beam trawl; male: 59.5 mm . Paratype: HUMZ 197930 . New Caledonia (field tag ORS 225 ) , R/V Vauban, cruise SMIB 1 , Stn. DW 2, 22°51.90’S, 167°13.00’E, 415 m, 5 Feb. 1986, Waren dredge; male: 61.5 mm . Paratype: MNHN 1994-0817 . New Caledonia . R / V Vauban, cruise MUSORSTOM 4, Stn. CP 213, 22°51’0”S, 167°12’0”E, 405-430 m depth, 28 Sep. 1985, beam trawl; male, 60.8 mm . Paratype: MNHN 1994-0826 . New Caledonia . R / V Coriolis, cruise Chalcal 2, Stn. CP 26, 23°18’0”S, 168°3’0”E, 296 m depth, 31 Oct. 1986, beam trawl; male: 44.7 mm . Paratype: MNHN 2006-1759 . New Caledonia (field tag BAT56.1 ) , R / V Alis, cruise Bathus 4, Stn. DW 925, 18°54.85’S, 163°23.75’E, 370-405 m depth, 7 Aug. 1994, Waren dredge; female, 48.1 mm . Paratype: MNHN 2006-1760 . New Caledonia (field tag ORS179 ) , R / V Vauban, cruise SMIB 1 , Stn. DW 2, 22°51.90’S, 167°13.00’E, 415 m, 5 Feb. 1986, Waren dredge; female, 41.9 mm . MNHN 2005-0010 . New Caledonia. R / V Vauban, cruise Musorstom 4, Stn. Dw 181, 18° 57’0”S, 163°22’1”E, 355 m, 18 Sep. 1985, Waren dredge; 42 mm . MNHN 2005-0015 . New Caledonia. R / V Vauban, cruise MUSORSTOM 4, Stn. Dw 212, 22°46’59”S, 167°10’1”E, 380 m, 28 Sep. 1985, Waren dredge; 4 spms (37.7-48.8 mm) .

Samariscus sunieri . - Syntypes: ZMA 109317 . Indonesia, Bali, Nicolaas Bay, Gier Expedition 24, Exp. 6, St 1187, 7 Sep. 1909, 108- 162 m depth, trawl; 5 spms (60.2-98.9 mm) . MNHN 2000- 4423 . Fiji Islands, Vanua balavu, N.O. Alis, Camp. Bordau 1, 1999, Stn CP 1429, 17°16’1”S, 179°1’1”E, 410 m, 1 Mar. 1999, beam trawl; 2 spms (49.1, 95.2 mm) . MNHN 2000-4425 . Fidji Islands, Vanua balavu, N.O. Alis, Camp Bordau 1, 1999, Stn CP 1445, 17°10’1”S, 178°40’59”E, 350 m, 3 Mar. 1999, beam trawl; 9 spms (57.3-87.2 mm) . MNHN 2000-4428 . Fidji Islands, Ride de lau, Yangasa, N.O. Alis, Camp Bordau 1, 1999, Stn CP 1501, 18°40’1”S, 178°30’0”E, 350 m, 12 Mar. 1999, beam trawl; 2 spms (72.9, 95.8 mm)

Samaricus nielseni . - MNHN 2006-0196 . Salomon islands , 8°36’4”S, 157°23’2”E, 176 m, 6 Nov. 2004, beam trawl, 79.7 mm .

Samariscus triocellatus . - MNHN 2008-0088 . Chesterfield Is. N.O. Coriolis, Camp Chalcal 1, Stn dc 7, 20°50’8”S, 161°36’9”E, 62 m, 14 Jul. 1984, Charcot dredge (drague Charcot), 33.9 mm . MNHN 2008-0089 . New Caledonia, N.O. Vauban, Camp Lagon 1, St. dw 50, 22°40’8”S, 166°12’0” E, 12 m, 25 May 1984, Waren dredge, 38.3 mm . MNHN 2008-0090 . New Caledonia, St. Vincent 22°1’1”S, 165°55’1”E, 8 m, 25 Mar. 1990, 40.5 mm . MNHN 2008- 0093 . New Caledonia. N.O. Vauban, St; 9, 22°46’5”S, 166°47’6”E, 10-12 m, 17 Jun. 1986, 62.7 mm . MNHN 2008-0095 . New Caledonia, St. Vincent, 22°1’1”S, 165°55’1”E, 8 m, 25 Mar. 1990, 39 mm .

Samariscus huysmani . - MNHN 2005-3375 . Vanuatu, N.O. Alis; Camp Boa 0, Stn CP 2327, 15°41’2”S, 167°2’49”E, 287-400 m, 17 Nov. 2004, beam trawl, 3 spms (87-114.5 mm) . MNHN 2005- 3377 . Vanuatu, N.O. Alis; Camp Boa 0 St. cp 2326, 15°40’59”S, 167°1’59”E, 260-313 m, 18 Nov. 2004, beam trawl, 3 spms (89.8- 101.7 mm) . MNHN 2005-3380 . Vanuatu, N.O. Alis; Camp Boa 0 St. cp 2326, 15°40’59”S, 167°1’59” E, 260-313 m, 18 Nov. 2004, beam trawl, 83.3 mm . MNHN 2009-1562 . Vanuatu, Santo, N.O. Alis; Camp Santo 06, St. at1, 15°33’47”S, 167°19’30”E, 167- 367 m, 14 Sep. 2006, beam trawl, 6 spms (55.6-81.5 mm) . ZMA 109325 . Topotype. Indonesia, Java, Gierexpeditie 4, Experiment 19, 6°26’S, 112°41’E, 14 Dec. 1907, 93.5 mm .

Samariscus latus . - MNHN 2002-1981 . Philippines, N.O. Coriolis; Camp Musorstom 3, St. cp143, 11°42’4”S, 121°45’11”E, 205- 214 m, Jun. 1985, Beam trawl, 77.5 mm . MNHN 2004-1980 . Philippines, N.O. Coriolis; Camp Musorstom 3, St. cp88, 14°0’4”S, 120°17’2”E, 183-187 m, 31 May 1985, beam trawl, 74.9 mm . MNHN 2004-1981 , Philippines, N.O. Coriolis; Camp. Musorstom 3, St. cp87, 14°0’7”S, 120°19’5”E, 191-197 m, 31 May 1985, 64 mm . MNHN 2004-1982 , Philippines, Luzon Is., N.O. Coriolis; Camp. Musorstom 3, St. cp108, 14°1’1”S, 120°17’10”E, 188-195 m, 2 Jun. 1985, beam trawl, 3 spms (58.4-83.6 mm) . MNHN 2004- 1983 . Philippines, N.O. Coriolis; Camp. Musorstom 3, St. cp145, 11°12’0”S, 124°2’24”E, 246 m, 7 Jun. 1985, beam trawl, 2 spms (92.7, 96.3 mm) . MNHN 2004-1984 . Philippines, N.O. Coriolis; Camp. Musorstom 3, St. cp100, 14°0’0”S, 120°10’48”E, 199 m, 1 Jun. 1985, beam trawl, 2 spms (72.2, 92.1 mm) . MNHN 2004- 1986 . Philippines, N.O. Coriolis; Camp. Musorstom 3, St. cp112, 14°0’0”S, 120°11’24”E, 199 m, 2 Jun. 1985, beam trawl, 88.8 mm . MNHN 2004-1988 . Philippines, N.O. Coriolis; Camp. Musorstom 3, St. cp119, 12°0 0”S, 121°7’48”E, 337 m, 3 Jun. 1985, beam trawl, 95.3 mm . MNHN 2004-1990 . Philippines, Lubang Is., N.O. Coriolis; Camp. Musorstom 3, St. cp97, 14°0’7”S, 120°18’7”E, 189-194 m, 1 Jun. 1985, beam trawl, 2 spms (83.5, 89.6 mm) . MNHN 2004- 1991 . Philippines, N.O. Coriolis; Camp. Musorstom 3, St. cp99, 14°6’0”S, 120°11’24”E, 204 m, 1 Jun. 1985, beam trawl, 15 spms (50.0- 84.8 mm) . MNHN 2004-1992 . Philippines, N.O. Coriolis; Camp. Musorstom 3, St. cp98, 14°0’0”S, 120°10’48”E, 205 m, 1 Jun. 1985, beam trawl, 2 spms (68.0, 90.5 mm) . MNHN 2004- 1993 . Philippines, N.O. Coriolis; Camp. Musorstom 3, St. cp109, 14°0’0” S, 120°16’59”E, 190-198 m, 2 Jun. 1985, beam trawl, 3 specimens (83.5-98.9 mm) . MNHN 2004-1994 . Philippines, N.O. Coriolis; Camp. Musorstom 3, St. cp101, 14°0’0”S, 120°11’24”E, 196 m, 1 Jun. 1985, beam trawl, 2 spms (73.5, 98.5 mm) . MNHN 2004-1995 . Philippines, N.O. Coriolis; Camp. Musorstom 3, St. cp111, 12°0’0”S, 120°10’12”E, 205 m, 2 Jun. 1985, beam trawl, 86.3 mm .

Samariscus macrognathus . - MNHN 2006-0195 . Salomon Is., N.O. Alis; Camp Salomon 2, St. cp2283, 8°36’4”S, 157°23’2”E, 176 m, 6 1, 25 Dec. 1993, 50 mm. Paratype : HUMZ 212428 . New Caledonia, 19°3.67’S, 168°28.05’E, 258 m, beam trawl, 8 Aug. 1994. 34.6 mm .

Samariscus filipectoralis . - Paratype: NTUM 05337 . Tung-Kang , Pingtung. 26 Oct. 1978. 76.5 mm .

Acknowledgements. – The authors are grateful to E. Voronina (Zoological Institute, Russian Academy of Sciences, St. Petersburg) for providing measurements, counts, and photographs of the holotype of S. leopardus . Yi-Jung Lin (NTUM) loaned the paratype of S. filipectoralis and T. Tawai (HUMZ) provided both the paratypes of S. neocaledonia and S. multiradiatus . The senior author is much indebted to R. de Ruiter (senior collection manager) for his kind assistance and support at the Naturalis Biodiversity Center in Leiden, the Netherlands and loan of five syntype specimens of S. sunieri . S. Grosjean and M. Silvain kindly assisted in preparing the photographs and taking the X-rays. The senior author is grateful to Pr. Guy Duhamel, Director of the Département Milieux et Peuplements Aquatiques, Muséum national d’Histoire naturelle, Paris for providing laboratory space and equipment. The technical assistance of C. Ferrara and Z. Gabsi in supplying the material examined is greatly appreciated. The Salomon 1 Survey was initiated by the Muséum national d’Histoire naturelle, Paris (MNHN) and the Institut de Recherche pour le Développement (IRD). We thank Dr Bertrand Richer de Forges and Sarah Samadi, Co-Pls on board R/V/ Alis, who collected the specimens. We sincerely thank the anonymous reviewers for making important and critical suggestions to improve the manuscript.

Figures

Figure 1. - Samariscus hexaradiatus n. sp. Ocular and blind sides. A, B: Holotype, MNHN 2002-3655, 100.3 mm SL. C, D: Paratype, MNHN 2002-3761, 80.9 mm SL.