Oryzias nigrimas, KOTTELAT, 1990 A

Parenti, Lynne R., 2008, A phylogenetic analysis and taxonomic revision of ricefishes, Oryzias and relatives (Beloniformes, Adrianichthyidae), Zoological Journal of the Linnean Society 154 (3), pp. 494-610 : 577-579

ORYZIAS NIGRIMAS KOTTELAT, 1990A

BLACK BUNTINGI

FIGURE 50

Oryzias nigrimas Kottelat, 1990a: 52–54 , fig. 2, tables 1 and 2 [type locality: Indonesia: Sulawesi Tengah, Lake Poso, eastern shore between Tentena and Peura].- Uwa, 1991b: 15–18 [karyotype, morphometrics].- Kottelat et al., 1993: 90 [listed; characters].- Naruse et al., 1994: 49 [cytogenetic data].- Schaller, 1994: 18–20 [photos, habitat description, taxonomy].-? Seegers, 1997: 15, 21, 22 [listed, photographs, possibly O. nebulosus ].

Differential diagnosis: Oryzias nigrimas is distinguished from all other ricefishes by a unique sexual dichromatism in life: adult males are dark bluish grey to black, especially when breeding, whereas females are a lighter greyish brown. Oryzias nigrimas shares with O. nebulosus a unique sexual dichromatism in preserved material: adult males are dark grey to black, whereas females are a lighter greyish yellow to brown. Relative to O. nebulosus , O. nigrimas is large (maximum size 51 mm) and slender-bodied, with precaudal vertebrae 13–14 (vs. 11–13). Oryzias nigrimas differs from O. orthognathus , the other large (both reach over 50 mm SL) Oryzias in Lake Poso, by having 34–37, as opposed to 45–57, scales in a lateral series, and six, as opposed to seven, pelvic-fin rays.

Description: Elongate, maximum size of specimens examined 51 mm. Body slender, elongate, laterally compressed; body depth 18–22. No pronounced abdominal concavity between pelvic fins and anal fin. Mouth terminal, jaws subequal. Dorsal and ventral body profile gently arching from head to dorsal- and anal-fin origins. Dorsal surface of head slightly convex just anterior to orbits. Head length 22–25; snout length 6–8; eye moderate to large, 8–10, orbits do not project beyond dorsal surface of head. Basal portions of dorsal and anal fin do not project significantly beyond primary body profile. Scales of moderate size, cycloid and somewhat deciduous; 34–37 in a lateral series. Elongate, filamentous dorsal- and analfin rays in males; anal-fin rays without bony contact organs. Medialmost pelvic-fin ray connected to body via a membrane along its proximal half. Caudal fin lunate, dorsal and ventral segmented caudal-fin rays just slightly longer than middle rays. Male with a short, slightly conical, tubular urogenital papilla; female with bilobed urogenital papilla.

Premaxilla short and broad with distinct ascending process; premaxilla and dentary with two irregular rows of caniniform teeth; males with two to three rows of external conical teeth on the upper and lower oral jaws. No preethmoid cartilage; ossified portions of mesethmoid disc-shaped; anterior border of ethmoid cartilage irregular. No flanges on the ventral surface of the palatine and the quadrate. Dorsal ramus of hyomandibula not distinctly bifid, single cartilage articulates with sphenotic and pterotic. Lacrimal sensory canal carried in open bony groove. First pleural rib on parapophysis of third vertebra; first epipleural bone attaches to parapophysis of first vertebra dorsal to, and not in horizontal line with, posterior epipleural bones; lateral process of pelvic bone attaches to fifth pleural rib. Caudal skeleton with two epural bones; one ventral accessory bone. There are two ventral accessory bones in one of the cleared and stained specimens (CMK 6361). Procurrent caudal-fin rays hooked at their base. Fifth ceratobranchial toothplates subtriangular, with pavement dentition anteriorly, followed by four to five discrete rows of unicuspid teeth; small, incomplete posterior row. Basihyal bone triangular, basihyal cartilage elongate and rectangular. Epibranchial elements fully ossified; epibranchial 2 notably smaller than the other epibranchial elements.

Dorsal-fin rays 8–11. Anal-fin rays 21–25. Pelvic-fin rays 6. Pectoral-fin rays 11–12. Principal caudal-fin rays i,4/5,i. Procurrent fin-rays, dorsal 5, ventral 6. Vertebrae 32–33 (13–14 + 19). Branchiostegal rays 5.

Cytogenetic data: Oryzias nigrimas has a fused chromosome constitution (sensu Uwa, 1986, 1991a, b; Naruse et al., 1994; Table 2) and has 38 diploid chromosomes, including six metacentrics, four submetacentrics and 28 acrocentrics. The metacentrics are extremely large and have been hypothesized to have been formed by centric fusion. Chromosome arm number (NF) totals 48 and nuclear organizing regions (NORs) are on the short arms of a submetacentric pair of chromosomes ( Uwa, 1991b).

Colour in life: (From Kottelat, 1990a: 53–54): Females greyish brown on dorsal and lateral surfaces, lighter grey belly; fins hyaline. Males dark bluish-grey to black on dorsal and lateral surfaces; fins dark bluishgrey to black, except for greyish caudal fin; filamentous dorsal- and anal-fin rays bluish-white at their tips. Eyes blue, and with a shiny blue patch on ‘throat’.

Colour in alcohol: Ground colour yellowish-grey, belly pale yellow. Pigmentation quite variable in preserved specimens from pale overall in smaller specimens to darkly pigmented in large males. Dorsal surface of head and dorsal and lateral surface of body with dense dark brown to black chromatophores. A diffuse row of melanophores from the dorsal surface of the head to the dorsal-fin origin, a midlateral black line from the head to base of the caudal fin. Females and lighter-coloured males with diffuse line of dark chromatophores dorsal from just posterior to anal-fin origin, along body just dorsal to anal-fin base to middle of caudal peduncle. Urogenital papilla heavily pigmented in gravid female, paler brown to cream in other specimens. Fins of females, and pectoral and pelvic fins of males, hyaline. Dorsal, anal and caudal fins of males dusky to darkly pigmented.

Distribution and habitat: A pelagic species endemic to Lake Poso, Sulawesi Tengah, Indonesia.

Remarks: The holotype, ZSM/LIPI 1 (42.6 mm), collected with the paratypes, below, was not examined by me. Data were augmented by those in Kottelat (1990a). Other common names for this species are black medaka or black ricefish ( Seegers, 1997: 21).

Material examined: 521 specimens (6.3–51 mm SL).

Paratypes. INDONESIA. Sulawesi Tengah: Lake Poso , east shore between Tentena and Peura (field number 88–26), CMK 6358 (formerly CMK 6236 ), 10 (20.6–46.0 mm), CMK 6361 (formerly CMK 6236 ), 3 (38.5–40.0 mm, cleared and counterstained), ZMA 120.335 , 10 (5 males, 5 females, 23.2–43.5 mm), M. Kottelat, 24–25.vi.1988 .

Non-type specimens. INDONESIA. Sulawesi Tengah: Lake Poso, east and west shore of lake from where it empties at Tentena , S about 1.5 km, USNM 348722 , 202 (6.3–27.5 mm), L. R. Parenti, K. D. Louie & boatmen, 11.viii.1995 ; Lake Poso at Peura , eastern shore about 10 km S of Tentena, USNM 350559 , 103 (10.1–46.9 mm), L. R. Parenti, K. D. Louie, P. Beta & boatmen, 13.viii.1995 ; Lake Poso , eastern shore about 17 km S of Tentena, USNM 348723 , 33 (17.4– 47.3 mm, 6 of which have been cleared and counterstained), L. R. Parenti, K. D. Louie, P. Beta & Young, 12.viii.1995 ; Lake Poso, west bank of Poso R. where it empties into lake at Pamona Caves, USNM 350558 , 92 (13.9–50.8 mm), L. R. Parenti, K. D. Louie, P. Beta & boatmen, 13.viii.1995 , USNM 350560 , 68 (12.9– 51 mm), L. R. Parenti, K. D. Louie, P. Beta & Young, 11.viii.1995 .

Figures

Figure 50. Oryzias nigrimas Kottelat, 1990a, Lake Poso, Sulawesi Tengah, Indonesia, CMK 6358, male, 45.5 mm SL.