Oryzias matanensis, (AURICH, 1935)

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 : 571-573

ORYZIAS MATANENSIS ( AURICH, 1935)

MATANO RICEFISH

FIGURES 12 , 19B , 25A , 46

Aplocheilus matanensis Aurich, 1935: 103–104 , fig. 1a [type locality: Indonesia: Sulawesi, East of Soroako, Lake Matano ].

Oryzias matenensis .- Incorrect spelling.- Yamamoto, 1975: 24 [listed].

Oryzias matanensis .- Whitten et al., 1987a: 295, table 4.10 [Sulawesi, distribution].- Whitten et al., 1987b: 43–48, table 1 [Sulawesi, conservation].- Kottelat, 1989a: 616, plate [report from Lake Matano].- Kottelat, 1990b: 159–161, figs 6, 7, tables 5 and 6 [redescription, comparisons].- Kottelat et al., 1993: 90 [listed; characters].- Naruse et al., 1994: 49 [cytogenetic data].- Seegers, 1997: 15, 18 [listed, photograph].- Albert et al., 1999: 650 [brain weight].- Parenti & Grier, 2004: 336 [atherinomorph testis type, listed].

Differential diagnosis: The Malili Lakes buntingi of Sulawesi, O. marmoratus , O. profundicola and O. matanensis , are readily distinguished from all other ricefishes by their distinctive pigmentation pattern: males have a series of regular midlateral blotches and irregular dark brown blotches on the entire lateral surface of the body. They are all somewhat deep bodied, reaching more than 26% SL; have a relatively large eye, diameter reaching 10% or more of SL; and have relatively long anal fins that range to over 24 anal-fin rays. Oryzias matanensis is distinguished by having 41–47 scales in a lateral series, whereas Oryzias marmoratus and O. profundicola have 31–32 and 32–34, respectively. Oryzias matanensis is further distinguished by the distinctive colour pattern of adult males: vertically elongate black blotches in a more-or-less regular midaxial row, and several smaller black blotches distributed irregularly on body, denser in posterior half. Oryzias marmoratus and O. matanensis have 8–12 or 8–9 dorsal-fin rays, respectively, whereas O. profundicola has 10–14.

Description: Intermediate, maximum size of specimens examined 47.3 mm SL. Body compressed laterally, moderately deep, body depth 26–31. No pronounced abdominal concavity between pelvic fins and anal fin. Mouth terminal, jaws subequal or lower jaw projects slightly beyond upper jaw. Dorsal body profile arching gently from head to dorsal-fin origin; ventral body profile somewhat convex from head to anal-fin origin. Dorsal surface of head slightly convex just anterior to orbits. Head length 25–29; snout length 7–9; eye large, 10–11; orbits do not project beyond dorsal surface of head. Basal portion of dorsal and anal fin does not project significantly beyond primary body profile. Scales of moderate size, cycloid, and somewhat deciduous; 41–47 in a lateral series. Elongate, slightly filamentous dorsal- and anal-fin rays in males; anal-fin rays without bony contact organs. Medialmost pelvic-fin ray connected to body via a membrane along its proximal half in males, along its entire length in females. Caudal fin truncate to slightly lunate. Male with a short, slender, slightly conical or blunt, tubular urogenital papilla; female with bilobed urogenital papilla ( Fig. 12 ).

Premaxilla short and broad with indistinct ascending process; premaxilla and dentary with two irregular rows of small, caniniform teeth, males with two to three rows of external conical teeth on the upper and lower oral jaws, and thick and fleshy lips through which tooth tips project; females with one or two large, conical teeth on lateral portion of the dentary. 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 third pleural rib. Caudal skeleton with two epural bones; one slightly convex, ventral accessory bone. Fifth ceratobranchial toothplates subtriangular, with teeth in irregular rows anteriorly, followed by eight discrete rows of unicuspid teeth, including a small, incomplete posterior row. Basihyal bone triangular, basihyal cartilage extremely elongate and rectangular. Epibranchial elements fully ossified; epibranchial 2 notably smaller than the other epibranchial elements.

Dorsal-fin rays 8–9. Anal-fin rays 20–25. Pelvic-fin rays 6. Pectoral-fin rays 11–12. Principal caudal-fin rays i,4–5/5,i. Procurrent fin-rays, dorsal 4–5, ventral 5–6. Vertebrae 30 (12 + 18). Branchiostegal rays 5.

Cytogenetic data: Oryzias matanensis has a fused chromosome constitution with 2 n = 42 chromosomes ( Table 2; Naruse et al., 1994).

Colour in life: (From Kottelat, 1990b: 160): Males greyish-brown on head and body. Vertically elongate black blotches in a more-or-less regular midaxial row; several smaller black blotches distributed irregularly on body, denser in posterior half. Eyes blue. Dorsal, anal, caudal and pelvic fins blackish; pectoral fin hyaline. Females with light brown head; body with smaller, indistinct black blotches or immaculate.

Colour in alcohol: Ground colour yellowish-grey. Dorsal surface of head and dorsal and lateral surface of body with dense dark brown to black chromatophores. A dense row of melanophores from dorsal surface of head to dorsal-fin origin, a thin, midlateral black line from head to just anterior to base of caudal fin. Females with diffuse line of dark chromatophores dorsal from a point just posterior to anal-fin origin, along body just dorsal to anal-fin base to middle of caudal peduncle. Fins of females hyaline or slightly dusky. Pectoral and pelvic fins of males dusky to dense melanophores. Urogenital papilla of females and of males immaculate or with a few, minute melanophores along posterior margin. Dorsal- and analfin rays of males dusky except at their margins which are hyaline. Caudal fin-rays of males dusky, dark line along proximal half of membranes between median caudal-fin rays; dorsal and anal margins of caudal fin hyaline.

Distribution and habitat: Endemic to Lake Matano of the Malili River basin, Sulawesi, Indonesia ( Parenti & Soeroto, 2004: fig. 1). Found around the lake in quiet backwaters and along steep shores ( Kottelat, 1990b).

Remarks: Kottelat (1990b: 159–160) designated a neotype for Oryzias matanensis (ZSM 27368) from material that he collected in 1988 from Lake Matano, after concluding that the ten syntypes from the lake were lost or destroyed. I did not examine the neotype. Data were augmented by those in Kottelat (1990b). Another common name for this species is Matano medaka ( Seegers, 1997: 20).

Material examined: 344 specimens (7.6–47.3 mm SL). INDONESIA. Sulawesi Selatan: Luwu: Muha: Lake Matano , E of Soroako, (field number 88–19), type locality, CMK 6195 , 10 (40.2–44.5 mm, of which one male, 42.5 mm, and one female, 44.5 mm, have been cleared and counterstained), M. Kottelat, 19.vi.1988 ; western shore of Lake Matano at Soroako , USNM 340422 , 12 (15.2–30.7 mm), local fisherman, 7.viii.1995 , USNM 340428 , 73 (14.9–47.3 mm), L. R. Parenti, K. D. Louie , T. Amos & Dahlan, 6.viii.1995 ; western shore of Lake Matano, stream entering small inlet approx. 6–7 km N of Soroako, USNM 340429 , 249 (7.6–46.1 mm), L. R. Parenti, K. D. Louie , T. Amos & boatmen, 7.viii.1995 .

Figures

Figure 12. Oryzias matanensis, CMK 6195, male, 44.5 mm SL (above), female, 40.2 mm SL (below), ventral view of midbody. Note small, single-lobed urogenital papilla in male, bilobed papilla in female.

Figure 19. A, O. javanicus, juvenile, USNM 348513, 18.5 mm SL; B, O. matanensis, CMK 6195, female, 44.5 mm SL. Detail of ethmoid region of skull and oral jaws. Note closed lacrimal canal in O. javanicus, open canal in O. matanensis.

Figure 25. A, Oryzias matanensis, CMK 6195, male, 42.5 mm SL; B, Oryzias carnaticus, CAS 37089, female, 26.5 mm SL. Diagrammatic representation of the dorsal portion of the gill arches. Scale bar = 1 mm.

Figure 46. Oryzias matanensis (Aurich, 1935), Lake Matano, Sulawesi Selatan, Indonesia, CMK 6195, male, 43.3 mm SL, above, female, 43.4 mm SL, below.