Oryzias haugiangensis, ROBERTS, 1998

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 : 563-564

ORYZIAS HAUGIANGENSIS ROBERTS, 1998

HAU GIANG MEDAKA

FIGURES 13A , 41

? Oryzias sp. ‘Vietnam’.- Stallknecht, 1989: 128 [report of a possibly new ricefish species from Vietnam].

Oryzias javanicus .- Rainboth, 1996: 171, figure (Mekong).

Oryzias haugiangensis Roberts, 1998: 222 , fig. 2f [type locality: Vietnam: Bassac R.[Hau Giang] at Can Tho and north bank of Mekong R. below Vinh Long].- Parenti, 2000a: 2150 [listed].- Parenti, 2000b: 600 [listed].

Differential diagnosis: Oryzias haugiangensis is a miniature species (largest specimen known 20.8 mm) in a group that includes O. carnaticus , O. dancena and O. javanicus that share closed, rather than open, lacrimal sensory canals (as does O. hubbsi ) and a pelvic bone with a lateral strut that is needle-like and elongate, as opposed to blunt. Oryzias haugiangensis shares with O. carnaticus , O. javanicus and another miniature, O. hubbsi , enlarged urogenital papilla in females. The miniatures Oryzias haugiangensis and O. hubbsi both have a large head (31% or more of SL), large eye diameter (reaching 10% or more of SL), and an anterior dorsal fin (its origin anterior to vertebra 22). They differ in that the lateral strut of the pelvic bone is blunt in O. hubbsi . Oryzias haugiangensis further differs from O. hubbsi in having a truncate, rather than rounded, caudal fin; urogenital papillae of females not as greatly enlarged; and 10–11 (as opposed to eight to nine) pectoral-fin rays.

Description: Miniature, maximum size of specimens examined 20.8 mm SL. Body compressed laterally, body relatively deep, depth 27–31 [30]. No pronounced abdominal concavity between pelvic fins and anal fin. Mouth terminal, jaws subequal or lower jaw projecting slightly beyond upper jaw. Dorsal body profile relatively straight from head to dorsal-fin origin; ventral body profile convex to anal-fin origin. Dorsal surface of head slightly convex just anterior to orbits. Head length 28–33 [28]; snout length 8–10 [9]; eye large, 10–12 [11], orbits meet dorsal surface of head. Basal portion of dorsal fin projects beyond primary body profile. Scales relatively large, cycloid; 24–28 [24] in a lateral series (scale count approximate). Dorsal-fin rays elongate, anal-fin slightly rounded; anal-fin rays of some males with small, bony contact organs. Medialmost pelvic-fin ray connected to body via a membrane along its proximal half. Caudal fin truncate. Male with short tubular urogenital papilla; female with relatively large, bilobed urogenital papilla.

Premaxilla short and broad with distinct ascending process; premaxilla and dentary with a single irregular row of caniniform; males with up to four large canine teeth on lateral ramus of the premaxilla and an opposing large tooth on the dentary in some male specimens. No preethmoid cartilage; ossified portions of mesethmoid large, disc-shaped; anterior border of ethmoid cartilage straight. 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 closed, 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; elongate lateral process of pelvic bone attaches to third pleural rib. Caudal skeleton with two epural bones; one ventral accessory bone and one accessory cartilage. Fifth ceratobranchial toothplate triangular, with teeth in irregular rows anteriorly, followed by four discrete rows of unicuspid teeth, and an incomplete posterior row. Basihyal bone elongate, triangular, basihyal cartilage elongate and rectangular. Epibranchial elements fully ossified; epibranchial 2 notably smaller than the other epibranchial elements.

Dorsal-fin rays 6–7. Anal-fin rays 19–22. Pelvic-fin rays 6. Pectoral-fin rays 10–11. Principal caudal-fin rays i,4/5,i. Procurrent fin-rays, dorsal 4–5, ventral 5. Vertebrae 27–29 (10–11 + 17–19). Branchiostegal rays 5–6.

Cytogenetic data: Unknown.

Colour in life: Unknown.

Colour in alcohol: Ground colour pale to medium brown. 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 that continues onto the caudal fin on the membrane just dorsal and ventral to the first ray above and below the midline, respectively. A faint black line along the anal-fin base. Dorsal and anal fin interradial membranes with scattered melanophores. Body covered with minute melanophores.

Distribution and habitat: Endemic to the Mekong delta, Vietnam, in tidal habitats.

Material examined: 269 specimens (10.4–20.8 mm SL).

Holotype. VIETNAM. UMMZ 233088 , male, 17.1 mm, Bassac R. [Hau Giang] at Can Tho, R. E. Arden & O. K. Minn, 3.xi.1974.

Paratypes. VIETNAM. UMMZ 218674 , 223 (13– 18.9 mm, 14 of which, 15.6–18.9 mm, have been cleared and stained solely for bone) , CAS 93898 (ex. UMMZ 218674 ) 25, (2 of which have been cleared and counterstained), Bassac R. [Hau Giang] at Can Tho , R. E. Arden & O. K. Minn, 3.xi.1974 ; UMMZ 224693 , 18 (10.4–20.8 mm), flooded sedge patch at E end of Can Tho Is. In Bassac R., 3.5 km SE of Can Tho, 19.vii.1974, M. L. Smith & R. P. Weidenbach ; UMMZ 227299 , 2 (14.7–18.1 mm), N bank of Mekong R. At mouth of canal 2 km below Vinh Long, 22.vi.1974, M. L. Smith , R. P. Weidenbach & Chanh .

Figures

Figure 13. A, Oryzias haugiangensis, CAS 93898, female, 16 mm SL. B, O. hubbsi, CAS 92322, female, 16 mm SL. Lateral view of body to show large bilobed urogenital papilla just posterior to pelvic fins of adult females. Extremely large urogenital papilla is an autapomorphy of the miniature O. hubbsi.

Figure 41. Oryzias haugiangensis Roberts, 1998, Bassac River, Vietnam, CAS 93898, paratype, female, 16.0 mm SL.