Wednesday, July 20, 2011

[Ichthyology • 2011] Oryzias haugiangensis • the First Record from the brackish waters in the Southeastern Thailand

FIGURE 2. Oryzias huagiangensis Roberts, 1998. Material specimens (A) NIFI 4260 from Thailand (fresh condition) and (B) CTU-P 2167 from Vietnam (fixed condition). Bars indicate 5 mm.


Specimens of the ricefish, Oryzias haugiangensis, reported here for the first time from the brackish waters in the southeastern Thailand, were caught in a mangrove forest habitat. This study compares the morphometric and meristic characters and the karyotype of O. haugiangensis with those of the Andaman sea specimens of O. javanicus which are clearly distinguishable by the length of the snout, head, preanal, preanal fin, prepelvic fin and anal fin base, plus the body depth at the anterior of the anal fin origin. Oryzias haugiangensis is similar to O. javanicus in the number of pelvic fin and branchiostegal rays present, and in the diploid chromosome number (2n = 48), but differs from the latter in that it has a lower number of anal fin and pectoral fin rays and has a different karyotype, with 2n = 48 (2 SM + 23 A; NF = 54). Oryzias haugiangensis belongs to monoarmed chromosome group within the genus Oryzias.

KEY WORDS: Oryzias haugiangensis, mangrove habitat, morphology, karyotype

FIGURE 3. Geographical distribution of Oryzias in south and southeast Thailand. Solid triangle, O. javanicus from Ranong; open triangle, O. javanicus from Phuket; solid circle, O. haugiangensis from Vietnam; open circle, O. haugiangensis from Thailand.

Magtoon, W. 2011. First Record of the Ricefish, Oryzias haugiangensis (Adrianichthyidae: Oryziinae), from Southeastern Thailand. Tropical Natural History 11(1): 9-20.