Oryzias javanicus (Bleeker, 1854)

Zainal Abidin, Danial Hariz, Lavoué, Sébastien, Mohd Abu Hassan Alshari, Norli Fauzani, Mohd. Nor, Siti Azizah, A. Rahim, Masazurah & Mohammed Akib, Noor Adelyna, 2021, Ichthyofauna of Sungai Merbok Mangrove Forest Reserve, northwest Peninsular Malaysia, and its adjacent marine waters, Check List 17 (2), pp. 601-631 : 619

Oryzias javanicus (Bleeker, 1854)

Material examined. MALAYSIA • 3, 28– 35 mm TL; Kedah State, Semeling, Semeling Bridge ; 05.680°N, 100.470°E; 17 Jul. 2019; Sébastien Lavoué leg.; USMFC (101) 00002. Identification. A small species of Adrianichthyidae (maximum TL <40 mm). Body deep, laterally compressed; eyes large; small mouth terminal; pectoral fins set relatively high on side of body; single dorsal fin set posteriorly; caudal fin truncate; no lateral line. Dorsal and anal fin rays of male longer and thicker than those of female .

Yusof et al. (2012) reported the presence of two species of Oryzias along the west coast of Peninsular Malaysia, O. javanicus and Oryzias dancena (Hamilton, 1822) . According to Yusof et al. (2012), O. javanicus is separated by its silvery eyes and dorsal black lines whereas O. dancena exhibits shiny blue eyes and no black line on body.

Furthermore, O. javanicus is a typical brackish species, living in higher salinity habitats than O. dancena which is more freshwater tolerant which may explain why we did not collect it ( Yusof et al. 2012). Oryzias javanicus is the first species (and so far, the only one) for which its whole genome has been sequenced from specimens originating from this region (i.e., Penang region) ( Takehana et al. 2020).