Oryzias songkhramensis Magtoon, 2010

Family:  Adrianichthyidae (Ricefishes), subfamily: Oryziinae
Max. size:  1.9 cm SL (male/unsexed)
Environment:  pelagic; freshwater
Distribution:  Asia: Songkhram and Mekong River basins, Northeastern Thailand
Diagnosis:  Dorsal soft rays (total): 6-7; Anal soft rays: 15-17; Vertebrae: 27-29. Oryzias songkhramensis is distinguished from all other congeners by possessing the following combination of characters: anal-fin rays 15 - 16 (modally 16), bony contact organs on the anal-fin rays in males; a relatively anterior dorsal fin origin, opposite anal fin 13 - 14 (modally 14); vertebrae 27 - 29 (modally 28); fourth vertebra without neural prezygapophysis; scale relatively large, cycloid; 26 - 29 (modally 27) in a lateral series, predorsal scale 19 - 21 (modally 21); snout length shorter than eye diameter, snout length 12.9 - 31.2% (mean 21.7%) of HL; eye diameter 35.2 - 53.4% (mean 43.2%) of HL; a black spot at the base of pectoral fin, pectoral fin length 13.1 - 24.9% (mean 19.7%) of SL; length of anal fin base 19.4 - 30.0% (mean 25.6%) of SL; caudal peduncle length 11.3 - 20.3% (mean 16.7%) of SL; caudal fin slightly, rounded, length 3.6 - 3.8 (mean 3.7) in SL, black and pale yellow marginal bands on the dorsal and ventral portions of the caudal fin (Ref. 84389).
Biology:  The species was collected in clear water from ditches and paddy fields by dip nets in the Songkhram and Mekong River basins. The area of collection is a small ditch, 3-6 m wide and 0.5 to 2 m deep, Substrate ranges from sand to detritus or mud. Associated species include Trichogaster trichopterus, Trichopsis vittatus, Rasbora rubrodorsalis, Channa striata and Machrobrachium lanchesteri; aquatic plants Nymphaea lotus, Jussiaea repens and Hydrilla verticillata. Water quality in the area: 27.5-28.7 ºC, conductivity 41.5-124.4 μm/l, dissolved oxygen 2.05-3.97 mg/l, pH 7.1-7.9 and salinity 0.1 ppt (Ref. 84389).
IUCN Red List Status: Data deficient (DD); Date assessed: 22 February 2011 Ref. (130435)
Threat to humans:  harmless


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