EMBRYONIC DEVELOPMENT IN INDIAN MEDAKA, ORYZIAS MELASTIGMA (MCCLELLAND, 1839)

Spawning of Oryzias melastigma in laboratory usually occurred in the morning or at twilight. Eggs laid per clutch ranged from 05 to 76 numbers and size of the eggs ranged from 1.1 to 1.4 mm in diameter. Twenty-four developmental stages of egg were observed based on their morphological differences. The developmental stages are: fertilized egg, blastodisc, two-cell, four-cell, eight-cell, sixteen-cell, thirty-two cell, early morula, late morula, early blastula, pre-early gastrula, pre-mid gastrula, mid-gastrula, late gastrula, early neurula, two-somite, six-somite, twelve-somite, twenty-two somite, thirty-somite, thirty-four somite, heart development, fully developed embryo and hatchling stage. Hatchling stage was observed after 264 hours i.e. 11 days at 24 to 25 0C temperature. The size of hatchlings ranged from 4.34 to 4.48 mm in length.