Embryonic Development of Discus, Symphysodon aequifasciatus Pellegrin, 1904 in Indian Condition

The experiment was conducted to investigate the embryonic development of discus (Symphysodon aequifasiatus) and determine the time required for major egg developmental stages and hatching. Regular observations were made using optical microscope and the images were recorded using a digital camera attached to the microscope. Important water quality parameters were kept optimal for the hatching of discus eggs. Newly laid eggs were oval-shaped and yellow in colour with an average diameter of 1.37 ± 0.14 mm. The embryonic development of fertilized eggs was divided into 16 stages and the development of each stage was recorded in times lapse. The result revealed that cleavage occurred after 1hr after fertilization followed by development of blastula and gastrula at 20.5 hr and 24 hr after fertilization respectively. The period of organogenesis started with the formation of embryonic notochord from 37.5 hrs after fertilization. The appearance of a defined head and tail of the embryo with 19 somites was observed at 40.0 hrs after fertilization, whereas heart beat along with blood circulation appeared after 55.5 hrs after fertilization. The eggs hatched after 69.06 hr after fertilization.