immediately_preceded_by developmental stage Medaka stage 23 Medaka stage 24 16 somite stage OlatDv:0000270 Start of heart beating Zoological Science 11: 825-839 (1994) - 1 day 20 hrs Stage 24 (1 day 20 hrs) 16 somite stage (Start of heart beating): The anterior portion of the heart, which exhibits a slow (about 33-64/min) pulsation, extends up to the anterior end of the fore-brain. Cuvierian ducts and the vitello-caudal vein are still in- complete. Kupffer's vesicles have almost disappeared. Otoliths are not yet present in the otic vesicles. The embryonic body encircles nearly 1/2 of the yolk sphere. The gut (digestive) tube is observed ventral to the dogleg-shaped somites. - 1 day 20 hrs medaka_ontology