immediately_preceded_by developmental stage Medaka stage 36 Medaka stage 37 OlatDv:0000400 Zoological Science 11: 825-839 (1994) - 7 days Stage 37 (7 days) Pericardial cavity formation stage: The tip of the tail lies just past the otic vesicle (total length ca. 3.1 mm). The pharyngeal teeth are visible in the posterior region of the gills between the otic vesicles. The pericardial cavity (cardiac sac) surrounding the heart is easily observed. The slowly moving gut tube has a narrow lumen. - 7 days medaka_ontology pericardial cavity formation stage