Fig. 1

The process of embryonic development of W. pigra. A-C Cleavage stages: embryo undergoes spiral division along with the teloplasm unequal distribution; D Blastocyst stage: SYC wrapped by blastoderm; E–F Gastrula stage: the embryo has a strong deformation movement, the shape of the blastopore (red triangle) changes; D-V and A-P axes formed after gastrulation. G-K Organogenesis and refinement. The development events in this stage include the differentiation and refinement of crop ceca and intestine, caudal sucker (red arrow, H, J), and eye spots (white arrow, J); L Juvenile. yolk depletion in embryos, the color of the five longitudinal body surface lines was darker. Larvae leave the cocoon and begin to feed for the first time. SYC, syncytial yolk cell; D-V, dorsal–ventral; A-P, anterior–posterior