Factors affecting the juvenile departure in Orientobdelloides siamensis (Oka, 1917)

The departure of juveniles from parental care is an important period influenced by various factors. In the laboratory, 3-5 days after copulation, ten parent individuals of Orientobdelloides siamensis deposited approximately 361.6±37.79 eggs on the substrate and covered them until departure. The parents incubated their single-egg cocoons for around 7-9 days until the juveniles hatched. Subsequently, the newborns turned to attach to the ventral annuli of the parent using their caudal sucker. Between seven to eleven days after hatching, when the caudal sucker of juveniles expanded over the parent’s annuli, signaling their readiness to depart, they detached from beneath the parent vent to the substrate but continued to live beneath it. Finally, to determine the timing of juvenile departure, the insufficient space availability beneath the parental vent and yolk depletion around 14-21 days after hatching were analyzed. Through these morphological characteristics and behavior, this study indicated the interactions among these factors contributing to the mechanisms influencing juvenile departure in O. siamensis .