The power of ultrasound: observation of nearly the entire gestation and embryonic developmental process of captive reef manta rays (Mobula alfredi)

The aim of this study was to make ultrasound observations of 2 captive reef manta rays (Mobula alfredi), thereby collecting the first known data regarding the embryonic development of reef manta rays throughout almost the entire gestation period. The gestation period and water temperature at parturition were similar to 1 year and similar to 27 degrees C, both of which are consistent with observations of wild individuals. On the basis of embryonic features observed through ultrasound, 3 developmental stages were recognized: early (0-80 d after copulation), middle (80-150 d after copulation), and late (150-360 d after copulation). The middle stage was distinguished from the early stage by the presence of large, wing-shaped pectoral fins, cephalic lobes, and buccal pumping, whereas the late stage was distinguished from the middle stage by the overlapping of the right and left pectoral fins and cessation of motion of the entire body in utero. These criteria will be useful for determining the gestation stages of wild reef manta rays.