Insights Into the Reproduction and Maturity of the Spinetail Devil Ray (Mobula mobular)

Little is known about the reproductive biology of the endangered spinetail devil ray (Mobula mobular). Here, we describe the reproductive behavior, estimates of age, size at maturity, embryonic development in the uterine cavity, and the morphology of a neonate produced by a male and female ray kept in Osaka Aquarium KAIYUKAN for 7.5 years. The reproductive behaviors observed included initiation, endurance, evasion, pre-copulation positioning, copulation, and separation. The disc widths (DW) of male and female rays displaying reproductive behaviors were 203 and 204 cm, respectively. The male was estimated to be 7.7 years old after elongation of claspers, while the female was estimated to be 8.9 years old at first mating. A neonate was born 464 days after successful copulation, weighing 11.32 kg, with a DW of 104 cm. These observations are consistent with those of previous studies conducted on wild individuals. This is one of the few reports on the reproductive behavior of spinetail devil ray. Research conducted on this species in captivity is expected to help fill the knowledge gaps for this poorly studied species.