Live-bearing manta rayPublished online on 06. June 2012
Live-bearing manta ray: how the embryo acquires oxygen without placenta and umbilical cord
Taketeru Tomita, Minoru Toda, Keiichi Ueda, Senzo Uchida and Kazuhiro Nakaya
We conducted an ultrasonographic experiment on a pregnant manta ray, Manta alfredi (Chondrichthyes, Batoidea). This study showed how the embryo of the live-bearing elasmobranchs respires in the body of the female. In the embryonic stage, the manta ray embryo takes in uterine fluid by buccal-pumping. After birth, the manta ray shifts its respiratory mode from buccal-pumping to ram-ventilation. The rapid reduction of the spiracle size in the young manta ray may reflect this shift of respiratory mode.
Unlike mammals or some carcharhinid sharks that acquire oxygen through a placenta and umbilical cord, the manta ray embryo does not have a direct connection with the mother. Thus, the manta ray embryo obtains oxygen by buccal-pumping of the uterine fluid, in the same way that the embryos of egg-laying species obtain oxygen from the water in the egg case. This finding extends our understanding of the diversity of embryonic respiratory systems in live-bearing vertebrates.
Biol. Lett. rsbl20120288; doi:10.1098/rsbl.2012.0288 1744-957X