Live-bearing manta ray: how the embryo acquires oxygen without placenta and umbilical cord.
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.
The Hokkaido University Museum, Minato-cho, Hakodate 041-8611, Japan. t-tomita@museum.hokudai.ac.jp
Taketeru
T
Tomita
Minoru
M
Toda
Keiichi
K
Ueda
Senzo
S
Uchida
Kazuhiro
K
Nakaya
D000818:Animals; D001696:Biomechanical Phenomena; D015509:Developmental Biology / Q000379:methods; D018940:Elasmobranchii / Q000196:embryology* / Q000502:physiology; D004625:Embryo, Nonmammalian / Q000502:physiology*; D005260:Female; D007564:Japan; D008322:Mammals; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D010920:Placenta / Q000502:physiology; D012119:Respiration; D014463:Ultrasonography / Q000379:methods; D014470:Umbilical Cord / Q000502:physiology; D014599:Uterus / Q000502:physiology
D010100:Oxygen