Fig. 1From: Progesterone initiates tendril formation in the oviducal gland during egg encapsulation in cloudy catshark (Scyliorhinus torazame)Changes in plasma steroid levels following the implantation of silicone tubing filled with P4. Non-breeding mature female catshark was used in this experiment. Note that plasma P4 level sharply increased following the implantation, while the level rapidly decreased to the initial low level after the removal of silicone tubingBack to article page