The role of arginine vasotocin and prostaglandin F 2α on oviposition and luteolysis in the common snapping turtle Chelydra serpentina

Abstract

The administration of arginine vasotocin (AVT) to gravid snapping turtles with steroidogenically active corpora lutea and high plasma progesterone concentration (1480 ± 155 pg/ml) did not trigger oviposition, whereas 12 days after ovulation when luteolysis occurred and plasma progesterone concentration was low (570 ± 78 pg/ml), treatment with AVT caused oviposition. Controls with high plasma progesterone concentration (1605 ± 185 pg/ml) oviposited 15–23 days after ovulation when plasma progesterone concentration dropped to 201 ± 35 pg/ml. Deluteinization-induced oviposition was initiated 15 hr after surgery and was completed by 30 hr. Oviposition of complete clutches occurred and was correlated with a significant drop in plasma progesterone. Sham-operated turtles did not exhibit oviposition and no significant change in progesterone concentration was observed. A single injection of prostaglandin F 2α (PGF) in recently ovulated turtles induced early luteolysis and a significant decrease in plasma progesterone concentration after 24–30 hr. A single administration of PGF caused the disappearance of steroidogenic features such as the smooth endoplasmic reticulum and mitochondria with tubular cristae 48 hr later. Also PGF triggered the invasion of a hyaline-like material from the luteal theca into the luteal cell mass which eventually induced luteolysis. The role of AVT, PGF, and progesterone in relation to egg retention and oviposition is discussed.