The annual reproductive cycle and sperm storage in the bearded dragon, Pogona barbata

Pogona barbata, a large lizard that inhabits the open woodlands of eastern Australia, has been reported to have a high annual reproductive output, whi ch is contrary to expectations for a large lizard. To better understand thi s anomaly, its reproductive cycle and morphology were investigated. Males w ere spermatogenic year round, with only a brief period of regression in Jan uary (late summer). Females were vitellogenic and gravid through August-Dec ember (spring to early summer). Two or three large clutches (14-26 eggs per clutch) were produced each breeding period. Females had two germinal beds in each ovary, and all four actively produced eggs simultaneously. Clutches overlapped such that the next clutch began vitellogenesis before the first was laid. These characteristics make this species' reproductive output one of the largest known among lizards. Reproductive females had sperm stored in oviductal crypts, but there was no evidence of sperm storage outside the breeding period. The short-term storage of sperm by breeding females may p romote sperm competition between males.