Hatching Plasticity in Captive-Bred Pickersgill's Reed Frog, Hyperolius pickersgilli (Raw 1982)

The Pickersgill's reed frog, Hyperolius pickersgilli (Raw 1982), is an Endangered frog species endemic to a narrow central coastal region of KwaZulu-Natal, South Africa. The Johannesburg Zoo's Amphibian Research Project breeds H. pickersgilli for release to the wild. This study aimed to determine if hatching plasticity occurs in this species in relation to direct disturbance of clutches by water spray, misting the containers housing the clutches to maintain the relative humidity above 75% is essential husbandry. Several clutches were assigned to either an undisturbed group or a disturbed group. Tadpoles from clutches mist-sprayed with reverse osmosis water on day 4 after oviposition hatched at a younger age than from undisturbed clutches. The disturbed H. pickersgilli tadpoles began hatching on average 10 s after the introduced disturbance on day 4 from the point of being laid, when the tadpoles were at Gosner stage 21 and still had yoke sacs attached, whereas the undisturbed developing embryos hatched at 6.6 days on average at Gosner stage 21 but when many of the tadpoles did not have yoke sacs attached. The proportion of the embryos that hatched did not differ significantly between the undisturbed clutches and the disturbed clutches. Tadpoles hatching from H. pickersgilli clutches with no direct disturbance had a greater survival rate at 30 days after hatching and therefore an increased likelihood of survival than tadpoles from disturbed clutches. Maintaining clutches undisturbed by essential husbandry methods is preferable in H. pickersgilli ex situ breeding programs.