Hydroperiod influences tadpole growth and development in the endangered
Littlejohn’s tree frog (Litoria littlejohni)
Abstract
Amphibians are among the most threatened vertebrate taxa globally. Their
global decline necessitates effective conservation actions to bolster
populations across both the larval and adult life stages. Constructing
man-made ponds is one such action proven to enhance reproduction in
pond-breeding amphibians. However, to achieve successful conservation
outcomes, extensive prior knowledge about the ecology and behaviour of
the target species is required. In this study, we investigated how
different hydroperiod regimes impact the growth and development of
Litoria littlejohni tadpoles. Over a 28-week period, tadpoles were
exposed to three hydroperiod treatments: Constant High, Declining, and
Constant Low water levels. Weekly measurements of snout-to-vent length,
body mass, and Gosner stage were taken to assess any treatment-related
changes. To determine whether different treatments affected locomotor
performance, a jump test was conducted three weeks post metamorphosis.
Individuals did not exhibit developmental plasticity in response to
declining water, with a mean time to metamorphosis of 93.3 days.
Comparatively, when L. littlejohni tadpoles were exposed to low water
volumes, they were able to speed up development and reduce time to
metamorphosis, with a mean time of 56.5 days. The speeding up of
development had an apparent consequence for L. littlejohni. We found
support for trade-offs between rapid development and reduced
morphometric measurements post-metamorphosis which resulted in reduced
locomotive ability. Individuals from Constant Low water treatments
exhibited an average total jumping distance of 170.5 cm over 10
consecutive jumps, compared to 235.8 cm in Constant High and 209.5 cm in
Declining treatments. Rapid larval development aids tadpoles in escaping
suboptimal aquatic conditions, but its effects on locomotion may impact
foraging efficiency and predator escape ability. Understanding
developmental plasticity in threatened amphibians, especially in
response to hydroperiod variations, is crucial for conservation
programs, particularly under future climate change scenarios predicting
increased drought and reduced hydroperiods in aquatic environments.