Phosphorus-limited food affects the moulting process in Daphnia commutata

Moulting is an energetically and nutritionally demanding process that likely depends on stoichiometric elemental balances. This study investigates the effect of phosphorus (P) limitation on the moulting process in Daphnia commutata from three different populations (two wild populations and a lab clone). We carried out experiments under two contrasting food conditions: P-rich and P-limited. We analysed the activity of two enzymes involved in the moulting process: Chitobiase (somatic and released) and Caspase-3, linking them to moulting frequency, intermoult duration, synchrony, and incomplete ecdysis. Our results revealed that P limitation significantly impairs all enzyme activities analysed. Furthermore, the P limited individuals showed delayed moulting, extended intermoult period, reduced somatic growth rates, and evidence of incomplete moulting. Collectively, these findings highlight a marked decline in the performance of populations experiencing P limitation.