Leg ablation during nymphal development shifts wing morph determination in Aquarius paludum (Hemiptera: Gerridae): Leg position‐specific and instar‐dependent effects on wing dimorphism, adult emergence and body size

Wing polymorphism is a widespread life history adaptation in insects; however, the extent to which physical injury during nymphal development influences wing morph determination remains poorly understood. We examined effects of unilateral leg ablation on wing morph, adult emergence rate (survival to adulthood), developmental period and body size in water strider Aquarius paludum (Hemiptera: Gerridae). One foreleg, midleg or hindleg was ablated at the coxa in the 2nd through 5th instar nymphs and compared with an intact control (384 individuals in total). Midleg ablation had the most pronounced effect on wing morph; no long‐winged adults were produced after ablation at the 2nd or 3rd instar (versus 74%–93% in control), and the proportion remained low at the 4th and 5th instars (21% and 23%, respectively). Foreleg ablation reduced the proportion of long‐winged adults, whereas hindleg ablation had a weaker effect. Effects of ablation on wing morph diminished as the instar advanced, consistent with the known sensitive period for wing morph determination. Foreleg ablation consistently reduced the adult emergence rate across all instars (29%–50%), whereas midleg and hindleg ablation resulted in less persistent effects. Midleg ablation significantly prolonged the duration of the immediately following instar in all instars; this developmental delay was partially compensated for in individuals ablated at the 2nd or 3rd instar, but persisted in those ablated at the 4th instar. These findings demonstrate, for the first time, that leg ablation shifts wing morph determination in hemipterans, with effects depending on both the position of the ablated leg and the instar at ablation.