Comportamento antipredação de Tetranychus urticae Koch (Trombidiformes: Tetranychidae) em melão

Abstract

Predator-prey interactions constitute one of the main mechanisms shaping population dynamics and prey behavior. Under predation risk, many prey species may develop antipredator strategies, including behavioral changes such as refuge use and shifts in oviposition. For small arthropods, structures such as leaf trichomes may be used as resources to avoid predation at low energetic cost. In plants such as melon (Cucumis melo L.), a high density of trichomes may act both as a barrier to predators and as a refuge for phytophagous organisms. Accordingly, the objectives of this study were to evaluate: 1) Does Tetranychus urticae Koch use melon leaf trichomes as an antipredator strategy? 2) Does the response of T. urticae vary under different levels of predation risk? 3) Does the response of T. urticae vary when exposed to the predators Neoseiulus idaeus Denmark & Muma (specialist) or Neoseiulus barkeri Hughes (generalist), and does predator identity modulate the response of T. urticae? 4) Do trichomes interfere with predator performance? To assess the oviposition behavior of T. urticae, female mites were placed on melon leaves under different predation-risk scenarios: control (no exposure to predators), high risk (direct exposure to the predatory mite), medium risk (indirect exposure to the predator), and low risk (exposure to simulated predation using crushed eggs). Antipredator responses were evaluated based on the daily oviposition rate and the oviposition site (trichomes, glabrous areas, and webbing). To evaluate the effect of trichomes on predator performance, prey encounter time and egg consumption were assessed on leaves with high (melon leaves) and low (jack bean leaves) trichome density. The results showed that T. urticae is able to alter its reproductive behavior in response to predation risk. Significant changes were observed following exposure to predators or their cues, with a greater reduction in oviposition rate when exposed to the specialist predator. An effect on the pattern of oviposition site selection was observed, with increased oviposition on webbing rather than on trichomes, indicating that trichomes are not used as oviposition refuges. In the assessment of predator performance, higher trichome density increased prey encounter time for N. idaeus and reduced egg consumption for both predators. Overall, the results indicate that T. urticae does not use melon leaf trichomes as an anti-predator strategy for egg laying, instead preferring oviposition on webbing when exposed to predation risk. However, melon trichomes appear to influence predator foraging behavior, reducing the efficiency of N. barkeri and N. idaeus in the predation of T. urticae eggs.