Deltamethrin-Mediated Toxicity and Cytomorphological Changes in the Midgut and Nervous System of the Mayfly Callibaetis radiatus

Abstract

Immature instars of mayflies are important constituents of the food web in aquatic ecosystems (especially in Neotropical regions) and they are among the most susceptible arthropods to pyrethroid insecticides. These insecticides have been recognized as important stressors of freshwater ecosystems, but their cellular effects in aquatic insects have been neglected. Here, we assessed the susceptibility to deltamethrin (a typical type II pyrethroid) as well as the deltamethrin-mediated cytomorphological changes in the central nervous system and midgut of the mayfly Callibaetis radiatus. While the deltamethrin LC50 for 24h of exposure was of 0.60 (0.46–0.78) μg of a.i/L, the survival of C. radiatus was significantly reduced in deltamethrin concentrations ≥ 0.25 μg a.i/L at 96h of exposure. Sub-lethal deltamethrin exposure severely affected the cytomorphology of C. radiatus midgut (e.g., muscle layer retraction, cytoplasm vacuolation, nucleus and striated border disorganization) and also induced slight cytomorphological changes in the brain (e.g., presence of pyknotic nuclei) and in the thoracic ganglia (e.g., vacuolation of neurons and presence of pyknotic nuclei) of these insects. However, DNA damage was absent in all of these organs, suggesting that the sublethal cellular stress induced by deltamethrin might disrupt physiological processes (e.g., metabolism or electrical signal transmission) rather than cause cell death (e.g., apoptosis) in C. radiatus. Thus, our findings indicated that deltamethrin actions at cellular levels represent a clear indication of sublethal effects on the C. radiatus survival abilities.

Deltamethrin toxicity and impaired swimming behavior of two backswimmer species

“…However, based on our results for deltamethrin toxicity, such conclusions should be analyzed with caution. Whereas the susceptibility of B. tarsalis to deltamethrin (LC50 ¼ 4.0 ng a.i./L) was similar to that of other backswimmer species (e.g., Anisops sardeu) in the subfamily Anisopinae [30], the deltamethrin LC50 for M. bentoi was several fold higher than that for B. tarsalis and A. sardeu, which reinforces the idea that differences in the toxicodynamics of insecticide poisoning, or in physiological and biochemical peculiarities associated with each aquatic insect species, regulate the susceptibilities of these organisms to insecticide exposure [1,4,14,15,26].…”

“…The susceptibility of aquatic insects to insecticides is related to physiological and behavioral constraints associated with aquatic ecosystems [1,15,20,26,27]. In the present study we demonstrated that 2 phylogenetically related backswimmer species (B. tarsalis and M. bentoi) had different susceptibilities to deltamethrin, which also had effects on individual swimming activities.…”

Histological description of immature Chironomus columbiensis (Diptera: Chironomidae): A potential contribution to environmental monitoring

“…The strongly basophilic nature of the microvilli of region III cells of the midgut (a characteristic not reported by Richardi et al () in C sancticaroli ) could be associated to the high presence of acid‐rich (DNA and RNA) organelles, such as the rough endoplasmic reticulum, the Golgi apparatus and free ribosomes, which indicate a secretory function of mitochondria in order to provide energy for active transport and the intake of substances (Jarial & Engstrom, ). Several studies in insects have shown that the midgut is a target organ for contamination, due to the absorption of xenobiotic substances acquired orally (El‐Saad, Kheirallah, & El‐Samad, ; Gutiérrez, Santos, Serrão, & Oliveira, ; Sumida et al, ). Nevertheless, there are few studies that have applied histopathological markers in the midgut of Chironomidae larvae (Lavarías et al, ; Rey, Long, Pautou, & Meyran, ; Rey, Pautou, & Meyran, ; Richardi et al, ).…”

Diversity and convergence of mechanisms involved in pyrethroid resistance in the stored grain weevils, Sitophilus spp.

“…Regarding the pyrethroid insecticides, the resistance management is complicated because resistance occurs in a variety of forms, including reduced insecticide penetration, metabolic resistance (through detoxification enzymes), behavioral resistance and target-site alterations 1 , 2 . Although the pyrethroid insecticides exert their toxicity primarily by disrupting the function of the voltage-gated sodium channels in excitable cells 3 – 8 , these compounds also have secondary action targets (e.g., ionic imbalance and osmoregulatory dysfunction) that contribute to their activity 9 – 11 .…”