RESUMEN

The control of triatomine vectors of Chagas disease is mainly based on the use of pyrethroid insecticides. Because chemical control is the primary method for managing these insects, it is crucial to diversify the range of products utilized to mitigate the risk of resistance development. This study evaluated the toxicity of two insecticides with different modes of action on Triatoma dimidiata Latreille and T. pallidipennis Stal first and third instar nymphs. Our study focused on the effects of two insecticides, buprofezin (a growth regulator) and flunocamid (an anti-feeder), on the mortality rate of triatomine bugs in a laboratory setting. Moreover, we investigated how direct and indirect (film method) exposure to these insecticides impacted the survival of the insects. Flonicamid emerged as a promising insecticide for triatomine control since it caused 100% mortality in first-instar nymphs 48 h after direct exposure. While, in third instar nymphs, the maximum mortality was 88% at 72 h after exposure. Our result can be used as a basis for future triatomine control plans.

Asunto(s)

Enfermedad de Chagas , Insecticidas , Piretrinas , Triatoma , Animales , Insecticidas/toxicidad , Insectos Vectores , Piretrinas/toxicidad , Ninfa

RESUMEN

The Na+/Ca2+ exchanger of Drosophila melanogaster, CALX, is the main Ca2+-extrusion mechanism in olfactory sensory neurons and photoreceptor cells. Na+/Ca2+ exchangers have two Ca2+ sensor domains, CBD1 and CBD2. In contrast to the mammalian homologs, CALX is inhibited by Ca2+ binding to CALX-CBD1, whereas CALX-CBD2 does not bind Ca2+ at physiological concentrations. CALX-CBD1 consists of a ß-sandwich and displays four Ca2+-binding sites at the tip of the domain. In this study, we used NMR spectroscopy and isothermal titration calorimetry (ITC) to investigate the cooperativity of Ca2+ binding to CALX-CBD1. We observed that this domain binds Ca2+ in the slow exchange regime at the NMR chemical shift timescale. Ca2+ binding restricts the dynamics in the Ca2+-binding region. Experiments of 15N chemical exchange saturation transfer and 15N R2 dispersion allowed the determination of Ca2+ dissociation rates (∼30 s-1). NMR titration curves of residues in the Ca2+-binding region were sigmoidal because of the contribution of chemical exchange to transverse magnetization relaxation rates, R2. Hence, a novel, to our knowledge, approach to analyze NMR titration curves was proposed. Ca2+-binding cooperativity was examined assuming two different stoichiometric binding models and using a Bayesian approach for data analysis. Fittings of NMR and ITC binding curves to the Hill model yielded nHill ∼2.9, near maximal cooperativity (nHill = 4). By assuming a stepwise model to interpret the ITC data, we found that the probability of binding from 2 up to 4 Ca2+ is approximately three orders of magnitude higher than that of binding a single Ca2+. Hence, four Ca2+ ions bind almost simultaneously to CALX-CBD1. Cooperative Ca2+ binding is key to enable this exchanger to efficiently respond to changes in the intracellular Ca2+ concentration in sensory neuronal cells.

Asunto(s)

Proteínas de Drosophila , Drosophila melanogaster , Animales , Antiportadores/metabolismo , Teorema de Bayes , Sitios de Unión , Calcio/metabolismo , Calorimetría , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Espectroscopía de Resonancia Magnética , Unión Proteica , Intercambiador de Sodio-Calcio/metabolismo

RESUMEN

BACKGROUND: Anthropized landscapes play a crucial role in biodiversity conservation, as they encompass about 90% of the remaining tropical forest. Effective conservation strategies require a deep understanding of how anthropic disturbances determine diversity patterns across these landscapes. Here, we evaluated how attributes and assembly mechanisms of dung beetle communities vary across the Selva El Ocote Biosphere Reserve (REBISO) landscape. METHODS: Community attributes (species diversity, abundance, and biomass) were assessed at the landscape scale, using spatial windows and vegetation classes. Windows were categorized as intact, variegated, or fragmented based on their percent cover of tropical forest. The vegetation classes analyzed were tropical forest, second-growth forest, and pastures. RESULTS: We collected 15,457 individuals and 55 species. Variegated windows, tropical forests, and second-growth forests showed the highest diversity values, while the lowest values were found in intact windows and pastures. Landscape fragmentation was positively and strongly related to dung beetle diversity and negatively related to their abundance; biomass was positively associated with forest cover. Beta diversity was the primary driver of the high dung beetle diversity in the landscape analyzed. DISCUSSION: The landscape heterogeneity and its biodiversity-friendly matrix facilitate the complementarity of dung beetle assemblages in the Selva El Ocote Biosphere Reserve. Random processes govern beta diversity patterns in intact and variegated windows. Therefore, vegetation cover in the region is sufficient to maintain a continuous flow of dung beetles between forested landscape segments. However, intense anthropic disturbances acted as deterministic environmental filters in fragmented windows and pastures sites, leading to biotic homogenization processes. Our results suggest that increasing habitat variegation in highly fragmented sites is an effective strategy to prevent or buffer homogenization processes in the REBISO landscape.