Comparative toxicity of fipronil, malathion, and thiamethoxam on the stingless bee Tetragonisca fiebrigi (Schwarz, 1938)

Ana Lúcia Paz Barateiro  Stuchi; Daiani Rodrigues  Moreira; Douglas  Galhardo; Simone Aparecida dos  Santos; Ludimilla  Ronqui; Liriana Belizario  Cantagalli; Denise Alves  Lopes; Adriana Aparecida  Sinópolis-Gigliolli; Vagner de Alencar Arnaut de  Toledo; Maria Claudia Colla  Ruvolo-Takasusuki

doi:10.4025/actascibiolsci.v44i1.57846

Authors

Ana Lúcia Paz Barateiro Stuchi Universidade Estadual de Maringá Author https://orcid.org/0000-0001-7097-0262
Daiani Rodrigues Moreira Universidade Estadual de Maringá Author https://orcid.org/0000-0002-5279-6624
Douglas Galhardo Universidade Estadual de Maringá Author https://orcid.org/0000-0002-2707-9076
Simone Aparecida dos Santos Universidade Estadual de Maringá Author https://orcid.org/0000-0001-7365-6201
Ludimilla Ronqui Universidade Federal de Rondônia Author https://orcid.org/0000-0002-0216-3087
Liriana Belizario Cantagalli Universidade Estadual de Maringá Author https://orcid.org/0000-0003-1608-6251
Denise Alves Lopes Faculdade Global de Umuarama Author https://orcid.org/0000-0002-6163-0466
Adriana Aparecida Sinópolis-Gigliolli Universidade Estadual de Maringá Author https://orcid.org/0000-0002-2752-642X
Vagner de Alencar Arnaut de Toledo Universidade Estadual de Maringá Author https://orcid.org/0000-0003-1814-9703
Maria Claudia Colla Ruvolo-Takasusuki Universidade Estadual de Maringá Author https://orcid.org/0000-0002-2028-9281

DOI:

https://doi.org/10.4025/actascibiolsci.v44i1.57846

Keywords:

chromatin; esterases; LC50; Meliponini; pesticide.

Abstract

Stingless bees are important pollinators for various plant crops. We investigated the susceptibility of Tetragonisca fiebrigi to sublethal concentrations of insecticides fipronil, malathion, and thiamethoxam (administered through contact and ingestion) by determining the LC₅₀ values after 24 hours of exposure and analyzing changes in the activity of esterase isoenzymes and the chromatin in brain cells. The LC₅₀ values showed that all three insecticides were highly toxic through contact and ingestion. Electrophoretic analysis revealed that the relative EST-4 (carboxylesterase) activity in T. fiebrigi was partially inhibited by malathion and fipronil ingestion. Moreover, the EST-4 band intensity was increased following high-concentration thiamethoxam (contact) exposure, indicating the increased relative activity of this isoenzyme to detoxify the compound. In the cytochemical analysis of brain cells, the critical electrolyte concentration (CEC) points for the control stingless bees and malathion ingestion-exposed and thiamethoxam-exposed (contact and ingestion) stingless bees were in the range of 0.20-0.30 M MgCl₂, whereas that for malathion contact-exposed bees was 0.15 M MgCl₂, indicating chromatin relaxation and suggesting an increase in gene expression. In conclusion, T. fiebrigi stingless bees are susceptible to the insecticides tested, and the parameters analyzed may be used as biomarkers to detect the presence of these compounds.