Análise da longevidade e qualidade espermática de zangões de Scaptotrigona aff. depilis (Apidae, Meliponini) expostos a estresse térmico agudo e infecção por Bacillus thuringiensis
Tipo
TCC
Data de publicação
2023-12
Periódico
Citações (Scopus)
Autores
Gagngi, Victoria Pietra
Orientador
Vieira, Leandro Tavares Azevedo
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ISSN da Revista
Título de Volume
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Resumo
As abelhas sociais sem ferrão (Apidae, Meliponini) enfrentam um declínio devido a ameaças antrópicas que impactam diretamente na sua reprodução e dispersão. Nos meliponíneos, a qualidade do sêmen do macho, que está constantemente exposto a múltiplos estressores durante o acasalamento, é um fator crucial para o sucesso reprodutivo da colônia. Diante desse cenário, esse trabalho objetivou avaliar a sobrevivência e a qualidade espermática de machos de Scaptotrigona aff. depilis expostos a estresse térmico agudo e alimentados com um biopesticida à base de Bacillus thuringiensis (Bt). Os zangões foram coletados no meliponário da Universidade de São Paulo (n = 68) e divididos em quatro tratamentos experimentais: Controle (C), Exposição a estresse térmico (ET), Exposição ao microrganismo (BT) e Exposição a estresse térmico e ao microrganismo (ET-BT). Os grupos foram aclimatados durante 24 horas a uma temperatura controlada de 28 ± 1 °C. Durante a aclimatação, os indivíduos dos grupos C e ET foram alimentados com 2,5 mL de solução de açúcar. Os tratamentos BT e ET-BT foram alimentados com 2,5 mL de solução de açúcar contaminada com a cepa 344 de B. thuringiensis tolworthi (concentração 5x106 UFC/ml). Após 24 horas de aclimatação, os animais dos grupos ET e ET-BT passaram pelo desafio térmico por uma hora a 40 ± 1°C. Os zangões foram dissecados e a viabilidade espermática foi analisada em microscopia de epifluorescência. Para avaliar a longevidade dos indivíduos, os grupos C (n = 22) e BT (n = 23) foram aclimatados a 28 ± 1 °C e observou-se a sobrevivência dos indivíduos a cada 24 horas ao longo de 144 horas. Os resultados demonstraram que apenas a temperatura afetou negativamente a capacidade dos zangões de S. aff. depilis de manterem a viabilidade de seus espermatozoides (viabilidade média: C: 88,2%; ET: 17,2 %; ET-BT: 21,24 %; BT: 79,1%). Não se detectou influência significativa da alimentação com B. thuringiensis na viabilidade espermática dos zangões (one way ANOVA, F = 50,498, P < 0,001). Também se comprovou que os efeitos letais da ingestão da bactéria iniciam-se nas primeiras 24 horas com sobrevivência dos indivíduos que ingeriram o biopesticida decaindo significativamente (teste log-rank, p < 0,05). Considerando o aumento na frequência das ondas de calor e no uso de microrganismos de controle biológico, a reprodução da espécie pode estar ameaçada em razão à queda na longevidade dos zangões acometidos pela infecção por B. thuringiensis e à queda na viabilidade espermática dos zangões que passaram pelo estresse fisiológico de um pico de temperatura.
Stingless social bees (Apidae, Meliponini) are facing a decline due to anthropogenic threats that directly impact their reproduction and dispersion. In stingless bee drones, the quality of male semen, which is constantly exposed to multiple stressors during mating, is a crucial factor for the reproductive success of the colony. Thus, this study aimed to evaluate the survival and sperm quality of Scaptotrigona aff. depilis drones exposed to acute thermal stress and fed with a biopesticide based on Bacillus thuringiensis (Bt). The drones were collected from the University of São Paulo's meliponary (n = 68) and divided into four experimental treatments: Control (C), Exposure to thermal stress (ET), Exposure to the microorganism (BT), and Exposure to thermal stress and the microorganism (ET-BT). The groups were acclimated for 24 hours at a controlled temperature of 28 ± 1 °C. During acclimation, individuals from groups C and ET were fed with 2.5 mL of sugar solution. BT and ET-BT treatments were fed with 2.5 mL of sugar solution contaminated with the strain 344 of B. thuringiensis tolworthi (concentration 5x106 CFU/ml). After 24 hours of acclimation, individuals from ET and ET-BT groups underwent thermal challenge for one hour at 40 ± 1°C. The drones were dissected, and sperm viability was analyzed using epifluorescence microscopy. To evaluate the longevity of individuals, groups C (n = 22) and BT (n = 23) were acclimated at 28 ± 1 °C, and the survival of individuals was observed every 24 hours for 144 hours. The results demonstrated that only temperature negatively affected the ability of S. aff. depilis drones to maintain the viability of their sperm (average viability: C: 88.2%; ET: 17.2%; ET-BT: 21.24%; BT: 79.1%). No significant influence of feeding with B. thuringiensis on drone sperm viability was detected (one-way ANOVA, F = 50.498, P < 0.001). It was also confirmed that the lethal effects of bacteria ingestion begin within the first 24 hours, with the survival of individuals ingesting the biopesticide decreasing significantly (log-rank test, p < 0.05). Considering the increase in the frequency of heatwaves and the use of biological control microorganisms, the species' reproduction may be threatened due to the decrease in the longevity of drones affected by B. thuringiensis infection and the decline in sperm viability in drones undergoing acute physiological thermal stress.
Stingless social bees (Apidae, Meliponini) are facing a decline due to anthropogenic threats that directly impact their reproduction and dispersion. In stingless bee drones, the quality of male semen, which is constantly exposed to multiple stressors during mating, is a crucial factor for the reproductive success of the colony. Thus, this study aimed to evaluate the survival and sperm quality of Scaptotrigona aff. depilis drones exposed to acute thermal stress and fed with a biopesticide based on Bacillus thuringiensis (Bt). The drones were collected from the University of São Paulo's meliponary (n = 68) and divided into four experimental treatments: Control (C), Exposure to thermal stress (ET), Exposure to the microorganism (BT), and Exposure to thermal stress and the microorganism (ET-BT). The groups were acclimated for 24 hours at a controlled temperature of 28 ± 1 °C. During acclimation, individuals from groups C and ET were fed with 2.5 mL of sugar solution. BT and ET-BT treatments were fed with 2.5 mL of sugar solution contaminated with the strain 344 of B. thuringiensis tolworthi (concentration 5x106 CFU/ml). After 24 hours of acclimation, individuals from ET and ET-BT groups underwent thermal challenge for one hour at 40 ± 1°C. The drones were dissected, and sperm viability was analyzed using epifluorescence microscopy. To evaluate the longevity of individuals, groups C (n = 22) and BT (n = 23) were acclimated at 28 ± 1 °C, and the survival of individuals was observed every 24 hours for 144 hours. The results demonstrated that only temperature negatively affected the ability of S. aff. depilis drones to maintain the viability of their sperm (average viability: C: 88.2%; ET: 17.2%; ET-BT: 21.24%; BT: 79.1%). No significant influence of feeding with B. thuringiensis on drone sperm viability was detected (one-way ANOVA, F = 50.498, P < 0.001). It was also confirmed that the lethal effects of bacteria ingestion begin within the first 24 hours, with the survival of individuals ingesting the biopesticide decreasing significantly (log-rank test, p < 0.05). Considering the increase in the frequency of heatwaves and the use of biological control microorganisms, the species' reproduction may be threatened due to the decrease in the longevity of drones affected by B. thuringiensis infection and the decline in sperm viability in drones undergoing acute physiological thermal stress.
Descrição
Palavras-chave
Meliponini , controle biológico , viabilidade espermática , fisiologia térmica , biological control , sperm viability , physiology