O papel das secreções das formigas-cortadeiras na defesa da colônia
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Data
2019-03-14
Autores
Pereira, Mayara Cristina [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Atualmente, a tribo Attini compreende 45 gêneros e entre eles estão as formigas-cortadeiras cultivadoras de fungo, pertencentes aos gêneros Atta e Acromyrmex, que causam grandes danos econômicos a agricultura devido ao intenso corte de materiais vegetais frescos para cultivo do seu fungo simbiôntico Leucogaricus gongylophorus. Essas formigas apresentam diferentes mecanismos de defesa para proteger seus ninhos contra organismos competidores. Dentre esses mecanismos está a defesa humoral e celular (inata e adquirida) do sistema imune interno e a defesa imune externa, que inclui qualquer característica atuando no ambiente capaz de melhorar sua proteção contra patógenos, sendo esta caracterizada em formigas pela remoção física de patógenos e pela secreção de compostos antimicrobianos advindos de glândulas exócrinas e simbiontes bacterianos. Poucos estudos buscam integrar os diferentes fatores envolvidos na capacidade defensiva das formigas a fim de compreender estratégias fisiológicas adquiridas para proteger a colônia. Diante disso, a presente pesquisa teve por objetivo investigar a defesa da formiga-cortadeira Atta sexdens contra patógenos. Para tanto, realizamos a revisão sistemática dos mecanismos de defesa das formigas discutidos na literatura, a qual nos direcionou para investigação da defesa química externa dessa espécie de formiga. Os ensaios conduzidos foram de atividade enzimática, análise cromatográfica e testes de inibição de fungos patógenos e antagonistas. Verificamos que secreções, frequentemente depositadas no jardim de fungo, como a secreção da glândula mandibular e do líquido fecal, inibem a germinação de cinco espécies fúngicas. Os resultados evidenciam a presença de compostos, como o peróxido de hidrogênio e o ácido lático, com capacidade antimicrobiana nessas secreções, as quais participam direta ou indiretamente da obtenção de um ambiente livre de patógenos e com pH controlado no ninho. A investigação de outros fatores, internos e externos, envolvidos nas estratégias defensivas das formigas-cortadeiras é necessária e poderá melhor esclarecer a capacidade de detecção e remoção de patógenos por esses insetos.
Currently Attini tribe comprises 45 genera and among them are fungus-growing leaf-cutting ants belonging to the genera Atta and Acromyrmex. They cause great economic damage to agriculture due to the intense cutting of fresh plant material for cultivation of its symbiotic fungus Leucogaricus gongylophorus. These ants present different defense mechanisms to protect their nests against competing organisms. Among these mechanisms is the humoral and cellular defense (innate and acquired) of the internal immune system and the external immune defense. This last one includes any hereditary characteristic acting in the environment and being capable of improve its protection against pathogens. It is characterized in ants by the physical removal of pathogens and by secretion of antimicrobial compounds from exocrine glands and bacterial symbionts. Few studies have sought to integrate the different factors involved in ants' defensive capacity in order to understand physiological strategies acquired to protect the colony. In this way, the present research had the goal to investigate the defense of the ant-cutter Atta sexdens against pathogens. For this, we performed the systematic review of ant defense mechanisms discussed in the literature, which directed us to investigate the external chemical defense of this ant species. The tests carried out were of enzymatic activity, chromatographic analysis and tests of inhibition of pathogenic and antagonistic fungi. We have observed that secretions frequently deposited in the fungal garden, such as the secretion of the mandibular gland and fecal fluid, inhibit the germination of five fungal species. The results evidenced the presence of compounds as hydrogen peroxide and lactic acid, both with antimicrobial capacity. They participate directly or indirectly in obtaining a pathogen free environment with controlled pH in the nest. The investigation of other factors internal and external involved in the defensive strategies of leaf-cutting ants is necessary and may better clarify the pathogen detection and removal capacity of these insects.
Currently Attini tribe comprises 45 genera and among them are fungus-growing leaf-cutting ants belonging to the genera Atta and Acromyrmex. They cause great economic damage to agriculture due to the intense cutting of fresh plant material for cultivation of its symbiotic fungus Leucogaricus gongylophorus. These ants present different defense mechanisms to protect their nests against competing organisms. Among these mechanisms is the humoral and cellular defense (innate and acquired) of the internal immune system and the external immune defense. This last one includes any hereditary characteristic acting in the environment and being capable of improve its protection against pathogens. It is characterized in ants by the physical removal of pathogens and by secretion of antimicrobial compounds from exocrine glands and bacterial symbionts. Few studies have sought to integrate the different factors involved in ants' defensive capacity in order to understand physiological strategies acquired to protect the colony. In this way, the present research had the goal to investigate the defense of the ant-cutter Atta sexdens against pathogens. For this, we performed the systematic review of ant defense mechanisms discussed in the literature, which directed us to investigate the external chemical defense of this ant species. The tests carried out were of enzymatic activity, chromatographic analysis and tests of inhibition of pathogenic and antagonistic fungi. We have observed that secretions frequently deposited in the fungal garden, such as the secretion of the mandibular gland and fecal fluid, inhibit the germination of five fungal species. The results evidenced the presence of compounds as hydrogen peroxide and lactic acid, both with antimicrobial capacity. They participate directly or indirectly in obtaining a pathogen free environment with controlled pH in the nest. The investigation of other factors internal and external involved in the defensive strategies of leaf-cutting ants is necessary and may better clarify the pathogen detection and removal capacity of these insects.
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Palavras-chave
Attini, Mecanismos de defesa, Glândulas exócrinas, Formigas cultivadoras de fungo., Defense mechanisms, Exocrine glands, Fungus-growing ants