Influência do status reprodutivo na resposta imune de rainhas de duas espécies de formigas-cortadeiras (Hymenoptera, Formicidae)
Data
2019/12/13
Autores
Nogueira, Bianca Raissa
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Os insetos apresentam uma resposta imune inata com células de defesa e enzimas específicas que evoluíram com a pressão do ambiente. Essa linha de defesa pode ser dividida em defesa humoral e celular. Os hemócitos são os principais mediadores da defesa celular e participam dos processos de fagocitose e encapsulamento. Rainhas de diferentes espécies de formigas vivem vários anos e ao darem início a uma nova colônia se encontram isoladas, de forma que um trade-off entre reprodução e imunidade pode reduzir o investimento nas defesas imunológicas dessas formigas fundadoras. Logo, sua resistência a doenças pode estar relacionada ao seu status reprodutivo. Dessa forma o objetivo da presente pesquisa foi verificar a resposta imune celular de rainhas de formigas das espécies Atta sexdens e Atta laevigata em diferentes status reprodutivos: fêmeas reprodutoras não acasaladas (RNA), rainhas recém-acasaladas (RRA) e rainhas acasaladas há aproximadamente seis meses (RA). Para avaliar a resistência a patógenos a nível individual, um fio de nylon foi introduzido e mantido por 24 horas no gáster das rainhas, simulando um antígeno padrão. Ao fim desse período, o fio de nylon foi retirado e a taxa de encapsulamento foi mensurada a partir de fotografias, com uso do software ImageJ. Os dados obtidos foram submetidos à análise de variância. Aspectos morfológicos como massa do corpo e largura da cabeça também foram avaliados e submetidos à análise de correlação (Pearson), a fim de verificar as relações com a resposta imune desencadeada. Os resultados obtidos indicam que o status reprodutivo interfere na resposta imune de encapsulamento das rainhas de formigas-cortadeiras. Os efeitos dos eventos reprodutivos produziram regulação positiva da defesa celular em A. laevigata e negativa em A. sexdens, já que RA de A. laevigata apresentou o maior nível de encapsulamento quando comparado aos demais grupos. Os valores de RNA dessa espécie foram menores e próximos ao grupo RRA, sugerindo que o intervalo entre o acasalamento e a fundação da colônia influencia nos custos metabólicos investidos no sistema imune celular. O nível de encapsulamento não apresentou correlação com a largura da cabeça e nem com a massa corpórea. Por se tratar de espécies pragas, estudos pioneiros quanto aos mecanismos de defesa celular das formigas-cortadeiras podem contribuir para o esclarecimento das respostas imunes desse inseto e para o aperfeiçoamento dos métodos de controle atuais.
Insects present an innate immune response with defense cells and specific enzymes that evolved with environmental pressure. This line of defense can be divided into humoral and cellular defense. Hemocytes are the main mediators of cellular defense and participate in the processes of phagocytosis and encapsulation. Queens of different species of ants have a long life span and when initiating a new colony find themselves isolated and a trade-off between reproduction and immunity could reduce the investment in these founding ants' immune defenses. Therefore, their resistance to disease may be related to their reproductive status. Thus, the present study aimed to verify the cellular immune response of the leafcutting ants Atta laevigata and Atta sexdens in different reproductive status: virgin queens (RNA), newly mated queens (RRA) and queens mated for approximately six months (RA). To assess pathogen resistance at an individual level, a nylon thread was introduced and maintained for 24 hours into the queens' gaster, simulating a standard antigen. At the end of this period, the nylon thread was removed and the encapsulation rate was measured from photographs using ImageJ software. The data obtained were submitted to analysis of variance. Morphological aspects such as body mass and head width were also evaluated and submitted to correlation analysis (Pearson), in order to verify the relationships with the triggered immune response. The results indicate that the reproductive status interferes with the encapsulation immune response of leaf-cutting ants. The effects of reproductive events produced positive regulation of cell defense in A. laevigata and negative regulation in A. sexdens, as RA of A. laevigata presented the highest level of encapsulation when compared to the other groups. The RNA values of this species were smaller and similar to the RRA group, suggesting that the interval between mating and colony founding influences the metabolic costs invested in the cellular immune system. The encapsulation level did not correlate with head width or body mass. Because they are pest species, pioneering studies on the cellular defense mechanisms of leaf-cutting ants may contribute to the clarification of this insect's immune responses and the improvement of current control methods.
Insects present an innate immune response with defense cells and specific enzymes that evolved with environmental pressure. This line of defense can be divided into humoral and cellular defense. Hemocytes are the main mediators of cellular defense and participate in the processes of phagocytosis and encapsulation. Queens of different species of ants have a long life span and when initiating a new colony find themselves isolated and a trade-off between reproduction and immunity could reduce the investment in these founding ants' immune defenses. Therefore, their resistance to disease may be related to their reproductive status. Thus, the present study aimed to verify the cellular immune response of the leafcutting ants Atta laevigata and Atta sexdens in different reproductive status: virgin queens (RNA), newly mated queens (RRA) and queens mated for approximately six months (RA). To assess pathogen resistance at an individual level, a nylon thread was introduced and maintained for 24 hours into the queens' gaster, simulating a standard antigen. At the end of this period, the nylon thread was removed and the encapsulation rate was measured from photographs using ImageJ software. The data obtained were submitted to analysis of variance. Morphological aspects such as body mass and head width were also evaluated and submitted to correlation analysis (Pearson), in order to verify the relationships with the triggered immune response. The results indicate that the reproductive status interferes with the encapsulation immune response of leaf-cutting ants. The effects of reproductive events produced positive regulation of cell defense in A. laevigata and negative regulation in A. sexdens, as RA of A. laevigata presented the highest level of encapsulation when compared to the other groups. The RNA values of this species were smaller and similar to the RRA group, suggesting that the interval between mating and colony founding influences the metabolic costs invested in the cellular immune system. The encapsulation level did not correlate with head width or body mass. Because they are pest species, pioneering studies on the cellular defense mechanisms of leaf-cutting ants may contribute to the clarification of this insect's immune responses and the improvement of current control methods.
Descrição
Palavras-chave
Sociedades de insetos, Imunidade celular, Resposta imune, Defesa celular, Inserção de fio de nylon, Encapsulamento, Saúvas, Cellular defense, Nylon thread insertion, Encapsulation