Cuidado com ovos e imaturos: polietismo e morfofisiologia das glândulas salivares em duas espécies de cupins (Isoptera: Rhinotermitidae, Termitidae)
Data
2019-05-24
Autores
Janei, Vanelize
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
As colônias de insetos sociais constituem grupos de indivíduos que vivem juntos e se reproduzem como uma unidade, sendo a divisão de trabalho entre os companheiros de ninho uma das mais importantes características dessas colônias. A alocação de trabalho pode ser baseada em casta, sexo, tamanho ou idade dos indivíduos e este processo é denominado polietismo, que pode ser temporal e, nesse caso, o desenvolvimento da tarefa está ligado a idade e a fisiologia do indivíduo. O desenvolvimento de glândulas exócrinas está relacionado com essas atividades e tarefas. As lacunas existentes no conhecimento atual do polietismo em Isoptera dizem respeito a grande dificuldade de observar o comportamento dos cupins em ambientes naturais, devido ao hábito críptico destes insetos. Visando elucidar a divisão de trabalho de reis e rainhas na parte de cuidados com os ovos e larvas na espécie exótica Coptotermes gestroi e na espécie nativa Cornitermes cumulans foram realizados estudos comportamentais e estudos morfológicos das glândulas salivares em diferentes fases da vida destes reprodutores. Estes estudos morfológicos envolveram histologia, histoquímica e morfometria dos ácinos das glândulas salivares de reis e rainhas. O cuidado biparental é uma importante estratégia para a sobrevivência dos insetos e representa um avanço na adaptação ao ambiente. Nos insetos sociais, como os cupins, o cuidado com ovos e a alimentação dos imaturos é tarefa dos operários, no entanto, no início da fundação de uma nova colônia, o cuidado com a prole é realizado pelo casal real, sendo bastante escassos esses estudos em reprodutores. Na presente pesquisa, colônias incipientes das duas espécies de cupins foram filmadas, durante o período que antecede o aparecimento dos operários, e avaliados os comportamentos com cuidados de ovos e larvas. Os resultados mostraram que o cuidado com os ovos foi realizado igualmente pelo rei e rainha na espécie C. gestroi. Contudo, em C. cumulans a rainha investiu significativamente mais que o rei na atividade de “grooming” dos ovos. Quanto ao cuidado com as larvas, os dados indicam diferenças significativas nos comportamentos de “grooming”, trofalaxia estomodeal e trofolaxia proctodeal entre os reis e rainhas de C. gestroi. Adicionalmente, a rainha da referida espécie investiu mais em trofalaxia do que o rei. Para C. cumulans o cuidado com os imaturos não apresentou diferença entre os reprodutores, mostrando ausência de polietismo sexual. A morfometria das glândulas salivares dos reprodutores no início da função das colônias mostrou que a área dos ácinos salivares foram similares em reis e rainhas de ambas as espécies de cupins, portanto, no início da fundação do ninho, glândulas salivares similares em reis e rainhas indicam o mesmo investimento de ambos os sexos na produção de saliva. Contudo, em colônias mais velhas de C. gestroi ocorreu uma diminuição da área dos ácinos salivares em ambos os reprodutores. A histologia das glândulas salivares mostrou ácinos salivares multicelulares, constituídos por células parietais e centrais, sendo que em C. cumulans foram observados dois tipos de células centrais. As células parietais são periféricas, menores em relação as centrais e são caracterizadas pela presença de um canalículo intracelular. As células centrais possuem muitas vesículas secretoras, e testes histoquímicos das glândulas salivares de reprodutores no início da formação das colônias mostraram a presença de proteínas e polissacarídeos, além de lipídios em C. gestroi. Nos reprodutores mais velhos de C. gestroi, a secreção proteica diminuiu, mas houve um acúmulo maior de polissacarídeos. Os resultados sugerem que após o aparecimento dos operários, os quais passam a alimentar a cria, a secreção salivar diminui e sofre alteração funcional em reis e rainhas. O cuidado biparental com ovos e larvas é importante pois aumenta a sobrevivência da prole durante o estabelecimento de novos ninhos, contudo, existem diferenças de polietismo entre as duas espécies estudadas que parecem estar ligados a biologia das mesmas, incluindo tipo de ninho e forrageamento.
Colonies of social insects constitute groups of individuals which live together and reproduce as a superorganism, and the most important characteristic of such colonies is a complex division of labor among nestmates. The task allocation may be based on the caste, sex, size and the age of the individuals, and this process is termed polyethism, which may be temporal and, in this case, the task development is associated to the age and physiology of the individual. The development of exocrine glands is associated to these colonial activities and tasks. The current knowledge gaps concerning the polyethism in Isoptera are consequences of the difficulty in observing the behavioral repertories performed by termites under natural conditions, especially due their cryptic habit. Aiming to elucidate the division of labor between kings and queens related to eggs and larval care in the exotic species Coptotermes gestroi and in the native species Cornitermes cumulans, behavioral bioassays and morphological studies of the salivary glands were performed on different life phases of these reproductives. These morphological studies involved histology, histochemistry and morphometry of the salivar acini of kings and queens. The biparental care is an important strategy for insect survival and represent an advance during the adaptation to the environment. Among the social insects, case of the termites, workers care for eggs and feed the immatures, although these tasks are performed by the royal couple during the establishment of a colony. Nevertheless, the available data concerning the parental care performed by kings and queens are quite limited. In the present research, incipient colonies of the studied species were filmed, during the period preceding the development of workers, and the behaviors performed during egg and larvae care were evaluated. The results showed that the care of eggs was equally performed by the king and the queen of C. gestroi, whereas queens of C. cumulans invested significantly more in egg-grooming than kings. Unlike eggs, the larval care varied between C. gestroi kings and queens in the following behaviors: grooming, proctodeal and stomodeal trophallaxis. Additionally, the C. gestroi queen invested more in trophallaxis when compared to the king. For C. cumulans, the larval care did not show differences between the reproductives, suggesting an absence of sexual polyethism in this species. The morphometry of the salivary glands of kings and queens during the colony establishment showed similar acinar area between the reproductives of both species, suggesting that during the colony foundation, kings and queens invest the same effort for saliva production. However, in old colonies of C. gestroi, both reproductives suffered a reduction in their acinar area. The histology of the salivary glands showed multicellular salivar acini, composed of parietal and central cells, the latter presenting two types in C. cumulans. The parietal cells are peripheral, smaller when compared to the central ones, and are characterized by the presence of an intracellular canaliculus. The central cells possess many secretory vesicles, and histochemical tests of the salivary glands of kings and queens during colony foundation showed the presence of proteins and polysaccharides, besides lipids in C. gestroi. In older reproductives of C. gestroi, the proteic secretion decreased, although there was a higher accumulation of polysaccharides. The results suggest that, after the emergence of workers which feed the larvae, the salivary secretion decreases and suffer functional changes in kings and queens. The biparental care on eggs and larvae is important, since it increases the brood survival during the initial phases of the colony, however, there was difference in the polyethism between the two studied species, which seems to be a consequence of their biology, including nesting and foraging aspects.
Colonies of social insects constitute groups of individuals which live together and reproduce as a superorganism, and the most important characteristic of such colonies is a complex division of labor among nestmates. The task allocation may be based on the caste, sex, size and the age of the individuals, and this process is termed polyethism, which may be temporal and, in this case, the task development is associated to the age and physiology of the individual. The development of exocrine glands is associated to these colonial activities and tasks. The current knowledge gaps concerning the polyethism in Isoptera are consequences of the difficulty in observing the behavioral repertories performed by termites under natural conditions, especially due their cryptic habit. Aiming to elucidate the division of labor between kings and queens related to eggs and larval care in the exotic species Coptotermes gestroi and in the native species Cornitermes cumulans, behavioral bioassays and morphological studies of the salivary glands were performed on different life phases of these reproductives. These morphological studies involved histology, histochemistry and morphometry of the salivar acini of kings and queens. The biparental care is an important strategy for insect survival and represent an advance during the adaptation to the environment. Among the social insects, case of the termites, workers care for eggs and feed the immatures, although these tasks are performed by the royal couple during the establishment of a colony. Nevertheless, the available data concerning the parental care performed by kings and queens are quite limited. In the present research, incipient colonies of the studied species were filmed, during the period preceding the development of workers, and the behaviors performed during egg and larvae care were evaluated. The results showed that the care of eggs was equally performed by the king and the queen of C. gestroi, whereas queens of C. cumulans invested significantly more in egg-grooming than kings. Unlike eggs, the larval care varied between C. gestroi kings and queens in the following behaviors: grooming, proctodeal and stomodeal trophallaxis. Additionally, the C. gestroi queen invested more in trophallaxis when compared to the king. For C. cumulans, the larval care did not show differences between the reproductives, suggesting an absence of sexual polyethism in this species. The morphometry of the salivary glands of kings and queens during the colony establishment showed similar acinar area between the reproductives of both species, suggesting that during the colony foundation, kings and queens invest the same effort for saliva production. However, in old colonies of C. gestroi, both reproductives suffered a reduction in their acinar area. The histology of the salivary glands showed multicellular salivar acini, composed of parietal and central cells, the latter presenting two types in C. cumulans. The parietal cells are peripheral, smaller when compared to the central ones, and are characterized by the presence of an intracellular canaliculus. The central cells possess many secretory vesicles, and histochemical tests of the salivary glands of kings and queens during colony foundation showed the presence of proteins and polysaccharides, besides lipids in C. gestroi. In older reproductives of C. gestroi, the proteic secretion decreased, although there was a higher accumulation of polysaccharides. The results suggest that, after the emergence of workers which feed the larvae, the salivary secretion decreases and suffer functional changes in kings and queens. The biparental care on eggs and larvae is important, since it increases the brood survival during the initial phases of the colony, however, there was difference in the polyethism between the two studied species, which seems to be a consequence of their biology, including nesting and foraging aspects.
Descrição
Palavras-chave
Térmitas, Blattaria, Coptotermes gestroi, Cornitermes cumulans, Colônias incipientes, Termites, Incipient colonies