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Master's Dissertation
DOI
10.11606/D.59.2014.tde-19052014-123237
Document
Author
Full name
Lohan Cláudio Abreu Valadares
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Ribeirão Preto, 2014
Supervisor
Committee
Nascimento, Fabio Santos do (President)
Bacci Junior, Mauricio
Chaline, Nicolas Gerard
Title in Portuguese
Variações no perfil de hidrocarbonetos cuticulares das operárias de Atta sexdens (Myrmicinae: Attini)
Keywords in Portuguese
Atta sexdens
Hidrocarbonetos cuticulares
subcasta morfológica
substrato foliar.
Abstract in Portuguese
A integridade das sociedades de insetos depende da capacidade dos indivíduos em discriminar aqueles que não pertencem às suas colônias; essas interações de reconhecimento são mediadas por hidrocarbonetos presentes na camada de cera da cutícula e atuam como mensageiros que codificam informação sobre o meio interno (colônia) e externo (ambiente). Os hidrocarbonetos são produzidos por células dérmicas e o perfil desses compostos recebe influência tanto de fontes endógenas quanto exógenas e isso o torna suscetível às mudanças temporais. A caracterização desses compostos em insetos-praga é importante, pois provêm subsídios tanto para pesquisa básica como para o manejo e controle de pragas. Nesse contexto, o presente estudo abordou as variações dos hidrocarbonetos cuticulares em relação às subcastas morfológicas das operárias (condição endógena) e utilização do substrato foliar (variável exógena) na formiga-cortadeira Atta sexdens, conhecida como uma das principais pragas herbívoras da região Neotropical. Os compostos foram extraídos em solvente apolar hexano e as amostras foram analisadas em sistema de cromatografia a gás acoplado à espectrometria de massas (CG-MS). Foram identificados 30 hidrocarbonetos com cadeia carbônica entre 19 e 40 átomos distribuídos em três classes de compostos, sendo a dos hidrocarbonetos ramificados a mais representativa, especificamente os trimetialcanos. Foram encontradas variações significativas para todas as variáveis analisadas, sugerindo que as subcastas possuem assinaturas químicas semelhantes quanto à diversidade de compostos, mas com grandes diferenças na proporção relativa dos mesmos. Em relação ao substrato foliar, colônias que tiveram acesso ao mesmo recurso apresentam uma composição química cuticular mais semelhante em relação àquelas que tiveram acesso a um recurso diferente. Complementarmente, os testes comportamentais mostraram que, na presença de uma coespecífica intrusa, as operárias residentes são muito mais agressivas em relação àquelas que utilizaram outro tipo de substrato foliar.
Title in English
Variations on the cuticular hydrocarbons profile of workers of Atta sexdens (Myrmicinae: Attini)
Keywords in English
Atta sexdens
Cuticular hydrocarbons
foliar substrate.
morphological subcaste
Abstract in English
The integrity of insect societies relies on the ability of individuals to discriminate between nesmates from non-nestmates. These interactions are mediated by hydrocarbons spread all over the cuticle that act as messengers coding information about the colony and external environment. Cuticular hydrocarbons are produced by dermic cells and its composition is influenced by both endogenous and exogenous sources which makes them subject to temporal changes. Thus, this study approached the variations on this chemical profile in relation to the worker subcastes and type of foliar substrate used by leafcutter ant Atta sexdens, this species is known as one of the major neotropical herbivore pests and this kind of study is important because it can provide subsides in researches related to both basic biology as to pest control methods. The compounds were extracted using apolar solvent (hexane) and the samples were analyzed using gas chromatography - mass spectrometry technique (GC-MS). It was found 30 hydrocarbons which carbon chains varies between 19 and 40 atoms separated in three classes of compounds and the branched hydrocarbons as the most abundant one, especially the trimethyalcanes. The statistical analysis revealed significant differences on all the variables analyzed suggesting that subcastes possess similar chemical signatures as to the variety of compounds but with great differences in relative proportions thereof. Furthermore, the results show that foliar substrate has influence on the composition of cuticular hydrocarbons and concomitantly affect the interspecific recognition, thus colonies that had access to the same substrate has similar cuticular composition comparing to those who do not. Additionally, behavior tests showed that in the presence of a conspecific intruder the resident workers tend to be much more aggressive in relation to those who had fed on a different foliar substrate.
 
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Publishing Date
2014-09-26
 
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