An investigation of cuticular hydrocarbon variation on Epiachna indica (Coleoptera : Coccinellidae) from Kota Samarahan, Sarawak: Implication for future chemotaxonomic study
The potential of cuticular hydrocarbon as an alternative method for recognition and classification of Epilachna indica was investigated by examining the distribution and variation of cuticular hydrocarbon across body parts, developmental stages, gender and locality. The relative change in cuticul...
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| 格式: | Thesis |
| 语言: | English |
| 出版: |
2011
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| 主题: | |
| 在线阅读: | http://ir.unimas.my/id/eprint/13759/1/Rizoh%20Bosorang%20ft.pdf |
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| 总结: | The potential of cuticular hydrocarbon as an alternative method for recognition and
classification of Epilachna indica was investigated by examining the distribution and
variation of cuticular hydrocarbon across body parts, developmental stages, gender and
locality. The relative change in cuticular hydrocarbon was described because changes
can occur due to various factors with minimal genetic and karyotypes changes.
Cuticular hydrocarbon extracted from 32 samples of Epilachna indica (comprise of 256
individuals) and 18 - 24 individuals each for other species of Coleoptera examined
were subjected to gas chromatography/mass spectrometry (GC/MS) analysis of the
cuticular hydrocarbons. Seventy out of 120 peaks in gas chromatogram were
recognized as cuticular hydrocarbon profile of E. indica) Hydrocarbons were made up
over 95% of the cuticular lipids peak areas detected with n-alkanes covered 21.05% of
total hydrocarbons extracted, ranging from n-octadecane (n-C18) to n-hexatriacontane
(n-C38). The odd-numbered alkanes dominated the distribution of n-alkane in E. indica.
Distribution of n-alkanes in E. indica is remaining consistent across body parts,
developmental stages and gender with small differences in the proportion of several
compounds were observed. Distribution pattern of cuticular hydrocarbons in adult E.
indica were wider and more complex compared to pupae and larvae from same species.
The distribution pattern of cuticular hydrocarbon between genders also differed with
female specimen having more compounds as compared to male specimen. The
quantitative differences between genders were clearly distinguished using discriminant
function analysis (DFA). There is a variation of 2.50 - 12.36 % between sample within
each gender and an average of 32.5 % differences between male and female. DFA was also successfully classified all individuals into their respective group based on locality
with cases and cross-validation are 100% and 7.7%, respectively. Cuticular
hydrocarbons profile of this beetle was successfully constructed and remarkably
different from other species examined in this study. Although the dendogram
constructed using n-alkanes data did not compliment with morphological insect
classification, however, it has clustered them based on food of the insects. Different
genders, localities and species showed different pattern of n-alkanes with sex- and
species-specificity, and thus potentially used for sex discrimination and species
identification. Information from other types of hydrocarbons such as methyl-branched
alkanes and alkenes were also essential for phylogenetic study and may be carried out
in future study. |
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