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Description:
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Chromatography and mass spectrometry analysis were used to identify and quantify 14 cuticular hydrocarbons in the developmental stages of S . invicta . The following quantitative and qualitative differences in hydrocarbons were observed among brood components . Cuticular hydrocarbons consisted of saturated n -alkanes and methylalkanes , ranging from C23 to C29 . The total amount of cuticular hydrocarbons was greatest in prepupae and least in pupal stages . While the total amount of cuticular hydrocarbons was several magnitudes greater in components of sexual brood , as expected since sexual forms are larger than worker forms , the ratio of n -alkanes to methylalkanes in worker brood was generally higher than its counterparts in sexual brood . Discriminant function analysis of the brood subcastes using the five most abundant hydrocarbons within and among colonies showed that the brood subcastes clustered together based on their respective developmental stage , with n -heptacosane being the major component responsible for the observed clustering .
Finally , several bioassays were conducted to determine whether cuticular hydrocarbons play a role in brood recognition . Worker retrieval response toward pupae immersed in hexane for 5 min was significantly lower than that towards a control . Immersing pupae in boiling water for 3 sec . also induced a similar response to that caused by hexane . Several concentrations of cuticular extracts in hexane of sexual prepupae applied to a paraffin dummy failed to induce any retrieval response by workers . In addition , manipulation of the composition of brood cuticular hydrocarbons did not seem to affect worker response toward the brood . Taken together , the results suggest that a chemical signal other than cuticular lipids is involved in brood recognition . |