Decoding nestmate recognition signals in

Sue Shemilt1, Falko Drijfhout1 & Stephen Martin2 1. Chemical Ecology group, Keele University, Staffordshire 2. Laboratory of Apiculture and Social , University of Sheffield, Sheffield

Introduction Results

C27 Ants are one of the most highly developed social , regularly Abundance feeding and grooming each other. However, for these behaviours to benefit only colony members, a sophisticated recognition system must 2e+07 An example exist. Like all ants, our studied species exsecta, a type of wood , chromatogram uses a blend of long chain hydrocarbons on the surface of the ant, known showing the C25 compounds as the cuticle, to act as a unique colony signature. This enables an individual 1.5e+07 present in the cuticular hydro- to recognise friend or foe. This chemical profile can be easily analysed carbon profile and using gas chromatography coupled to mass spectrometry, providing a way their ratios. Each 1e+07 pair of peaks of visually comparing the profiles present. consists of an alkene followed by an alkane. The C29 length of the 0.5e+07 carbon chain is indicated

Method C23 C31

l The cuticular hydrocarbons are extracted: Time--> 10.00 12.00 14.00 16.00 Chromatograms GC vial are processed to Hexane produce percentage compositions. These are compared to others to determine the profile similarity

Colony 2 60 Colony Profile Comparison 70

50 60 n n o o i i t t i i s GC insert Hydrocarbons s o o 50 p p 40 m m o o c c

e e l l

i 40 i f f o o 30 r r p p

l e e

g 30 Sample is injected into the GC-MS and a chromatogram obtained g a a t t n n

20 e e c c r r

e 20 e P P Peak areas of the 10 alkenes and the 10 alkanes are totalled 0 0 separately. Each peak Ant 1 Ant 2 Ant 3 Colony 2 Colony 3 Colony 4

is calculated as a Tricosene Pentacosene Heptacosene Nonacosene Tricosene Pentacosene Heptacosene Nonacosene percentage of the total. This gives a graphical representation of the profile

H H H H H H H C C C C H H C C C C H H H H H H H H H The chemical profile indicates these ants The chemical profile indicates these ants Alkenes contain at least Alkanes contain only are nestmates; therefore they show are not nestmates; they show aggressive one double bond single bonds mutually beneficial behaviour. These ants behaviour. These ants are both posturing Alkenes Alkanes are feeding each other defensively and preparing to fight

Summary

l Every ant possesses a colony specific chemical signature, made up of various long chain hydrocarbons l This is secreted onto the ants bodies both as waterproofing and to produce an individuals ‘profile’ l This ‘profile’ is the same between colony members but varies between colonies l Other ants can read this signature, allowing them to distinguish between nestmates and non nestmates and behave appropriately l The profile is analysed using gas chromatography mass spectrometry, and a graphical representation can be produced to allow individual profiles to be easily compared

For further information contact: [email protected] Photo credit: Ant behaviour images - Alex Wild (left) & Tilde Nielsson (right). Title images Sue Shemilt