Agonistic interactions, cuticular and hemolymphatic lipid variations during the foraging period in spider females Brachypelma albopilosa (Theraphosidae)

Agonistic behaviour and lipid state were examined in tarantula Brachypelma albopilosa females during the foraging period. Modulation of the agonistic behaviour of females was not connected to their body size. Results show that the agonistic pattern of females differed significantly from the predation pattern at the behavioural and lipid levels. Aggressive-foraging females had low predation behaviour. Quantitative lipid changes were observed in relation to agonistic behaviour and predation. The total lipid index was studied by colorimetric methods, and lipid compounds were analyzed by gas chromatography-mass spectrometry in cuticle and hemolymph of females. The lipid components were free fatty acids, methyl esters, cholesterol, and long-chain aliphatic hydrocarbons. Methyl esters were much more abundant in cuticular lipids; unsaturated free fatty acids (linoleic and oleic acids) and methyl esters (methyl linoleate and methyl stearate) predominated in the hemolymph. Spider aggression was positively correlated with lipid concentration (cholesterol, fatty acids, methyl esters and hydrocarbons) in the hemolymph and the levels of cuticular fatty acids. Lipid levels are hypothesized to have evolved as a regulatory factor of predation and agonistic behaviours in tarantula females.