IDENTIFICATION OF MALE-PRODUCED SEX PHEROMONE OF Sennius leptophyllicola (COLEOPTERA: CHRYSOMELIDAE: BRUCHINAE)

Abstract

Sennius leptophyllicola is a seed predator of Cassia leptophylla (Caesalpinioideae: Fabaceae), a Brazilian native species associated with the secondary formation of a Mixed Ombrophilous Forest. The damage caused by this species is due to the lifespan which develops inside the host-plant, that result in a decrease in the number of viable seeds for germination and developing. Thereby, the goal of this work is to study the chemical communication in the seed beetle S. leptophyllicola. For this, adults of the seed beetles were collected from mature fruit valves of C. leptophylla and separated by sex for the collection of volatiles (headspace). The extracts were analyzed by GC-MS and attractiveness bioassays were performed with 2-6 old virgin insects in a binary choice Y-tube olfactometer using one male or one female equivalent. The GC-MS analysis showed four male-specific compounds with mass spectra fragments that suggest short chain carboxylic acids (Eg. 60, 73 and 87 m/z). In addition, bioassays showed a high attraction of females-to-male extract from volatile collection. In contrast, the attraction of males from male or female extract of volatiles was low. The male-specific compounds were derivatized to methyl esters by reaction with diazomethane and compared to standards. As a result, compound 1 was identified as caproic acid (hexanoic acid, RT: 7.060), 2 as caprylic acid (octanoic acid, RT: 10.058), 3 as pelargonic acid (nonanoic acid, RT: 11.500) and 4 as capric acid (decanoic acid, RT: 12.900). During 24h, each male insect emitted a mean amount of 40.82 ng ±27.46 (1), 20.53 ng ±21.28 (2), 8.16 ng ±12.52 (3) and 2.65 ng ±3.22 (4), in the ratio 15:8:3:1 respectively. With the identification of the compounds, next steps will be to test the attractiveness of females of S. leptophyllicola via synthetic compounds.