Bioactive Male-Produced Volatiles from Anastrepha obliqua and their Role in Attraction of Conspecific Females.

The study of insect semiochemicals, especially pheromones, is of fundamental importance for the development of strategies for controlling agricultural pests. In this study, volatile compounds involved in the communication between males and females of the fruit fly, Anastrepha obliqua (Diptera: Tephritidae), for mating purposes were characterized to develop attractant formulations for females of this species. Extracts containing volatile compounds released by males of A. obliqua were obtained by the dynamic headspace technique and analyzed by gas chromatography coupled with an electroantennographic detector (GC-EAD) and gas chromatography coupled with mass spectrometry (GC-MS). Twenty-one volatile compounds were identified in the aeration extracts of males. Five of them caused EAD responses from the antennae of females: 1-heptanol, linalool, (Z)-3-nonen-1-ol, (E,Z)-3,6-nonadien-1-ol, and (Z,E)-α-farnesene. Six synthetic mixtures of these compounds, including the five-component blend and all possible four-component blends, were formulated in a biopolymer and used in behavioral bioassays conducted in the laboratory arena with conspecific virgin females. One blend of 1-heptanol, linalool, (Z)-3-nonen-1-ol, and (Z,E)-α-farnesene attracted more females than the collection of volatiles from virgin males used as control. The other mixtures were as attractive to A. obliqua females as the control treatment. This study indicates potential for use of these compounds in monitoring and control strategies for this pest.

Genetic structure and diversity in Brazilian populations of Anastrepha obliqua (Diptera: Tephritidae).

Anastrepha obliqua (Macquart), the West Indian fruit fly, is one of the most economically important pest species in the Neotropical region. It infests an extensive range of host plants that include over 60 species. The geographic range of A. obliqua is from northern Mexico to southern Brazil and includes the Caribbean Islands. Previous molecular studies have revealed significant genetic structure among populations. We used sequences from a fragment of the mitochondrial protein-coding gene cytochrome c oxidase I to estimate structure and genetic diversity of A. obliqua populations from Brazil. We analyzed a total of 153 specimens from the Amazon Forest, Atlantic Forest, Cerrado, and Caatinga biomes. Our study revealed weak genetic structure among the A. obliqua Brazilian populations sampled. Collections from the Amazon Forest had similar haplotype diversity compared to previously reported estimates for collections from the Caribbean and both populations are also closely related to each other, thus challenging the hypothesis that A. obliqua originated in the Caribbean and then moved to other regions of the Americas. Therefore, further evidence is necessary to draw a definite conclusion about the putative center of origin for A. obliqua. Additionally, we suggest a putative historical migration from the west to the east for the A. obliqua Brazilian populations, which could explain the high genetic diversity for this fly in the Amazon Forest and low genetic diversity in the other Brazilian biomes.

Antimicrobial activities of components of the glandular secretions of leaf cutting ants of the genus Atta.

The secretions of the mandibular and metapleural glands of leaf cutting ants contain antimicrobial substances that protect the mutualistic fungal colony within the nest from attack by parasitic micro-organisms. The major constituents of these secretions (citral, 4-methyl-3-heptanol, 2-heptanone, 3-octanone, 4-methyl-2-heptanone, beta-citronellol, geraniol, phenylacetic, indolacetic, hexanoic and octanoic acids were tested against resistant strains of the human pathogens, Escherichia coli, Staphylococcus aureus and Candida albicans. Assays were carried out using filter paper discs impregnated with either hexane or water solutions of the analytes in the concentration range 250-6,000 ng/microl. Although most of the tested compounds presented strong antibacterial and antifungal activities, citral, geraniol, 4-methyl-3-heptanol, hexanoic and octanoic acids were the most effective, particularly against C. albicans. The results suggest that these compounds may be of potential value as antibiotics in the treatment of human candidiasis.

Comparative survey of abdominal gland secretions of the ant subfamily Ponerinae.

The chemical contents of three abdominal glands were investigated in representative species of the ponerine ants. The Dufour glands of 14 species show a wide variety of contents. In Mystrium camillae and Proceratium itoi, no volatile substances were found in either the Dufour or venom glands. In Ectatomma sp., Diacamma ceylonense, Diacamma indicum, Pachycondyla obscuricornis, and Pachycondyla striata, volatile chemicals were found in the venom glands as well as in the Dufour glands. Platythyrea punctata was examined, but unusually it does not have a Dufour gland and its venom gland contained no volatile substances. Epoxides were found in ants for the first time in the Dufour glands of Amblyopone reclinata. Venom glands of Pachycondyla tarsata were also found to contain volatile material, including bitter-tasting cyclic dipeptides. In all, 16 species have been added to the list of those examined. All of the 27 known analyses of Dufour glands, 21 analyses of venom glands, and 4 of pygidial glands of workers of ponerine ant species have been brought together in order to seek some pattern in the type of glandular contents. Although the great majority of species produce hydrocarbons in their worker Dufour glands, and some have terpenes, there is no observable pattern for this gland on a tribe or genus level. Volatile compounds have been found in the venom glands of some species of the tribe Ponerini only. The information on pygidial glands is still too fragmentary for any conclusions.