Rubén Palma

Evidence of Contact Pheromone Use in Mating Behavior of the Raspberry Weevil (Coleoptera: Curculionidae)

ABSTRACT Numerous studies of insect species have shown that a subset of female cuticular hydrocarbons is used as short-range or contact pheromones. Here, we studied the possible use of contact pheromones in the mating behavior of the weevil Aegorhinus superciliosus, a native species of Chile. Males mounted females only after antennal contact with the females cuticle, and only 33% of the males attempted to mate with dead females washed with solvent. When a glass rod (dummy) was coated with female cuticular extracts, males exhibited behaviors similar to those observed with females. A preliminary gas chromatography-mass spectrometry (GC-MS) analysis of cuticular extracts indicated that males and females share a series of aliphatic hydrocarbons but that the relative abundance of some of these compounds differ between the sexes. These results suggest that cuticular lipids mediate mating behavior of the raspberry weevil and provide the first evidence of contact pheromones in curculionids.

Influence of genotype and harvest year on polyphenol content and antioxidant activity in murtilla (Ugni molinae Turcz) fruit

Polyphenol content and antioxidant activity in murtilla (Ugni molinae Turcz) fruit from three genotypes (the 14-4 genotype and the Red Pearl-INIA and South Pearl-INIA varieties) were studied over five growing seasons. Our results showed significant differences in total polyphenol content among yearly harvests. The lowest value (283 ± 72 mg GAE/100 g dw) was obtained for the 14-4 genotype in the 2008 harvest, and the highest value (2,152 ± 290 mg GAE/100 g dw) was observed for the variety South Pearl-INIA in 2007. The lowest value for antioxidant activity (2,234 ± 337 μmol TE/100 g dw) was obtained for the Red Pearl-INIA variety in 2008, and the highest value (4,073 ± 76 μmol TE/100 g dw) was observed for the 14-4 genotype in 2007. There was a significant effect of genotype and growing season on polyphenol content, antioxidant activity and dry matter content for the murtilla fruits evaluated in this study, but additional studies examining other abiotic and biotic factors are required to fully explain causality.

Behavioral and electrophysiological responses of Hylastinus obscurus to volatiles released from the roots of Trifolium pratense L.

Root volatiles from field-collected red clover plants, Trifolium pratense L., of five different ages were trapped by solid-phase microextraction (SPME) and analyzed by gas chromatography-mass spectrometry (GC-MS). Ethanol, E-2-hexenal, hexanal, 3-octanone, limonene and α-pinene were identified. The electroantennographic (EAG) and olfactometric responses of clover root borer, Hylastinus obscurus, to the identified compounds were studied. The GC-MS with SPME as a solvent-free col- lection method identified ethanol and hexanal compounds that have not previously been reported in T. pratense. The EAG experiments showed that all of the tested compounds were perceived by H. obscurus, but mixed responses were found in be- havioral assays. For females, ethanol and E-2-hexenal were attractive at one or more of the tested doses, while hexanal, 3-octanone, R-limonene and S-limonene were repellent at one or more of the tested doses. Females responded to a larger number of tested compounds and a wider range doses compared to males. This behavior could reflect a more active role of females in host finding and colonization.

Olfactory response of Haematobia irritans (Diptera: Muscidae) to cattle-derived volatile compounds.

ABSTRACT In Chile, the horn fly, Hematobia irritans (L., 1758), is a major pest of grazing cattle and affects livestock production during the summer. Previous studies in Europe and the United States have shown that cattle flies, including H. irritans, are differentially attracted to individual cattle within herds and that volatile semiochemicals are responsible for this phenomenon. This study provides evidence that similar differential attractiveness occurs for the interaction between Chilean Holstein-Friesian cattle herds and local H. irritans populations. Thus, Holstein-Friesian dairy cattle, Bos taurus, which were of similar age and physiological condition, were shown to possess an uneven distribution of H. irritans. Heifers h6904 and h8104 were defined as low-carrier heifers and h5804, h2304 and h1404 as high-carrier heifers. Gas chromatography (GC) and coupled GC-mass spectrometric (GC-MS) analysis of samples collected from heifers revealed the presence of compounds previously reported as semiochemicals for cattle flies, including meta- and para-cresol, methylketones (C8–C11), and 6-methyl-5-hepten-2-one. Other compounds identified included carboxylic acids (butanoic, 3-methylbutanoic, pentanoic, and hexanoic acids), 1-hexanol, and 3-octanone. In Y-tube olfactometer studies, both m- and p-cresol attracted H. irritans at the highest doses tested (10-6 g), as did the positive control l-octen-3-ol. Of the other compounds tested, only 2-decanone and 2-undecanone produced a behavioral response, with significantly more flies being recorded in the control arm when the former compound was tested (at 10-6 and 10-8 g), and more flies being recorded in the treated arm for the latter compound (at 10-7 g). This demonstration of behavioral activity with the identified compounds represents a first step for research into the application of semiochemicals in monitoring and control of cattle flies in Chile.

Males of Hylamorpha elegans Burmeister (Coleoptera: Scarabaeidae) Are Attracted to Odors Released from Conspecific Females

Abstract The behavioral responses of Hylamorpha elegans L. (Coleoptera: Scarabaeidae, Rutelinae) to the semiochemicals released from conspecific individual adults were studied, with particular attention paid to female attraction of males. Odors released from virgin females significantly attracted male conspecifics in both the field and laboratory olfactometer and wind tunnel bioassays. However, females did not attract other females, and males attracted no one. The response of male H. elegans to (1) compounds (1,4-hydroquinone and 1,4-benzoquinone) released only by unmated females; (2) the essential oil of the secondary host (Nothofagus obliqua); and (3) the blend of 1,4-hydroquinone and 1,4-benzoquinone with N. obliqua essential oil was studied. The blend of 1,4-benzoquinone mixed with essential oil at the trial concentration was attractive with males. The same response was found with 1,4-hydroquinone alone. The essential oil did not have the expected attractant effect on conspecific males. These results suggest that, when combined with essential oil, 1,4-benzoquinone may function in the sexual behavior of males and females. These findings are discussed in terms of the ecological role of this putative sexual pheromone and its potential use in a strategy of control of this pest.

Type and Distribution of Sensilla in the Antennae of the Red Clover Root Borer, Hylastinus obscurus

Abstract In order to determine the type, distribution, and structures of sensilla, the antennae of the red clover root borer, Hylastinus obscurus Marsham (Coleoptera: Curculionidae: Scolytinae), were examined by light and electron microscopy (both scanning and transmission). Four different types of sensilla were identified in the club, and one type of chaetica was found in the scape and funicle of both male and female individuals. Chaetica and basiconica were the most abundant sensilla types in the club. They were present in the three sensory bands described, totaling approximately 80% of sensilla in the antennal club of H. obscurus. Chaetica were predominantly mechanoreceptors, although gustatory function could not be excluded. Basiconica forms showed characteristics typical of olfactory sensilla. Trichoidea were not found in the proximal sensory band, and they exhibited abundant pores, suggesting olfactory function. Styloconica were the least abundant sensillum type, and their shape was similar to that reported as having hygro- and thermoreceptor functions. There was no difference in the relative abundance of antennal sensilla between males and females. Finally, the sensillar configuration and abundance of receptors in the H. obscurus antennae suggest that these sensilla have chemoreceptive and other functions.

Electroantennographic and Behavioral Responses of Adults of Raspberry Weevil Aegorhinus superciliosus (Coleoptera: Curculionidae) to Odors Released From Conspecific Females

ABSTRACT The raspberry weevil, Aegorhinus superciliosus (Guérin) (Coleoptera: Curculionidae), is the most important pest in blueberry and raspberry fields in the south of Chile. In this study, we investigated the electroantennographic and behavioral responses of A. superciliosus to semiochemicals released from conspecific individual adults, with particular attention to male attraction to females. Odors released from females significantly attracted males in a Y-tube olfactometer. Gas chromatographic and mass spectral analysis of female volatile extracts revealed the presence of limonene and &agr;-pinene. Electroantennogram recordings from both sexes indicated that males of A. superciliosus possess olfactory sensitivity for the R isomer of limonene and &agr;-pinene, whereas females only perceived R-limonene. Behavioral assays using synthetic compounds showed that only R-limonene elicited an attraction response from male weevils. Field experiments confirmed the laboratory results, showing that R-limonene was attractive to weevils. This is the first report of intraspecific chemical communication in this weevil. We discuss the origin of these compounds, their possible role in the sexual behavior of this species, and their potential use in a pest control strategy.

Morphology and Distribution of Sensilla on the Antennae of Hylamorpha elegans Burmeister (Coleoptera: Scarabaeidae)

Considering that sensilla constitute important functional elements of sensory systems in insects, the aim of this study was to determine the type and distribution of sensilla in the antennae of Hylamorpha elegans Burmeister examined by scanning electron microscopy. Hylamorpha elegans antennae are lamellate and consist of the scape, pedicel, and flagellum. The antennal club of this beetle consists of three terminal plates: proximal, middle, and distal lamellae. Four types of sensilla were observed in the lamellae from both sexes: sensilla trichoidea, chaetica, coeloconica, and placodea. Antennal length was larger in males than in females, and significant sexual variation in the number of sensilla placodea and sensilla coeloconica was observed.

Courtship behavior and potential indications for chemical communication in Artemia franciscana (Kellog 1906)

Se realizaron dos experimentos conductuales para evaluar que A. franciscana muestra patrones de cortejo especificos, que en parte, serian gobernados por semioquimicos liberados por hembras. El etograma del cortejo, construido a partir de la grabacion individual de 30 parejas adultas virgenes (1 hembra v/s 1 macho) durante 1 hora, revelo que los machos mostraron cuatro patrones de actividad independientes: 1) acercamiento y toque, 2) nado en retroceso, 3) intento de monta, y 4) exito de monta. El analisis de las transiciones entre los patrones observados sugirio dos maneras de conseguir una monta exitosa, en ambas el patron acercamiento y toque fue fundamental. La primera transicion consistio en que una vez que los machos se acercan y tocan a las hembras, intentan montar a las hembras (27% de probabilidad de ocurrencia), pero si esto no ocurre los machos comienzan nuevamente a acercarse y tocar a las hembra (23% de probabilidad de ocurrencia) para finalmente lograr una monta exitosa (19% de probabilidad de ocurrencia). La ruta alternativa es mediante la aproximacion y toque para luego desarrollar el nado en retroceso (7% de probabilidad de ocurrencia) y montaje exitoso (5% de probabilidad de ocurrencia). El rol de los semioquimicos liberados por hembras fue evaluado mediante el uso de la solucion polar (SP) obtenida desde agua acondicionada con 40 hembras virgenes. Machos virgenes fueron empapados con SP para obtener pseudo hembras. Luego, se enfrentaron 1 pseudo hembra, 1 hembra, 1 macho control a ya sea 1 o 5 machos. En todos los casos, la conducta fue registrada durante 1 hora (n=10), y se analizaron las frecuencia de ocurrencia de cada uno de los patrones de cortejo. Los resultados mas importantes mostraron que: 1) la hembra virgen y pseudo hembra elicito la misma frecuencia de respuesta en 1 macho en los cuatro patrones de cortejo (P˃0,05); b) hembras virgenes y pseudo hembras obtuvieron la misma respuesta cuando se evaluaron contra 5 machos en acercamiento y toque, nado en retroceso e intento de monta (P˃0,05). El hecho que en todo los casos el macho control siempre elicito el menor valor de frecuencia en cada patron de cortejo sugiere el posible rol de semioquimicos sexuales en la conducta de cortejo de A. franciscana. La combinacion de senales quimicas y conductuales sugieren un elaborado reconocimiento de pre-cortejo.