Lepidoptera: Cossidae)
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Scientia Agropecuaria 11(2): 233 – 236 (2019) SCIENTIA AGROPECUARIA a. Facultad de Ciencias Agropecuarias Scientia Agropecuaria Universidad Nacional de Website: http://revistas.unitru.edu.pe/index.php/scientiaagrop Trujillo SHORT COMMUNICATION Influence of dietary condition on the ratio of the compounds emitted by larvae Chilecomadia valdiviana (Lepidoptera: Cossidae) 1,* 1 2 Luis J. Reyes-García ; María José Muñoz ; Pamela Cuevas 1 Departamento de Ciencias Básicas, Facultad de Ciencias, Universidad Santo Tomás, Chile. 2 Escuela de Tecnología Médica, Universidad Santo Tomás, Limonares 190, Viña del Mar, Chile. Received February 8, 2020. Accepted May 22, 2020. Abstract Chilecomadia valdiviana (Lepidoptera, Cossidae), locally known as "Gusano del Tebo", is a polyphagous pest that, in its larval stage, feeds on the wood of the host species. C. valdiviana is distributed in the southern region of Chile and Argentina and its larvae mainly attack eucalyptus and fruit trees. Previous research has reported the identification of the volatile compounds produced by this species in its larval stage. In this work, the effects of two dietary conditions on these volatile compounds were described: groups of individuals fed with wood vs. others without food. The results obtained provide empirical evidence that C. valdiviana modulates the emission of the compounds according to the effect of stimulus. Keywords: volatile emission; Tebo worm; Chilecomadia valdiviana; dietary condition. acetate, and (Z)-5-Tetradecenyl acetate, 1. Introduction with relative abundances of 44%, 37%, and Chilecomadia valdivian (Philippi) (Lepidop- 14%, respectively (Bergmann et al., 2007). tera, Cossidae) is a polyphagous insect There is no consensus about the biological native to Chile that is associated with activity of these compounds. However, Eucalyptus nitens, Nothofagus antarctica, empirical evidence suggests that the ace- Nothofagus dombey, as well as other fruit tate compound of (Z)-5,13-tetradecadienyl species with economic importance for Chile, could act as an aggregation pheromone such as avocados, apple trees, olives, and (Reyes-García et al., 2011). This work aimed pears (Herrera et al., 2016). The larva forms to study the effects of two dietary numerous galleries in the host species, with conditions: groups of individuals fed with diameters of between 10 and 12 mm, wood vs. others without food. Based on the producing a large amount of sawdust and results of the feeding performance assay, debris. These consequences, the action of we further hypothesized that the nutritional woodpeckers and the entrance of orga- status of the larva (starved vs. nonstarved nisms such as fungi, ultimately cause rotting larvae) affects the ratio of the volatile of the wood (Ramos-González, 2017). There compounds emitted by the insect. No is little clarity about the life cycle of this previous reports are describing this species, but this has been estimated at behavior in larvae. between 1 and 3 years (Urra, 2016). This insect produces a series of volatile 2. Materials and methods compounds (short-chain acetates, 2.1 Insects. Larvae of C. valdiviana were saturated and unsaturated) that, in previous purchased in fishing equipment stores in studies, were identified in larval hexane Quilpué and were identified according to the extracts. The major compounds found were morphological characteristics described by (Z)-5,13-tetradecadienyl acetate, dodecyl Olivares and Angulo (1992). Cite this article: Reyes-García, L.J; Muñoz, M.J.; Cuevas, P. 2020. Influence of dietary condition on the ratio of the compounds emitted by larvae Chilecomadia valdiviana (Lepidoptera: Cossidae). Scientia Agropecuaria 11(2): 233 – 236. --------- * Corresponding author © 2020 All rights reserved E-mail: [email protected] (L. Reyes-García). DOI: 10.17268/sci.agropecu.2020.02.10 -233- L.J. Reyes-García et al. / Scientia Agropecuaria 11(2): 233 – 236 (2020) 2.2 Extracts. The crude extract of larvae was mode with an injector temperature of 250 °C. prepared by maceration according to Teh et Helium was used as a carrier gas. al., (2017). For the analyzes of the studied The GC-MS analysis was performed with a treatments, larvae were taken at 24, 48, and Shimadzu team (Shimadzu, GCMS-QP2010 72 h. Ultra, Kyoto, Japan), using an RTX-5 column, and was programmed in a similar 2.3 Collection of volatiles. Larvae in their way to that described in the previous para- last stage were kept under controlled graph. The mass spectrum was acquired at conditions (25 ± 2°C, 40% relative humidity, 70 eV, and Helium was used as the carrier photoperiod L16: D8); ten individuals were gas. placed in each of two 2.5-L glass bottles conditioned as aeration chambers (Vera et 2.5 Statistic analysis. The relative per- al., 2016). Teflon tubes were used. centage of each compound was determined Eucalyptus wood was used to feed the in triplicate and analyzed by analysis of larvae. Air purified by activated charcoal variance (ANOVA), followed by the Tukey (50–200 mesh, Fisher Scientific Company, test (p ≤ 0.05), using the XLSTAT program Pittsburgh, PA) was passed through the (2009). chamber at a flow of approximately 2.5 L min-1. Volatiles were adsorbed on 200 mg of 3. Results and discussion activated charcoal (50–200 mesh, Fisher In the treatment of wood-fed larvae, a Scientific Company, Pittsburgh, PA), which gradual decrease (every 24 h) in the was placed in a glass tube (4 mm in diameter emission of compounds generated by the and 5 cm long). Glass wool was used to fix larva was detect, including (Z)-5-dodecenyl the charcoal in the tube. Samples were acetate (Z5-12:OAc), 7-dodecenyl acetate taken after 24, 48, and 72 h from the (7-12:OAc), 11-tetradecenyl acetate (11- beginning of the experiment. The adsorbed 12:OAc), and dodecyl acetate (12:OAc). volatiles was eluted with 1.5 mL of hexane About the compounds of (Z)-5,13- (Suprasolv, Merck). The samples were tetradecadienyl acetate (Z5,13-14:OAc) and concentrated using a gentle flow of (Z)-5-tetradecenyl acetate (Z5,14:OAc), an nitrogen. Samples were stored in screw cap increasing trend in the emission was vials at -20 °C until further analysis. detected (Fig. 1A). These compounds were detected in a greater proportion. In this ex- 2.4 Chemical analysis. The analysis by gas periment, the compounds 13-tetradecenyl chromatography was carried out using a acetate (13,14:OAc) and tetradecyl acetate Shimadzu equipment (Shimadzu, GC-2010 (14:OAc) were not detected. The ratio of Plus, Kyoto, Japan), which was equipped compounds present in the larva was with a flame ionization detector (FID), and a determined by the realization of hexane fused silica RTX-Wax capillary column RTX extracts, as described by Bergmann et al. was used (30 m × 0.25 mm RTX®-5 film, (2007), a study that described only the Restek, Bellefonte, PA, USA). This was percentage of compounds in the hexane programmed as follows: from 60 °C for 5 min extract, and in which variation in the up to 220 °C at 10 °C min-1. The gas emission of volatiles, overtime was not chromatograph was operated in splitless described. Figure 1. The relative percentage of volatiles emitted by larvae of C. Valdiviana; A: feeding with wood and B: no feed. Statistical analysis was performed-by-compound. The values followed by different letters are statistically different (p < 0.05 according to ANOVA followed by the Tukey-Kramer test). -234- L. Reyes-García et al. / Scientia Agropecuaria 11(2): 233 – 236 (2020) About the experiment where the larva was different phenotype from the ancestor kept without food, an increase in the (Henneken et al., 2017; Baker, 2002). For emissions of compounds Z5-12:OAc, 7- example, in the case of the species 12:OAc, 11-12:OAc, and 12:OAc was Trichoplusia ni (Lepidóptera, Noctuidae), increase; this effect is opposite to that the female moth can change the ratio of detected in the species fed. On the other compounds emitted due to a mutation of the hand, the compounds Z5,13-14:OAc and gene responsible for the production of Z5,14:OAc showed a decreasing emission pheromones, a change that is permanent (Fig. 1B), which is opposite to the results of and represents a reproductive disadvan- the first experiment (Fig. 1A). In this tage since this new mixture of compounds is experiment, the compounds 9-tetradecenyl not recognized by the males of this species acetate (9,14:OAc) and tetradecatrienyl (Allison, 2016). In other cases, diet- acetate (1,3,5-12:OAc) were not detected. mediated variation in the signal may provide Thus, the emission of these volatile indirect information about the signaller’s compounds differs according to the genotype, such as the genes responsible for stimulus over the insect is subjected, while an individual’s foraging ability (Henneken et the percentage of compounds found in al., 2017). extracts made by maceration of the larva In the case of the specific object of this was similar under the two tested conditions. study, the change in the ratio of compounds The compounds produced by the larva of the emitted is not permanent and can be C. Valdiviana species have been found in associated with epigenetic factors. In this other adult specimens of species belonging sense, the fact that the production of Z5,13- to the lepidopteran order and have various 14:OAc increases and the emission of reported biological activities. Thus, Z5- 12:OAc decreases (in the situation where 12:OAc, 7-12:OAc, and 11-12:OAc act the larvae are maintained with food), would mainly as pheromones of sexual attraction in indicate an alert to other individuals of their adult specimens (Zhang et al., 2016; species about the availability of food and Chynoweth et al., 2018; Williams et al., 2019; absence of threats, which would be a Fu-cun et al., 2017).