Perception, signaling and molecular basis of oviposition-mediated plant responses.

Eggs deposited on plants by herbivorous insects represent a threat as they develop into feeding larvae. Plants are not a passive substrate and have evolved sophisticated mechanisms to detect eggs and induce direct and indirect defenses. Recent years have seen exciting development in molecular aspects of egg-induced responses. Some egg-associated elicitors have been identified, and signaling pathways and egg-induced expression profiles are being uncovered. Depending on the mode of oviposition, both the jasmonic acid and salicylic acid pathways seem to play a role in the induction of defense responses. An emerging concept is that eggs are recognized like microbial pathogens and innate immune responses are triggered. In addition, some eggs contain elicitors that induce highly specific defenses in plants. Examples of egg-induced suppression of defense or, on the contrary, egg-induced resistance highlight the complexity of plant-egg interactions in an on-going arms race between herbivores and their hosts. A major challenge is to identify plant receptors for egg-associated elicitors, to assess the specificity of these elicitors and to identify molecular components that underlie various responses to oviposition.

Efecto de la temperatura en la tasa de puesta de reinas de la hormiga argentina, Linepithema humile (Mayr, 1868), (Hymenoptera, Dolichoderine) bajo condiciones experimentales de monoginia y poliginia = Effect of temperature on the oviposition rate of the argentine ant queens, Linepithema humile (Mayr 1868), (Hymenoptera, Dolichoderine) under experimental conditions

Data concerning the effect of temperature on different physiological parameters of an invasive species can be a useful tool to predict its potential distribution range through the use of modelling approaches. In the case of the Argentine ant these data are too scarce and incomplete. The aim of the present study is to compile new data regarding the effect of temperature on the oviposition rate of the Argentine ant queens. We analysed the oviposition rate of queens at twelve controlled temperatures, ranging from 10ºC to 34ºC under different monogynous and polygynous conditions. The oviposition rate of the Argentine ant queens is affected by temperature in the same manner, independently of the number of queens in the nest. The optimal temperature for egg laying was 28ºC, and its upper and lower limits depended on the degree of polygyny

Flowering phenology, seed set and arthropod guilds in Trichogoniopsis adenantha (DC) (Asteraceae) in south-east Brazil

and glades. This species blooms throughout the year, attracting arthropods of various guilds, including herbivores, pollinators and predators. In this study, done over a two year period, we described the phenology of T. adenantha and assessed the seasonal variation in arthropod numbers of different guilds. We also determined the periods of lowest and highest seed set. T. adenantha population showed a peak in flowering in March-April (rainy season) with greater production of achenes in December-April. April and October had respectively highest and lowest number of fertilized, undamaged ovules, and this pattern is possibly related with population dynamics of pollinators and herbivores. In August, which was the period of greatest damage to the stigma (by geometrid larvae), there was a positive relationship between the proportion of unfertilized ovules and flowers with damaged stigma, suggesting that floral herbivory may affect reproduction in T. adenantha. We discuss the complex dynamics of the beneficial and harmful interactions between arthropods and the host plant.

Racemic and Enantioselective Total Syntheses of Mosquito Oviposition Pheromone from a Naturally Available Unsaturated Fatty Acid

The unnatural threo-6-acetoxy-5-hexadecanolide and the natural mosquito oviposition pheromone erythro-6-acetoxy-5-hexadecanolide were synthesized in a diastereodivergent fashion in 44% and 33% overall yield respectively from 5-bromovaleric acid and undecanal. The key step utilized a chemoenzymatic epoxidation-lactonization of a naturally available fatty acid to form the 6-hydroxy-5-hexadecanolide core.17 The epoxidation strategy was later adapted to allow for an asymmetric synthesis. Shi epoxidation afforded highly enantioenriched (5R, 6R)-6-hydroxyhexadecanolide (er = 10) in 70 % overall yield. Other derivatives of the chiral ketone catalyst were also screened. Finally, attempts were made to obtain the correct stereochemistry at C(6) of the target with a dynamic kinetic transformation using lipase and a transfer hydrogenation catalyst. Epimerization of the lactol with the transfer hydrogenation catalyst was successful, but lipase mediated reactions halted at <10 % conversion.

Feeding and oviposition preferences of the diamondback moth Plutella xylostella (Lepidoptera: Plutellidae) on six Brassicaceae host plant species

Plutella xylostella (diamondback moth, DBM) is a globally distributed Lepidopteran that feeds and oviposits almost exclusively on plants in the Brassicaceae family. DBM disperses from the southern United States and Mexico into Canada in the spring and summer. Establishment of DBM in Ontario is partially dependent upon the quantity and quality of host plants available and the preference of DBM for different hosts. Host plants include many crops such as broccoli, canola and cabbage, as well as landscape ornamentals and wild plants. It has previously been established that DBM are attracted to host plants by chemicals, specifically glucosinolates. I examined the preference of DBM among crop, wild and ornamental host plant species and how preference varies with insect life stage (3rd and 4th instar larvae and adults). Experiments included exposing DBM larvae from five populations coming from different locations in Canada to six Brassicaceae species and evaluating the preferences and weight gain over one hour. Then adult females were exposed to these same plant species and their oviposition preferences were examined. Populations from Alberta, Saskatchewan and Ontario were compared to assess differences in preference associated with geographic region or species of host plant. The ultimate goal of my study was to understand the potential of various Brassicaceae species to act as reservoirs to sustain and promote population growth of DBM, as well as sinks that may decrease DBM abundance. Results showed that garden cress (Lepidium sativum) was highly preferred over other species (wintercress, black mustard, aubretia, broccoli and ornamental kale) for both food and oviposition sources. Previous studies report that garden cress contains saponins, chemicals shown to be toxic to developing DBM larvae, however no studies have yet shown a preference for garden cress. These results provide information on a novel host plant with the potential to control DBM population growth. No difference in preferences was found among populations of DBM from various sources in Canada.

What limits insect fecundity? Body size- and temperature-dependent egg maturation and oviposition in a butterfly

1. Large female insects usually have high potential fecundity. Therefore selection should favour an increase in body size given that these females get opportunities to realize their potential advantage by maturing and laying more eggs. However, ectotherm physiology is strongly temperature-dependent, and activities are carried out sufficiently only within certain temperature ranges. Thus it remains unclear if the fecundity advantage of a large size is fully realized in natural environments, where thermal conditions are limiting. 2. Insect fecundity might be limited by temperature at two levels; first eggs need to mature, and then the female needs time for strategic ovipositing of the egg. Since a female cannot foresee the number of oviposition opportunities that she will encounter on a given day, the optimal rate of egg maturation will be governed by trade-offs associated with egg- and time-limited oviposition. As females of different sizes will have different amounts of body reserves, size-dependent allocation trade-offs between the mother’s condition and her egg production might be expected. 3. In the temperate butterfly Pararge aegeria , the time and temperature dependence of oviposition and egg maturation, and the interrelatedness of these two processes were investigated in a series of laboratory experiments, allowing a decoupling of the time budgets for the respective processes. 4. The results show that realized fecundity of this species can be limited by both the temperature dependence of egg maturation and oviposition under certain thermal regimes. Furthermore, rates of oviposition and egg maturation seemed to have regulatory effects upon each other. Early reproductive output was correlated with short life span, indicating a cost of reproduction. Finally, large females matured more eggs than small females when deprived of oviposition opportunities. Thus, the optimal allocation of resources to egg production seems dependent on female size. 5. This study highlights the complexity of processes underlying rates of egg maturation and oviposition in ectotherms under natural conditions. We further discuss the importance of temperature variation for egg- vs. time-limited fecundity and the consequences for the evolution of female body size in insects.

Biased oviposition and biased survival together help resolve a fig-wasp conflict

We report evidence that helps resolve two competing explanations for stability in the mutualism between Ficus racemosa fig trees and the Ceratosolen fusciceps wasps that pollinate them. The wasps lay eggs in the tree's ovules, with each wasp larva developing at the expense of a fig seed. Upon maturity, the female wasps collect pollen and disperse to a new tree, continuing the cycle. Fig fitness is increased by producing both seeds and female wasps, whereas short-term wasp fitness increases only with more wasps, thereby resulting in a conflict of interests. We show experimentally that wasps exploit the inner layers of ovules first (the biased oviposition explanation), which is consistent with optimal-foraging theory. As oviposition increases, seeds in the middle layer are replaced on a one-to-one basis by pollinator offspring, which is also consistent with biased oviposition. Finally, in the outer layer of ovules, seeds disappear but are only partially replaced by pollinator offspring, which suggests high wasp mortality (the biased survival or ‘unbeatable seeds’ explanation). Our results therefore suggest that both biased oviposition and biased survival ensure seed production, thereby stabilizing the mutualism. We further argue that biased oviposition can maintain biased survival by selecting against wasp traits to overcome fig defenses. Finally, we report evidence suggesting that F. racemosa balances seed and wasp production at the level of the tree. Because figs are probably selected to allocate equally to male and female function, a 1:1 seed:wasp ratio suggests that fig trees are in control of the mutualism.

Local and landscape effects on bee functional guilds in pigeon pea crops in Kenya

Pollinators face many challenges within agricultural systems due to landscape changes and intensification which can affect resource availability that can impact pollination services. This paper examines pigeon pea pollination and considers how landscape context and agricultural intensification in terms of pesticide use affects the abundance of bees characterized by species guilds on crops. The study was conducted on six paired farms across a gradient of habitat complexity based on the distance of each farm from adjacent semi-natural vegetation in Kibwezi Sub-county, Kenya. The study found that farms which do not use insecticides in farm management, but are in close proximity to natural habitat have greater bee guild abundance, but at further distances, overall abundance is reduced with or without insecticide use. At 1 km landscape radius, the complexity of habitats but not patch size had a positive impact on the abundance of cavity nesting bees and mason bees, which can be attributed to the interspersion of the small-holder farms with semi-natural habitats across the landscapes producing mosaics of heterogeneous habitats. The study revealed the strongest relationships between fruit set and bee abundance to be with the carpenter bee, social bee and solitary bee guilds, which are among the most abundant bees visiting pigeon pea flowers in this system. Our findings provide the foundation for conservation efforts by identifying which bee guilds pollinated pigeon peas. From this study, we suggest managing the floral and nesting resources that would best support the most abundant crop pollinators, and also reducing insecticide application to the crop.

Oviposition site selection by the bromeliad-dweller harvestman Bourguyia hamata (Arachnida : Opiliones)

Bourguyia hamata females oviposit almost exclusively inside the rosette formed by the curled leaves of the epiphytic bromeliad Aechmea nudicaulis. We investigated whether the architecture of the individual bromeliads influences oviposition site selection by this harvestman species. We collected data on the presence of clutches inside bromeliads, rosette length, rosette slope in relation to tree trunks, and the amount of debris inside the rosette. Additionally, we measured the water volume inside the rosettes as well as the variation in the humidity inside and outside bromeliads with long and short rosettes. Longer rosettes were preferred as oviposition site possibly because they accumulate more water and maintain lower internal humidity variation than the external environment. Although the slope of the rosettes did not influence the occurrence of oviposition, the probability of debris accumulation inside the rosettes increased with their slope, and the frequency of clutches was greater in bromeliads with small amounts of debris. A field experiment showed that bromeliads with water inside the rosette were more frequently used as oviposition sites than bromeliads without water. In conclusion, females oviposit predominantly in bromeliads that accumulate more water and have small amounts of debris inside the rosettes, probably because these characteristics promote a more adequate microhabitat for egg development.

Oviposition preference hierarchy in Ceratitis capitata (Diptera, Tephritidae): influence of female age and experience

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Adult attractiveness and oviposition preference of Bemisia tabaci (Genn.) (Homoptera: Aleyrodidae) B-biotype in cotton genotypes

Considerada importante praga do algodoeiro, a mosca-branca Bemisia tabaci biótipo B pode através de sua alimentação, diminuir o vigor das plantas, trasmitir vírus e prejudicar a qualidade da fibra. Visando avaliar a resistência de genótipos de algodoeiro, Gossypium hirsutum (L.), à mosca-branca Bemisia tabaci biótipo B, realizaram-se testes de atratividade e não-preferência para oviposição, com e sem chance de escolha, em telado, a temperatura ambiente. Verificou-se baixa atratividade das plantas dos genótipos Fabrika, CNPA Ita 90, Makina, Coodetec 407 e IAC 01-639 CPA 02-24 a adultos dessa mosca-branca, o que pode representar um componente de resistência destes materiais genéticos ao inseto. Os genótipos BRS Aroeira, Coodetec 406, Fabrika e Coodetec 401 apresentaram resistência do tipo não-preferência para oviposição, nos testes com e sem chance de escolha. Os números de tricomas e de glândulas de gossipol por cm² não foram adequados para se avaliar a não-preferência para oviposição de adultos da mosca-branca em genótipos de algodoeiro.

Nonpreference of whitefly for oviposition in tomato genotypes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Within plant distribution of Anthonomus grandis (Coleoptera: Curculionidae) feeding and oviposition damages in cotton cultivars

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Oviposition of Quesada gigas (Hemiptera: Cicadidae) in coffee plants

Branches of coffee-plant were collected in Sao Sebastiao do Paraiso County, Minas Gerais State, at the Experimental Station of the Agricultural Research Company (Empresa de Pesquisa Agropecuaria de Minas Gerais - EPAMIG), with the aim of studying various aspects of oviposition by Quesada gigas (Hemiptera: Cicadidae). The number of branches with Q. gigas egg nests was analyzed, as well as the number of nests per branch, the eggs per nest and the diameter of the egg nest location on the branch. The preference for oviposition either on alive or dry branches and the size of the egg were assessed. Egg-laying occurred only on dry branches. The mean of the branch diameter on which the egg nests occurred was 2.5 +/- 0.53 mm. The number of eggs per nest averaged 13.2 +/- 4.9, and the number of egg nests per branch was 2.2 +/- 1.74. The eggs were 1.9 +/- 0.08 mm long by 0.5 +/- 0.04 mm wide. The largest diameters of the branches containing egg nests were found on the upper third of the trees, as well as the greatest amount of branches with egg nests, of egg nests per branch and of eggs per nest. The correlation relationship between all of the experiment variables was positive.

Diamondback moth oviposition nonpreference in cauliflower genotypes

The Diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), is one of the main plague-insect specie of Brassicaceae plants in Brazil and all over the world. The resistant genotypes use to its control is a promising alternative. This work aimed evaluates the eggs distribution along the plant, the adults' density per plant, and determine the cauliflower genotypes effect in the P. xylostella oviposition. The experiment was carried out at FCAV/UNESP-Jaboticabal Campus Phytossanity Department (Departamento de Fitossanidade). It was evaluated the eggs distribution, the P. xylostella adults density effect using Sharon hybrid, and tests with or without choose choice to determine the P. xylostella nonpreference in the Teresopolis Gigante, Verona, Barcelona, Sharon, Silver Streak, and Piracicaba Precoce genotypes. It is possible conclude that P. xylostella has higher willingness to oviposits in the stem than in the basal leaves. The three couple density of P. xylostella per plant is the best to discriminate cauliflower genotypes regarding the resistance grade to nonpreference choose choice to oviposition. During the P. xylostella oviposition preference tests with choose choice, the genotypes Sharon, Piracicaba Precoce, Barcelona, Verona e Teresopolis Gigante are less desirable to oviposition; while during the no choose choice tests the genotypes did not differ among them.