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Exploring Life History Choices: Using Temperature and Substrate Type as Interacting Factors for Blowfly Larval and Female Preferences

Blowflies (Diptera: Calliphoridae) present a wide range of larval lifestyles, typically classified as obligate parasitism, facultative parasitism, and ...

University of São Paulo

The genotype-phenotype interactions among traits governing feeding preference are of fundamental importance to behavioral genetics and evolutionary biology. The genetic basis of behavioral traits has been explored in different taxa using different approaches. However, the complex nature of the genetic mechanisms undergirding behavior is poorly understood. Here, we present an evolutionary study of candidate genes related to parasitism in Calliphoridae (Diptera: Calyptratae). Closely related species in this family exhibit distinct larval feeding habits, most notably necro-saprophagy and obligate parasitism.

Evolution of genes involved in feeding preference and metabolic processes in Calliphoridae (Diptera: Calyptratae).

One limitation of the widely used RNA-seq method is that long transcripts are represented by more reads than shorter transcripts, resulting in a biased estimation of expression levels. The 3' RNA-seq method, which yields only one sequence per transcript, bypasses this limitation. Here, RNA was extracted from two samples, in which we expected to find differentially expressed genes. Each was processed by both traditional and 3' RNA-seq protocols. Both methods yielded similar differentially expressed genes and estimated expression levels in a comparable way, confirming they both represent valid tools for RNA-seq analysis. Notably, however, we identified more differentially expressed transcripts with the 3' RNA-seq method, suggesting a greater power to detect expression variation using this method. Hence, when little genomic information is available for the species studied, the standard RNA-seq presents a better cost-benefit compromise, whereas for model species, the 3' RNA-seq method might more accurately detect differential expression.

Traditional  3' RNA-seq in a non-model species.

The cattle tick Rhipicephalus microplus is one of the most important ectoparasites with great sanitary and economic impact for cattle rearing worldwide. Ivermectin is commonly used to control tick populations, but its use over the last 30 years has led to the development of resistant populations of R. microplus, and a concomitant loss of efficacy. In this context, we aimed to determine the metabolic mechanisms that contribute to ivermectin resistance in a resistant strain of this species. We performed lethal time bioassays with inhibitors of detoxifying enzymes and xenobiotic transporters (four detoxification pathways) using two strains of ticks: a susceptible strain, Mozo, and a resistant strain, Juarez. We used four inhibitors to test the involvement of different families of proteins responsible for detoxification of ivermectin, namely cytochrome P450, esterases, glutathione-S-transferase, and ATP Binding Cassette Transporters. We calculated the synergistic factor for each inhibitor and strain. To different degrees, all tested inhibitors altered the mortality rates in the strain Juarez, indicating that multiple mechanisms are responsible for the resistant phenotype. Detoxification mechanisms mediated by ABC transporters were observed to be the most important. Esterases, glutathione-S-transferases, and cytochrome-oxidases played less important roles in detoxification.

Detoxification mechanisms involved in ivermectin resistance in the cattle tick, Rhipicephalus (Boophilus) microplus.

The Oestroidea superfamily is characterized by the diversity of feeding preferences among closely-related species; these flies are saprophagous, obligate parasites, or facultative parasites. We used gene expression and coding sequence data from five species (Cochliomyia hominivorax, Chrysomya megacephala, Lucilia cuprina, Dermatobia hominis, and Oestrus ovis) to identify underlying genetic differences involved in the diverse lifestyles. We tested whether 1287 orthologs have different expression and evolutionary constraints under different scenarios. We found two up-regulated genes; one in species causing cutaneous myiasis that is involved in iron transportation/metabolization (ferritin), and another in species causing traumatic myiasis that responds to reduced oxygen levels (anoxia up-regulated-like). Our evolutionary analysis showed a similar result. In the Co. hominivorax branch, we found one gene with the same function as ferritin that may be evolving under positive selection, spook. This is the first step towards understanding origins and evolution of parasitic strategy diversity in Oestroidea.

Evolution of coding sequence and gene expression of blowflies and botflies with contrasting feeding habits.

The emergence of insecticide resistance is a fast-paced example of the evolutionary process of natural selection. In this study, we investigated the molecular basis of resistance in the myiasis-causing fly Cochliomyia hominivorax (Diptera: Calliphoridae) to dimethyl-organophosphate (OP) insecticides.

Molecular basis of resistance to organophosphate insecticides in the New World screw-worm fly.

Spiders constitute more than 49,000 described species distributed all over the world, and all ecological environments. Their order, Araneae, is defined by a set of characteristics with no parallel among their arachnid counterparts (e.g., spinnerets, silk glands, chelicerae that inoculate venom, among others). Changes in developmental pathways often underlie the evolution of morphological synapomorphies, and as such spiders are a promising model to study the role of developmental genes in the origin of evolutionary novelties. With that in mind, we investigated changes in the evolutionary regime of a set of six developmental genes, using spiders as our model. The genes were mainly chosen for their roles in spinneret ontogeny, yet they are pleiotropic, and it is likely that the origins of other unique morphological phenotypes are also linked to changes in their sequences. Our results indicate no great differences in the selective pressures on those genes when comparing spiders to other arachnids, but a few site-specific positive selection evidence were found in the Araneae lineage. These findings lead us to new insights on spider evolution that are to be further tested.

Tatiana Teixeira Torres

Department of Genetics and Evolutionary Biology,
Institute of Biosciences,
Department of Genetics and Evolutionary Biology, Institute of Biosciences

University of São Paulo

Exploring Life History Choices: Using Temperature and Substrate Type as Interacting Factors for Blowfly Larval and Female Preferences

Tatiana Teixeira Torres

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Genetics and Evolutionary Biology,Institute of Biosciences,Department of Genetics and Evolutionary Biology, Institute of Biosciences

University of São Paulo

Exploring Life History Choices: Using Temperature and Substrate Type as Interacting Factors for Blowfly Larval and Female Preferences

Department of Genetics and Evolutionary Biology,
Institute of Biosciences,
Department of Genetics and Evolutionary Biology, Institute of Biosciences