This repository contains a collection of data on D.sechellia loss of immune response against parasitoid wasps.
It is analysed in Chapter 5 of my PhD thesis "Evolutionary genomics of the parasitoid resistance in Drosophila", and
comprises a lab experiment with a noni extract and a field survey in Cousin Island, Seychelles.
Background information can be found in two comparative studies, a genomics study (Salazar-Jaramillo et al., 2014 Evolution of a cellular immune response in Drosophila: a phenotypic and 249 genomic comparative analysis. Genome Biology and Evolution 6:273–289) and a transcriptomic study (Salazar-Jaramillo et al., 2017. Inter- and intra-species variation in genome-wide gene expression of Drosophila in response to 246 parasitoid wasp attack. BMC Genomics 18:331).
The details of the lab experiment and field study are included below. Scripts and data can be downloaded from this repository
Experiments tested the effect of the exposure to noni on the survival of D. melanogaster and D. simulans, and on the parasitization by the parasitoid Asobara citri. The species are the genome project strains from the Drosophila Stock Center (San Diego University) (Drosophila 12 Genomics Consortium 2007). The parasitoid strain of A. citri was collected in Ivory Coast, West Africa, in 1995, and has been maintained on D. melanogaster at 25°C. For the survival and parasitization assays, adult flies were placed on petridishes of 70mm diameter filled with standard medium (26g dried yeast, 54g sugar, 17g agar and 13 mL nipagine solution per litre) and a layer of either noni extract ("Hawaiian Health Ohana" brand) or yeast. They were incubated overnight for egg-laying, after which the adult flies were removed from the petridishes. Eggs were transferred to new petridishes at standardized density (25 eggs/petridish),and kept at 25°C. After two days, when the larvae were in the second instar stage, a female of A. citri was introduced to half of the petridishes for 24 hours, while the rest of cultures were used as unparasitized control. After pupation, the fly pupae were transferred to vials to complete development.
We collected flies and parasitic wasps on Cousin island in the Seychelles, using two approaches: 1) a choice assay: baits of noni, papaya and banana were used to score egg laying and 2) collection of fruit flies and wasps found to develope on noni. The field survey took place during March-April 2014 throughout the island. For the choice assay, 21 baits were placed containing a substrate of North Carolina instant medium and a layer of either banana, papaya or noni. Each set of three fruit types were placed in 7 different locations across the island and left during 24 hours to allow ies to lay eggs. Banana trees are not present in Cousin and papaya trees are removed as they are considered invasive.
For the natural inventory, we collected noni fruit that had fallen of the plant, at different stages of maturity. A total of 28 noni fruit were collected. The fruits were placed in plastic containers to capture larvae that would leave to the fruit surface for pupation. The containers and fruits were left open at the site of collection to enable further oviposition by insects, for a period varying from 1-5 days depending on the stage of maturity of the noni fruit. Thereafter, the containers were closed with a piece of gauze to ensure that all insects that emerged from the fruit could be retrieved. The containers were brought to the field station and checked regularly for any emerging insects. Emerged adult insects from both surveys were collected and preserved in 70% alcohol for taxonomic identification.