The evolution of parasitic sex ratio distortion

Lead Research Organisation: University of Leeds
Department Name: Inst of Integrative & Comparative Biolog


Host-parasite interactions are pervasive throughout the natural world, forming a critical component of plant and animal communities. Among them, parasites that distort host sex ratios are widespread in invertebrates. The effect of sex ratio distorters can have a powerful effect on biodiversity; they can cause populations to become extinct and change the composition of animals in the community. Additionally as they can affect harmful as well as beneficial hosts, there is currently a great deal of interest in the use of such parasites for biological control. Sex ratio distortion has evolved in diverse parasites (eukaryotes and bacteria) and affects diverse hosts. Why distort sex ratio? These parasites are passed from mother to offspring in the eggs and are only transmitted by females. These parasites have evolved a number of strategies to increase the relative frequency of female hosts (so increasing the spread of the parasite). Feminisation is induced by the bacterium Wolbachia and by microsporidia (eukaryotic parasites) in Crustacea. In contrast Wolbachia causes male killing in insects. Discovering the mechanisms of male killing and feminisation is key to understanding host-parasite coevolution. We propose that these intracellular parasites are most likely to act by secreting molecules into the host cell which will then influence host molecular pathways, they may modify the response to external hormonal signals or even induce programmed cell death (apoptosis). Such changes could disrupt patterns of sexual development or lead to sex-specific embryo mortality. AIMS: We will investigate the evolution of sex ratio distortion in distantly related parasites by testing the hypotheses that - Similar mechanisms lead to contrasting strategies of sexual manipulation by Wolbachia (male killing in insect hosts, feminisation in crustacean hosts) - Parallel mechanisms of feminisation have evolved in distantly related parasites (Wolbachia and microsporidia) OBJECTIVES I. WE WILL INVESTIGATE THE MOLECULAR BASIS OF WOLBACHIA INDUCED MALE KILLING AND FEMINISATION. We will use state of the art techniques (proteomics) to identify molecules secreted into the host cytoplasm that cause feminisation or male killing, and to follow the changes they induce in the host. We will study this initially in the Drosophila (fruit fly)/Wolbachia male killing system. The genome of both these organisms is known and will help us to identify proteins and their function. We will then go on to study feminising Wolbachia in the crustacean Armadillidium vulgare (woodlouse). II. WE WILL INVESTIGATE THE CELLULAR BASIS OF WOLBACHIA AND MICROSPORIDIA INDUCED FEMINISATION BY TESTING FOR MANIPULATION OF THE PATTERN OF CELL DEATH IN THE DEVELOPING HOST Parasites cause feminisation in Crustacea by inhibiting development of the androgenic gland (the gland that controls male sexual differentiation). To pinpoint the site of action, we will map the distribution of feminising microsporidia and Wolbachia during sexual differentiation of their crustacean hosts. We have recently observed an association between male killing in Drosophila bifasciata by Wolbachia and apoptosis (programmed cell death). We will test whether feminising parasites also induce apoptosis in the androgenic gland in order to feminise the host.


10 25 50
Description joint grant. with NE D1087x/1 and NE /Do12937/1

1. microsporidian sex ratio distorters act by inhibition of androgenic gland function in the host

2. development and testing of in situ hybridisation probes for microsporidian parasites

3. Illustration of importance of parasitic disease for wildlife ecology

4. illustration that microsporidia are emergent pathogens in aquatic ecosystems

See NE/D011000/1 for outputs
Exploitation Route ISH probes can be used to detect specific microsporidian parasites for example as disease agents in beneficial insects or biocontrol agents for pests
Sectors Agriculture, Food and Drink,Environment

Description Yorkshire Wildlife Trust Volunteer Day presentation 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Supporters
Results and Impact Volunteer Day for Yorkshire Wildlife Trust to tell volunteers about the wider work of the trust. 20+ volunteers attended along with 4 Wildlife Trust Staff and trainees. Presentation/workshop on biosecurity delivered in partnership with Wildlife trust staff. Volunteers participated enthusiastically and said that it had really made them think about the importance of biosecurity both in their volunteering activities with the trust and on a personal level. Yorkshire Wildlife Trust staff have since reported that some of the volunteers had taken the message on board to the extent of discussing what biosecurity measures were needed with their task day leader.
Year(s) Of Engagement Activity 2017