Endosymbiont Infections in Spiders

Abstract

Endosymbiotic bacteria such as Wolbachia infect a wide range of arthropods and can dramatically influence their host’s biology through mechanisms such as skewing the sex ratio towards females or causing reproductive incompatibilities between infected and uninfected individuals. These bacteria can also have substantial negative or positive effects on the fitness, immunity and behaviour of their hosts. Research to date has largely focussed on infections in insect and nematode hosts, but more recently interest in spiders has gained momentum. Here we discuss key developments in this area, presenting evidence for effects of endosymbionts on reproductive and non-reproductive traits in spiders. We further provide an overview of known infections in spiders, which seem to differ from those in other invertebrate groups surveyed thus far, particularly in the prevalence of particular symbionts such as Cardinium. Studies carried out so far indicate that endosymbiont infections in spiders may cause sex-ratio bias, potentially through male-killing. Microbially induced cytoplasmic incompatibility, feminisation of males and parthenogenesis have not yet directly been observed, but the possibility that they occur merits investigation. Symbiont infections in spiders have been shown also to cause various alterations in both reproductive and non-reproductive behaviours. We suggest that spiders will prove to be eminently useful models for studying the effect of microbial infections on the evolution of their host and we provide suggestions for future evolutionary research questions tailored to spider biology.