BIOL 312 Lecture Notes - Lecture 28: Spiroplasma, Symbiosis, Cytoplasmic Incompatibility
14 Dec 2017
School
Department
Course
Professor
Document Summary
Facultative inherited symbionts: not essential to the host. Unrelated insects are infected with closely related symbiont strains. Some ecologically related insects have closely related strains (e. g. parasitoids and hosts, predators and prey). Many facultative inherited symbionts are conditional mutualists - benefit hosts (increase fitness) only under certain situations e. g. provide protection against natural enemies. Spiroplasma bacterial symbiont protects its drosophila host against a parasitic nematode. Flies are sterilized by worms unless they also carry spiroplasma. Flies have most eggs when spiroplasma and worms are present. Flies that have symbiont are more common than those that don"t. Reproductive manipulation: some inherited symbionts have evolved unusual strategies. They manipulate host reproduction to increase the frequency of infected females by a) distorting sex ratios (e. g. turning males into females or by killing males) b) causing mating incompatibilities. Male killers: symbionts transmitted from mother offspring any male that is infected dies early in development.
