Wolbachia is a
cytoplasmically inherited intracellular bacterium. It can generally be found in the reproductive organs of its host species, and can be transferred from female to offspring through the egg cytoplasm. Traditionally,
M. uniraptor determines the sex of offspring using
haplodiploidy. The males are produced as haploids from unfertilized eggs while the females are produced as diploids from fertilized eggs. According to this practice,
M. uniraptor would normally produce both male and female offspring. However, in
M. uniraptor,
Wolbachia causes thelytoky, a type of
parthenogenesis in which females asexually reproduce only female offspring. When
M. uniraptor females receive experimentally administered antibiotics, such as
rifampicin, the strains of
Wolbachia become eradicated, and the females should hypothetically be able to produce both male and female offspring since the bacteria are not present to induce thelytoky. However, the resulting male offspring of these experiments do not carry viable sperm. This implies that
Wolbachia establishes itself early in the females in order to ensure its transfer into further hosts, at the risk of removing the current host's ability to sexually reproduce by not allowing it to produce fertile, viable male offspring. There are three primary reasons for why
M. uniraptor has become so dependent on
Wolbachia for survival and reproduction. The males of the species no longer produce viable sperm for sexual reproduction, and the females do not respond to any cues or advances by the males for sexual reproduction. Finally, the females lose a major muscle in their
spermathecae that allow them to contain sperm after sexual reproduction. Therefore, without the symbiotic relationship between
Wolbachia and
M. uniraptor, the wasp species would not persist alone by means of sexual reproduction because of these evolutionary alterations that increase the fitness of the persisting relationship with the bacteria. The bacteria have seemingly inhibited the wasps' reproductive pathways through selective pressures to increase the fitness of their relationship, and the wasp is unlikely to regress to its former state of sexual reproduction as a result of these genetic alterations.
Muscidifurax uniraptor now holds an
endosymbiotic relationship with
Wolbachia, and it has evolved to depend on these bacteria for reproduction and survival which results in the successful relationship we currently observe. ==References==