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231.
Wolbachia bacteria are obligatory intracellular parasites of arthropods and have been detected in about 70 species of parasitic wasps
and three parasitoid flies. Wolbachia are transmitted cytoplasmically (maternally) and modify host reproduction in different ways to enhance their own transmission:
parthenogenesis induction (PI), cytoplasmic incompatibility (CI), or feminization (F) of genetic males. Only PI and CI are
known in parasitoids. PI-Wolbachia cause thelytoky in otherwise arrhenotokous parasitoids by generating diploid (rather than haploid) unfertilized wasp eggs.
CI-Wolbachia cause incompatibility of crosses between infected males and uninfected females because the paternally derived chromosomes
fail to decondense and are destroyed after syngamy. More complex situations arise when hosts harbor multiple infections, which
can lead to bidirectional incompatibility and may be involved in parasitoid speciation. The relative fitness of infected and
uninfected hosts is important to the population dynamics of Wolbachia, and more data are needed. Evolutionary conflict should be common between host genes, Wolbachia genes, and other "selfish" genetic elements. Wolbachia-specific PCR primers are now available for several genes with different rates of evolution. These primers will permit rapid
screening in future studies of spatial and temporal patterns of single and multiple infection. Molecular phylogenies show
that CI- and PI-Wolbachia do not form discrete clades. In combination with experimental transfection data, this result suggests that host reproductive
alterations depend on the interaction between attributes of both Wolbachia and host. Moreover, Wolbachia isolates from closely related hosts do not usually cluster together, and phylogenies suggest that Wolbachia may have radiated after their arthropod hosts. Both results support considerable horizontal transmission of Wolbachia between host species over evolutionary time. Natural horizontal transmisson between parasitoids and their hosts, or with
entomoparasitic nematodes or ectoparasitic mites, remains a tantalizing but equivocal possibility.
Received: November 27, 1998 / Accepted: January 15, 1999 相似文献
232.
233.
Hersberger-Langloh Sophie E. von Schnurbein Georg Kang Chulhee Almog-Bar Michal García-Colín Jacqueline Butcher García Marta Rey 《Voluntas: International Journal of Voluntary and Nonprofit Organizations》2022,33(3):428-442
VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations - Although episodic volunteering is a popular form of volunteering and has received increasing attention from researchers,... 相似文献
234.
Greene RR Graham SA Haulotte SM Nixon-Garcia C Gleason-Wynn P 《Journal of gerontological social work》2005,45(4):101-123
This article discusses the findings of a consumer-oriented survey to ascertain the perceptions of Texas nursing home residents, their families, and nursing home administrators about what factors they believe contribute to quality of care. The findings from previous studies and established practice standards are then used to further delineate the practice roles and functions of social workers in nursing facilities (NFs) and to inform social work curriculum. 相似文献
235.