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PubMed1980

Teratocarcinogenesis and spontaneous parthenogenesis in mice.

Teratomas are rare in most strains of mice. Testicular teratomas are common in some sublines of inbred strain 129. Ovarian teratomas are common in inbred strain LT. Testicular teratomas are derived from primordial germ cells and can be experimentally produced by grafting 121/2-day genital ridges to the testes of adults. They develop into testes and for some strains most have teratomas. Ovarian teratomas are derived from parthenogenetically activated ovarian oocytes that have completed the first meiotic division. Teratomas of either sex can be experimentally produced by grafting early embryos to various sites in adults. Embryo-derived teratomas originate directly from undifferentiated embryonal cells. Occasionally teratomas are malignant (teratocarcinomas) and can be maintained as transplantable tumors. Some form embryoid bodies that resemble normal early embryos. When the stem cells of some transplantable teratocarcinomas are injected into blastocysts and transferred to the uteri of pseudopregnant females, they participate in normal development and contribute to the formation of all major tissues including functional sperm and eggs. Spontaneous parthenogenesis is common in strain LT oocytes after ovulation. The eggs cleave, form blastocysts which implant in the uterus, but after the egg cylinder stage they become disorganized and are aborted. Eight-cell embryos from the pigmented LT strain were aggregated with embryos of albino strain 129 and transferred to the uteri of pseudopregnant females. They participated in development and contributed to the formation of normal chimeric tissues. Offspring from eggs derived from parthenogenetic embryonal cells were produced, demonstrating that parthenogenetic embryonic cells are totipotent. It is still a mystery why parthenogenetic embryos will not survive in utero.

Animals↗
PubMed1994

Parthenogenesis in the genus Schistosoma: electrophoretic evidence for this reproduction system in S. japonicum and S. mansoni.

Mixed infections with Schistosoma japonicum and S. mansoni were carried out in mice. S. japonicum females paired with S. mansoni males developed normally and produced numerous viable eggs; very little sperm was found in the female genital tract. The eggs yielded many miracidia infective to Oncomelania hupensis, the host of S. japonicum. Cercariae arising from miracidia developed into male worms with an electrophoretic pattern of malate dehydrogenase (MDH) corresponding only to the maternal species S. japonicum. S. mansoni females paired with S. japonicum produced few viable eggs; sperm was found in the female genital tract. Miracidia hatched from some of these eggs were infective to Biomphalaria glabrata, the host of S. mansoni. Cercariae arising from miracidia developed into female worms with an electrophoretic pattern of MDH typical of the maternal species S. mansoni. It was concluded that S. japonicum females paired with S. japonicum males reproduce parthenogenetically. Parthenogenesis in schistosomes is discussed.

Animals↗
PubMed1991

Sexual behavior in laboratory strains of Drosophila mercatorum that have spontaneously adopted parthenogenesis.

Three instances are described in which bisexual laboratory strains spontaneously adopted an exclusively parthenogenetic mode of reproduction, even in the presence of fertile, bisexual males. The few males produced by the parthenogenetic strains lack a Y chromosome and are sterile but, nevertheless, showed no correlated impairment of normal mating behavior. In contrast, females show a strong reluctance to accept copulation. This behavioral correlate of parthenogenesis also has been observed previously in experimentally produced parthenogenetic lines. We suggest that genetic breakdown in female mating behavior may contribute to an evolutionary stimulus that results in a selective increase in the frequency of diploidizing events in unfertilized eggs. This ultimately might lead to the origin of an exclusively parthenogenetic reproductive mode.

Animals↗
PubMed2006

The first finding of a Rickettsia bacterium associated with parthenogenesis induction among insects.

The larval endoparasitoid, Neochrysocharis formosa (Westwood), is an important natural enemy of the leafminer Liriomyza trifolii (Burgess) in Japan. The thelytokous strain of N. formosa mostly produces female progeny. Male progeny were produced by females treated with tetracycline, suggesting that microorganisms induce thelytoky in N. formosa. The result of nucleotide sequencing of the 16S rRNA gene indicated that the parasitoid is infected with a Rickettsia bacterium, which appears to be causative of the thelytoky. Although Rickettsia-bellii-like bacteria have been found to be associated with various reproductive disorders, this is the first finding of a parthenogenesis-inducing Rickettsia among insects.

Animals↗
PubMed1989

Parthenogenesis in Xenopus eggs injected with centrosomes from synchronized human lymphoid cells.

In Xenopus eggs, normal development requires the participation of the centrosome provided by the sperm. Injection of foreign centrosomes purified from exponentially growing mammalian cells enables the eggs to undertake parthenogenesis. In order to know whether such a complementation required centrosomes already committed to duplication, we have prepared centrosomes from human cells synchronized at different stages of the cell cycle (G0, G1, G2). We show that the three types of centrosome possess a similar parthenogenetic activity and conclude that duplication of heterologous centrosome can be triggered in Xenopus eggs.

Animals↗
PubMed2006

Geographic parthenogenesis: recurrent patterns down under.

A recent study reports striking similarities in the origin and spread of parthenogenesis in two distantly related animals of the Australian arid zone, suggesting that the loss of sex was driven by a very general selective force.

Animals↗
PubMed2004

Artificial parthenogenesis and control of voltinism to manage transgenic populations in Bombyx mori.

In order to improve the management of transformed populations in a routine application of transgenesis technology in Bombyx mori, we modified its mode of reproduction and its voltinism. On one hand, after a stable integration of the gene of interest by transgenesis, it is preferable to maintain this gene in an identical genomic context through successive generations. This can be obtained by artificial parthenogenetic reproduction (ameiotic parthenogenesis) giving isogenic females identical to their transformed mother. On the other hand, it is essential to obtain continuous generations (polyvoltinism) after microinjection, in order to screen positive transgenic insects and study genetics and insertion of the transgene. Thereafter, it is more convenient to store these populations, as diapause eggs before their use in biotechnology application. We obtained such polyvoltine parthenoclones, first by selection for a parthenogenetic character in polyvoltine races, and second, by selection for a polyvoltine character in a parthenogenetic, but diapausing clone of B. mori. As diapause was directly under the control of diapause hormone (DH), we also tested direct injection of DH in female pupae of polyvoltine strains, as well as anti-DH antibody treatment to eliminate diapause in univoltine strains. We discussed the advantages and limitations of these methods and proved the feasibility in obtaining polyvoltine parthenoclones and determining the voltinism in B. mori. These methods would permit us to improve the management of populations used in transgenesis technology.

Animal Husbandry↗
PubMed2005

Aster self-organization at meiosis: a conserved mechanism in insect parthenogenesis?

Unfertilized eggs usually lack maternal centrosomes and cannot develop without sperm contribution. However, several insect species lay eggs that develop to adulthood as unfertilized in the absence of a preexisting centrosome. We report that the oocyte of the parthenogenetic viviparous pea aphid Acyrthosiphon pisum is able to self-organize microtubule-based asters, which in turn interact with the female chromatin to form the first mitotic spindle. This mode of reproduction provides a good system to investigate how the oocyte can assemble new centrosomes and how their number can be exactly monitored. We propose that the cooperative interaction of motor proteins and randomly nucleated surface microtubules could lead to the formation of aster-like structures in the absence of pre-existing centrosomes. Recruitment of material along the microtubules might contribute to the accumulation of pericentriolar material and centriole precursors at the focus of the asters, thus leading to the formation of true centrosomes. The appearance of microtubule asters at the surface of activated oocytes could represent a possible common mechanism for centrosome formation during insect parthenogenesis.

Animals↗
PubMed1994

Interspecific stimulation of parthenogenesis in Schistosoma intercalatum and S. mansoni.

Experimental studies of mating behaviour of Schistosoma intercalatum and Schistosoma mansoni in mixed infections in mice showed that in simultaneous infections, without the possibility of choice of mate, heterologous pairing occurs readily. The paired females reach sexual maturity, are inseminated and lay parthenogenetic eggs. Miracidia originating from the S. mansoni male x S. intercalatum female are non infective to either Biomphalaria glabrata or Bulinus forskalii, whereas those from the reverse cross show a very low infectivity to only B. glabrata. The resulting haploid male cercariae also show a very low infectivity to mice (1.1%) and consequently only a very small number of adult worms develop. It appears from this study, on chromosomal and electrophoretic evidence, that generative (haploid) parthenogenesis occurs in S. mansoni females paired with S. intercalatum males.

Animals↗
PubMed1984

Intergeneric reproductive stimulation and parthenogenesis in Schistosoma mansoni.

When mice were infected with female cercariae of Schistosoma mansoni and male cercariae of Schistosomatium douthitti, many mixed pairs formed. The paired females were approximately the same size as those in unisexual infections, far smaller than females paired with S. mansoni males. Although the Sch. douthitti males possessed well-developed testes, sperm were not found in their female partners, which developed scanty vitelline glands and produced laterally spined eggs typical of S. mansoni. Such eggs yielded swimming miracidia infective to the snail host of S. mansoni, Biomphalaria glabrata, but not to the lymnaeid snail host of Sch. douthitti. Sporocysts arising from these miracidia were haploid and produced cercariae infective to mice. Parthenogenetically derived female cercariae in mice co-infected with either parthenogenetically derived male or normal diploid male S. mansoni developed to large adults of normal appearance, whose eggs yielded diploid miracidia and subsequent generations of normal diploid schistosomes. Parthenogenetically derived females co-infected with Sch. douthitti males also paired and produced some eggs containing viable miracidia, which gave rise once again to haploid sporocysts. These observations confirm previous suggestions that the stimulus for maturation in female S. mansoni is distinct from that for growth, and is independent of insemination and fertilization. It is concluded that both diploid and haploid S. mansoni females are capable either of parthenogenesis or of bisexual reproduction when appropriately stimulated.

Animals↗
PubMed2002

Parthenogenesis, calling behavior, and insect-released volatiles of leafminer moth Phyllonorycter emberizaepenella.

We proved that the leafminer moth Phyllonorycter emberizaepenella (Lepidoptera: Gracillariidae) reproduces by parthenogenesis of the thelytoky type. Despite a complete absence of males, parthenogenetically reproducing females diurnally demonstrated the calling posture normally used for releasing signaling compounds. Two compounds, which we collected from a calling female, were identified as potential sex pheromone components: (8E, 10E)-8,10-tetradecadienyl acetate and (8E,10E)-8,10-tetradecadienol, the latter occurring only in trace amounts. In field experiments, no males were attracted to traps baited with either the potential sex pheromone or with virgin females. Both the pattern of behavior and the chemical characteristics of the pheromone of Ph. emberizaepenella species were similar to those known for Lepidoptera with the usual amphimictic mode of reproduction. Theoretical speculations that in thelytoky, where there is no need to find a sexual partner, the individuals would obtain certain advantages due to reduction in their sexual behavior, were, thus, not confirmed for Ph. emberizaepenella.

Animal Communication↗
PubMed2002

Genetic diversity and the phylogeography of parthenogenesis: comparing bisexual and thelytokous populations of Nemasoma varicorne (Diplopoda: Nemasomatidae) in Denmark.

The millipede, Nemasoma varicorne, represents a textbook example of geographic parthenogenesis with thelytokous populations being distributed north, east, south and west of the distribution of the bisexual ancestor in the deciduous forests of central Europe. We here describe variation in amplified fragment length polymorphisms (AFLP's) in sympatric bisexual and thelytokous populations of N. varicorne in Denmark and compare the relationships of Danish populations with animals from The Czech Republic, England and Poland. Thelytokes from Denmark, England and Poland form a monophyletic cluster that differs from bisexuals from Denmark and Czechia for about 30% of the fragments. A single clone is widely spread over Denmark (34 of 38 localities), with rare clones being detected at four other localities. The phylogenetic pattern implies strongly that thelytoky evolved prior to the post-glacial colonization of northern Europe. This further suggests that the two forms have interacted extensively during this colonization and that the thelytokes have been excluded from older forests by competition with the bisexual forms. Our results further suggest that the success of the thelytokous form, at least in Denmark, is not due to abundant clonal diversity as hypothesized by the frozen niche variation model.

Animals↗
PubMed2000

Infectious parthenogenesis.

Parthenogenesis-inducing Wolbachia bacteria are reproductive parasites that cause infected female wasps to produce daughters without mating. This manipulation of the host's reproduction enhances the transmission of Wolbachia to future generations because the bacteria are passed on vertically only from mothers to daughters. Males are dead ends for cytoplasmically inherited bacteria: they do not pass them on to their offspring. Vertical transmission of Wolbachia has been previously considered to be the main mode of transmission. Here we report frequent horizontal transmission from infected to uninfected wasp larvae sharing a common food source. The transferred Wolbachia are then vertically transmitted to the new host's offspring. This natural and unexpectedly frequent horizontal transfer of parthenogensis-inducing Wolbachia intraspecifically has important implications for the co-evolution of Wolbachia and their host.

Animals↗
PubMed2005

Genetics of female functional virginity in the parthenogenesis-Wolbachia infected parasitoid wasp Telenomus nawai (Hymenoptera: Scelionidae).

A lepidopteran egg parasitoid species Telenomus nawai consists of two distinct populations with different reproductive modes. One is a completely thelytokous population consisting of females only, whereas the other displays arrhenotokous reproduction where fertilized eggs develop into diploid females and unfertilized eggs into haploid males. Thelytoky in T. nawai is caused by a bacterial symbiont, the parthenogenesis-inducing (PI) Wolbachia. Recent theoretical studies have shown that when a PI-Wolbachia is spreading in a population, mutations that allow uninfected females to produce more male offspring will spread rapidly eventually becoming fixed. The consequence of such a mutation is that sexual reproduction is no longer successful in infected females. Here we determine the genetic basis of the females' inability to reproduce sexually by introgressing the genome of a thelytokous line into an arrhenotokous line. The results suggest that the mutations are recessive and inherited either as a single-locus major gene with some modifiers, or as two partially linked loci.

Animals↗
PubMed1998

Phylogenetic analysis of parthenogenesis-inducing Wolbachia in the genus Aphytis (Hymenoptera: Aphelinidae).

Parthenogenesis-inducing intracellular bacteria of the genus Wolbachia are found in a variety of parasitoid wasp genera. The presence of Wolbachia in the uniparental Aphytis species A. lingnanensis Compere, A. diaspidis (Howard), A. chilensis Howard, and A. chrysomphali (Mercet) was tested using primers specific for the ftsZ gene. The symbiont was detected in all of these species. Wolbachia ftsZ genes that were sequenced from the four hosts show a high degree of similarity. Both the PCR with specific primers for group 'A' and phylogenetic analysis place these Wolbachia in group 'A'. The fact that the tested Aphytis species belong to different phylogenetic groups and harbour what seem to be almost identical Wolbachia, lends credence to the horizontal transmission hypothesis.

Animals↗
PubMed1990

Parthenogenesis in Xenopus eggs requires centrosomal integrity.

Xenopus eggs are laid arrested at second metaphase of meiosis lacking a functional centrosome. Upon fertilization, the sperm provides the active centrosome that is required for cleavage to occur. The injection of purified centrosomes mimics fertilization and leads to tadpole formation (parthenogenesis). In this work we show that the parthenogenetic activity of centrosomes is inactivated by urea concentrations higher than 2 M. The loss of activity is correlated with a progressive destruction of the centriolar cylinder and extraction of proteins. This shows that centrosomes are relatively sensitive to urea since complete protein unfolding and solubilization of proteins normally occurs at urea concentrations as high as 8-10 M. When present, the parthenogenetic activity is always associated with a pelletable fraction showing that it cannot be solubilized by urea. The parthenogenetic activity is progressively inactivated by salt concentrations higher than 2 M (NaCl or KCl). However, only a few proteins are extracted by these treatments and the centrosome ultrastructure is not affected. This shows that both parthenogenetic activity and centrosomal structure are resistant to relatively high ionic strength. Indeed, most protein structures held by electrostatic forces are dissociated by 2 M salt. The loss of parthenogenetic activity produced at higher salt concentrations, while the structure of the centrosome is unaffected, is an apparent paradox. We interpret this result as meaning that the native state of centrosomes is held together by forces that favor functional denaturation by high ionic strength. The respective effects of urea and salts on centrosomal structure and activity suggest that the centrosome is mainly held together by hydrogen and hydrophobic bonds. The in vitro microtubule nucleating activity of centrosomes can be inactivated at salt or urea concentrations that do not affect the parthenogenetic activity. Since egg cleavage requires the formation of microtubule asters, we conclude that the extracted or denatured microtubule nucleating activity of centrosomes can be complemented by components present in the egg cytoplasm. Both parthenogenetic and microtubule nucleating activities are abolished by protease treatments but resist nuclease action. Since we find no RNA in centrosomes treated by RNase, they probably do not contain a protected RNA. Taken together, these results are consistent with the idea that the whole or part of the centrosome structure acts as a seed to start the centrosome duplication cycle in Xenopus eggs.

Animals↗
PubMed1991

The origin and evolution of parthenogenesis in Heteronotia binoei (Gekkonidae): evidence for recent and localized origins of widespread clones.

The parthenogenetic form of the gecko lizard species Heteronotia binoei has an unusually broad geographic range and high genetic diversity. Restriction enzyme analysis revealed two basic types of mitochondrial DNA (mtDNA) among the parthenogens. One type is restricted to western populations. The other type, analyzed in detail here, was widespread, being found in populations from central to western Australia. The diversity within this widespread type was low. The variation among parthenogens from central to western Australia was similar to that found within local populations of the sexual species that provided the mtDNA, and was an order of magnitude less than the differentiation shown between sexual populations across the same geographic distance. Phylogenetic analysis revealed that the widespread type of mtDNA in the parthenogens is most closely related to mtDNAs from western populations of the "CA6" sexual parent. These data suggest that these parthenogenetic clones arose recently within a small geographic area, most probably in Western Australia. The parthenogens must have spread rapidly to occupy much of the central and western Australian deserts. This rapid and extensive range expansion provides strong evidence that parthenogenesis can be a successful strategy for lizards in an environment with low and unpredictable rainfall.

Animals↗
PubMed2003

Genetic variation in oocyte phenotype revealed through parthenogenesis and cloning: correlation with differences in pronuclear epigenetic modification.

Previous studies revealed that oocytes of different genetic strains (e.g, C57BL/6 and DBA/2) modify maternal and paternal pronuclei differently, affecting early preimplantation development. To determine whether these strain-dependent effects would also apply to oocyte modifications of somatic cell nuclei introduced during cloning procedures, we compared the efficiency of development of parthenogenetic and cloned embryos made with DBA/2, C57BL/6, and (B6D2)F1 oocytes. Our results reveal significant differences in the ability of oocytes of different genetic backgrounds to support parthenogenetic development in different culture media. Additionally, our results reveal oocyte strain-dependent differences in the ability to support cloned embryo development beyond what can be accounted for on the basis of differences in parthenogenesis. Thus, the previously documented differences in oocyte-directed parental genome modification are accompanied in the same strains by differences in the ability of oocytes to modify somatic cell nuclei and support clonal development, raising the possibility that these oocyte functions may be mediated by related mechanisms. These results provide a genetic basis for further studies seeking to identify specific genes that determine oocyte phenotype, as well as genes that determine the success of nuclear reprogramming and clonal development.

Animals↗