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PubMed1979

Enzyme polymorphism and cyclic parthenogenesis in Daphnia magna. II. Heterosis following sexual reproduction.

Cyclical parthenogenesis exaggerates the force of selection relative to recombination and will therefore enhance interlocus effects. Observations of electrophoretic variation in a natural population of Daphnia magna Straus (Crustacea: Cladocera) are interpreted in this light. Sexual reproduction led to Hardy-Weinberg equilibrium, but heterozygote excesses rapidly developed at each of three observed loci during subsequent parthenogenesis. Homozygote fecundity was often lower than that of heterozygotes; this may have been the cause of some of the observed frequency changes. The superior fitness of the enzyme heterozygotes does not imply that selection was necessarily acting on the enzyme loci thermselves, since apparent heterosis is the expected result of linkage disequilibrium.

Animals↗

PubMed1996

Reproductive strategies of the cat flea (Siphonaptera:Pulicidae): parthenogenesis and autogeny?

The objective of this study was to determine if there is evidence of parthenogenesis or autogenous reproduction in the cat flea, Ctenocephalides felis (Bouché). To examine parthenogenesis, 400 newly eclosed virgin female fleas were collected from a laboratory colony and 100 were placed into each of 4 feeding cages and fed bovine blood through a Parafilm membrane. Three of the feeding cages were monitored for egg production for 7 d and each group of 100 virgin female fleas produced an average 1,119 eggs per cage, but none was viable. Fifty male fleas were added to those 3 feeding cages on day 7, and within 24 h the female fleas began ovipositing fertile eggs and nearly quadrupled their egg output. The other cage in which no males were introduced served as a control and did not produce a single viable egg in the 14-d experimental period. A similar experiment examined the continuance of virgin females to lay nonviable eggs and it was found that they continued to lay nonviable eggs for at least 58 d. Egg production was also studied in unfed fleas and it was found that unfed fleas did not produce eggs. These results suggest that neither parthenogenetic reproduction nor autogeny are exhibited by the cat flea.

Animals↗

PubMed2005

Dynamics of microtubules and positioning of female pronucleus during bovine parthenogenesis.

The zygote centrosome, consisting of both paternal and maternal centrosomal components, is the microtubule-organizing center necessary for pronuclear migration and positioning in fertilization. Maternal centrosomal function in microtubule organization and pronuclear positioning, however, remains unclear. In the present study, we sought to elucidate the function of maternal centrosomes during bovine parthenotes in the microtubule organizational processes required to move the pronucleus to the cell center without sperm centrosomal components. Microtubule organization, pronuclear position, and distribution of gamma-tubulin, which is thought to be the major component of maternal centrosomal material, were imaged by immunocytochemistry and conventional epifluorescence microscopy. In bovine parthenotes treated with paclitaxel, a microtubule-stabilizing drug, the cytoplasmic microtubule asters became organized after chemical activation, and the microtubules radiated dynamically toward the female pronucleus. The microtubule patterns correlated well with pronuclear movement to the cell center. Microtubules aggregated at regions of gamma-tubulin concentration, but gamma-tubulin did not localize to a spot until the first interphase of bovine parthenogenesis. These findings indicate that gamma-tubulin is responsible for microtubule organization as the maternal centrosome. In bovine parthenogenesis, the maternal centrosome then organizes cytoplasmic microtubules to move the female pronucleus into the cell center. We propose that the maternal centrosome plays a role as a functional centrosome despite the lack of a sperm contribution, making this structure less competent for microtubule organization in comparison with centrosomes containing sperm centrosomal components.

Animals↗

PubMed1997

Horizontal transmission of parthenogenesis-inducing microbes in Trichogramma wasps.

Complete parthenogenesis (thelytoky) in species of the parasitic wasp Trichogramma is usually caused by the cytoplasmically inherited bacterium Wolbachia. This symbiont induces gamete duplication, which, in these haplodiploid organisms, results in all-female broods. Antibiotic treatment "cures' this condition, restoring normal sexual reproduction. Phylogenetic analysis of Wolbachia has shown that, in contrast with the strains in other host organisms (where the symbiont also induces different reproductive alterations), those in Trichogramma form a monophyletic group. This might be an indication of symbiont-host cocladogenesis. To test this, we performed comparative molecular phylogenetics on 20 parthenogenetic Trichogramma cultures and their Wolbachiae. We conclude that there is, in fact, little evidence for cocladogenesis. Instead, the phylogenetic distribution of the symbionts appears to result from occasional horizontal transmission, which probably takes place inside the hosts of Trichogramma parasitoids (usually lepidopteran eggs). This study therefore suggests that parthenogenesis is not only curable, it can sometimes be contagious also.

Alphaproteobacteria↗

PubMed2001

Wolbachia-mediated parthenogenesis in the predatory thrips Franklinothrips vespiformis (Thysanoptera: Insecta).

Wolbachia are bacterial endosymbionts in arthropods and filarial nematodes. They cause thelytoky, which is a form of parthenogenesis in which females produce females without males, in hymenopteran insects. Infection of this parthenogenesis-inducing Wolbachia has been restricted to the order Hymenoptera, but was found in another insect order, Thysanoptera. A parthenogenetic colony of a predatory thrips Franklinothrips vespiformis (Aeolothripidae) possessed B-group Wolbachia. Male progeny were produced from this thrips by heat and tetracycline treatments. Males produced motile sperm, which were transferred to the female spermatheca by mating. However, the mating did not affect the sex ratios of the next generation, suggesting that the sperm do not fertilize the eggs.

Animals↗

PubMed2004

Natural interspecific and intraspecific horizontal transfer of parthenogenesis-inducing Wolbachia in Trichogramma wasps.

The intracellular bacterium Wolbachia is one of the most common symbionts in arthropods and, because of its manipulative effects on host reproduction, is assumed to be an important factor in several evolutionary processes. These bacteria are mainly vertically transmitted from mother to daughter through the egg cytoplasm, and horizontal transmission is generally assumed to be rare. Here, we show natural inter- and intraspecific horizontal transfer of parthenogenesis-inducing Wolbachia between parasitoid wasps of the genus Trichogramma. Horizontal transfer was observed when infected and uninfected larvae shared the same host egg. This is the first report, to our knowledge, on interspecific horizontal transfer of Wolbachia between closely related sympatric species. Some originally uninfected immature wasps acquired Wolbachia while inside the host egg, but not all of these newly infected females exhibited the parthenogenesis phenotype. In general, intraspecific horizontal transfer was more successful than interspecific transfer. Wolbachia underwent vertical transmission in the new species but the infection tended to be lost within several generations. Our results have important implications for understanding the evolution of Wolbachia-host associations.

Animals↗

PubMed2003

The Australian scincid lizard Menetia greyii: a new instance of widespread vertebrate parthenogenesis.

Molecular data derived from allozymes and mitochondrial nucleotide sequences, in combination with karyotypes, sex ratios, and inheritance data, have revealed the widespread Australian lizard Menetia greyii to be a complex of sexual and triploid unisexual taxa. Three sexual species, three presumed parthenogenetic lineages, and one animal of uncertain status were detected amongst 145 animals examined from south-central Australia, an area representing less than one-seventh of the total distribution of the complex. Parthenogenesis appears to have originated via interspecific hybridization, although presumed sexual ancestors could only be identified in two cases. The allozyme and mtDNA data reveal the presence of many distinct clones within the presumed parthenogenetic lineages. This new instance of vertebrate parthenogenesis is a first for the Scincidae and only the second definitive case of unisexuality in an indigenous Australian vertebrate.

Animals↗

PubMed2006

Patterns of recurrent evolution and geographic parthenogenesis within apomictic polyploid Easter daises (Townsendia hookeri).

Geographic patterns of parthenogenesis and the number of transitions from sexual diploidy to asexual (apomictic) autopolyploidy were examined for 40 populations of the Easter daisy, Townsendia hookeri. Analyses of pollen diameter and stainability characterized 15 sexual diploid and 25 apomictic polyploid populations from throughout the plant's western North American range. Sexual diploids were restricted to two Wisconsin refugia: Colorado/Wyoming, south of the ice sheets, and northern Yukon/Beringia. Chloroplast DNA sequencing uncovered 17 polymorphisms within the ndhF gene and trnK intron, yielding 10 haplotypes. Phylogenetic analyses indicated that five exclusively polyploid haplotypes were derived from four haplotypes that are shared among ploidies, conservatively inferring a minimum of four origins of apomictic polyploidy. Three of these apomictic polyploid origins were derived from southern sexual diploids, while the fourth origin was derived from northern sexual diploids. Analyses of regional diversity were suggestive of a formerly broad distribution for sexual diploids that has become subsequently fragmented, possibly due to the last round of glaciation. As sexual diploids were exclusively found north and south of the glacial maximum, while formerly glaciated areas were exclusively inhabited by asexual polyploids derived from both northern and southern sexual lineages, it is more likely that patterns of glaciation, as opposed to a particular latitudinal trend, played a causal role in the establishment of the observed pattern of geographic parthenogenesis in Easter daisies.

Asteraceae↗

PubMed2004

Conditional use of sex and parthenogenesis for worker and queen production in ants.

The near-ubiquity of sexual reproduction in animal species has long been considered a paradox because sexually reproducing individuals transmit only half of their genome to their progeny. Here, we show that the ant Cataglyphis cursor circumvents this cost by using alternative modes of reproduction for the production of reproductive and nonreproductive offspring. New queens are almost exclusively produced by parthenogenesis, whereas workers are produced by normal sexual reproduction. By selectively using sex for somatic growth and parthenogenesis for germline production, C. cursor has taken advantage of the ant caste system to benefit from the advantages of both sexual and asexual reproduction.

Alleles↗

PubMed2005

Can artificial parthenogenesis sidestep ethical pitfalls in human therapeutic cloning? An historical perspective.

The aim of regenerative medicine is to reconstruct tissue that has been lost or pathologically altered. Therapeutic cloning seems to offer a method of achieving this aim; however, the ethical debate surrounding human therapeutic cloning is highly controversial. Artificial parthenogenesis-obtaining embryos from unfertilised eggs-seems to offer a way to sidestep these ethical pitfalls. Jacques Loeb (1859-1924), the founding father of artificial parthenogenesis, faced negative public opinion when he published his research in 1899. His research, the public's response to his findings, and his ethical foundations serve as an historical argument both for the communication of science and compromise in biological research.

Attitude of Health Personnel↗

PubMed2002

Lack of parthenogenesis by Amblyomma cajennense (Acari: Ixodidae).

Some reproductive parameters of adult stages of Amblyomma cajennense ticks were studied. The capacity of virgin females to reproduce by parthenogenesis was evaluated, during an experimental infestation, in absence of males, on a horse (Equus cabalus). Ticks were spread either completely free or in limited sites on the body of the animal. The engorged virgin females showed longer feeding periods and lighter body weights than those that had been fertilized. Some of these unmated females produced smaller egg masses, which had no embryonary development. On the other hand, females that had been inseminated produced larger egg masses, with normal embryonary development that led to viable larvae. Under the studied conditions, A. cajennense females did not reproduce by parthenogenesis.

Animals↗

PubMedDate not supplied

[Parthenogenesis in mammals].

A review of studies dealing with spontaneous and induced parthenogenesis in mammals. The main methods of artificial egg activation, ways of their development and causes of mortality of the parthenogenetic mouse embryos are considered. The possibilities of using parthenogenesis for solving urgent problems of mammalian developmental biology are estimated and prospects of further studies in this field are outlined.

Animals↗

PubMed1984

[In vitro parthenogenesis in the human species].

During the examination of some 800 oocytes prior to in vitro fertilization, twelve exhibited evidence of parthogenetic activation. Four of these twelve underwent cleavage, the cleavage of one being normal. In vitro parthenogenesis is compared with two forms of parthenogenesis observed in vivo, namely ovarian teratomas and hydatidiforms moles.

Female↗

PubMed1995

Parthenogenesis in schistosomatidae.

Among which species, in what situations and how, does parthenogenesis occur in the biology of reproduction of schistosomes? Here, José Jourdane, Daniéle Imbert-Establet and Louis Albert Tchuem Tchuenté review the literature on parthenogenesis in schistosomes, and debate the evolutionary aspects of this type of reproduction.

Journal Article↗

PubMed2003

Maternal gamma (gamma)-tubulin is involved in microtubule reorganization during bovine fertilization and parthenogenesis.

In this study, gamma-tubulin distribution was determined chronologically in conjunction with microtubule dynamics during bovine fertilization and parthenogenesis. In unfertilized bovine oocytes, gamma-tubulin was identified in the cytoplasm, mainly in the cortex and concentrated in the meiotic spindle. Following sperm penetration, gamma-tubulin in the cytoplasm was recruited by a sperm component. During pronuclear apposition, gamma-tubulin was localized as spots at the spindle poles. gamma-tubulin spots were observed in blastomeres of embryos cleaved in vitro. Following electrical stimulation, gamma-tubulin and microtubule matrix were noted in oocyte cortex. In the late pronuclear stage, considerably less gamma-tubulin and microtubules were detected in the cytoplasm. At the mitotic metaphase of parthenotes, gamma-tubulin was recruited to the condensed chromatin and concentrated in the spindle. The gamma-tubulin spots were not detected until the 8-cell stage of parthenotes. This suggests that maternal gamma-tubulin is recruited by a sperm component to reconstitute the zygotic centrosome. In the absence of sperm components, the cell cycle-related assembly of gamma-tubulin organizes microtubule nucleation for positioning the pronucleus and spindle protein of mitotic metaphase during the first cell cycle of bovine parthenotes.

Animals↗

PubMed1994

Microtubule organization in the cow during fertilization, polyspermy, parthenogenesis, and nuclear transfer: the role of the sperm aster.

Microtubule organization in bovine oocytes during fertilization, polyspermy, parthenogenesis, and nuclear transfer is examined with the goal of understanding microtubule activity and the manner in which the centrosome during fertilization and mitotic spindle poles are established. In the unfertilized bovine oocyte, microtubules are detected only in the metaphase-arrested second meiotic spindle; no cytoplasmic asters are observed. After insemination, a small aster of microtubules is seen adjacent to the incorporated sperm head. This aster enlarges and, at the time of pronuclear apposition, fills the cytoplasm. At prophase, the aster splits and forms the poles for the first mitotic spindle, which is anastral, fusiform, and often located eccentrically. During anaphase, asters assemble at each spindle pole. After telophase, these asters develop into the interphase array of microtubules in the daughter blastomeres. During polyspermy, an aster forms from a site between each incorporated sperm head and tail. Multiple mitotic spindles are observed in polyspermic zygotes; multipolar spindles are not seen. Parthenogenetic activation with 5 microns ionomycin followed by a 4-hr incubation in 1.9 mM dimethylaminopurine results in > 80% activation, and antitubulin immunofluorescence microscopy demonstrates that initially disarrayed microtubules are observed and the some microtubules extend from the remnants of the second meiotic spindle. At the time normal for cell division, these parthenogenotes form anastral, barrel-shaped bipolar mitotic spindles. Asters form at the spindle poles at anaphase and the parthenogenotes divide from one to two blastomeres. Nuclear fusion of a morula-derived blastomere to a parthenogenetically activated oocyte results in either a single microtubule aster or at times, two asters, formed in association with the donated nucleus. These results demonstrate that fertilization in the cow is a blending of paternally and maternally derived centrosomal material.

Animals↗

PubMed1995

Parthenogenesis in Urechis caupo (Echiura). I. Persistance of functional maternal asters following activation without meiosis.

A peptide (P23) isolated from sperm acrosomal protein initiates development in eggs of the marine worm Urechis caupo (Echiura). However, in these earlier experiments the eggs were exposed continuously to P23 and did not cleave unless they were provided with a sperm centrosome. The present study reports that parthenogenetic cleavage can be induced when the eggs are exposed to P23 for 1.5 to 2 min in seawater at pH 8 followed by acidifying the seawater to pH 7 or washing off the peptide at pH 7 or 8. The mechanism of parthenogenesis induction was studied by comparing the behavior of maternal and paternal centrosomes (microtubule organizing centers), chromosomes, nuclei and nucleoli in fertilized eggs, P23-activated eggs that failed to cleave, and P23-activated eggs that cleaved, using bright-field, phase-contrast, and fluorescence microscopy following anti-tubulin and bis-benzimide staining. Parthenogenetic cleavage to mostly diploid embryos occurred in eggs that underwent germinal vesicle breakdown without polar body formation. The centrosomes used for cleavage were the persistent maternal centrosomes that did not cycle through meiosis. When cytochalasin B was used to suppress polar body formation without inhibiting the meiotic cycles, eggs did not subsequently cleave even though all four maternal centrosomes were retained. When fertilized eggs were transferred to pH 7 seawater at 1.5 to 2 min after insemination, they underwent a partial activation like the P23-activated eggs and did not form polar bodies. Subsequent cleavage was very abnormal due to the presence of multiple asters formed by the persistant active maternal centrosomes. These results show that maternal centrosomes are normally inactivated by a maternal mechanism associated with meiotic cycling.

Animals↗

PubMed2006

Paternal dual barrier by Ifg2-H19 and Dlk1-Gtl2 to parthenogenesis in mice.

The functional difference between the maternal and paternal genome, which is characterized by epigenetic modifications during gametogenesis, that is genomic imprinting, prevents mammalian embryos from parthenogenesis. Genomic imprinting leads to nonequivalent expression of imprinted genes from the maternal and paternal alleles. However, our research showed that alteration of maternal imprinting by oocyte reconstruction using nongrowing oocytes together with deletion of the H19 gene, provides appropriate expression of maternally imprinted genes. Here we discuss that further alteration of paternally imprinted gene expressions at chromosomes 7 and 12 allows the ng/fg parthenogenetic embryos to develop to term, suggesting that the paternal contribution is obligatory for the descendant.

Animals↗