Fertile Offspring Research Articles

P–805 Artificial oocytes: from somatic cells to fertile pups

Abstract Study question We analyzed the efficacy of generating artificial oocytes using somatic cells (SCs) from two mouse strains (B6D2F1 and FVB) and followed their full pre-/post-implantation development. Summary answer While artificial oocytes generated from the new strain (FVB) had higher fertilization rates, those from the standard strain (B6D2F1) provided expanded blastocysts and fertile pups. What is known already B6D2F1 is a popular hybrid mouse strain for cloning and transgenic creation due to its geno-/pheno-typic uniformity and high oocyte yield and quality. Indeed, B6D2F1 oocytes have a distinct metaphase II (MII) spindle complex, making them an ideal candidate to generate ooplasts used in SC nuclear transfer (SCNT). However, because they lack genetic variance, they are less suitable for reciprocal SCNT studies. In contrast, FVB mice have single nucleotide polymorphisms and indels on each chromosome that can aid in tracing the pedigree of progeny. Study design, size, duration A total of 10 experiments were performed over the course of 3 months, using 30 stimulated mice. SCs were retrieved from cumulus oophorus harvested from FVB and B6D2F1 mice. SCs from both strains were injected into enucleated MII B6D2F1 oocytes. Unmanipulated B6D2F1 oocytes were piezo-ICSI inseminated, serving as controls. The occurrence of haploidization, fertilization, and full preimplantation development was compared. Some blastocysts were transferred into pseudo-pregnant CD–1 mice to obtain offspring. Participants/materials, setting, methods Oocyte enucleation was performed under Oosight™ visualization and cytochalasin B exposure. An FVB or B6D2F1 SC was transferred into the perivitelline space of the ooplast with Sendai virus to promote fusion. Haploidization was monitored by pseudo-meiotic spindle formation followed by extrusion of a pseudo-polar body after insemination. Conceptuses were cultured in a time-lapse imaging system, with piezo-ICSI controls. Expanded blastocysts were transferred into uterine horns of pseudo-pregnant mice. Offspring were mated to test their fertility. Main results and the role of chance FVB (n = 278) and B6D2F1 (n = 905) SCs at G0 phase, with a diameter <10 mm, were chosen for SCNT and transferred into enucleated B6D2F1 ooplasts. Enucleation of 1,212 oocytes yielded a survival rate of 97.6%. Both FVB and B6D2F1 SCNT resulted in similar survival rates of 100% and 98.5%, respectively. Successful haploidization, determined by the presence of a pseudo-meiotic spindle 2 hours after SCNT, was also comparable, with 59.9% of FVB and 63.7% of B6D2F1. Survival after piezo-ICSI was also comparable between FVB- and B6D2F1-reconstituted oocytes, with rates of 64.3% and 60.3%, respectively, albeit lower than the control (75.2%, P < 0.00001). FVB embryos fertilized at a rate of 88.7%, comparable to the control zygotes at 85.8%, while B6D2F1 conceptuses demonstrated a lower fertilization rate (70.8%, P < 0.00001). Blastulation of FVB- and B6D2F1-derived embryos was 15.1% and 24.0%, respectively, while the control was 80.7% (P < 0.00001). Whole-genome karyotyping of 9 B6D2F1-derived blastocysts confirmed 5 of the samples to be euploid. FVB blastocysts (N = 8) and B6D2F1 blastocysts (N = 81) were transferred into pseudo-pregnant mice, resulting in 3 fertile offspring only from the B6D2F1 conceptuses. Limitations, reasons for caution This is still a limited number of observations, and pups were delivered only from the B6D2F1 strain. The utilization of a strain with higher genetic variance may help facilitate offspring fingerprinting. Wider implications of the findings: This study demonstrates the ability to generate artificial genotyped conceptuses, yielding live offspring. The identification of a feasible donor cell, together with optimization of cell cycle stage and standardization of post-implantation development, will help promote this technique for human reproduction in couples with age-related infertility or poor ovarian reserve. Trial registration number N/A

Hybridization with mountain hares increases the functional allelic repertoire in brown hares

Brown hares (Lepus europaeus Pallas) are able to hybridize with mountain hares (L. timidus Linnaeus) and produce fertile offspring, which results in cross-species gene flow. However, not much is known about the functional significance of this genetic introgression. Using targeted sequencing of candidate loci combined with mtDNA genotyping, we found the ancestral genetic diversity in the Finnish brown hare to be small, likely due to founder effect and range expansion, while gene flow from mountain hares constitutes an important source of functional genetic variability. Some of this variability, such as the alleles of the mountain hare thermogenin (uncoupling protein 1, UCP1), might have adaptive advantage for brown hares, whereas immunity-related MHC alleles are reciprocally exchanged and maintained via balancing selection. Our study offers a rare example where an expanding species can increase its allelic variability through hybridization with a congeneric native species, offering a route to shortcut evolutionary adaptation to the local environmental conditions.

High macro-collinearity between Crassostrea angulata and C. gigas genomes was revealed by comparative genetic mapping with transferable EST-SNP markers

Comparative genomics has become an important strategy for transferring genetic information from a well-characterized model species to one that is less described and can facilitate in functional gene mining and genomic evolution. Crassostrea angulata and Crassostrea gigas are closed related species that they can hybridize to produce fertile offspring, and C. gigas has accumulated a considerable number of genetic and genomic resources while C. angulata lags far behind. In the current study, 684 single nucleotide polymorphism (SNP) markers developed from C. gigas expressed sequence tags (ESTs) were used for transferability test in C. angulata, and 635 loci were successfully amplified. Then a genetic linkage map of C. angulata was for the first time constructed using these transferable SNP markers. A total of 988 transferable SNP markers were used for polymorphism screening in a mapping family, and 273 loci were distributed on the genetic map which was composed of 10 linkage groups and estimated 1040.29 cM in total length. The average spacing between markers was 3.96 cM. By comparing the shared EST-SNP marker locations on homologous linkage groups, comparative mapping analysis between the C. angulata genetic map and an integrated map of C. gigas revealed putative macro-collinearity in the two oyster genomes with little difference in markers order. These transferable SNP markers could be applied in genetic diversity and population structure studies, and the genetic map would be useful for quantitative trait loci mapping and genetic improvement through marker-assisted selection for C. angulata.

Trends in taxonomy of Triatomini (Hemiptera, Reduviidae, Triatominae): reproductive compatibility reinforces the synonymization of Meccus St\xe5l, 1859 with Triatoma Laporte, 1832

BackgroundMeccus' taxonomy has been quite complex since the first species of this genus was described by Burmeister in 1835 as Conorhinus phyllosoma. In 1859 the species was transferred to the genus Meccus and in 1930 to Triatoma. However, in the twentieth century, the Meccus genus was revalidated (alteration corroborated by molecular studies) and, in the twenty-first century, through a comprehensive study including more sophisticated phylogenetic reconstruction methods, Meccus was again synonymous with Triatoma. Events of natural hybridization with production of fertile offspring have already been reported among sympatric species of the T. phyllosoma subcomplex, and experimental crosses demonstrated reproductive viability among practically all species of the T. phyllosoma subcomplex that were considered as belonging to the genus Meccus, as well as between these species and species of Triatoma. Based on the above, we carried out experimental crosses between T. longipennis (considered M. longipennis in some literature) and T. mopan (always considered as belonging to Triatoma) to evaluate the reproductive compatibility between species of the T. phyllosoma complex. In addition, we have grouped our results with information from the literature regarding crosses between species that were grouped in the genus Meccus with Triatoma, in order to discuss the importance of experimental crosses to confirm the generic reorganization of species.ResultsThe crosses between T. mopan female and T. longipennis male resulted in viable offspring. The hatching of hybrids, even if only in one direction and/or at low frequency, demonstrates reproductive compatibility and homeology between the genomes of the parents.ConclusionConsidering that intergeneric crosses usually do not result in viable offspring in Triatominae, the reproductive compatibility observed between the T. phyllosoma subcomplex species considered in the Meccus genus with species of the Triatoma genus shows that there is “intergeneric” genomic compatibility, which corroborates the generic reorganization of Meccus in Triatoma.Graphical

Queen loss increases worker survival in leaf-cutting ants under paraquat-induced oxidative stress.

Longevity is traded off with fecundity in most solitary species, but the two traits are positively linked in social insects. In ants, the most fecund individuals (queens and kings) live longer than the non-reproductive individuals, the workers. In many species, workers may become fertile following queen loss, and recent evidence suggests that worker fecundity extends worker lifespan. We postulated that this effect is in part owing to improved resilience to oxidative stress, and tested this hypothesis in three Myrmicine ants: Temnothorax rugatulus, and the leaf-cutting ants Atta colombica and Acromyrmex echinatior. We removed the queen from colonies to induce worker reproduction and subjected workers to oxidative stress. Oxidative stress drastically reduced survival, but this effect was less pronounced in leaf-cutting ant workers from queenless nests. We also found that, irrespective of oxidative stress, outside workers died earlier than inside workers did, likely because they were older. Since At. colombica workers cannot produce fertile offspring, our results indicate that direct reproduction is not necessary to extend the lives of queenless workers. Our findings suggest that workers are less resilient to oxidative stress in the presence of the queen, and raise questions on the proximate and ultimate mechanisms underlying socially mediated variation in worker lifespan. This article is part of the theme issue 'Ageing and sociality: why, when and how does sociality change ageing patterns?'

Rescue of male infertility through correcting a genetic mutation causing meiotic arrest in spermatogonial stem cells.

Azoospermia patients who carry a monogenetic mutation that causes meiotic arrest may have their biological child through genetic correction in spermatogonial stem cells (SSCs). However, such therapy for infertility has not been experimentally investigated yet. In this study, a mouse model with an X-linked testis-expressed 11 (TEX11) mutation (Tex11PM/Y) identified in azoospermia patients exhibited meiotic arrest due to aberrant chromosome segregation. Tex11PM/Y SSCs could be isolated and expanded in vitro normally, and the mutation was corrected by clustered regularly interspaced short palindromic repeats (CRISPR)–CRISPR-associated endonuclease 9 (Cas9), leading to the generation of repaired SSC lines. Whole-genome sequencing demonstrated that the mutation rate in repaired SSCs is comparable with that of autonomous mutation in untreated Tex11PM/Y SSCs, and no predicted off-target sites are modified. Repaired SSCs could restore spermatogenesis in infertile males and give rise to fertile offspring at a high efficiency. In summary, our study establishes a paradigm for the treatment of male azoospermia by combining in vitro expansion of SSCs and gene therapy.

ZbAGL11, a class D MADS-box transcription factor of Zanthoxylum bungeanum, is involved in sporophytic apomixis

Apomixis is a reproductive model that bypasses sexual reproduction, so it does not require the combination of paternal and maternal gametes but instead results in the production of offspring directly from maternal tissues. This reproductive mode results in the same genetic material in the mother and the offspring and has significant applications in agricultural breeding. Molecular and cytological methods were used to identify the reproductive type of Zanthoxylum bungeanum (ZB). Fluorescence detection of the amplified products of 12 pairs of polymorphic SSR primers showed consistent fluorescence signals for mother and offspring, indicating that no trait separation occurred during reproduction. In addition, the cytological observation results showed differentiation of ZB embryos (2n) from nucellar cells (2n) to form indefinite embryonic primordia and then form adventitious embryos (2n), indicating that the apomictic type of ZB is sporophytic apomixis. The MADS-box transcription factor ZbAGL11 was highly expressed during the critical period of nucellar embryo development in ZB. Unpollinated ZbAGL11-OE Arabidopsis produced fertile offspring and exhibited an apomictic phenotype. The overexpression of ZbAGL11 increased the callus induction rate of ZB tissue. In addition, the results of the yeast two-hybrid experiment showed that ZbAGL11 could interact with the ZbCYP450 and ZbCAD11 proteins. Our results demonstrate that ZbAGL11 can cause developmental disorders of Arabidopsis flower organs and result in apomixis-like phenotypes.

The effect of sodium thiosulfate in a culture medium on the sexual reproduction of three species of Bacillariophyta

It was studied the effect of sulfur in the form of sodium thiosulfate pentahydrate on the capability of clonal cultures of Pleurosigma sp., Toxarium undulatum, Pseudo-nitzschia calliantha to interbreed successfully and produce fertile offspring if they were cultivated in artificially prepared marine water (ESAW medium). Differences in the time of the beginning of the sexual process and the intensity of its passage for clones contained on ESAW with the addition of sodium thiasulfate and in the absence of it are shown.

Weed invasive

Biological invasions are increasingly attracting the attention of ecologists, so it seems that this phenomenon is relatively new. However, the beginning of the study of biological invasions is publication of the book "The Ecology of Invasions by Animals and Plants" (1958), which is classified as classic works of invasions. Research of biological invasion is focused on the study of crucial biological and ecological characteristics which enable species invasiveness, as well as the characteristics of the recipient community. Despite the intensive study of this phenomenon, there are still differing views whether only introduced alien species or even native species can be considered as invasive species. While some researchers consider that native species cannot belong to the invasive category, others thought that a species that is native, when expend to adjacent habitats, may also be considered as invasive. Understanding biological invasions as if there no difference between native and introduced allochthonous species eliminates the dilemma that arises in the case of cryptogenic species (species that cannot be clearly classified into one of these two groups), whether it is native or introduced species, the success of the spreading depends on ecological adaptations. In addition, there is also disagreement about the stages of biological invasions. One point of view is, invasion processes take place through three phases (introduction, colonization and naturalization), while to other, the introduction is an elementary requirement for invasion, colonization is an integral part of the concept of naturalization, and naturalization which is referred in to previous point of view, is the phase that corresponds to the term "invasiveness". The time and route of introduction, as well as the mode and pathways of spreading for a large number of adventitious weed species have not been precisely established. Depending on whether weed species are introduce accidentally or intentionally, they are divided into boyletophytes (intentionally introduce) and aboyletophytes (accidentally introduce), while according to period of introduction they are divided into archeophytes (introduced in the Paleozoic to Neolithic period), paleophytes (introduced during the Old and Middle Ages until the discovery of America), neophytes (introduced after the discovery of America until to World War II), and neotophytes (introduced from the World War II until nowadays). Invasive processes are very complex, and it is not easy to predict and evaluate the behavior of introduced species in a new environment. Depending on the shape, structure and size of the reproductive organs, invasive weeds can be spread in several ways: autochthonous (selfpropagating), anemohoric (spreading through the wind), hydrohorn (spreading through water), zohornous (spreading by animals) and anthroporous (spreading by human). The success of invasive processes depends on the ecological characteristics of species, environmental resources and degree of ecosystem damage into which species has reached. According to success of survival in the new environment, allochthonous species can have status of the ephemeral (species which temporarily retained in the new environment and do not form stable populations), naturalized (species that are maintained in the new habitat but do not have an expansive character) and invasive (species that are adapted to the new habitat, spreading, forming indigenous part of flora and leave fertile offspring). The ecological-genetic potential of these species is the result of genetic diversity and their capacity for ecological adaptation; mutations, recombination, hybridization and introgression are the main processes responsible for genetic diversity. In the area of introduction, allochthonous species manifest numerous negative impacts on agriculture, ecosystems, human and domestic animal health, socioeconomic relationships and can jeopardize the survival of native species. Invasions are generally classified as negative occurrences, although in some circumstances they may also have a positive effect on the environment. For example, introduction of allochthonous species can enrich biodiversity, in case when number of introduced species far exceeds the number of extinct species. Despite the great scientific and technological progress, the problem of biological invasions cannot be completely resolved, but it is possible to limit these processes and reduce their negative consequences. The European and Mediterranean Plant Protection Organization (EPPO) dedicate special attention to the risks of invasive plant species and recommends measures to prevent their introduction and spread, with special reference to organisms that cause damage in agriculture. Control of these species implies application of all available preventive and direct measures, integrated into a system of integral measures.

Development and Cytomolecular Identification of Monosomic Alien Addition and Substitution Lines of Triticale (×Triticosecale Wittmack) With 2Sk Chromosome Conferring Leaf Rust Resistance Derived From Aegilops kotschyi Boiss.

Alien chromosome introgression has become a valuable tool to broaden the genetic variability of crop plants via chromosome engineering. This study details the procedure to obtain monosomic addition and monosomic substitution lines of the triticale carrying 2Sk chromosome from Aegilops kotchyi Boiss., which harbors Lr54 + Yr37 leaf and stripe rust-resistant gene loci, respectively. Initially, A. kotschyi × Secale cereale artificial amphiploids (2n = 6x = 42 chromosomes, UUSSRR) were crossed with triticale cv. “Sekundo” (2n = 6x = 42, AABBRR) in order to obtain fertile offspring. Cyto-molecular analyses of five subsequent backcrossing generations revealed that 2Sk chromosome was preferentially transmitted. This allowed for the selection of monosomic 2Sk addition (MA2Sk) lines of triticale. Finally, the 2Sk(2R) substitution plants were obtained by crossing MA2Sk with the nullisomic (N2R) plants of triticale. The presence of 2Sk chromosome in subsequent generations of plants was evaluated using SSR markers linked to Lr54 + Yr37 loci. Disease evaluation of the monosomic 2Sk(2R) substitution plants for the reaction to leaf and stripe rust infection were carried out under controlled conditions in a growth chamber. The results showed significant improvement of leaf rust resistance severity of monosomic substitution plants compared with control (“Sekundo”). In contrast, the introgression of the Lr54 + Yr37 loci did not lead to improvement of stripe rust resistance. In summary, the creation of monosomic addition and monosomic substitution lines of triticale is the starting point for the precise and guided transfer of Lr54 + Yr37 loci. The results showed that the developed materials could be exploited for the development of triticale varieties with resistance to leaf rust.

Morphological description of a novel synthetic allotetraploid(A1A1G3G3) of Gossypium herbaceum L.and G.nelsonii Fryx. suitable for disease-resistant breeding applications.

Wild species of Gossypium ssp. are an important source of traits for improving commercial cotton cultivars. Previous reports show that Gossypium herbaceum L. and Gossypium nelsonii Fryx. have better disease resistance characteristics than commercial cotton varieties. However, chromosome ploidy and biological isolation make it difficult to hybridize diploid species with the tetraploid Gossypium hirsutum L. We developed a new allotetraploid cotton genotype (A1A1G3G3) using a process of distant hybridization within wild cotton species to create new germplasms. First of all, G. herbaceum and G. nelsonii were used for interspecific hybridization to obtain F1 generation. Afterwards, apical meristems of the F1 diploid cotton plants were treated with colchicine to induce chromosome doubling. The new interspecific F1 hybrid and S1 cotton plants originated from chromosome duplication, were tested via morphological and molecular markers and confirmed their tetraploidy through flowrometric and cytological identification. The S1 tetraploid cotton plants was crossed with a TM-1 line and fertile hybrid offspring were obtained. These S2 offsprings were tested for resistance to Verticillium wilt and demonstrated adequate tolerance to this fungi. The results shows that the new S1 cotton line could be used as parental material for hybridization with G. hirsutum to produce pathogen-resistant cotton hybrids. This new S1 allotetraploid genotype will contributes to the enrichment of Gossypium germplasm resources and is expected to be valuable in polyploidy evolutionary studies.

Cyclosporin A and FGF signaling support the proliferation/survival of mouse primordial germ cell-like cells in vitro†.

Primordial germ cells (PGCs) are the founding population of the germ cell lineage that undergo a multistep process to generate spermatozoa or oocytes. Establishing an appropriate culture system for PGCs is a key challenge in reproductive biology. By a chemical screening using mouse PGC-like cells (mPGCLCs), which were induced from mouse embryonic stem cells, we reported previously that forskolin and rolipram synergistically enhanced the proliferation/survival of mPGCLCs with an average expansion rate of ~20-fold. In the present study, we evaluated other chemicals or cytokines to see whether they would improve the current mPGCLC culture system. Among the chemicals and cytokines examined, in the presence of forskolin and rolipram, cyclosporin A (CsA) and fibroblast growth factors (FGFs: FGF2 and FGF10) effectively enhanced the expansion of mPGCLCs in vitro (~50-fold on average). During the expansion by CsA or FGFs, mPGCLCs comprehensively erased their DNA methylation to acquire a profile equivalent to that of gonadal germ cells in vivo, while maintaining their highly motile phenotype as well as their transcriptional properties as sexually uncommitted PGCs. Importantly, these mPGCLCs robustly contributed to spermatogenesis and produced fertile offspring. Furthermore, mouse PGCs (mPGCs) cultured with CsA ex vivo showed transcriptomes and DNA methylomes similar to those of cultured mPGCLCs. The improved culture system for mPGCLCs/mPGCs would be instructive for addressing key questions in PGC biology, including the mechanisms for germ cell migration, epigenetic reprogramming, and sex determination of the germline.

Using genomic resources for linkage analysis in Peromyscus with an application for characterizing Dominant Spot

BackgroundPeromyscus are the most common mammalian species in North America and are widely used in both laboratory and field studies. The deer mouse, P. maniculatus and the old-field mouse, P. polionotus, are closely related and can generate viable and fertile hybrid offspring. The ability to generate hybrid offspring, coupled with developing genomic resources, enables researchers to conduct linkage analysis studies to identify genomic loci associated with specific traits.ResultsWe used available genomic data to identify DNA polymorphisms between P. maniculatus and P. polionotus and used the polymorphic data to identify the range of genetic complexity that underlies physiological and behavioral differences between the species, including cholesterol metabolism and genes associated with autism. In addition, we used the polymorphic data to conduct a candidate gene linkage analysis for the Dominant spot trait and determined that Dominant spot is linked to a region of chromosome 20 that contains a strong candidate gene, Sox10. During the linkage analysis, we found that the spot size varied quantitively in affected Peromyscus based on genetic background.ConclusionsThe expanding genomic resources for Peromyscus facilitate their use in linkage analysis studies, enabling the identification of loci associated with specific traits. More specifically, we have linked a coat color spotting phenotype, Dominant spot, with Sox10, a member the neural crest gene regulatory network, and that there are likely two genetic modifiers that interact with Dominant spot. These results establish Peromyscus as a model system for identifying new alleles of the neural crest gene regulatory network.

Germ cell depletion in recipient testis has adverse effects on spermatogenesis in orthotopically transplanted testis pieces via retinoic acid insufficiency

Germ cell depletion in recipient testes is indispensable for successful transplantation of spermatogonial stem cells. However, we found that such treatment had an adverse effect on spermatogenesis of orthotopically transplanted donor testis tissues. In the donor tissue, the frequency of stimulated by retinoic acid (RA) 8 (STRA8) expression was reduced in germ cells, suggesting that RA signalling indispensable for spermatogenesis was attenuated in germ cell-depleted recipient testes. In this context, germ cell depletion diminished expression of testicular Aldh1a2, which is responsible for testicular RA synthesis, while Cyp26b1, which is responsible for testicular RA metabolism, was still expressed even after germ cell depletion, suggesting an alteration of the RA synthesis/metabolism ratio. These observations suggested that RA insufficiency was one of the causes of the defective donor spermatogenesis. Indeed, repetitive RA administrations significantly improved donor spermatogenesis to produce fertile offspring without any side effects. These findings may contribute to improving fertility preservation techniques for males, especially to prevent iatrogenic infertility induced by chemotherapy in prepubertal cancer patients.

Assessing the dynamics of hybridization through a matrix modelling approach

Hybridization affects the evolution and conservation status of species and populations. Because the dynamics of hybridization is driven by reproduction and survival of parental and admixed individuals, demographic modelling is a valuable tool to assess the effects of hybridization on population viability, e.g., under different management scenarios. While matrix models have been used to assess the long-term consequences of hybridization between crops and wild plants, to our knowledge they have not been developed for animal species. Here, we present a new matrix population model to project population dynamics in a system with two parental species or populations that interbreed. We consider the dynamics of males and females of the two parental groups as separate components, each described by species-specific vectors of initial abundance and projection matrices. Then we model hybridization as the production of hybrid fertile offspring due to the interaction of reproductive individuals of different parental species. Finally, we apply the model to two real-world case studies regarding a terrestrial and a marine mammal species in the presence of hybridization. Specifically, we investigate 1) the genomic extinction probability of two interbreeding dolphin species within a semi-enclosed gulf in Greece, under different hybrids’ fitness scenarios, 2) the possible outcomes of wolf x dog hybridization events for an expanding wolf population in Italy, under different reproductive isolation scenarios, 3) the sensitivity of the probability of genomic extinction to the main demographic parameters in the two case studies.

Identification of hybrid green peafowl using mitochondrial and nuclear markers

Green peafowl (Pavo muticus), a representative of the Southeast Asia Phasianidae, is assessed as globally endangered with populations that are declining. It is highly sensitive to human disturbance and habitat change, two threats that are unlikely to be removed soon in present range countries, and that increase the need for long-term continuous effort for in situ conservation. Captive breeding for reintroduction is potentially an important measure for localized population restoration. But green peafowl can hybridize with blue peafowl (P. cristatus) and produce fertile offspring that can backcross with ancestral species. Hybrids backcrossed to green peafowl for a few generations are indistinguishable from pure green peafowl in appearance. Such hybrids must be excluded from captive breeding programs to avoid anthropogenic genetic contamination. In this study, we developed technology to identify hybrids using mitochondrial Cyt b and COI gene sequences, and 16 microsatellites. We studied maternal species assignment for excluding individuals of the blue peafowl maternal line and genetic clustering analysis to exclude individuals containing blue peafowl nuclear genes. Maternal species assignment was accomplished using K2P pairwise genetic distance computed using transition nucleotide substitution. Nuclear genetic clustering analysis was performed using STRUCTURE (assuming K = 2) and NewHybrids. The method was validated using reference pure green (n = 18) and blue (n = 21) peafowl and known hybrids (n = 12). Two criteria were set up to discriminate hybrids based on the probability that an individual is either pure green or pure blue peafowl at 95% confidence. This method was applied to identification of 59 peafowl of ambiguous genetic composition. Our study provides an example for establishing a purity test workflow for other species that can hybridize and has potential for use in reintroduction of genetically pure green peafowl.

Giraffe taxonomy, geographic distribution and conservation

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Birds rarely hybridize: A citizen science approach to estimating rates of hybridization in the wild.

The rate of hybridization among taxa is a central consideration in any discussion of speciation, but rates of hybridization are difficult to estimate in most wild populations of animals. We used a successful citizen science dataset, eBird, to estimate the rates of hybridization for wild birds in the United States. We calculated the frequency at which hybrid individuals belonging to different species, families, and orders of birds were observed. Between 1 January 2010 and 31 December 2018, a total of 334,770,194 species records were reported to eBird within the United States. Of this total, 212,875 or 0.064% were reported as hybrids. This estimate is higher than the rate of hybridization (0.00167%) reported by Mayr based on impressions from a career studying museum specimens. However, if the 10 most influential hybrid species are removed from the eBird dataset, the rate of hybridization decreases substantially to about 0.009%. We conclude that the rate of hybridization for individuals in most bird species is extremely low, even though the potential for birds to produce fertile offspring through hybrid crosses is high. These findings indicate that there is strong prezygotic selection working in most avian species.

Opinion: Menstruation One of the Oldest Non-Issues

The Planet Earth is a magical place where thousands of animal and plant species co-inhabit. It overflows with life. All living things share characteristics as movement, respiration, sensitivity, growth, reproduction, excretion, and nutrition. The organisms who have similarity between those characteristics and can breed with each other producing fertile offspring they belong to the same species.

Hybridization promotes asexual reproduction in Caenorhabditis nematodes.

Although most unicellular organisms reproduce asexually, most multicellular eukaryotes are obligately sexual. This implies that there are strong barriers that prevent the origin or maintenance of asexuality arising from an obligately sexual ancestor. By studying rare asexual animal species we can gain a better understanding of the circumstances that facilitate their evolution from a sexual ancestor. Of the known asexual animal species, many originated by hybridization between two ancestral sexual species. The balance hypothesis predicts that genetic incompatibilities between the divergent genomes in hybrids can modify meiosis and facilitate asexual reproduction, but there are few instances where this has been shown. Here we report that hybridizing two sexual Caenorhabditis nematode species (C. nouraguensis females and C. becei males) alters the normal inheritance of the maternal and paternal genomes during the formation of hybrid zygotes. Most offspring of this interspecies cross die during embryogenesis, exhibiting inheritance of a diploid C. nouraguensis maternal genome and incomplete inheritance of C. becei paternal DNA. However, a small fraction of offspring develop into viable adults that can be either fertile or sterile. Fertile offspring are produced asexually by sperm-dependent parthenogenesis (also called gynogenesis or pseudogamy); these progeny inherit a diploid maternal genome but fail to inherit a paternal genome. Sterile offspring are hybrids that inherit both a diploid maternal genome and a haploid paternal genome. Whole-genome sequencing of individual viable worms shows that diploid maternal inheritance in both fertile and sterile offspring results from an altered meiosis in C. nouraguensis oocytes and the inheritance of two randomly selected homologous chromatids. We hypothesize that hybrid incompatibility between C. nouraguensis and C. becei modifies maternal and paternal genome inheritance and indirectly induces gynogenetic reproduction. This system can be used to dissect the molecular mechanisms by which hybrid incompatibilities can facilitate the emergence of asexual reproduction.