Effects of reproductive aging and postovulatory aging on the maintenance of biological competence after oocyte vitrification: insights from the mouse model

Cryopreservation of female reproductive cells allows preservation of fertility and provides materials for research. Although freezing protocols have been optimized, and there is a high survival rate after thawing, the in vitro fertilization (IVF) pregnancy rate is still lower in cycles with cryopreserved oocytes, thus highlighting the importance of identifying intrinsic limiting factors characterizing the cells at time of freezing. The aim of the present study is to investigate in the mouse model the impact of reproductive aging and postovulatory aging on oocyte biological competence after vitrification. Metaphase II oocytes were vitrified soon after retrieval from young and reproductively old mice. Part of the oocytes from young animals was vitrified after 6 h incubation (in vitro aged oocytes). All classes of oocytes showed similar survival rate after vitrification. Moreover, vitrification did not alter chromosomal organization in young cells, whereas in vitro aged and old oocytes presented an increase of slightly aberrant metaphase configurations. Compared to fresh young oocytes, in vitro aged and old oocytes showed increased ROS levels which remained unchanged after vitrification. By contrast, cryopreservation significantly increased ROS production in young oocytes. Both the aging processes negatively impacted oocyte ability to undergo pronucleus formation and first cleavage after vitrification by stimulating cellular fragmentation. These results could be helpful for establishing the correct time table for cryopreservation in the laboratory routine and improving its application in reproductively old females. Moreover, our observations highlight the importance of oxidative stress protection during vitrification procedures.     

The evolution and loss of oil-offering flowers: new insights from dated phylogenies for angiosperms and bees

The interactions between bees that depend on floral oil for their larvae and flowers that offer oil involve an intricate mix of obligate and facultative mutualisms. Using recent phylogenies, new data on oil-offering Cucurbitaceae, and molecular-dating, we ask when and how often oil-offering flowers and oil-foraging bees evolved, and how frequently these traits were lost in the cause of evolution. Local phylogenies and an angiosperm-wide tree show that oil flowers evolved at least 28 times and that floral oil was lost at least 36–40 times. The oldest oil flower systems evolved shortly after the K/T boundary independently in American Malpighiaceae, tropical African Cucurbitaceae and Laurasian Lysimachia (Myrsinaceae); the ages of the South African oil flower/oil bee systems are less clear. Youngest oil flower clades include Calceolaria (Calceolariaceae), Iridaceae, Krameria (Krameriaceae) and numerous Orchidaceae, many just a few million years old. In bees, oil foraging evolved minimally seven times and dates back to at least 56 Ma (Ctenoplectra) and 53 Ma (Macropis). The co-occurrence of older and younger oil-offering clades in three of the four geographical regions (but not the Holarctic) implies that oil-foraging bees acquired additional oil hosts over evolutionary time. Such niche-broadening probably started with exploratory visits to flowers resembling oil hosts in scent or colour, as suggested by several cases of Muellerian or Batesian mimicry involving oil flowers.     

New insights into the evolution of Wolbachia infections in filarial nematodes inferred from a large range of screened species

Background

Wolbachia are intriguing symbiotic endobacteria with a peculiar host range that includes arthropods and a single nematode family, the Onchocercidae encompassing agents of filariases. This raises the question of the origin of infection in filariae. Wolbachia infect the female germline and the hypodermis. Some evidences lead to the theory that Wolbachia act as mutualist and coevolved with filariae from one infection event: their removal sterilizes female filariae; all the specimens of a positive species are infected; Wolbachia are vertically inherited; a few species lost the symbiont. However, most data on Wolbachia and filaria relationships derive from studies on few species of Onchocercinae and Dirofilariinae, from mammals.

Methodology/Principal Findings

We investigated the Wolbachia distribution testing 35 filarial species, including 28 species and 7 genera and/or subgenera newly screened, using PCR, immunohistochemical staining, whole mount fluorescent analysis, and cocladogenesis analysis. (i) Among the newly screened Onchocercinae from mammals eight species harbour Wolbachia but for some of them, bacteria are absent in the hypodermis, or in variable density. (ii) Wolbachia are not detected in the pathological model Monanema martini and in 8, upon 9, species of Cercopithifilaria. (iii) Supergroup F Wolbachia is identified in two newly screened Mansonella species and in Cercopithifilaria japonica. (iv) Type F Wolbachia infect the intestinal cells and somatic female genital tract. (v) Among Oswaldofilariinae, Waltonellinae and Splendidofilariinae, from saurian, anuran and bird respectively, Wolbachia are not detected.

Conclusions/Significance

The absence of Wolbachia in 63% of onchocercids, notably in the ancestral Oswaldofilariinae estimated 140 mya old, the diverse tissues or specimens distribution, and a recent lateral transfer in supergroup F Wolbachia, modify the current view on the role and evolution of the endosymbiont and their hosts. Further genomic analyses on some of the newly sampled species are welcomed to decipher the open questions.     

Alternative morphs and plasticity of vulval development in a rhabditid nematode species

The nematode species Rhabditis sp. SB347 (Family Rhabditidae) in standard culture conditions displays two developmental morphs with distinct modes of sexual reproduction: (1) females and males that develop through four feeding juvenile (larval) stages; (2) self-fertile protandric hermaphrodites that develop through an obligatory non-feeding third juvenile stage, the dauer larva. In females and males, somatic gonad development begins in the first larval stage, whereas in hermaphrodites it is delayed to the second larval stage. Vulval development also differs between females and hermaphrodites: (1) the P8.p cell divides in females but stays undivided in hermaphrodites; (2) the number, timing, and source of inductive signals from the gonad to the vulval precursor cells differ between the two morphs. These results show that discrete vulva developmental routes can be adopted by animals of the same genotype.Edited by D. Tautz     

Morphological redescription and molecular characterization of three species of Travassosinematidae (Nematoda: Oxyurida: Thelastomatoidea) from Gryllotalpa africana Beauv (Orthoptera: Gryllotalpidae)

Binema mirzaia (Basir, 1942a) Basir, 1956, Cameronia nisari (Parveen and Jairajpuri, 1985) Adamson and Van Waerebeke, 1992a and Mirzaiella meerutensis Singh and Malti, 2003 are redescribed morphologically along with molecular identification from the intestine of mole cricket Gryllotalpa africana. Molecular characterization was carried out using the D2–D3 expansion domains of the 18S ribosomal DNA region. This study first time presents molecular data for the above three nematode species.     

Attributes and congruence of three molecular data sets: inferring phylogenies among Septoria-related species from woody perennial plants

To improve our understanding of phylogenetic relationships within the anamorphic genus Septoria, three molecular data sets representing 2,417 bp of nuclear and mitochondrial genes were evaluated. Separate gene analyses and combined analyses were performed using first, the maximum parsimony criterion and second, a Bayesian framework. The homogeneity of data partitions was evaluated via a combination of homogeneity partition tests and tree topology incongruence tests before conducting combined analyses. A last incongruence re-evaluation using partitioned Bremer support was performed on the combined tree, which corroborated the previous estimates. After each separate data set attributes were examined, simple explanations were advocated as the causes of the significant incongruences detected. The analysis of multiple gene partitions showed unprecedented phylogenetic resolution within the genus Septoria that supported the results from previously published single gene phylogenies. Specifically, we have delimited distinct but closely related species representing monophyletic groups that frequently correlated with their respective host families. Conversely, the occurrence of well-supported groups including closely related but distinct molecular taxa sampled on unrelated host-plants allowed us to reject, in these particular cases, the co-evolutionary concept expected between a parasite and its host and to discuss alternative evolutionary models recently proposed for these pathogens.     

Reproductive costs in terrestrial male vertebrates: insights from bird studies

Reproduction requires resources that cannot be allocated to other functions resulting in direct reproductive costs (i.e. trade-offs between current reproduction and subsequent survival/reproduction). In wild vertebrates, direct reproductive costs have been widely described in females, but their occurrence in males remains to be explored. To fill this gap, we gathered 53 studies on 48 species testing direct reproductive costs in male vertebrates. We found a trade-off between current reproduction and subsequent performances in 29% of the species and in every clade. As 73% of the studied species are birds, we focused on that clade to investigate whether such trade-offs are associated with (i) levels of paternal care, (ii) polygyny or (iii) pace of life. More precisely for this third question, it is expected that fast species (i.e. short lifespan, early maturity, high fecundity) pay a cost in terms of survival, whereas slow species (with opposite characteristics) do so in terms of fecundity. Our findings tend to support this hypothesis. Finally, we pointed out the potential confounding effects that should be accounted for when investigating reproductive costs in males and strongly encourage the investigation of such costs in more clades to understand to what extent our results are relevant for other vertebrates.     

Embryology of the lamprey and evolution of the vertebrate jaw: insights from molecular and developmental perspectives

Evolution of the vertebrate jaw has been reviewed and discussed based on the developmental pattern of the Japanese marine lamprey, Lampetra japonica. Though it never forms a jointed jaw apparatus, the L. japonica embryo exhibits the typical embryonic structure as well as the conserved regulatory gene expression patterns of vertebrates. The lamprey therefore shares the phylotype of vertebrates, the conserved embryonic pattern that appears at pharyngula stage, rather than representing an intermediate evolutionary state. Both gnathostomes and lampreys exhibit a tripartite configuration of the rostral-most crest-derived ectomesenchyme, each part occupying an anatomically equivalent site. Differentiated oral structure becomes apparent in post-pharyngula development. Due to the solid nasohypophyseal plate, the post-optic ectomesenchyme of the lamprey fails to grow rostromedially to form the medial nasal septum as in gnathostomes, but forms the upper lip instead. The gnathostome jaw may thus have arisen through a process of ontogenetic repatterning, in which a heterotopic shift of mesenchyme-epithelial relationships would have been involved. Further identification of shifts in tissue interaction and expression of regulatory genes are necessary to describe the evolution of the jaw fully from the standpoint of evolutionary developmental biology.     

MicroRNAs: recently discovered key regulators of proliferation and apoptosis in animal cells

The relatively recent discovery of miRNAs has added a completely new dimension to the study of the regulation of gene expression. The mechanism of action of miRNAs, the conservation between diverse species and the fact that each miRNA can regulate a number of targets and phenotypes clearly indicates the importance of these molecules. In this review the current state of knowledge relating to miRNA expression and gene regulation is presented, outlining the key morphological and biochemical features controlled by miRNAs with particular emphasis on the key phenotypes that impact on cell growth in bioreactors, namely proliferation and apoptosis.     

Reproductive biology of bisexual and all-female populations of chaetodontid fishes from the southern Great Barrier Reef

Synopsis The reproductive biology of three species of chaetodonts from One Tree Reef (southern GBR) is described by analysis of gonads and population structure. Reproductive biology is related to age by a capture-markrecapture study of growth. For Chaetodon rainfordi there was a significant habitat effect. On the reef slope, females outnumbered males by 5.6: 1 and both sexes became reproductively active by the age of 2 years. In the lagoon, no males were found and females were reproductively inactive. For C. plebius, males were essentially missing from all samples and no reproductively active females were found. For Chelmon rostratus (1 :1 sex ratio) some males had mature testes but there was no evidence of female reproductive activity. This species is likely to be gonochoristic, but the reproductive mode of the other two species remains ambiguous.     

Embryonic gut differentiation in nematodes: endocytosis of macromolecules and its experimental inhibition

During embryogenesis of Caenorhabditis elegans cytoplasmic components are transferred from nongut cells into the developing gut primordium and an exo/endocytosis mechanism has been hypothesized (Bossinger and Schierenberg 1992). To test endocytotic activity of the gut primordium, we compared the uptake of different fluorochrome-conjugated marker molecules in two nematode species, C. elegans and Cephalobus spec., which differ in the pattern of early cleavage and cell-cell communication. We found no uptake of dextran (as a marker for pinocytosis) but rapid internalization of 30-fold larger transferrin molecules (as a marker for receptor-coupled endocytosis) into the differentiating gut primordium in both nematodes. The two studied species differ with respect to when this process starts. While the uptake of macromolecules in the fast developing C. elegans is first observed at a stage when essentially all cells of the hatching juvenile have been generated, in the slow developing Cephalobus endocytosis begins during the early proliferation phase when only two gut precursor cells are present. We found that the polysulfated hydrocarbon dye trypan blue and the cationic amphiphilic drug chlorpromazine both inhibit endocytosis into the gut primodium.     

Origin and early evolution of the vertebrates: new insights from advances in molecular biology, anatomy, and palaeontology

Recent advances in molecular biology and microanatomy have supported homologies of body parts between vertebrates and extant invertebrate chordates, thus providing insights into the body plan of the proximate ancestor of the vertebrates. For example, this ancestor probably had a relatively complex brain and a precursor of definitive neural crest. Additional insights into early vertebrate evolution have come from recent discoveries of Lower Cambrian soft body fossils of Haikouichthys and Myllokunmingia (almost certainly vertebrates, possibly related to modern lampreys) and Yunnanozoon and Haikouella (evidently stem-group vertebrates). The earliest vertebrates had an unequivocally marine origin, probably evolved mineralised pharyngeal denticles before the dermal skeleton, and evidently utilised elastic recoil of the visceral arch skeleton for suction feeding. Moreover, the new data emphasise that the advent of definitive neural crest was supremely important for the evolutionary origin of the vertebrates.     

Reproductive protein evolution within and between species: maintenance of divergent ZP3 alleles in Peromyscus

In a variety of animal taxa, proteins involved in reproduction evolve more rapidly than nonreproductive proteins. Most studies of reproductive protein evolution, however, focus on divergence between species, and little is known about differentiation among populations within a species. Here we investigate the molecular population genetics of the protein ZP3 within two Peromyscus species. ZP3 is an egg coat protein involved in primary binding of egg and sperm and is essential for fertilization. We find that amino acid polymorphism in the sperm-combining region of ZP3 is high relative to silent polymorphism in both species of Peromyscus . In addition, while there is geographical structure at a mitochondrial gene ( Cytb ), a nuclear gene ( Lcat ) and eight microsatellite loci, we find no evidence for geographical structure at Zp3 in Peromyscus truei . These patterns are consistent with the maintenance of ZP3 alleles by balancing selection, possibly due to sexual conflict or pathogen resistance. However, we do not find evidence that reinforcement promotes ZP3 diversification; allelic variation in P. truei is similar among populations, including populations allopatric and sympatric with sibling species. In fact, most alleles are present in all populations sampled across P. truei's range. While additional data are needed to identify the precise evolutionary forces responsible for sequence variation in ZP3, our results suggest that in Peromyscus , selection to maintain divergent alleles within species contributes to the pattern of rapid amino acid substitution observed among species.     

Normal mode analysis with molecular geometry restraints: bridging molecular mechanics and elastic models

A new method for normal mode analysis is reported for all-atom structures using molecular geometry restraints (MGR). Similar to common molecular mechanics force fields, the MGR potential contains short- and long-range terms. The short-range terms are defined by molecular geometry, i.e., bond lengths, angles and dihedrals; the long-range term is similar to that in elastic network models. Each interaction term uses a single force constant parameter, and is determined by fitting against a set of known structures. Tests on proteins/non-proteins show that MGR can produce low frequency eigenvectors closer to all-atom force-field-based methods than conventional elastic network models. Moreover, the “tip effect”, found in low frequency eigenvectors in elastic network models, is reduced in MGR to the same level of the modes produced by force-field-based methods. The results suggest that molecular geometry plays an important role, in addition to molecular shape, in determining low frequency deformational motions. MGR does not require initial energy minimization, and is applicable to almost any structure, including the one with missing atoms, bad contacts, or bad geometries, frequently observed in low-resolution structure determination and refinement. The method bridges the two major representations in normal mode analyses, i.e., the molecular mechanics models and elastic network models.     

Trypanosomatidae: isoleucine requirement and threonine deaminase in species with and without endosymbionts

Abomasal and duodenal concentrations of Haemonchus contortus eggs were measured in four lambs fitted with permanent abomasal and duodenal cannulas and infected with 25,000 Haemonchus contortus larvae. During the period of maximal egg laying, i.e., when the abomasal H. contortus egg concentration was above 2000 eggs/ml, the animals received cimetidine (20 mg/kg) intravenously or pentagastrin (5 μg·kg^?1·h^?1) for 90 min and the changes in abomasal and duodenal egg concentrations were followed for 2.5 hr. Pentagastrin infusion reduced the abomasal and duodenal pH significantly and in less than 15 min decreased the abomasal and duodenal egg concentrations which represented only 21.4 and 12.0% of the control values at the end (90 min) of infusion. During pentagastrin infusion, both the abomasal (r = 0.56, P ? 0.01) and the duodenal (r = 0.72, P ? 0.01) egg concentrations correlated positively with the corresponding pH values. After cimetidine injection, the abomasal and duodenal pH had increased 150 min later to, respectively, pH 6.16 and 6.27. During the first 30 min for an abomasal pH lower than 4.5–5.0, egg production increased by 106%; then the abomasal and duodenal egg concentrations decreased progressively, representing, respectively, only 39.3 and 16.4% of the control values 120 min later. It is concluded that the level of egg laying of adult H. contortus was related to the abomasal acidity, the maximal egg production occurring when the abomasal pH was between pH 4 and 4.5.     

Sexual development and cryptic sexuality in fungi: insights from Aspergillus species

Major insights into sexual development and cryptic sexuality within filamentous fungi have been gained from investigations using Aspergillus species. Here, an overview is first given into sexual morphogenesis in the aspergilli, describing the different types of sexual structures formed and how their production is influenced by a variety of environmental and nutritional factors. It is argued that the formation of cleistothecia and accessory tissues, such as Hülle cells and sclerotia, should be viewed as two independent but co-ordinated developmental pathways. Next, a comprehensive survey of over 75 genes associated with sexual reproduction in the aspergilli is presented, including genes relating to mating and the development of cleistothecia, sclerotia and ascospores. Most of these genes have been identified from studies involving the homothallic Aspergillus nidulans, but an increasing number of studies have now in addition characterized 'sex-related' genes from the heterothallic species Aspergillus fumigatus and Aspergillus flavus. A schematic developmental genetic network is proposed showing the inter-relatedness between these genes. Finally, the discovery of sexual reproduction in certain Aspergillus species that were formerly considered to be strictly asexual is reviewed, and the importance of these findings for cryptic sexuality in the aspergilli as a whole is discussed.