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In this work, an inadvertent discovery revealed that the prolonged starvation of brooding Crepidulafomicata L. caused the irreversible shell loss of the offspring. This study hypothesized that the shell loss resulted from the hypoxia suffered by the embryos during the incubation period, given that if a brooding snail is starved, the pumping rate is reduced, producing a drop in oxygen diffusion through the egg capsule walls, and thus hypoxic conditions in the intracapsular environment occur. As a result, the embryos trapped within the capsules suffer hypoxia and are forced to shift into anaerobic metabolism to survive. producing CaC[O.sub.3] destined for the shell to be alternatively used as a pH buffer during metabolic acidosis. Under these sublethal conditions, embryos continue their development until hatching. The resulting shell-less larvae continue their free-swimming period and undergo metamorphosis to give way to crawling radula-feeder juveniles. Several experiments were carried out to test this hypothesis. First, the reduction in the pumping rate of starved snails (13.3[+ or -]0.3mL [h.sup.-1]) was confirmed compared with led snails (31.6[+ or -]0.3mL [h.sup.-1]). The calcium content of larvae from egg capsules from fed and starved snails was 537.4 and 125.4 ngCa [micro]gdt[w.sup.-1], respectively. To simulate conditions inside the mantle cavity of the mother, groups of detached egg capsules were exposed for 24days to different water flows in open-flow glass chambers. The results indicated egg capsule survival of 93% and 83% at flow rates of 197 and 103mL [h.sup.-1]. respectively. Total capsule mortality was found on days 12and 15,at 16 and 811 mL [h.sup.-1]. respectively, indicating a flow range for the normal development of the encapsulated embryos and larvae. Morphological features of embryos, larvae, and juveniles from fed and starved brooding snails were compared using a scanning electron microscope. The results supported the original hypothesis that starvation of adult egg-bearing C. fomicata results in irreversible shell loss in offspring. KEY WORDS: hypoxia, water transport, shell-less larvae, shell formation, slipper limpet, Crepidula fomicata, INTRODUCTION The common Atlantic slipper snail Crepidula fomicata (Linnaeus. 1758) is a prosobranch gastropod that is considered a pest in various European countries, affecting mainly the oyster and scallop aquaculture [...]

Orchid embryo development is unusual among flowering plants with many distinctive characteristics. This review highlights the unique features of orchid embryos. After fertilization, the polarity is established in the zygote before its first asymmetric division. In species such as Epidendrum ibaguense H.B.K., the zygote elongates before the first asymmetric division, while others such as Cymbidium sinense (Andr.) Willd. divide without an apparent cell elongation phase. An obvious structural polarity with a prominent vacuole at the micropylar end is not necessarily present in orchid zygotes. The suspensor is derived from the basal cell of a two-celled embryo, and varied morphologies can be found. The suspensor functions in nutrient uptake and can have a morphogenetic role to play in embryo proper development. For embryos without an expanded suspensor, nutrients have to be acquired directly through their surface. The embryo proper develops from the terminal cell of a two-celled embryo. It undergoes a limited number of cell divisions resulting in a tiny embryo with a protocorm body plan. Despite their simple structural organization, orchid embryos have developmental programs as complex as other flowering plants. The ultimate goal of embryo development is to generate a protocorm body plan ready for germination. Key words: orchids, embryo, suspensor, integuments, phytohormones, protocorm Le développement de l'embryon d'orchidée, avec ses nombreuses caractéristiques distinctives, est inhabituel parmi les plantes à fleurs. Cette synthèse souligne les caractéristiques uniques des embryons d'orchidées. Après la fécondation, la polarité est établie dans le zygote avant sa première division asymétrique. Chez des espèces comme Epidendrum ibaguense H.B.K., le zygote s'allonge avant la première division asymétrique, tandis que d'autres, comme Cymbidium sinense (Andr.) Willd., se divisent sans phase apparente d'allongement cellulaire. Une polarité structurale évidente avec une vacuole proéminente à l'extrémité micropylaire n'est pas nécessairement présente dans les zygotes d'orchidées. Le suspenseur est dérivé de la cellule basale d'un embryon à deux cellules, et on peut trouver des morphologies variées. Le suspenseur fonctionne dans l'absorption des nutriments et peut avoir un rôle morphogénétique à jouer dans le développement approprié de l'embryon. Pour les embryons sans suspenseur étendu, les nutriments doivent être acquis directement par leur surface. L'embryon se développe correctement à partir de la cellule terminale d'un embryon à deux cellules. Il subit un nombre limité de divisions cellulaires, ce qui produit un embryon minuscule avec un plan corporel de type protocorme. Malgré leur organisation structurale simple, les embryons d'orchidées présentent des programmes de développement aussi complexes que ceux des autres plantes à fleurs. Le but ultime du développement embryonnaire est de générer un plan corporel de protocorme prêt pour la germination. [Traduit par la Rédaction] Mots-clés : orchidées, embryon, suspenseur, téguments, protocorme, phytohormones, Introduction The beauty of orchid flowers and the unique reproductive processes have captured the imagination of laymen and scientists over the past centuries. One of the unique features of orchid [...]

Protein arginine methyltransferase 5 (PRMT5) catalyzes symmetric dimethylation (SDM) of arginine, a posttranslational modification involved in oncogenesis and embryonic development. However, the role and mechanisms by which PRMT5 modulates Th cell polarization and autoimmune disease have not yet been elucidated. Here, we found that PRMT5 promoted SREBP1 SDM and the induction of cholesterol biosynthetic pathway enzymes that produce retinoid-related orphan receptor (ROR) agonists that activate [ROR[gamma]t. Specific loss of PRMT5 in the [CD4.sup.+] Th cell compartment suppressed Th17 differentiation and protected mice from developing experimental autoimmune encephalomyelitis (EAE). We also found that PRMT5 controlled thymic and peripheral homeostasis in the [CD4.sup.+] Th cell life cycle and invariant NK (iNK) T cell development and [CD8.sup.+] T cell maintenance. This work demonstrates that PRMT5 expression in recently activated T cells is necessary for the cholesterol biosynthesis metabolic gene expression program that generates [ROR[gamma]t agonistic activity and promotes Th17 differentiation and EAE. These results point to Th PRMT5 and its downstream cholesterol biosynthesis pathway as promising therapeutic targets in Th17-mediated diseases., Introduction Arginine methylation is a posttranslational modification of histones and other proteins that regulates important physiological processes, including stem cell biology, differentiation, and development. Conversely, arginine methylation dysregulation occurs in [...]

Long-lasting embryonic dormancy in invertebrates defies our understanding of what constitutes life because, for example, eggs of some copepods can delay hatching for decades or even centuries. Copepods, often millimeter-sized crustaceans, are some of the most numerous multicellular organisms on earth and are key organisms in most aquatic food webs. Some important free-living marine and estuarine species overwinter or oversummer by arrested embryogenesis in dormancy. The present contribution discusses the complex mechanisms behind embryonic dormancy by compiling knowledge from the 42 calanoid copepods from the superfamily Centropagoidea with well-described embryonic dormancy, which has been of scientific interest for decades. However, the determination of categories of copepod resting eggs--that is, diapause and quiescence, transitions between categories, the mechanisms controlling arrested development by the embryos, and how they interact with their surroundings--is not fully understood. Moreover, a clear link between the presence of the free-swimming population and their resting eggs in sediments is still not convincingly demonstrated. Here I evaluate the relative significance of potential cues driving the production of and the phase shift between egg categories. Understanding the initiation and termination of embryonic dormancy is of great importance for fundamental science--that is, population and food web ecology as well as climate science, aquaculture live feed, and ballast water research. Molecular techniques are developing rapidly, especially within health sciences, thus providing relevant tools applicable for plankton research. Here I suggest that applying molecular methods in addition to traditional physiological approaches in future research will lead to greater understanding of copepod embryonic dormancy, one of nature's wonders., Introduction The (epi)genetic and biochemical mechanisms regulating dormancy still puzzle scientists. Some organisms can survive in a state of 'suspended animation' by having virtually no metabolism and by consisting only [...]

In western countries, alcohol consumption is widespread in women of reproductive age, and in binge quantities. These countries also continue to have high incidences of unplanned pregnancies, with women often reported to cease drinking after discovering their pregnancy. This suggests the early embryo may be highly exposed to the detrimental effects of alcohol during the periconception period. The periconception and pre-implantation windows, which include maturation of the oocyte, fertilisation, and morphogenesis of the pre-implantation embryo, are particularly sensitive times of development. Within the oviduct and uterus, the embryo is exposed to a unique nutritional environment to facilitate its development and establish de-novo expression of the genome through epigenetic reprogramming. Alcohol has wide-ranging effects on cellular stress, as well as hormonal, and nutrient signalling pathways, which may affect the development and metabolism of the early embryo. In this review, we summarise the adverse developmental outcomes of early exposure to alcohol (prior to implantation in animal models) and discuss the potential mechanisms for these outcomes that may occur within the protected oviductal and uterine environment. One interesting candidate is reduced retinoic acid synthesis, as it is implicated in the control of epigenetic reprogramming and cell lineage commitment, processes that have adverse consequences for the formation of the placenta, and subsequently, fetal programming. Key words: ethanol, programming, embryo, epigenetics, retinoic acid. Dans les pays occidentaux, la consommation d'alcool en quantite excessive est repandue chez les femmes en age de procreer. Ces pays continuent aussi de presenter une haute incidence de grossesses non planifiees, les femmes rapportant souvent cesser l'alcool apres avoir appris qu'elles etaient enceintes. Cela suggere que l'embryon precoce peut avoir ete hautement expose aux effets nocifs de l'alcool durant la periconception. La fenetre situee entre la periconception et la preimplantation, qui comprend la maturation de l'ovocyte, la fertilisation et la morphogenese de l'embryon avant l'implantation, est une periode particulierement sensible du developpement. A l'interieur de l'oviducte et de l'uterus, l'embryon est expose a un environnement nutritionnel unique qui facilite son developpement et etablit l'expression de novo du genome a travers la reprogrammation epigenetique. L'alcool exerce des effets multiples sur le stress cellulaire et sur les voies de signalisation hormonales et nutritionnelles, qui peuvent affecter le developpement et le metabolisme de cet embryon precoce. Dans cette synthese, les auteurs resument les consequences developpementales indesirables de l'exposition precoce a l'alcool avant l'implantation dans des modeles animaux, et discutent des mecanismes potentiels qui peuvent survenir a l'interieur de l'environnement protege de l'oviducte et de l'uterus. La synthese reduite d'acide retinoique est un mecanisme candidat interessant car il est implique dans le controle de la reprogrammation epigenetique et l'engagement vers un lignage cellulaire particulier, processus qui peuvent avoir des consequences indesirables dans la formation du placenta et, subsequemment, dans la programmation foetale. [Traduit par la Redaction] Mots-cles : ethanol, programmation, embryon, epigenetique, acide retinoique., Introduction It is well established that the period around conception is a 'critical window' during development, in which suboptimal conditions can result in the programming of adult disease (Kwong et [...]