Early developmental biology ofPlatymantis vitianaincluding supportive evidence of structural specialization unique to the ceratobatrachidae

(1) Avian egg size is commonly held to be an important index of egg 'quality' because it reflects the quantity of yolk reserves available to the chick during embryonic development and on hatching. (2) The assumption that egg size may therefore play an important part in determining chick survival overlooks the confounding variable of parental quality which may influence both egg size and fledging success. (3) In order to test the hypothesis that the abilities to produce large eggs and to rear chicks successfully may be positively related, and to investigate the relative contributions of parental quality (ability to produce large eggs) and egg size per se to chick fledging success, a clutch transfer experiment was performed in which clutches of large eggs were cross fostered with clutches of small eggs. (4) Large eggs produced chicks which were not only skeletally larger (tarsus length) but also heavier for their size than those from smaller eggs, both of which could contribute to increased chances of survival. (5) Logistic regression analysis showed that both egg size and the quality of the foster parents contributed significantly to the probability of fledging. Parental quality was more important than egg size in determining chick survival, which suggests that correlations between survival and egg size found by other workers in nonexperimental situations may be due to the confounding effect of parental quality. (6) The contribution of large egg size to chick survival in the lesser black-backed gull Larus fuscus L., appears to be mediated via advantages of increased skeletal size, rather than body condition, on hatching. (7) As large egg size is advantageous, selection for increasing egg size is implied. The likely counterbalancing forces are discussed.

Human embryonic development: from peri-implantation to gastrulation.

Intraspecific variation in embryonic and larval traits of the dorid nudibranch mollusc Adalaria proxima (Alder and Hancock) around the northern coasts of the British Isles

Olivier Gros, Liliane Frenkiel, , Embryonic, Larval, and Post-Larval Development in the Symbiotic Clam Codakia orbicularis (Bivalvia: Lucinidae), Invertebrate Biology, Vol. 116, No. 2 (Spring, 1997), pp. 86-101

tor and are distinguished from anamniotes by the form of their eggs (Carroll, 1982; Packard and Seymour, 1997). Instead of a naked egg, which must be incubated in an essentially aquatic environment, amniotes have an eggshell that provides some protection from desiccation (Little, 1983), and, instead of gas exchange by diffusion from the environment to the embryo, gas diffuses through the eggshell between the environment and extra-embryonic membranes where it is transported in the blood to the embryo (Packard and Seymour, 1997). Thus, the diffusion distance is essentially that of the thickness of the eggshell in eggs of amniotes. It is often postulated that the limitation on the size of the anamniote eggs of amphibians is the slow rate of diffusion of 02 from the outside of the egg to the embryo in large eggs (Seymour and Bradford, 1995). The maximum rate of 02 consumption in large amphibian eggs seems to be compromised by limitations of rates of diffusion of 02 through the gelatinous capsule of amphibian eggs (Packard and Seymour, 1997). Rates of 02 consumption and total energetic cost of development have been measured in a number of amphibian and reptilian eggs (Vleck and Hoyt, 1991; Seymour and Bradford, 1995; Packard and Seymour, 1997). However, all the reptilian eggs measured to date are larger than those of the amphibians so far measured. To make comparisons of the rates of 02 consumption and energetics of reptilian and amphibian eggs by using regressions beyond the size range for each taxon is not statistically valid. The largest of amphibian eggs has had their rates of 02 consumption and/or energetics measured (Packard and Seymour, 1997); larger eggs are not available to extend regressions of these parameters against egg mass. Thus, we chose to measure these parameters in the smallest of available reptilian (amniote) eggs, those of the Australian skink Menetia greyii, to test the null hypothesis that the maximum rate of 02 consumption during embryonic development is not greater in reptiles than in amphibians of equivalent size. Eggs of M. greyii, one of the smallest lizards in Australia (Greer, 1989), are smaller than the largest of amphibian eggs. We quantified the rates of 02 consumption and energetic cost of development to enhance understanding of the evolution of amniote eggs from anamniancestors. At the same time, we provide det iled information on the energy contents of eggs and neonates and quantify how much energy is consumed during embryonic development for comparison with other species of reptiles.

Egg size-dependent embryonic development in the desert locust, Schistocerca gregaria

Central nervous system development of cats (Felis catus L. 1758)

Temperature-dependent sex determination (TSD) is a mechanism in which environmental temperature, rather than innate zygotic genotype, determines the fate of sexual differentiation during embryonic development. Reeves’ turtle (also known as the Chinese three-keeled pond turtle, Mauremys reevesii) exhibits TSD and is the only species whose genome has been determined in Geoemydidae to date. Thus, M. reevesii occupy phylogenetically important position for the study of TSD and can be compared to other TSD species to elucidate the underlying molecular mechanism of this process. Nevertheless, neither embryogenesis nor gonadogenesis has been described in this species. Therefore, herein, we investigated the chronology of normal embryonic development and gonadal structures in M. reevesii under both female- and male-producing incubation temperatures (FPT 31 °C or MPT 26 °C, respectively). External morphology remains indistinct between the two temperature regimes throughout the studied embryonic stages. However, the gonadal ridges present on the mesonephros at stage 16 develop and sexually differentiate at FPT and MPT. Ovarian and testicular structures begin to develop at stages 18–19 at FPT and stages 20–21 at MPT, respectively, and thus, the sexual differentiation of gonadal structures began earlier in the embryos at FPT than at MPT. Our results suggest that temperature sensitive period, at which the gonadal structures remain sexually undifferentiated, spans from stage 16 (or earlier) to stages 18–19 at FPT and to stages 20–21 at MPT. Understanding the temperature-dependent differentiation in gonadal structures during embryonic development is a prerequisite for investigating molecular basis underlying TSD. Thus, the result of the present study will facilitate further developmental studies on TSD in M. reevesii.

We examined inter- and intra-clutch egg-size variation in the bluethroat (Luscinia s. svecica), an open-nesting passerine breeding in the sub-alpine region in southern Norway. By removing first clutches shortly after egg-laying, we induced laying of a repeat clutch. Females significantly reduced the number of eggs from the first to the second nesting attempt, but increased mean egg size. Females in good condition laid significantly larger eggs than those in poor condition. Consistent with predictions of the “brood survival” hypothesis, assuming an adaptive investment in last eggs to ensure survival of all eggs in the clutch, we found that the size of the last eggs in first clutches was generally larger than the mean egg size of the clutch, and that the relative size of the last egg increased with clutch size. However, a large last egg reflected a general increase in egg size throughout the laying sequence rather than a specific investment in the last egg only. Egg size was not significantly influenced by sex or paternity (within-pair versus extra-pair) of the embryo. In repeat clutches the last egg was not consistently larger than the mean for the clutch. We conclude that female bluethroats face resource limitations during egg formation early in the season, and that the patterns of increase in egg size with laying order for first clutches, and from first to repeat clutches, can largely be explained by proximate constraints on egg formation.

Bone morphogenetic proteins (BMPs) act as multifunctional regulators in morphogenesis during development. In particular they play a determinant role in the formation of cartilage molds and their replacement by bone during endochondral ossification. In cell culture, BMP-2 favors chondrogenic expression and promotes hypertrophic maturation of chondrocytes. In mouse chondrocytes we have identified a BMP-2-sensitive gene encoding a protein of 301 amino acids. This protein, named mIFT46, is the mouse ortholog of recently identified Caenorhabditis elegans and Chlamydomonas reinhardtii intraflagellar transport (IFT) proteins. After generation of a polyclonal antibody against mIFT46, we showed for the first time that the endogenous protein is located in the primary cilium of chondrocytes. We also found that mIFT46 is preferentially expressed in early hypertrophic chondrocytes located in the growth plate. Additionally, mIFT46 knockdown by small interfering RNA oligonucleotides in cultured chondrocytes specifically stimulated the expression of several genes related to skeletogenesis. Furthermore, Northern blotting analysis indicated that mIFT46 is also expressed before chondrogenesis in embryonic mouse development, suggesting that the role of mIFT46 might not be restricted to cartilage. To explore the role of IFT46 during early development, we injected antisense morpholino oligonucleotides in Danio rerio embryos to reduce zebrafish IFT46 protein (zIFT46) synthesis. Dramatic defects in embryonic development such as a dorsalization and a tail duplication were observed. Thus our results taken together indicate that the ciliary protein IFT46 has a specific function in chondrocytes and is also essential for normal development of vertebrates.

Do amphibious crabs have amphibious eggs? A case study of Armases miersii

Abstract: Octopus hubbsorum Berry 1953 occurs in a wide region of the tropical eastern Pacific. It is the principal target species in the octopus fisheries, but no information is available with regard to embryonic and larval development. The objective of this study was to describe O. hubbsorum eggs, embryos, and paralarvae under laboratory conditions. One O. hubbsorum female with egg clutch was collected (15°39′N, 96°31′W) on 26 October 2012. Embryonic development lasted from 20 to 30 days. The newly hatched paralarvae are planktonic; morphologically, this feature is expressed by a relatively small arm-length, 3 suckers per arm, and mean mantle length of 1.27 ± 0.14 mm. This article provides a detailed survey of O. hubbsorum, embryogenesis from organogenesis through hatching under laboratory conditions; including detailed descriptions of externally visible morphological features that are easily distinguished in either live or freshly fixed organisms under a dissecting microscope.

Effect of nanoparticles of silver and gold on metabolic rate and development of broiler and layer embryos

-The effects of polyploidy on embryonic developmental rate and temperature tolerance of salamanders in the Ambystoma laterale-texanum hybrid complex were examined. Neither initial size, genotype nor ploidy of eggs affected embryonic rates and tolerance limits. Larger eggs gave rise to larger hatchlings at cold temperatures only, and body size of hatchlings from large and small eggs was larger at cold temperatures than at warm temperatures. Although polyploidy does not affect embryonic development, one selective benefit of polyploidy is large egg size.

The chicken hatching egg is a self-contained life-supporting system for the developing embryo. However, the post-hatch performance of birds depends on several factors, including the breeder management and age, egg storage conditions and duration before incubation, and the incubation conditions. Studies have determined the effect of incubation factors on chick post-hatch growth potential. Therefore, chick physical quality at hatch is receiving increasing attention. Indeed, although incubation temperature, humidity, turning and ventilation are widely investigated, the effects of several variables such as exposure of the embryo to high or low levels, time of exposure, the amplitude of variations and stage exposures on embryo development and post-hatch performance remain poorly understood. This review paper focuses on chick quality and post-hatch performance as affected by incubation conditions. Also, chick physical quality parameters are discussed in the context of the parameters for determining chick quality and the factors that may affect it. These include incubation factors such as relative humidity, temperature, turning requirements, ventilation, in ovo feeding and delay in feed access. All these factors affect chick embryo physiology and development trajectory and consequently the quality of the hatched chicks and post-hatch performance. The potential application of adapted incubation conditions for improvement of post-hatch performance up to slaughter age is also discussed. It is concluded that incubation conditions affect embryo parameters and consequently post-hatch growth differentially according to exposure time and stage of exposure. Therefore, classical physical conditions are required to improve hatchability, chick quality and post-hatch growth.