Pelvis morphology suggests that early Mesozoic birds were too heavy to contact incubate their eggs.

Numerous new fossils have driven an interest in reproduction of early birds, but direct evidence remains elusive. No Mesozoic avian eggs can be unambiguously assigned to a species, which hampers our understanding of the evolution of contact incubation, which is a defining feature of extant birds. Compared to living species, eggs of Mesozoic birds are relatively small, but whether the eggs of Mesozoic birds could actually have borne the weight of a breeding adult has not yet been investigated. We estimated maximal egg breadth for a range of Mesozoic avian taxa from the width of the pelvic canal defined by the pubic symphysis. Known elongation ratios of Mesozoic bird eggs allowed us to predict egg mass and hence the load mass an egg could endure before cracking. These values were compared to the predicted body masses of the adult birds based on skeletal remains. Based on 21 fossil species, we show that for nonornithothoracine birds body mass was 187% of the load mass of the eggs. For Enantiornithes, body mass was 127% greater than the egg load mass, but some early Cretaceous ornithuromorphs were 179% heavier than their eggs could support. Our indirect approach provides the best evidence yet that early birds could not have sat on their eggs without running the risk of causing damage. We suggest that contact incubation evolved comparatively late in birds.

The impact of egg incubation temperature on the personality of oviparous reptiles.

Personality traits, defined as differences in the behavior of individual animals of the same species that are consistent over time and context, such as 'boldness,' have been shown to be both heritable and be influenced by external factors, such as predation pressure. Currently, we know very little about the role that early environmental factors have upon personality. Thus, we investigated the impact of incubation temperature upon the boldness on an oviparous reptile, the bearded dragon (Pogona vitticeps). Eggs, from one clutch, were incubated at two different average temperatures within the normal range. After hatching the lizards were raised under the same environmental conditions. Novel object and novel environment tests were used to assess personality. Each test was repeated in both the short term and the long term. The results revealed that incubation temperature did impact upon 'boldness' but only in the short term and suggests that, rather than influencing personality, incubation temperature may have an effect on the development of behavioral of oviparous reptiles at different stages across ontogeny.

Adventitious Embryogenesis and the in vitro culture of Apple Seed Parts.

Immature apple seeds from four scion cultivars, Bramley, Cox, Greensleeves and Spartan, and four rootstocks, M.9, M.25, M.26 and M.27 (Malus púmila Mill.), were collected at 30 and 50 days post-anthesis, dissected into nucellus, endosperm and zygotic embryo and cultured in vitro. The basal media of Linsmaier and Skoog (LS) and Murashige and Tucker (MT) were compared with hormone-containing media for their effects on adventitious embryogenesis, nucellus and endosperm callus formation and zygotic embryo development. Nucellar tissues from 30-day-old seeds formed callus only in the presence of an auxin, 2,4-D or NAA, and a cytokinin, BA. Concentrations of 4.4 × 10(-6)M and 2.2 × 10(-5) M were effective. Adventitious embryos arose from the micropylar ends of the nucellus or endosperm in 50-day-old seeds at a frequency of 0-23 % depending on the cultivar. The number of adventitious embryos varied from 1 to 9 per seed. Generally the inclusion of growth regulators had no beneficial effects and the inclusion of malt extract at 500 mg · l(-1) to the basal media was inhibitory. Embryos could be induced to undergo shoot proliferation for subsequent plantlet production. Endosperm callus growth was obtained on both basal and hormone-supplemented media in excised 50-day-old seeds. The frequency of callus formation was cultivar and media dependent and ranged from 0-80%. Growth on LS media was prolific and the hormone-autotrophic nature of this callus has persisted after more than a year in culture. Excised zygotic embryos from 50-day-old seeds could be stimulated to produce multiple shoots from single embryo shoot apices on media containing 4.4 × 10(-6)M and 2.2 × 10(-5) M BA. This effect was reduced by the inclusion of 500 mg·1(-1) casein hydrolysate. Secondary adventitious embryogenesis could also be induced on the cotyledon surface of both adventitious and zygotic embryos at specific combinations of NAA and BA. On basal media zygotic embryos developed into seedlings in vitro and the addition of GA3 sometimes enhanced the process.