Biosynthetic events of hydrid regeneration

Summary The results of a combined morphological and biochemical study of the role of DNA synthesis during distal regeneration inHydra oligactis revealed that a burst of³H-thymidine incorporation into DNA preceded the elaboration of each of the initial three tentacles. In addition, the relative level of each burst of precursor incorporation relfected the number of tentacles formed at that time. Cytological localization of concentrated amounts of labeled material in nuclei of the hypostome and tentacle regions provided corroborative evidence for the biochemical findings.Evidence that the increased DNA specific activity levels described above are associated with tentacle initiation derived from studies in which regenerating hydra were cultured in hydroxyurea and studies in which hydra regenerated proximally rather than distally. Hydra regenerating in 8 mg/ml (0.105 M) hydroxyurea developed morphologically recognizable hypostomes but no tentacles, and incorporated³H-thymidine into DNA at a level distinctly below that exhibited by uncut, untreated animals. Similarly, hydra regenerated a normal, functional basal disc in the absence of any increased DNA specific activity. Therefore, it is suggested that tentacle initiation inH. oligactis requires concomitant DNA synthesis and, as such, represents an epimorphic phenomenon.     

Genome-wide association mapping for grain manganese in rice (Oryza sativa L.) using a multi-experiment approach

Manganese (Mn) is an essential trace element for plants and commonly contributes to human health; however, the understanding of the genes controlling natural variation in Mn in crop plants is limited. Here, the integration of two of genome-wide association study approaches was used to increase the identification of valuable quantitative trait loci (QTL) and candidate genes responsible for the concentration of grain Mn across 389 diverse rice cultivars grown in Arkansas and Texas, USA, in multiple years. Single-trait analysis was initially performed using three different SNP datasets. As a result, significant loci could be detected using the high-density SNP dataset. Based on the 5.2 M SNP dataset, major QTLs were located on chromosomes 3 and 7 for Mn containing six candidate genes. In addition, the phenotypic data of grain Mn concentration were combined from three flooded-field experiments from the two sites and 3 years using multi-experiment analysis based on the 5.2 M SNP dataset. Two previous QTLs on chromosome 3 were identified across experiments, whereas new Mn QTLs were identified that were not found in individual experiments, on chromosomes 3, 4, 9 and 11. OsMTP8.1 was identified in both approaches and is a good candidate gene that could be controlling grain Mn concentration. This work demonstrates the utilisation of multi-experiment analysis to identify constitutive QTLs and candidate genes associated with the grain Mn concentration. Hence, the approach should be advantageous to facilitate genomic breeding programmes in rice and other crops considering QTLs and genes associated with complex traits in natural populations.Subject terms: Genome-wide association studies, Plant breeding     

Some aspects of the system of Haversian canals in the diaphysary compact bone in man

The general aspect of the network of Haversian canals was studied on tangential and radial sections from the diaphysary compact bone of the human long bones. The network-like aspect was much varied even in the same bone and at the same level from which the samples were obtained. No obvious differences were found between the studied bones or between the two limbs. Certain peculiarities of the canal system were noticed as regards the trajectory of canals, disposition and number of anastomoses, and the network aspect, depending on the region of the diaphysis, but especially on the depth.     

Obesity and Television Watching in Preschoolers in Greece: The GENESIS Study

The aim of the current work was to evaluate the effect of preschoolers' television (TV) watching time on the prevalence of obesity even after controlling for their total energy intake and their physical activity status. A representative sample of 2,374 Greek children aged 1–5 years was examined (“Growth, Exercise and Nutrition Epidemiological Study in preSchoolers”, GENESIS study). Children's TV watching time on a usual weekday and at a usual weekend was recorded. The overall mean of children's TV viewing time was 1.32 h/day. The majority of participants (74.0%) spent <2 h/day watching TV whereas only 3.1% spent >4 h/day in front of a TV set. Overall, 65.2% of participants were normal weight, 17.2% were overweight, and the rest 17.6% were obese. The prevalence of obesity was significantly higher among those with TV viewing time ≥2 h/day (21.7%) compared to those watching TV <2 h/day (16.1%, P = 0.003). TV viewing time remained significantly associated with the likelihood of being obese even after controlling for potential confounders (i.e., socio demographic and other characteristics and physical activity status) only among children aged 3–5 years. However, further adjusting for children's total energy intake revealed that the association between the TV viewing time and the probability of being obese was no longer statistically significant. On the other hand, physical activity status continued to be an independent factor of being obese. The current findings support the hypothesis that the effect of TV viewing time on childhood obesity is independent of physical activity status and may be attributed to the increased total energy intake during TV watching.     

Terrestrial–aquatic transitions: Local abundances and movements of mature female caddisflies are related to oviposition habits but not flight capability

1. Movement behaviours of adult aquatic insects can produce distinct spatial distribution patterns. Studies of adult abundance with distance away from water bodies are common and may invoke flight capability to explain species differences. In contrast, distribution patterns along river channels are poorly described, but are no less important for understanding population dynamics. Longitudinal patterns in adult abundance along short river lengths may differ between sexes and at different life stage transitions between aquatic and terrestrial environments, i.e. at emergence and oviposition. Flight capability is unlikely to influence longitudinal patterns created at emergence, but may influence local abundances of mature females seeking to lay eggs. We tested hypotheses about how local abundances of mature females might differ according to oviposition habits and flight capability.
2. We surveyed abundances of mature female caddisflies at adjacent riffle–pool pairs along short river lengths with homogeneous riparian cover. Our survey included nine species in three families (Hydrobiosidae, Leptoceridae, Hydropsychidae), which encompassed multiple different oviposition habits and a range of wing sizes and shapes. Several of the species oviposit preferentially in riffles. Accordingly, we tested for differences in female abundance between channel units (adjacent riffle–pool pairs). We also tested whether females attained higher abundances in some places along channels than others (i.e. over larger spatial scales and regardless of channel unit) which imply movements along the channel and aggregation in some locations. Wing morphology was used as a proxy measure of flight capability and included measures of wing span, area, aspect ratio and the second moment of wing area.
3. Three distinctly different distribution patterns of mature female caddisflies were identified. The abundance of three species varied over larger scales only (multiple channel units). Six species that oviposit preferentially in riffles had higher female abundances at riffles than pools, but for only one did abundances also vary over larger scales. There was no association between these different patterns and measures of wing morphology, after removing metrics that were correlated and that differed systematically between taxonomic families. However, we could not reject the hypothesis that some aspect of flight behaviour may have contributed to observed patterns.
4. The diverse but distinct distributions of mature female caddisflies we observed along short channel lengths are novel and suggest that species differ in their propensity for movement along streams, which could have consequences for local densities of eggs and juveniles in the aquatic environment. The degree to which population sizes are coupled across the terrestrial-to-aquatic transition is rarely investigated in aquatic insects and may provide fresh insight into sources of spatial variation within populations. Similarly, a more nuanced approach to research on the flight of aquatic insects, including age- and sex-specific phenomena, may provide greater insight into the diverse ecological functions and consequences of movement.

     

Multiple convergent evolution of arboreal life in oribatid mites indicates the primacy of ecology

Frequent convergent evolution in phylogenetically unrelated taxa points to the importance of ecological factors during evolution, whereas convergent evolution in closely related taxa indicates the importance of favourable pre-existing characters (pre-adaptations). We investigated the transitions to arboreal life in oribatid mites (Oribatida, Acari), a group of mostly soil-living arthropods. We evaluated which general force—ecological factors, historical constraints or chance—was dominant in the evolution of arboreal life in oribatid mites. A phylogenetic study of 51 oribatid mite species and four outgroup taxa, using the ribosomal 18S rDNA region, indicates that arboreal life evolved at least 15 times independently. Arboreal oribatid mite species are not randomly distributed in the phylogenetic tree, but are concentrated among strongly sclerotized, sexual and evolutionary younger taxa. They convergently evolved a capitate sensillus, an anemoreceptor that either precludes overstimulation in the exposed bark habitat or functions as a gravity receptor. Sexual reproduction and strong sclerotization were important pre-adaptations for colonizing the bark of trees that facilitated the exploitation of living resources (e.g. lichens) and served as predator defence, respectively. Overall, our results indicate that ecological factors are most important for the observed pattern of convergent evolution of arboreal life in oribatid mites, supporting an adaptationist view of evolution.