Incubation capacity limits maximum clutch size in black-tailed gulls Larus crassirostris

Factors determining clutch size of birds have long been the central issue in studies in life histories. It is assumed that the configuration of brood patches could limit the maximum clutch size. To test this hypothesis we manipulated clutch sizes and measured egg temperature as well as reproductive consequences in black-tailed gulls Larus crassirostris , which usually lay two egg clutches and have three brood patches. Mean egg temperature in 4-egg clutches (32.6±1.0°C) was significantly lower than in 2-egg (34.6±0.4°C) and 3-egg clutches (34.1±0.4°C), because egg temperature of the coolest egg within a 4-egg clutch was often substantially lower than the other three eggs. The proportion of eggs hatching from 4-egg clutches (11.6%) was lower than those of 2-egg (49.1%) and 3-egg clutches (52.0%). Four-egg clutches had longer incubation periods (29.6±1.3 day) than 2-egg (28.1±1.7 day) and 3-egg clutches (28.0 ±1.3 day). The results indicate that incubation capacity, which may be determined by the configuration of brood patches, limits the maximum clutch size in black tailed gulls, but not the actual clutch size typically laid.     

TopBP1 functions with 53BP1 in the G1 DNA damage checkpoint

TopBP1 is a checkpoint protein that colocalizes with ATR at sites of DNA replication stress. In this study, we show that TopBP1 also colocalizes with 53BP1 at sites of DNA double‐strand breaks (DSBs), but only in the G1‐phase of the cell cycle. Recruitment of TopBP1 to sites of DNA replication stress was dependent on BRCT domains 1–2 and 7–8, whereas recruitment to sites of DNA DSBs was dependent on BRCT domains 1–2 and 4–5. The BRCT domains 4–5 interacted with 53BP1 and recruitment of TopBP1 to sites of DNA DSBs in G1 was dependent on 53BP1. As TopBP1 contains a domain important for ATR activation, we examined whether it contributes to the G1 cell cycle checkpoint. By monitoring the entry of irradiated G1 cells into S‐phase, we observed a checkpoint defect after siRNA‐mediated depletion of TopBP1, 53BP1 or ATM. Thus, TopBP1 may mediate the checkpoint function of 53BP1 in G1.     

Prudent investment in rearing nestlings in bull-headed shrikes

I investigated seasonal changes in the relationships between brood size, body mass of nestlings and body mass of parents of the bull-headed shrike, Lanius bucephalus, in Ishikari, northern Japan. When the broods were 12days old, the body mass of the heaviest nestling in a brood did not differ among brood sizes, or throughout the season. However, the body mass of the lightest nestlings in a brood was different among brood sizes. The body mass of the lightest nestling in five- and six-nestling broods decreased throughout the season. The lightest nestling in four-nestling broods, and the lightest and the second lightest nestlings in five-nestling broods, were significantly lighter than the heaviest nestling in broods of this size. It is likely that pairs with six nestlings at 12days old can feed at least five of these nestlings enough to ensure their survival . The standardized body mass of parents (SBM), which was defined as the body mass divided by the length of the tarsus, did not differ among brood sizes, or throughout the season. It is possible that the relationship between the constancy of the SBM and the seasonal decline in the body mass of nestlings indicates that bull-headed shrikes have a limit to their parental efforts.     

Isolation and characterization of the fission yeast gene Sprpa12+ reveals that the conserved C-terminal zinc-finger region is dispensable for the function of its product

RNA polymerase I of Saccharomyces cerevisiae contains a small subunit, A12.2, encoded by RPA12, that was previously shown to be involved in the assembly and/or stabilization of the largest subunit, A190, of RNA polymerase I. To examine whether an equivalent subunit is present in another eukaryotic RNA polymerase I, we have cloned a Schizosaccahromyces pombe cDNA that is able to complement the rpa12 mutation in S. cerevisiae. The gene, named Sprpa12+, encodes a polypeptide of 119 amino acids that shows 55% identity to S. cerevisiae A12. 2 over its entire length, including two zinc-finger motifs. Disruption of the chromosomal Sprpa12+ gene shows that it is required for growth at higher temperatures but not at lower temperatures. Expression of Sprpa190+/nuc1+, which encodes the largest subunit of the S. pombe RNA polymerase I, from a multicopy plasmid can partially suppress the growth defect of the Sprpa12 disruptant at higher temperatures. These findings suggest that A12.2 subunit is functionally and structurally conserved between S. cerevisiae and S. pombe. Finally, the analysis of mutants suggests that SpRPA12 requires the zinc-finger domain in the N-terminal region but not the one in the C-terminal region for its function.     

Effects of habitat use on food acquisition and food caching during a nonbreeding season in a winter-breeding,food-storing passerine

ABSTRACT

Capsule: Wintering male Bull-headed Shrikes Lanius buchepalus preferred vegetable fields with perch sites to search for and detect terrestrial prey, and males occupying territories with large areas of vegetable fields acquired more prey and cached more food.

Aims: To better understand effects of habitat use on food acquisition and food caching of the Bull-headed Shrike, we investigated relationships between habitat quality (measured through foraging-site selection and foraging success) and food caching during the non-breeding season.

Methods: We monitored 66 territorial male shrikes during the non-breeding season from 2014 to 2016, and collected data on foraging-site selection, foraging success, and food caching.

Results: Our field observations showed that male shrikes preferred to forage over vegetable fields and that males occupying territories incorporating large areas of that habitat were able to acquire more food items and store more food caches in their territories during the nonbreeding season.

Conclusion: We suggest that for male Bull-headed Shrikes, a winter-breeding food-storing passerine, the quality of habitat in the nonbreeding season has the potential to affect their subsequent fitness.     

Development of the skeleton in Japanese quail embryos

In the research fields of experimental embryology, teratological testing, and developmental engineering in avian species, a knowledge of normal embryonic development is necessary so that research may be performed efficiently and precisely. A series of normal stages based on external appearance has been established in both chicken and quail embryos. Those based on skeletal features, however, have not been elucidated. The present study newly established a series of normal stages for the development of the Japanese quail embryo skeleton. This series is composed of 15 stages determined by observing the timing of chondrification and calcification of the skeleton every 24 h, from 3 to 17 days of incubation. Cartilage and ossified bones were stained blue and red with Alcian blue 8GX and alizarin red S, respectively. These skeletogenous stages of the Japanese quail embryo will be useful as a normal control not only in studies of experimental embryology, teratological testing, and developmental engineering, but also in the analysis of mutant embryos with skeletal abnormalities.     

Enzyme Immunoassay of the Myelin Basic Protein

Abstract: An enzyme immunoassay using a double-antibody solid-phase technique for myelin basic protein (MBP) has been developed. Antisera were prepared by immunizing rabbits with the purified MBP from chick brain. The conjugation of MBP with horseradish peroxidase was performed by the periodate oxidation method in triethanolamine-acetate buffer (pH 8.5). The sample, antiserum, and conjugate were incubated at 4°C for 16 h, after which the insoluble second antibody was added and the reaction mixture was incubated at 4°C for 3 h. The peroxidase activity of the insoluble conjugate was assayed fluorometrically with hydrogen peroxide and 3-( p -hydroxyphenyl)propionic acid as substrates. The method had an analytical range from 50 pg to 1 ng (from 2.3 × 10⁻¹⁵ to 4.5 × 10⁻¹⁴ mol). The within-assay coefficient of variation (CV) was between 4 and 11% and the between-assay CV for 200 and 400 pg of MBP was 5.5 and 7.1%, respectively. A weak cross-reactivity was observed between chick MBP and bovine MBP, while no reactivity was shown with calf thymus histone. The MBP content of the brain during development increased markedly from the 3rd embryonic week to the 3rd post-hatch week (from 0.01 to 2.4 mg/g of fresh tissue), and the adult level was 3.2 mg/g of fresh tissue.