The role of partial incubation and egg repositioning within the clutch in hatching asynchrony and subsequent effects on breeding success

The main mechanism to achieve hatching asynchrony (HA) for incubating birds is to start heating the eggs before clutch completion. This might be achieved through partial incubation and/or early incubation. Even in the absence of incubation behaviour during the laying phase, clutches still experience a certain degree of asynchrony. Recent studies have shown that eggs located in the centre of the nest receive more heat than peripheral ones during incubation. As eggs receiving more heat would develop faster, we hypothesized that HA should be shorter in nests where eggs were moved homogeneously along the centre–periphery space during incubation than in those nests where eggs repeatedly remained in the same locations, either centrally or peripherally. We explored the relative roles of egg repositioning and partial incubation in determining HA in wild birds by (1) removing eggs from 20 Great Tit Parus major nests on the day of laying and replacing them with fake eggs to avoid partial incubation, and returning them when full incubation began; (2) monitoring twice a day the position of each individually marked egg relative to the clutch centre during incubation, and estimating the coefficient of variation of the distances; and (3) determining HA in each nest. Preventing partial incubation reduced HA by 51% days in experimental nests. It also caused negative effects for the incubating females (lengthening the full incubation period) and positive effects for the brood (increasing fledging success). However, our hypothesis about the role of egg repositioning on HA was not supported: all the females moved the eggs with remarkable consistency, generally attaining a coefficient of variation of the distances around 33%, and it was not related to the HA experienced. We therefore conclude that partial incubation is an important factor regulating HA, and females compensate for the potential effects of differential heating by moving the eggs homogeneously within the clutch.     

When an advantageous reproductive trait turns bad: Eggs of the threatened fish Genidens barbus as a natural bait in recreational fisheries

This study describes a recreational fishing method focused on marine catfish, Genidens barbus (Endangered-EN), through the adoption of its eggs as a natural bait during its reproductive period in southern Brazilian ecosystems. Male G. barbus perform parental care, collecting eggs released by females after the fertilization process. Owing to this male behavioural pattern during the reproductive period, these individuals are easily caught in recreational fisheries that use eggs of the same species as a natural bait. The current adoption of G. barbus eggs as bait may intensify the fishing pressure on its populations.     

Post-parturial reproduction in terrestrial isopods: a partial review

This review deals with some aspects of terrestrial isopod reproduction including breeding season, breeding periods, patterns and strategies, parturition, number and size of broods and mancae. Reproductive period is described by the exact dates (i.e. season) marsupial females were collected in the field, and the duration of the breeding period. The information for both aspects was generally obtained through field work by observing marsupial females. Two reproductive patterns are used by terrestrial isopods, either a discrete (i.e. seasonal) or a continuous (i.e. non-seasonal) pattern. The discrete pattern can be either annual when females breed once a year, or they can breed biannually or multi-annually (two or more times during the year). This conclusion is based generally on observing marsupial females in the field. Therefore, this information does not apply to the reproductive pattern of the individual female since a female may use either or both patterns, i.e. seasonal and continuous. Only by raising individual females singly (with a male) can this point be clarified. This way, the breeding strategy of the same individual female can be studied. The subject is discussed and reviewed based on my research data.     

The Dual-Oscillator System of Drosophila melanogaster Under Natural-Like Temperature Cycles

Dual-oscillator systems that control morning and evening activities can be found in a wide range of animals. The two coupled oscillators track dawn and dusk and flexibly adapt their phase relationship to seasonal changes. This is also true for the fruit fly Drosophila melanogaster that serves as model organism to understand the molecular and anatomical bases of the dual-oscillator system. In the present study, the authors investigated which temperature parameters are crucial for timing morning and evening activity peaks by applying natural-like temperature cycles with different daylengths. The authors found that the morning peak synchronizes to the temperature increase in the morning and the evening peak to the temperature decrease in the afternoon. The two peaks did not occur at fixed absolute temperatures, but responded flexibly to daylength and overall temperature level. Especially, the phase of the evening peak clearly depended on the absolute temperature level: it was delayed at high temperatures, whereas the phase of the M peak was less influenced. This suggests that the two oscillators have different temperature sensitivities. The bimodal activity rhythm was absent in the circadian clock mutants Clk^Jrk and cyc⁰¹ and reduced in per⁰¹ and tim⁰¹ mutants. Whereas the activity of Clk^Jrk mutants just followed the temperature cycles, that of per⁰¹ and tim⁰¹ mutants did not, suggesting that these mutants are not completely clockless. This study revealed new characteristics of the dual-oscillator system in Drosophila that were not detected under different photoperiods. (Author correspondence: yoshii@cc.okayama-u.ac.jp)     

Circadian clock speed increases during aging in the male Syrian hamster: A large-scale study

There are conflicting reports in the literature as to whether or not the circadian period in Syrian hamsters shortens with age, and those studies were conducted with small sample sizes. This report mines data from a large number of experiments resulting in more than 1000 measurements of circadian period in hamsters during aging up to 6 months, and this was correlated with both age and weight. Circadian period was calculated while hamsters were in running wheels in constant darkness. There is a weak correlation between hamster weight and circadian period, and there is significant shortening of circadian period during aging.     

Turkish nationalism and the Kurdish question

This article addresses the ways in which Turkish nationalism has perceived the Kurdish question. It is shown that both Turkish nationalism and the Kurdish question have passed through some paradigmatic moments in the twentieth century. This, I argue, has shaped the way that the Kurdish question has been perceived by Turkish nationalism. While the Kurdish question had been seen by Turkish nationalism mostly in terms of a fatal rivalry between the backward, pre-modern and tribal past and the prosperous present in the first half of the century, it was perceived in terms of a tension between the peripheral economy and national market in the fifties and sixties. In the 1970s, the Kurdish unrest was believed to be a product of communist incitement. Despite this impurity in perception, one thing has remained nearly unchanged for Turkish nationalism: Kurds could become Turkish. In other words, Turkish nationalism of the republican era has principally perceived Kurds as future-Turks. However, the signs in circulation at present indicate that the confidence of Turkish nationalism as to Kurds’ potential of becoming Turkish is not as firm as it used to be. At present, Turkish nationalism seems to be getting prepared to abandon its contention that Kurds are future-Turks.     

Factors affecting incidence and severity of leaf spot disease on lettuce caused by Septoria birgitae

In the 1990s during wet seasons a new disease causing brown leaf spots on lettuce (Lactuca sativa) was found for the first time in many lettuce‐growing areas of Austria and Germany. The causal agent, a new pathogenic species called Septoria birgitae, may be responsible for total crop loss. To study how temperature, inoculum density and leaf wetness period influence disease incidence and severity of leaf spot on lettuce caused by S. birgitae, we carried out in vivo experiments in growth chambers and in the field. Additionally, we evaluated the relevance of infected plant debris acting as a primary inoculum source in soil for subsequent crops. S. birgitae produces spores over a wide temperature range between 5°C and 30°C, and can infect plants at temperatures between 10°C and 30°C, with an optimum between 20°C and 30°C. Spores of S. birgitae at a density of at least 10³ conidia mL^–1 are essential for disease outbreak on lettuce. Because leaf wetness is crucial for releasing conidia from pycnidia, we studied the impact of leaf wetness duration on disease development under various temperature conditions. For relevant leaf spot disease development on lettuce in vivo, a leaf wetness duration of at least 24 h and temperatures higher than 10°C were necessary. Leaf spot disease development in the field required several leaf wetness periods longer than 20 h at approximately 15°C at the beginning of crop cultivation. Incorporating S. birgitae infected plant debris in soil as a primary inoculum was not relevant for leaf spot disease outbreak in the next year. However, in cases of continuous cropping of lettuce on the same field and in the same season, Septoria‐infected lettuce debris may become more relevant.     

Spatial memory deficits in maternal iron deficiency paradigms are associated with altered glucocorticoid levels

"The goal of this study was to examine the effect of maternal iron deficiency on the developing hippocampus in order to define a developmental window for this effect, and to see whether iron deficiency causes changes in glucocorticoid levels. The study was carried out using pre-natal, post-natal, and pre + post-natal iron deficiency paradigm. Iron deficient pregnant dams and their pups displayed elevated corticosterone which, in turn, differentially affected glucocorticoid receptor (GR) expression in the CA1 and the dentate gyrus. Brain Derived Neurotrophic Factor (BDNF) was reduced in the hippocampi of pups following elevated corticosterone levels. Reduced neurogenesis at P7 was seen in pups born to iron deficient mothers, and these pups had reduced numbers of hippocampal pyramidal and granule cells as adults. Hippocampal subdivision volumes also were altered. The structural and molecular defects in the pups were correlated with radial arm maze performance; reference memory function was especially affected. Pups from dams that were iron deficient throughout pregnancy and lactation displayed the complete spectrum of defects, while pups from dams that were iron deficient only during pregnancy or during lactation displayed subsets of defects. These findings show that maternal iron deficiency is associated with altered levels of corticosterone and GR expression, and with spatial memory deficits in their pups."     

Fringes of the empire: Diet and cultural change at the Roman to post‐Roman transition in NW Iberia

A growing number of paleodiet investigations over recent years have begun to reveal the stark dietary differences that existed between regions of the Roman Empire, as well as significant changes in subsistence strategies after its fall. The present study explores the dietary changes at the Roman to post‐Roman (Germanic) transition in the Northwest Iberian Peninsula, in order to improve our understanding of the changes that occurred at end of the Roman Empire in different regions across Europe and to also consider the influence of climate had on them. The carbon and nitrogen stable isotope investigation in bone collagen from A Lanzada, NW Spain (100–700 AD), which was an important commercial, coastal settlement has been presented. A human sample of 59 individuals, 6 of them subadults, is compared with 31 faunal specimens, which include a number of marine fish. Isotope data for the terrestrial fauna reveal the influence of the sea on the local isotope baseline. Analysis of the human samples indicates a mixed marine‐terrestrial diet. A shift in mean human δ¹³C values from ?16.7‰ to ?14.3‰ provides clear evidence for a significant change in diet in the post‐Roman period, probably through the intensification of both marine resources exploitation and C₄‐plant consumption (presumably millet). A deterioration of paleoenvironmental conditions, together with a poor socioeconomic situation and the arrival of new people, the Sueves, who brought a new political and socioeconomic system have been discussed as the main causes for the dietary modification in post‐Roman times.