scholarly journals Neuroendocrine control of reduced persistence of egg-laying in domestic hens: evidence for the development of photorefractoriness

Reproduction ◽  
1992 ◽  
Vol 94 (1) ◽  
pp. 221-235 ◽  
Author(s):  
P. J. Sharp ◽  
I. C. Dunn ◽  
S. Cerolini
Keyword(s):  
Egg Laying ◽  
Neuroendocrine Control

Experimental increase in female mass during the fertile phase leads to enhanced extra-pair paternity in pied flycatchers Ficedula hypoleuca

2019 ◽  
Author(s):  
Mireia Plaza ◽  
Alejandro Cantarero ◽  
Juan Moreno
Keyword(s):  
Negative Relationship ◽  
Ficedula Hypoleuca ◽  
Egg Laying ◽  
Female Dominance ◽  
Laying Date ◽  
Control Group ◽  
Wing Loading ◽  
Potential Fecundity ◽  
Fertile Phase ◽  
Extra Pair Paternity

Female mass in most altricial birds reaches its maximum during breeding at egg-laying, which coincides temporally with the fertile phase when extra-pair paternity (EPP) is determined. Higher mass at laying may have two different effects on EPP intensity. On the one hand, it would lead to increased wing loading (body mass/wing area), which may impair flight efficiency and thereby reduce female’s capacity to resist unwanted extra-pair male approaches (sexual conflict hypothesis). On the other hand, it would enhance female condition, favouring her capacity to evade mate-guarding and to search for extra-pair mates (female choice hypothesis). In both cases, higher female mass at laying may lead to enhanced EPP. To test this prediction, we reduced nest building effort by adding a completely constructed nest in an experimental group of female pied flycatchers (Ficedula hypoleuca). Our treatment caused an increase in mass and thereby wing loading and this was translated into a significantly higher EPP in the manipulated group compared with the control group as expected. There was also a significant negative relationship between EPP and laying date and the extent of the white wing patch, an index of female dominance. More body reserves at laying mean not only a higher potential fecundity but a higher level of EPP as well. This interaction had not previously received due attention but should be considered in future studies of avian breeding strategies.

Elevated nest predation risk promotes offspring size variation in birds with prolonged parental care.

2019 ◽  
Author(s):  
Gretchen F. Wagner ◽  
Emeline Mourocq ◽  
Michael Griesser
Keyword(s):  
Predation Risk ◽  
Reproductive Cycle ◽  
Perceived Risk ◽  
Nest Predation ◽  
Bird Species ◽  
Size Variation ◽  
Egg Laying ◽  
Offspring Size ◽  
Natural Predation ◽  
Risk Spreading

Predation of offspring is the main cause of reproductive failure in many species, and the mere fear of offspring predation shapes reproductive strategies. Yet, natural predation risk is ubiquitously variable and can be unpredictable. Consequently, the perceived prospect of predation early in a reproductive cycle may not reflect the actual risk to ensuing offspring. An increased variance in investment across offspring has been linked to breeding in unpredictable environments in several taxa, but has so far been overlooked as a maternal response to temporal variation in predation risk. Here, we experimentally increased the perceived risk of nest predation prior to egg-laying in seven bird species. Species with prolonged parent-offspring associations increased their intra-brood variation in egg, and subsequently offspring, size. High risk to offspring early in a reproductive cycle can favour a risk-spreading strategy particularly in species with the greatest opportunity to even out offspring quality after fledging.

Autumn Migration of Waders (Charadrii) at the Reda Mouth (N Poland)

Ring ◽  
2009 ◽  
Vol 31 (1) ◽  
pp. 23-39 ◽  
Author(s):  
Włodzimierz Meissner ◽  
Anna Włodarczak-Komosińska ◽  
Dariusz Górecki ◽  
Cezary Wójcik ◽  
Mateusz Ściborski ◽  
...  
Keyword(s):  
Migration Pattern ◽  
Egg Laying ◽  
Autumn Migration ◽  
Tundra Zone ◽  
Age Classes ◽  
Calidris Alpina ◽  
Mouth Region ◽  
Baltic Coast ◽  
Northern Latitudes ◽  
Vanellus Vanellus

Autumn Migration of Waders (Charadrii) at the Reda Mouth (N Poland) The migration of waders was investigated at the Reda mouth (Polish Baltic coast) between 1996 and 2001. During the study 496 counts were conducted in the period between 5 July and 5 October. The most numerous species observed were: the Lapwing (Vanellus vanellus) - 39.5% and Dunlin (Calidris alpina) - 29.8% of all waders. Because of a variety of habitats in the Reda mouth region, among the waders staging numerously in the Reda mouth there were species typical both for coastal and inland habitat. It was shown that birds from tundra zone migrated later than those from more southern breeding areas, which was caused by much later beginning of egg laying in northern latitudes. Moreover, in the species from tundra zone, e.g. the Knot (Calidris canutus), Little Stint (C. minuta), Curlew Sandpiper (C. ferruginea), the migration of both age classes were well separated, whereas in those from more southern areas, e.g. the Little Ringed Plover (Charadius dubius), Common Sandpiper (Actitis hypoleucos), such difference was less pronounced and the period of common passage of adults and juveniles was much longer. A comparison of the obtained data on migration pattern with some other sites in Poland where regular counts were conducted showed several similarities and some discrepancies, which are discussed in the paper.

Structure-Reactivity Relationships on Substrates and Inhibitors of the Lysine Deacylase Sirtuin 2 from Schistosoma Mansoni (SmSirt2)

2019 ◽  
Author(s):  
Daria Monaldi ◽  
Dante Rotili ◽  
Julien Lancelot ◽  
Martin Marek ◽  
Nathalie Wössner ◽  
...  
Keyword(s):  
Schistosoma Mansoni ◽  
Human Cancer ◽  
Egg Laying ◽  
Human Cancer Cells ◽  
Parasite Survival ◽  
Survival And Reproduction ◽  
Emergence Of Resistance ◽  
First Time ◽  
Parasitic Life Cycle

The only drug for treatment of Schistosomiasis is Praziquantel, and the possible emergence of resistance makes research on novel therapeutic agents necessary. Targeting of Schistosoma mansoni epigenetic enzymes, which regulate the parasitic life cycle, emerged as promising approach. Due to the strong effects of human Sirtuin inhibitors on parasite survival and reproduction, Schistosoma sirtuins were postulated as therapeutic targets. In vitro testing of synthetic substrates of S. mansoni Sirtuin 2 (SmSirt2) and kinetic experiments on a myristoylated peptide demonstrated lysine long chain deacylation as an intrinsic SmSirt2 activity for the first time. Focused in vitro screening of the GSK Kinetobox library and structure-activity relationships (SAR) of identified hits, led to the first SmSirt2 inhibitors with activity in the low micromolar range. Several SmSirt2 inhibitors showed potency against both larval schistosomes (viability) and adult worms (pairing, egg laying) in culture without general toxicity to human cancer cells.<br>

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