scholarly journals Pre-ovulation control of hatchling sex ratio in the Seychelles warbler

2002 ◽  
Vol 269 (1495) ◽  
pp. 1067-1072 ◽  
Author(s):  
J. Komdeur ◽  
M. J. L. Magrath ◽  
S. Krackow
Keyword(s):  
Sex Ratio ◽  
Seychelles Warbler

scholarly journals Facultative sex ratio bias in the offspring of Seychelles warblers

1996 ◽  
Vol 263 (1370) ◽  
pp. 661-666 ◽  
Keyword(s):  
Reproductive Success ◽  
Sex Ratio ◽  
Inclusive Fitness ◽  
Breeding Birds ◽  
High Quality ◽  
Cumulative Mortality ◽  
Sex Ratio Bias ◽  
Seychelles Warbler ◽  
Biased Sex Ratio ◽  
Male To Female

Young Seychelles warblers ( Acrocephalus sechellensis ) frequently remain in their natal territories as helpers. Helpers on low-quality territories (as measured by food availability) reduce their parents' future reproductive success, whereas helpers on high-quality territories increase their parents' future reproductive success, thereby improving their own indirect component of inclusive fitness. Helpers are mainly females, which remain longer in their natal territories than males. The Seychelles warbler shows extreme skews in sex ratios of offspring at six months of age, varying from mainly males on low-quality territories to mainly females on high-quality territories. It appears that breeding birds avoid having helpers on low-quality territories and gain helpers on high-quality territories, thereby increasing their reproductive success. There is evidence that the biased sex ratio is caused by biased production, and not because of biased mortality at younger ages: (i) cumulative mortality from the egg stage to the stage at six months of age is insufficient to generate a consistent deviation from sex ratio parity; (ii) all 30 nestlings produced by two pairs on low-quality territories survived to be sexed as sons, and all nestlings produced by two pairs on high-quality territories survived to be sexed as 17 daughters and one son; and (iii) in addition, breeding pairs that were transferred from low- to high-quality territories, switched from the production of male to female nestlings.

Die unbehandelten Kranken: Ältere Männer mit Depression

2008 ◽  
Vol 27 (07) ◽  
pp. 617-619 ◽  
Author(s):  
M. Wittmann ◽  
E. Haen ◽  
H. Spießl ◽  
H. Hausner
Keyword(s):  
Sex Ratio ◽  
Epidemiologische Studien

ZusammenfassungZahlreiche epidemiologische Studien zeigen, dass sich das Geschlechterverhältnis der Prävalenz depressiver Erkrankungen ab der 6. Lebensdekade – also nach der weiblichen Menopause – wieder annähert. Wir haben untersucht, ob sich dieser epidemiologische Effekt auch in der stationären Versorgung abbildet. Unter Verwendung der AGATE-Stichtagsdaten der Jahre 2000 bis 2004, wurde der Zusammenhang zwischen Geschlecht und Alter bei stationär behandelten depressiven Patienten analysiert. Der Zusammenhang zwischen Geschlechterverhältnis und dem Alter wurde mithilfe des Korrelationskoeffizienten nach Spearman sowie mit χ2-Test untersucht. In der 5. und 6. Lebensdekade lag die Sex-Ratio F/M bei 1,7:1, sie stieg in der 7. Dekade auf 2,2:1 und in der 8. Dekade auf 2,6:1 an. Anders als aufgrund epidemiologischer Studien zu erwarten wäre, nähert sich in der stationär psychiatrischen Versorgung das Verhältnis depressiver Patienten im Alter nicht an. Depressive ältere Männer sind also im stationären Versorgungssystem unterrepräsentiert.

Fecundity and Gonado-somatic Index of Trichiurus lepturus (Linnaeus, 1758) Along the Zamboanga del Norte Coast

2018 ◽  
Vol 6 (7) ◽  
pp. 120
Author(s):  
Ma. Dulce C. Guillena
Keyword(s):  
Sex Ratio ◽  
Stock Assessment ◽  
Chi Square ◽  
Moon Phases ◽  
Ovary Weight ◽  
Moment Coefficient ◽  
Trichiurus Lepturus ◽  
Significant Difference ◽  
The Relationship ◽  
Somatic Index

Gonado-somatic index and fecundity are tools for measuring the sexual maturity and ability of animals to reproduce.  This study investigates the reproduction of Trichiurus lepturus. Specifically, this aimed to determine the sex ratio, the GSI, the relationship between fecundity and total length, fecundity and total weight, fecundity and ovary weight. The Descriptive Method of research was used.  Percentage and chi-square was utilized in determining the percentage of occurrence and sex ratio respectively.   Pearson r Product Moment Coefficient of Correlation was used to determine the relationships of the parameters. The study revealed that females outnumbered males and the sex ratio for different month showed significant difference.  Spawning season was observed to occur in November and December as revealed in its GSI values and it synchronized with the full and new moon phases.  Fecundity is positively correlated with body weight, body size, and ovary weight where ovary weight is observed to be the best index for fecundity.  The results of this study could be used further for formal stock assessment of cutlassfish fishery.

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