Twinning and fetal sex ratio in moose: effects of maternal age and mass

1997 ◽  
Vol 75 (11) ◽  
pp. 1945-1948 ◽  
Author(s):  
T. Nygrén ◽  
I. Kojola
Keyword(s):  
Sex Ratio ◽  
Litter Size ◽  
Female Competition ◽  
Offspring Sex Ratio ◽  
Female Age ◽  
Maternal Characteristics ◽  
Low Degree ◽  
Offspring Sex ◽  
Limited Food ◽  
Female Bias

To evaluate hypotheses concerning the effects of maternal characteristics on litter size and offspring sex ratio in a polygynous mammal, we examined how female age and mass affected the number and sex ratio of fetuses in moose (Alces alces). We analysed 420 fetuses collected from 297 females killed in Finland. Females that carried two fetuses were older than females with one fetus, while mass did not affect litter size. Sex ratio was not conclusively linked with maternal quality. The overall lack of difference in the sex ratio (no male bias among fetuses carried by the heaviest females) can be explained by the rather low degree of polygyny and the lack of intense female – female competition for a limited food supply (no female bias among fetuses carried by the heaviest females).

scholarly journals Age-Dependent Constraints of Sex Allocation in a Parasitoid Wasp

2014 ◽  
Vol 2014 ◽  
pp. 1-4 ◽  
Author(s):  
Takatoshi Ueno
Keyword(s):  
Sex Ratio ◽  
Sex Ratios ◽  
Parasitoid Wasp ◽  
Maternal Control ◽  
Offspring Sex Ratio ◽  
Female Age ◽  
Physiological Constraints ◽  
Offspring Sex ◽  
Age Dependent ◽  
Control Failure

The offspring sex ratios of parasitoid wasps often depend on the age of ovipositing females. Physiological constraints such as sperm depletion and senescence are a likely cause. Also, maternal control in response to female age may be an alternative explanation. Here valvifer or abdominal tip movements were used to assess whether age-dependent sex ratio was due to physiological constraints or maternal control with an ichneumonid wasp,Pimpla nipponica; the offspring sex ratio at the time of wasp emergence was compared with the sex ratio predicted from abdominal tip movements. When the female was relatively young, there was little difference between the sex ratios examined. However, as the age of the females increased, the realized offspring sex ratio at wasp emergence was more male-biased than the sex ratio predicted at the time of oviposition. Thus, there was an inconsistency between the sex ratios. Curiously, the predictions of continuous movements for male egg deposition were always perfect, regardless of maternal age; fertilization control failure was detected when the females had decided to lay female eggs. Thus, physiological constraints are a likely explanation for the inconsistency in relation to female age forP. nipponica.

Breeding of Djungarian hamsters (Phodopus sungorus): influence of parity and litter size on weaning success and offspring sex ratio

1995 ◽  
Vol 29 (2) ◽  
pp. 172-176 ◽  
Author(s):  
Alexander Lerchl
Keyword(s):  
Sex Ratio ◽  
Confidence Interval ◽  
Litter Size ◽  
Breeding Success ◽  
Oestrous Cycle ◽  
Phodopus Sungorus ◽  
Offspring Sex Ratio ◽  
Older Parents ◽  
Long Day ◽  
Offspring Sex

The reproduction of 368 breeding pairs of Djungarian hamsters ( Phodopus sungorus) has been recorded and evaluated during 5 consecutive years. Three-hundred-and-eight pairs (=83.7%) were successful breeders giving birth to 2113 litters (up to 13 per dam) with a total of 12,591 offspring (mean: 6.0α2.2 [αSD] per litter). One-hundred-and-fifty dams delivered within 25 days after pairing, indicating a breeding success in the first oestrous cycle of 40.8% of all pairs (95% confidence interval: 35.7%-46.0%). The average number of offspring was higher in the 2nd than in the first litter, reaching a maximum in the 3rd (6.8α2.0), and decreasing thereafter. The loss of offspring (mean: 24.2%) was higher in older parents and influenced by the number of offspring per litter, indicating that experience and stress contribute to breeding success. A small, but significantly higher number of females was recorded only when no loss of offspring occurred until weaning (females: 2.36α1.75; males: 2.16α1.63, P<0.001). There was no indication of a shift of the offspring sex ratio towards favouring females with increased litter numbers, in contrast to the predictions of the Trivers-Willard hypothesis, at least with respect to the species and the breeding conditions as described in this report. Since all breeders were kept under long-day type photoperiods (16L : 8D), no signs of seasonality in breeding outcome were noted.

Maternal age, paternal age, and litter size interact to affect the offspring sex ratio of German Shepherd dogs

2019 ◽  
Vol 135 ◽  
pp. 169-173
Author(s):  
Anna Carolina Lopes Martins ◽  
Marília Andreia Vaz ◽  
Max Mendes Macedo ◽  
Renato Lima Santos ◽  
Conrado Aleksander Barbosa Galdino ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Litter Size ◽  
Maternal Age ◽  
Paternal Age ◽  
German Shepherd ◽  
Offspring Sex Ratio ◽  
Offspring Sex

scholarly journals Effects of age and parity on litter size and offspring sex ratio in golden hamsters (Mesocricetus auratus)

Reproduction ◽  
1988 ◽  
Vol 83 (1) ◽  
pp. 209-214 ◽  
Author(s):  
U. W. Huck ◽  
N. C. Pratt ◽  
J. B. Labov ◽  
R. D. Lisk
Keyword(s):  
Sex Ratio ◽  
Litter Size ◽  
Mesocricetus Auratus ◽  
Offspring Sex Ratio ◽  
Golden Hamsters ◽  
Offspring Sex

Offspring sex ratio in moose Alces alces in relation to paternal age: an experiment

2004 ◽  
Vol 10 (1) ◽  
pp. 51-57 ◽  
Author(s):  
Bernt-Erik Sæther ◽  
Erling J. Solberg ◽  
Morten Heim ◽  
John E. Stacy ◽  
Kjetill S. Jakobsen ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Alces Alces ◽  
Paternal Age ◽  
Offspring Sex Ratio ◽  
Offspring Sex

Breeding system can affect the offspring sex ratio in Syrian hamsters

2011 ◽  
Vol 45 (1) ◽  
pp. 55-57 ◽  
Author(s):  
M O M Chelini ◽  
N L Souza ◽  
E Otta
Keyword(s):  
Sex Ratio ◽  
Breeding System ◽  
Offspring Sex Ratio ◽  
Syrian Hamsters ◽  
Offspring Sex

scholarly journals Is biasing offspring sex ratio adaptive? A test of Fisher's principle across multiple generations of a wild mammal in a fluctuating environment

2018 ◽  
Vol 285 (1891) ◽  
pp. 20181251 ◽  
Author(s):  
Andrea E. Wishart ◽  
Cory T. Williams ◽  
Andrew G. McAdam ◽  
Stan Boutin ◽  
Ben Dantzer ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Tamiasciurus Hudsonicus ◽  
Red Squirrels ◽  
Offspring Sex Ratio ◽  
Offspring Sex ◽  
Adult Sex Ratio ◽  
Secondary Sex Ratio ◽  
North American Red Squirrels ◽  
Negative Frequency Dependent Selection ◽  
Fisher’S Principle

Fisher's principle explains that population sex ratio in sexually reproducing organisms is maintained at 1 : 1 owing to negative frequency-dependent selection, such that individuals of the rare sex realize greater reproductive opportunity than individuals of the more common sex until equilibrium is reached. If biasing offspring sex ratio towards the rare sex is adaptive, individuals that do so should have more grandoffspring. In a wild population of North American red squirrels ( Tamiasciurus hudsonicus ) that experiences fluctuations in resource abundance and population density, we show that overall across 26 years, the secondary sex ratio was 1 : 1; however, stretches of years during which adult sex ratio was biased did not yield offspring sex ratios biased towards the rare sex. Females that had litters biased towards the rare sex did not have more grandoffspring. Critically, the adult sex ratio was not temporally autocorrelated across years, thus the population sex ratio experienced by parents was independent of the population sex ratio experienced by their offspring at their primiparity. Expected fitness benefits of biasing offspring sex ratio may be masked or negated by fluctuating environments across years, which limit the predictive value of the current sex ratio.

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