Factors Affecting the Primary Sex Ratio in Cows

2012 ◽  
Vol 29 (3) ◽  
pp. 96-102 ◽  
Author(s):  
Hisataka Iwata
Keyword(s):  
Sex Ratio ◽  
Factors Affecting ◽  
Primary Sex Ratio

scholarly journals Factors Affecting the Ratio of Female to Male of Pinewood Nematodes Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 763
Author(s):  
Pengfei Wei ◽  
Yongxia Li ◽  
Wei Zhang ◽  
Mengge Gao ◽  
Zhenkai Liu ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Maternal Age ◽  
Environmental Changes ◽  
Population Change ◽  
Bursaphelenchus Xylophilus ◽  
Pinewood Nematode ◽  
Factors Affecting ◽  
Primary Sex Ratio ◽  
Pinewood Nematodes ◽  
In The Wild

The pinewood nematode Bursaphelenchus xylophilus (B. xylophilus) is responsible for a devastating disease of pine forests. Its pathogenicity is closely related to the numbers of individual B. xylophilus. The ratio of female to male (sex ratio) is key to understanding population change in this species. The sex ratio of B. xylophilus varies widely, but it is unclear how it is affected by environmental changes. The sex ratios of nematodes, isolated from different samples in the wild, varied between 0.93 and 2.20. Under laboratory conditions, maternal age and the population did not affect the sex ratio of progeny. A change from good to poor nutritional status was associated with a reduction of the sex ratio of progeny from 1.85 to 1.41, which was speculated to result from a change in the primary sex ratio. Thus, B. xylophilus effectively maintains the sex ratio with maternal age and population changes but adjusts the sex ratio of progeny on the basis of the changes in nutrition.

The Life-History of Badumna-Candida (Araneae, Amaurobioidea)

1993 ◽  
Vol 41 (5) ◽  
pp. 441 ◽  
Author(s):  
MF Downes
Keyword(s):  
Sex Ratio ◽  
Egg Production ◽  
Production Cycle ◽  
Social Spider ◽  
Social Spiders ◽  
Primary Sex Ratio ◽  
The Social ◽  
The Status ◽  
History Of ◽  
Changes Over Time

A two-year study of the social spider Badumna candida at Townsville, Queensland, provided information on colony size and changes over time, maturation synchrony, temperature effects on development, sex ratio, dispersal, colony foundation, fecundity and oviposition. Key findings were that B. candida outbred, had an iteroparous egg-production cycle between March and October, had an even primary sex ratio and achieved maturation synchrony by retarding the development of males, which matured faster than females at constant temperature. There was no overlap of generations, the cohort of young from a nest founded by a solitary female in summer dispersing the following summer as subadults (females) or subadults and adults (males). These findings confirm the status of B. candida as a periodic-social spider (an annual outbreeder), in contrast to the few known permanent-social spider species whose generations overlap. Cannibalism, normally rare in social spiders, rose to 48% when spiders were reared at a high temperature. This may be evidence that volatile recognition pheromones suppress predatory instincts in social spiders.

scholarly journals Primary sex ratio adjustment to experimentally reduced male UV attractiveness in blue tits

2006 ◽  
Vol 17 (4) ◽  
pp. 539-546 ◽  
Author(s):  
Peter Korsten ◽  
C. (Kate) M. Lessells ◽  
A. Christa Mateman ◽  
Marco van der Velde ◽  
Jan Komdeur
Keyword(s):  
Sex Ratio ◽  
Primary Sex Ratio ◽  
Sex Ratio Adjustment ◽  
Blue Tits

scholarly journals Facultative primary sex ratio variation: a lack of evidence in birds?

2004 ◽  
Vol 271 (1545) ◽  
pp. 1277-1282 ◽  
Author(s):  
John G. Ewen ◽  
Phillip Cassey ◽  
Anders P. Møller
Keyword(s):  
Sex Ratio ◽  
Primary Sex Ratio ◽  
Ratio Variation

scholarly journals Maternal Diet and Other Factors Affecting Offspring Sex Ratio: A Review

2004 ◽  
Vol 71 (4) ◽  
pp. 1063-1070 ◽  
Author(s):  
Cheryl S. Rosenfeld ◽  
R. Michael Roberts
Keyword(s):  
Sex Ratio ◽  
Maternal Diet ◽  
Offspring Sex Ratio ◽  
Factors Affecting ◽  
Offspring Sex

II.—Prenatal Death in the Pig and its Effect upon the Sex-Ratio

1927 ◽  
Vol 46 ◽  
pp. 9-14 ◽  
Author(s):  
F. A. E. Crew
Keyword(s):  
Sex Ratio ◽  
Sex Chromosome ◽  
Selective Mortality ◽  
Cytological Evidence ◽  
Male And Female ◽  
Primary Sex Ratio ◽  
The Future ◽  
Secondary Sex Ratio

The cytological evidence concerning the pig is that the sex of the future individual is determined at the time of fertilisation, and that in respect of the elements of the sex-chromosome sex-determining mechanism the male is digametic. If this is so, if the two sorts of sperm are produced in equal numbers, if each kind is equally viable and functional, and if fertilisation is at random, then a primary sex-ratio (that which obtains at the time of conception) of equality must follow. If male and female zygotes are equally viable, then the secondary sex-ratio (that which obtains at the time of gestation) will also be equality. A secondary sex-ratio other than equality must be the reflection of an unequal primary sex-ratio, the result of a differential production of the two sorts of gametes elaborated by the digametic sex, of a selective fertilisation by these, or of a sexually selective mortality among the embryos or/and fœtuses. A secondary sex-ratio of equality can follow a pronounced inequality in the primary sex-ratio if a sexually selective mortality operates prenatally.

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