Search results for "FECUNDITY"

Abstención sexual durante la Cuaresma en Andalucía a lo largo del siglo XX y su impacto en la estacionalidad de los nacimientos

2018

Durante siglos ha permanecido vigente en las poblaciones católicas un precepto religioso que prohibía las relaciones sexuales durante la Cuaresma. Esta interdicción repercutía en una disminución de concepciones y en un repunte tras dicho periodo, ambos difíciles de detectar porque, en poblaciones que no ejercían un control efectivo de la fecundidad, también se registraba un pico de concepciones durante la primavera. En la actualidad este precepto ha desaparecido como consecuencia de un proceso de erosión que no conocemos suficientemente. Con los datos anonimizados de todas las personas nacidas en Andalucía y supervivientes a 1 de enero de 2003 (n=8.397.206), este trabajo pretende determinar…

Feeding habits, post-embryonic and adult survival, mating, virility and fecundity of the predacious miteAmblyseius swirskii [Acarina: Phytoseiidae] o…

1977

The nutritional value forAmblyseius swirskiiAthias-Henriot, of eggs or crawlers ofCoccus hesperidum L.,Saissetia oleae (Olivier),S. coffeae (Walker),Pseudococcus citriculusGreen, andP. longispinusTarg.-Tozz, even with the addition of honeydew, was low; only a few young reached adulthood and the oviposition rate was negligible. However, addition of honeydew toTetranychus cinnabarinusBoisd. enhanced the oviposition rate ofAmblyseius swirskii. Honeydew was a favourite food forA. swirskii, whereas the eggs and crawlers tested were not eagerly attacked and consumed. Females and males fed honeydew ofSaissetia oleae mated readily and the females were inseminated, but fecundity was negligible.

Rodent plagues, immunocontraception and the mousepox virus

2001

Abstract Rodent plagues cause a major problem for agriculture in many temperate regions, and immunocontraception offers a new method to control fertility in these and other pest vertebrates. However, it is difficult to find an effective carrier for contraceptives for large numbers of pest animals in the field. In a new study, Jackson et al. manipulated the mousepox virus to boost the immune response in infected mice Mus musculus when testing the basis for controlling their fecundity rates. However, all infected mice (and half of recently immunized mice) died. Despite these unexpected and dramatic results of the engineering of mousepox virus, immunocontraception remains the most promising me…

Antioxidants may protect against infertility.

1998

Laboratory relationships between adult lifetime reproductive success and fitness surrogates in a Drosophila littoralis population

2011

The difficulties in measuring total fitness of individuals necessitate the use of fitness surrogates in ecological and evolutionary studies. These surrogates can be different components of fitness (e.g. survival or fecundity), or proxies more uncertainly related to fitness (e.g. body size or growth rate). Ideally, fitness would be measured over the lifetime of individuals; however, more convenient short-time measures are often used. Adult lifetime reproductive success (adult LRS) is closely related to the total fitness of individuals, but it is difficult to measure and rarely included in fitness estimation in experimental studies. We explored phenotypic correlations between female adult LRS…

Factors affecting abundance of Triaenophorus infection in Cyclops strenuus, and parasite-induced changes in host fitness.

2000

Factors affecting the abundance of Triaenophorus crassus and Triaenophorus nodulosus procercoids in their copepod first intermediate host, Cyclops strenuus, and effects of infection on feeding behaviour, reproduction and survival of the host were studied experimentally. When exposed to the same number of coracidia, copepods harboured considerably less procercoids in the trials where ciliates or Artemia salina nauplii were given as alternative food items. The prevalence of infection was higher in adult copepods as compared with copepodite stage IV and stage V, and higher in stage V than in stage IV. The prevalences in adult females and males did not differ significantly from each other. The …

Effects of the insect growth regulator cyromazine on the fecundity, fertility and offspring development of Mediterranean fruit fly,Ceratitis capitata…

1995

Addition of cyromazine to adult diet affected negatively the development of Ceratitis capitata Wied. (Dipt., Tephritidae) offspring. Five concentrations of cyromazine (0.00001 mg/ml, 0.01 mg/ml, 0.1 mg/ml, 1 mg/ml and 10 mg/ml) have been tested. A reduction of Mediterranean fruit fly populations has been found mainly due to the effects of fertility and larval development. At these concentrations, cyromazine does not affect Ceratitis capitata fecundity.

Asexual multiplication of larval parasitic worms: a predictor of adult life-history traits in Taeniidae?

2001

The hypothesis that asexual multiplication inside the intermediate host and adult life-history traits within the final host are independent is tested among Cestoda. Using phylogenetic relationships among the Cestoda species, we can show that asexual multiplication appears to have been lost and recovered several times throughout Taeniidae evolution; this allows a comparison of the adult life-history traits of species with and without asexual multiplication at the larval stage. The adult trait considered is the size of the parasite, since numerous life-history traits, such as fecundity and longevity, are correlated with size. If adult traits are independent of whether the larval stage reprodu…

Evolution of male and female choice in polyandrous systems

2017

We study the evolution of male and female mating strategies and mate choice for female fecundity and male fertilization ability in a system where both sexes can mate with multiple partners, and where there is variation in individual quality (i.e. in the availability of resources individuals can allocate to matings, mate choice and production of gametes). We find that when the cost of mating differs between sexes, the sex with higher cost of mating is reluctant to accept matings and is often also choosy, while the other sex accepts all matings. With equal mating costs, the evolution of mating strategies depends on the strength of female sperm limitation, so that when sperm limitation is stro…

An experimental manipulation of life-history trajectories and resistance to oxidative stress

2006

Optimal investment into life-history traits depends on the environmental conditions that organisms are likely to experience during their life. Evolutionary theory tells us that optimal investment in reproduction versus maintenance is likely to shape the pattern of age-associated decline in performance, also known as aging. The currency that is traded against different vital functions is, however, still debated. Here, we took advantage of a phenotypic manipulation of individual quality in early life to explore (1) long-term consequences on life-history trajectories, and (2) the possible physiological mechanism underlying the life-history adjustments. We manipulated phenotypic quality of a co…