Fecundity ratios

In further analysis of the Buck et al. (1999) study summarized above and the Buck et al. (1997) study summarized in Section 3.2.5.2.1 (Female Reproductive Effects), Buck et al. (2000) combined maternal and paternal fish consumption into one model looking at fecundability ratios as the outcome, rather than TTP (continuous variable used in 1997 paper) or conception delay (>12 months unprotected intercomse used in 1999 paper). The sample included 606 women with known and unknown TTP who discontinued... 

In this chapter, we will examine the multiple roles that CHCs play in a wide variety of behaviors (courtship, mate discrimination, learning, aggregation, dominance), and in factors related to reproduction (fecundity, sex ratio). We will focus on the variety of effects that have been observed, rather than providing an exhaustive account of all hydrocarbons that have been detected in every species of dipteran. A word of warning may be necessary, however most studies have focused on the main compound in a given species, and have tended to neglect the role of quantitatively minor compounds or of ratios. The very success of the model established in the early 1970s, coupled with evidence from our own work in Drosophila, indicates that other aspects of dipteran pheromones may be overlooked. 

Continue to develop and enhance population-based surveillance systems for the real-time capture of sentinel health end-points. This includes current surveillance systems such as vital registration for birth size and gestation and birth defects registries for capture of major malformations. Consideration of emerging sentinel end-points such as fecundability, as measured by time to pregnancy and sex ratios, should receive added research consideration. 

Fertility end-points include live births, plurality of birth, and secondary sex ratio, or the ratio of male to female live births. Xenobiotics that selectively impact the X or Y chromosome may result in decrements of the sex ratio, possibly due to differences in rates of conception or pregnancy loss. In fact, investigators have used this ratio as a sentinel marker of male fecundity (Davis et al.,... 

A complete and up-to-date reproductive history should be obtained and available for all naval personnel (men and women active duty and reservists). Such a history should be updated annually or after a reproductive outcome. This would provide important baseline information and permit study of maternally and paternally mediated effects. The reproductive history should address sexual activity and inactivity, sexual libido, sexual dysfunction, semen analysis, menstruation history, pregnancy intentions, time-to-pregnancy (conception delays, fecundability, infertility), and pregnancy outcomes (e.g., ectopic pregnancy, spontaneous loss, fetal demise, birth size, secondary sex ratios, birth defects, mental retardation, developmental disabilities). Recording this information is in keeping with the definition for reproductive health and the need to address all health aspects of individuals. 

As with the trends previously mentioned, proposals have been promulgated for internal and external constraints. At first pass, it is tempting to account for relations between life history variables almost purely on the basis of fundamental allometric constraints. Metabolic rate, lifespan, fecundity, age at maturity, and maternal investment all vary with body mass as power functions. In fact, relations are invariant between some of these variables. For example, lifespan scales with body mass by a 1/4 power, and heart rate (or the rate of ATP synthesis) scales with body mass by a — 1/4 power. The product yields an approximately constant number of metabolic events in mammal species, independent of body mass or lifespan. Age at maturity / lifespan, and annual maternal investment / lifespan (for indeterminate growers), are also invariant ratios (Chamov, 1993 Chamov et al., 2001 Steams, 1992). West and Brown (2004) point out that invariant ratios, and universal quarter-power allometric trends in general, suggest underlying physical first principles. They employ their model to explain these life history relations (Enquist et al., 1999 Niklas and Enquist, 2001 West et al., 2001). 

Genetic manipulation of arthropod natural enemies Is an old concept (9-10), although field Implementation of genetically-improved natural enemies was not achieved until recently (8,11). Various biological and behavioral attributes have been discussed as amenable to genetic selection. Including sex ratio, temperature tolerance, developmental rate, fecundity, diapause, and host preference, as well as pesticide resistances (12). 

Development time, fecundity, sex ratio, mating compatibilities and competition, diapause, persistence of the carbaryl resistance, and the capability to control spider mite populations under carbaryl sprayed and unsprayed conditions were evaluated. The resistant strain did not differ significantly from the susceptible strains tested In the absence of carbaryl treatment. 

Niu H, Zhao L, Lu M, Zhang S, Sun J (2012) The ratio and concentration of two monoterpenes mediate fecundity of the pinewood nematode and growth of its associated fiuigi. PLoS One 7 e31716. doi 10.1371/joumal.pone.0031716... 

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