Maternal Mass (maternal + mass)

Distribution by Scientific Domains

Selected Abstracts


EVOLUTION, Issue 2 2006
Farrah Bashey
Abstract The existence of adaptive phenotypic plasticity demands that we study the evolution of reaction norms, rather than just the evolution of fixed traits. This approach requires the examination of functional relationships among traits not only in a single environment but across environments and between traits and plasticity itself. In this study, I examined the interplay of plasticity and local adaptation of offspring size in the Trinidadian guppy, Poecilia reticulata. Guppies respond to food restriction by growing and reproducing less but also by producing larger offspring. This plastic difference in offspring size is of the same order of magnitude as evolved genetic differences among populations. Larger offspring sizes are thought to have evolved as an adaptation to the competitive environment faced by newborn guppies in some environments. If plastic responses to maternal food limitation can achieve the same fitness benefit, then why has guppy offspring size evolved at all? To explore this question, I examined the plastic response to food level of females from two natural populations that experience different selective environments. My goals were to examine whether the plastic responses to food level varied between populations, test the consequences of maternal manipulation of offspring size for offspring fitness, and assess whether costs of plasticity exist that could account for the evolution of mean offspring size across populations. In each population, full-sib sisters were exposed to either a low- or high-food treatment. Females from both populations produced larger, leaner offspring in response to food limitation. However, the population that was thought to have a history of selection for larger offspring was less plastic in its investment per offspring in response to maternal mass, maternal food level, and fecundity than the population under selection for small offspring size. To test the consequences of maternal manipulation of offspring size for offspring fitness, I raised the offspring of low- and high-food mothers in either low- or high-food environments. No maternal effects were detected at high food levels, supporting the prediction that mothers should increase fecundity rather than offspring size in noncompetitive environments. For offspring raised under low food levels, maternal effects on juvenile size and male size at maturity varied significantly between populations, reflecting their initial differences in maternal manipulation of offspring size; nevertheless, in both populations, increased investment per offspring increased offspring fitness. Several correlates of plasticity in investment per offspring that could affect the evolution of offspring size in guppies were identified. Under low-food conditions, mothers from more plastic families invested more in future reproduction and less in their own soma. Similarly, offspring from more plastic families were smaller as juveniles and female offspring reproduced earlier. These correlations suggest that a fixed, high level of investment per offspring might be favored over a plastic response in a chronically low-resource environment or in an environment that selects for lower reproductive effort [source]

Influence of maternal mass and condition on energy transfer in Weddell seals

Summary 1Environmental variation influences food abundance and availability, which is reflected in the reproductive success of top predators. We examined maternal expenditure, offspring mass and condition for Weddell seals in 2 years when individuals exhibited marked differences in these traits. 2For females weighing 355 kg there was a positive relationship between maternal post-partum mass (MPPM) and lactation length, but below this there was no relationship, suggesting that heavier females were able to increase lactation length but lighter females were restricted to a minimum lactation period of 33 days. 3Overall, females were heavier in 2002, but in 2003 shorter females were lighter than similar-sized females in 2002 suggesting that the effects of environmental variability on foraging success and condition are more pronounced in smaller individuals. 4There was no relationship between MPPM and pup birth mass, indicating pre-partum investment did not differ between years. However, there was a positive relationship between MPPM and pup mass gain. Mass and energy transfer efficiency were 10·2 and 5·4% higher in 2002 than 2003, which suggests costs associated with a putatively poor-resource year were delayed until lactation. 5Heavier females lost a higher proportion of mass during lactation in both years, so smaller females may not have been able to provide more to their offspring to wean a pup of similar size to larger females. 6MPPM had only a small influence on total body lipid; therefore, regardless of mass, females had the same relative body composition. Females with male pups lost a higher percentage of lipid than those with female pups, but by the end of lactation female pups had 4·5% higher lipid content than males. 7It appears that for Weddell seals the consequences of environmentally induced variation in food availability are manifested in differences in maternal mass and expenditure during lactation. These differences translate to changes in pup mass and condition at weaning with potential consequences for future survival and recruitment. [source]

Mass-dependent reproductive strategies in wild bighorn ewes: a quantitative genetic approach

In the Ram Mountain bighorn sheep (Ovis canadensis) population, ewes differing by more than 30% in body mass weaned lambs with an average mass difference of only 3%. Variability in adult body mass was partly due to additive genetic effects, but inheritance of weaning mass was weak. Maternal effects could obscure genetic effects in the phenotypic expression of weaning mass, particularly if they reflected strategies of maternal expenditure that varied according to ewe mass. We performed a quantitative genetic analysis to assess genetic and environmental influences on ewe mass and on maternal expenditure. We used the mean daughters/mother regression method and Derivative Free Restricted Maximum Likelihood models to estimate heritability (h2) of ewe mass and indices of maternal expenditure. We found additive genetic effects on phenotypic variation in maternal mass, in lamb mass at weaning (absolute maternal expenditure) and in weaning mass relative to maternal mass at weaning (relative maternal expenditure). Heritability suggests that maternal expenditure has the potential to evolve. The genetic correlation of ewe mass and absolute maternal expenditure was weak, while ewe mass and relative maternal expenditure were strongly negatively correlated. These results suggest additive genetic effects on mass-dependent reproductive strategies in bighorn ewes. Mass-dependent reproductive strategies could affect lamb survival and phenotypic variation in adult mass. As population density increased and reproduction became costlier, small females reduced maternal expenditure more than large females. Constraints on reproductive strategy imposed by variations in resource availability are therefore likely to differ according to ewe mass. A general trend for a decrease in maternal expenditure relative to maternal size in mammals suggests that size-dependent negative maternal effects may be common. [source]

Maternal effort and joey growth in koalas (Phascolarctos cinereus)

J. R. Tobey
Abstract The extent to which sex-biased maternal investment characterizes mammals is controversial, with less information available for evaluating patterns of maternal effort in marsupials than in placentals. Koalas Phascolarctos cinereus are size-dimorphic animals with a lengthy period of dependency and they reside in mating systems that might favour sex-biased maternal investment. We examined 18 years of data recorded from koalas living at the San Diego Zoo in order to examine how joey development and maternal condition might be connected. Koalas are pregnant for only 1 month, but joey emergence from the pouch does not occur until 32 weeks of age. Neither maternal condition nor age affected sex ratio at joey emergence, and both sexes had the same survivorship prospects. Koala dams transport and nurse joeys for close to 1 year, at which time the two sexes are size dimorphic. Given the poor-quality diet of koalas, combined with maternal transport of infants who are at least 25% of maternal mass, we suggest that infant rearing poses high energetic costs on koala females. We suggest that ecological and energetic constraints have moulded koala maternal strategies such that females maximize allocation of resources to offspring, regardless of sex, in order to increase prospects for joey survivorship. [source]

Growth in colony living anubis baboon infants and its relationship with maternal activity budgets and reproductive status

Cécile Garcia
Abstract Early growth is of interest because it is susceptible to maternal effects and linked to fitness components for a range of species. Here we present anthropometric measurements on 23 infant olive baboons born into a captive colony in order to describe growth over the first 2 years of life, to explore maternal influences on growth, and to assess the impact of growth profiles on maternal reproduction. Six main findings emerged: 1) Infant growth rates in our colony were higher than those reported for wild populations but comparable to those observed for food-enhanced animals. 2) The ratio of infant mass to maternal mass was positively associated with reproductive parameters, such as duration of post-partum amenorrhea and interbirth interval. 3) Mothers resumed cycling and reconceived when their infants attained a relatively consistent threshold mass. 4) Infant mass-for-age was associated with maternal rank and, independently, with maternal mass such that females of high dominance rank and heavy females had relatively large infants at their resumption of cycling. 5) Low-ranking and lighter females had longer investment periods but smaller infants. They continued investment in infant through prolonged lactation until their infants reached a mass similar to that of infants of high-ranking/heavy mothers, suggesting that the lengthening of investment is essentially compensatory for slow early growth. 6) There was no relationship between infant growth and maternal activity budgets. Maternal physical and social factors, not energetics, contributed to differences among infants in growth trajectories, and infant growth temporally influenced successive reproductive events. Am J Phys Anthropol 2009. © 2008 Wiley-Liss, Inc. [source]

Placental insulin-like growth factor II (IGF-II) and its relation to litter size in the common marmoset monkey (Callithrix jacchus)

Julienne N. Rutherford
Abstract The primate placenta produces a wide variety of hormones throughout gestation that regulate placental function and fetal growth. One such hormone is insulin-like growth factor-II (IGF-II), a peptide implicated in cell division, differentiation, and amino acid transport. IGF-II concentrations were measured in 23 common marmoset (Callithrix jacchus) term placentas from twin and triplet litters in order to determine whether previously described differences in fetoplacental phenotype such as placental and litter mass and placental surface area were related to differences in endocrine function. IGF-II was extracted from frozen tissue samples and measured using an enzyme-linked immunosorbent assay kit designed for human tissue, which was validated for marmoset placenta. IGF-II concentrations were not related to placental or litter mass, and twin and triplet placentas did not differ in total concentration. However, per individual fetus, triplets were associated with a significant 42% reduction in IGF-II concentration (P=0.03), and IGF-II concentration per gram of fetal mass was a third lower in triplet litters. The triplet placenta exhibits a global expansion of the surface area which was contrasted by a per unit area reduction in IGF-II concentration (r=,0.75, P=0.01), a pattern that explains why twin and triplet placentas overall did not differ in concentration. Per fetus, triplet pregnancies are associated with relatively less maternal mass, placental mass and microscopic surface area suggesting that the intrauterine growth of triplets is supported by systems that increase the efficiency of nutrient transfer. The finding that individual triplet fetuses are also associated with significantly lower IGF-II concentrations is consistent with the view that the marmoset fetoplacental unit exhibits a flexible pattern of placental allocation and metabolism. Plasticity in placental endocrine and metabolic function is likely to play an important role in the ability of the fetus to sense and accommodate the intrauterine environment and, by extension, the external ecology. Am. J. Primatol. 71:969,975, 2009. © 2009 Wiley-Liss, Inc. [source]