Early Life Survival Research Articles

The role of the placenta in the developmental origins of health and disease—Implications for practice

The placenta is actively involved in transporting nutrients to the fetus, it has both direct and indirect effects on fetal cardiovascular function and has endocrine influences on the mother and fetus. As such, a properly functioning placenta is crucial for normal fetal development and plays a central role in mediating effects of the maternal environment on the fetus. An altered external environment or abnormal placental function can induce developmental changes in the fetus and may have important consequences for the risk of cardiovascular and metabolic disease in adult life. The developmental origins hypothesis proposes that the early environment, from the periconceptional period until early childhood, can predispose an individual to adult cardiovascular and metabolic disease. This hypothesis is supported by epidemiological studies and by work in animals. These effects do not just act in low birth weight babies but have been shown to occur within the normal range of birth weight. It is thought that fetal adaptations to an impaired intra-uterine environment may enhance survival in early life but have deleterious effects in later life. Experimental studies suggest that maternal diet and body composition can alter placental structure and function, and we have recently demonstrated associations between a woman's nutritional state before pregnancy and placental function at term. To elucidate these relationships, further work is needed to define markers of placental function and to characterize their relation to rates of fetal growth. Understanding how the placenta mediates maternal influences will be crucial in determining the mechanisms underlying developmental programming. This will allow the design of targeted public health interventions, both before and during pregnancy, to enhance placental function and thereby improve the health of the offspring throughout life.

Effects of maternally transferred organochlorine contaminants on early life survival in a freshwater fish

Laboratory research has shown that female fish can pass toxic organochlorines (OCs) from their bodies to their eggs, killing their offspring if sufficient quantities are transferred. We conducted a controlled incubation study using gametes from a wild, OC-contaminated walleye (Sander vitreus) population (Bay of Quinte, Lake Ontario, Canada) in order to assess among-female variation in offspring early life survival in relation to ova concentrations of planar OCs (polychlorinated dibenzo-p-dioxins and furans and planar polychlorinated biphenyls) and a suite of other maternal and ova characteristics. Equal volumes of ova from each female were fertilized, pooled, and incubated together as an experimental cohort. Relative survival of each female's offspring was estimated as the proportion of surviving larvae (at approximately 5 d posthatch) that she contributed to the cohort as determined by microsatellite DNA parentage assignment. Total planar OC concentration (expressed as toxic equivalency of 2,3,7,8-tetrachlorodibenzo-p-dioxin) of ova was positively related to maternal age and size and to ova lipid content. However, early life survival did not decline with increasing ova planar OC concentrations. Similarly, we observed no significant relationships between early life survival and ova thiamine content, ova fatty acid composition, or maternal age or size. Early life survival was more strongly correlated with date of spawn collection, thyroid hormone status of the ova, and ovum size. Maternally transferred planar OCs do not appear to negatively influence female reproductive success in this walleye population.

Variation in survival of Iris pumila L. juvenile plants grown in two nutrient regimes

I analyzed variability of early life survival on 881 Iris pumila juvenile plants in their prereproductive period. Seedlings were produced by applying half-sib mating scheme on clones originating from two Deliblato Sand populations that were accommodated to common garden conditions. Nineteen clones served as pollen donors (sires), and the other 90 clones served as pollen recipients (dames). Seedlings were grown in two nutrient levels (full strength and 1/10 of full-strength Hoagland solution). While I failed to detect significant mean nutrient level effect as well as significant between population differentiation for prereproductive survival, a statistically significant additive genetic variability for this ultimate prereproductive measure of fitness was detected.

Lower fitness of hatchery and hybrid rainbow trout compared to naturalized populations in Lake Superior tributaries.

We have documented an early life survival advantage by naturalized populations of anadromous rainbow trout Oncorhynchus mykiss over a more recently introduced hatchery population and outbreeding depression resulting from interbreeding between the two strains. We tested the hypothesis that offspring of naturalized and hatchery trout, and reciprocal hybrid crosses, survive equally from fry to age 1+ in isolated reaches of Lake Superior tributary streams in Minnesota. Over the first summer, offspring of naturalized females had significantly greater survival than offspring of hatchery females in three of four comparisons (two streams and 2 years of stocking). Having an entire naturalized genome, not just a naturalized mother, was important for survival over the first winter. Naturalized offspring outperformed all others in survival to age 1+ and hybrids had reduced, but intermediate, survival relative to the two pure crosses. Averaging over years and streams, survival relative to naturalized offspring was 0.59 for hybrids with naturalized females, 0.37 for the reciprocal hybrids, and 0.21 for hatchery offspring. Our results indicate that naturalized rainbow trout are better adapted to the conditions of Minnesota's tributaries to Lake Superior so that they outperform the hatchery-propagated strain in the same manner that many native populations of salmonids outperform hatchery or transplanted fish. Continued stocking of the hatchery fish may conflict with a management goal of sustaining the naturalized populations.

An Exploration of Factors Influencing Crappie Early Life History in Three Alabama Impoundments

Although black crappie Pomoxis nigromaculatus and white crappie P. annularis represent important sport fisheries in North America, we still know little about what influences their variable recruitment. Several abiotic (e.g., water level fluctuations) and biotic (e.g., prey abundance and size structure) factors have been suggested as important to crappie recruitment, but results have not been consistent among studies. We quantified adult characteristics, larval abundance, growth, diet, and postlarval juvenile abundance of crappies in three Alabama impoundments to determine factors consistently affecting crappie life stages across systems. Although adult condition (relative weight, Wr), fecundity, egg diameter, gonadosomatic index, and ovary weight differed among the three impoundments, the differences were not consistent with among-lake differences in chlorophyll-a concentration. Larval density was highest in the least productive system (Lake Martin), and larval production was not related to either adult condition or fecundity. Diet analysis indicated that larvae 4-14 mm in total length strongly selected the smallest prey available in all lakes but that larvae in Lake Martin consumed greater numbers and a higher biomass of crustacean zooplankton than those in Weiss and Jones Bluff lakes, probably because of the higher density of large zooplankton in Lake Martin. Despite the generally earlier presence in spring of crappie larvae in Lake Martin during both years, age-0 crappies in that lake were not larger than those in the other two lakes in summer. This is probably attributable to cooler early-spring water temperatures in Lake Martin. The catch of postlarval juvenile crappies was higher in the more productive lakes than in Lake Martin. Collectively, our results were not consistent with our expectation that lake productivity would positively influence the density of both zooplankton and age-0 crappies. The lack of a positive relationship between larval crappie density and system productivity or zooplankton size was an unexpected result that is probably important to the early life survival and eventual recruitment of crappies and that warrants further investigation.

SELECTION EXPERIMENTS IN THE PENNA MODEL FOR BIOLOGICAL AGING

We consider the Penna model for biological aging to investigate correlations between early fertility and late life survival rates in populations at equilibrium. We consider inherited initial reproduction ages together with a reproduction cost translated in a probability that mother and offspring die at birth, depending on the mother age. For convenient sets of parameters, the equilibrated populations present genetic variability in what regards both genetically programmed death age and initial reproduction age. In the asexual Penna model, a negative correlation between early life fertility and late life survival rates naturally emerges in the stationary solutions. In the sexual Penna model, selection experiments are performed where individuals are sorted by initial reproduction age from the equilibrated populations and the separated populations are evolved independently. After a transient, a negative correlation between early fertility and late age survival rates also emerges in the sense that populations that start reproducing earlier present smaller average genetically programmed death age. These effects appear due to the age structure of populations in the steady state solution of the evolution equations. We claim that the same demographic effects may be playing an important role in selection experiments in the laboratory.

Early Life Survival of the AnchovetaEngraulis ringensOff Central Chile during the 1995 and 1996 Winter Spawning Seasons

For fish populations occurring in coastal upwelling areas, the timing of spawning has been proposed to occur during seasons when transport offshore is reduced. Along the coastal zone off central Chile, the anchoveta Engraulis ringens spawns preferentially during winter. Spawning in this season, however, might represent a period of increased risk to eggs and larvae due to the harsh and variable oceanographic conditions. This study determined the mortality rates of egg and larval anchoveta in an area located close to the species' southern limit of distribution during its winter spawning season. Two temporal scales of variability, interseasonal (between years), and intraseasonal (individual daily cohort mortality rates) show that (1) mean seasonal mortality rates were not different between years and (2) mortality rates considering the egg and larval stages together (96% daily in 1995 and 98% daily in 1996) were much higher than those estimated using only the larval stage (4.4% daily in 1995 and 6.8% daily in 1996). The results of the individual cohort mortality rates, especially in 1995, revealed a tendency toward a decrease in mortality rates as the winter season progressed (from 52 to 9% daily). Because the maximum egg abundance in the water column occurred early in the season in 1995, we propose that the largest fraction of the mean seasonal mortality was due to egg mortality occurring early in winter. The information on the environmental characteristics and the reported larval growth rates in different periods during the winter spawning season do not support the hypothesis of larval food limitation but, instead, suggest that oceanographic factors (e.g., cross-shelf transport, low water temperature, presence of river plumes) play a major role in the development and success of the early life stages in this southern spawning area.

VEGF is required for growth and survival in neonatal mice.

We employed two independent approaches to inactivate the angiogenic protein VEGF in newborn mice: inducible, Cre-loxP- mediated gene targeting, or administration of mFlt(1-3)-IgG, a soluble VEGF receptor chimeric protein. Partial inhibition of VEGF achieved by inducible gene targeting resulted in increased mortality, stunted body growth and impaired organ development, most notably of the liver. Administration of mFlt(1-3)-IgG, which achieves a higher degree of VEGF inhibition, resulted in nearly complete growth arrest and lethality. Ultrastructural analysis documented alterations in endothelial and other cell types. Histological and biochemical changes consistent with liver and renal failure were observed. Endothelial cells isolated from the liver of mFlt(1-3)-IgG-treated neonates demonstrated an increased apoptotic index, indicating that VEGF is required not only for proliferation but also for survival of endothelial cells. However, such treatment resulted in less significant alterations as the animal matured, and the dependence on VEGF was eventually lost some time after the fourth postnatal week. Administration of mFlt(1-3)-IgG to juvenile mice failed to induce apoptosis in liver endothelial cells. Thus, VEGF is essential for growth and survival in early postnatal life. However, in the fully developed animal, VEGF is likely to be involved primarily in active angiogenesis processes such as corpus luteum development.

Squid stock fluctuations and water temperature: temporal analysis of English Channel Loliginidae

1. Monthly series of abundance indexes for the English Channel squid stock, based on fishery statistics of the United Kingdom (1980–93) and France (1986–96), were compared with water temperature data. The two objectives of the study were to test empirical predictive models and to analyse the stock–environment relationship at various time scales; both correlation and time‐series statistical techniques were applied. Sea surface temperature (SST) showed inter‐annual fluctuations and month‐to‐month auto‐correlation in addition to the annual cycle. 2. Trends in squid landings and temperature at the annual scale were found to be related, whatever the statistical method used (moving averages, cumulative functions or regression using averaged data). 3. Variable selection applied in a ‘multi‐month’ model suggested that fishing season indexes could be predicted from temperatures observed in the previous winter. The link between mild winter conditions and cohort success in winter/spring spawning species suggested that early life survival (and/or growth) was involved. This empirical model is a first step in the development of environment‐predicted recruitment indexes useful for management advice. 4. Seasonal decomposition was performed on both the squid resource data and SST data in search of short‐term relationships. In spite of the flexibility of the loliginid life‐cycle, no significant relationship was found between squid seasonally adjusted indexes and temperature anomalies in the previous months. This underlined the conclusion that temperature effect on cohort success was not constant throughout the year.

Vulnerability of newly settled red drum ( Sciaenops ocellatus ) to predatory fish: is early-life survival enhanced by seagrass meadows?

We conducted predation experiments to evaluate the vulnerability of red drum Sciaenops ocellatus (Linnaeus) larvae and early juveniles to pinfish Lagodon rhomboides (Linnaeus) predators. Experiments were designed to analyze the effects of habitat complexity, prey size, and rearing condition on prey vulnerability. Three structurally different habitats [unvegetated (substrate only), shoal grass Halodule wrightii (Aschers) and turtle grass Thalassia testudinum (Bank ex Konig)] were simulated in experimental mesocosms. Instantaneous hourly mortality rates (Z h−1 predator−1) for hatchery-reared red drum were significantly higher in the unvegetated habitat (0.189) than in either shoal grass (0.069) or turtle grass (0.046). A similar trend in predation mortality was observed for wild-caught red drum; instantaneous hourly mortality rates were 0.166, 0.047, and 0.021 in unvegetated, shoal grass, and turtle grass habitats, respectively. Mortality rates (adjusted means) for hatchery red drum were higher than for wild individuals in all three habitats; however, the differences were not significant. Predation mortality decreased with increasing prey size (3 to 9% decrease in Z per mm increase in length), suggesting that small red drum (i.e. new settlers) were most vulnerable to predators. We conclude that habitat complexity is critical to the survival of newly settled red drum, and changes in the complexity or areal coverage of natural seagrass meadows may affect early-life survival and possibly recruitment levels.

The linkage among ecosystem perturbations, remediation, and the success of the Nipigon Bay fishery

Since the inception of the commercial fishery in Nipigon Bay of Lake Superior, walleye (Stizostedion vitreum) and lake sturgeon (Acipenser fulvescens) have been extirpated and the abundance of lake trout (Salvelinus namaycush), brook trout (Salvelinus fontinalis), and northern pike (Esox lucius) has declined significantly while the abundance of lake whitefish (Coregonus clupeaformis ) and lake herring (Coregonus artedii) has increased. Systemic stresses including eutrophication, airborne contribution of contaminants, and exploitation (reduced by closure of the commercial fishery in 1988) remain but may not impair populations of lake whitefish and herring, which interact less with tributaries and nearshore waters. Improvements in habitat, through water flow management in the Nipigon River, removal of logs in the nearshore, shoreline and stream restoration, cessation of log drives, as well as artificially increasing adult abundance have resulted in resumption of some limited reproduction by walleye and increased egg deposition and early life survival by brook trout. Multiple stresses are still ubiquitous in the Nipigon ecosystem, but relief of several stresses in tributaries and nearshore environments at least appears to have resulted in an initially encouraging response by two species dependent upon these areas.

Source of Dietary Carbohydrate Affects Life Span of Fischer 344 Rats Independent of Caloric Restriction

Previous investigations suggest that increased life span of calorie-restricted rodents is a function of caloric intake rather than the macro- or micronutrient composition of the diet. However, the dietary source of carbohydrate has not been widely investigated. We hypothesized that the dietary carbohydrate source may affect the life span of rats independent of caloric restriction. This hypothesis was tested in male Fischer 344 rats fed ad libitum or restricted to 60% of ad libitum, an isocaloric diet containing 14% protein, 10% fat, and 66% sucrose or cornstarch. Body weights of the ad libitum- and restricted-fed sucrose rats were consistently greater throughout the experimental period compared to diet-matched animals. Food intake did not differ significantly. The survival curves of ad libitum starch- vs sucrose-fed rats were significantly different. That is, the mean, median and upper 10th percentile survival were significantly greater in the ad libitum starch- vs sucrose-fed rats (mean life span: cornstarch-fed, 720 +/- 23 days; sucrose-fed, 659 +/- 19 days). Calorie-restricted starch-fed rats had poorer early life survival, and no significant increase in mean life span compared to ad libitum cornstarch-fed animals (726 vs 720 days). These animals did, however, have the greatest upper 10th percentile survival of all four experimental groups. Mean life span of calorie-restricted sucrose-fed rats was significantly greater than that of all other groups (890 +/- 18 days). The differences in survival rates between sucrose- and cornstarch-fed animals could not be attributed to the effects of carbohydrate source on body weight, energy absorption, or on the timing and severity of the pathological lesions normally associated with aging and/or caloric restriction in this species. These data support the hypothesis that the dietary source of carbohydrate, i.e., sucrose vs cornstarch, can significantly affect life span independently of caloric intake.

Pollution and developmental abnormalities of Atlantic fishes

Planktonic ‘eggs’ of Atlantic mackerel,Scomber scombrus, provide evidence that pollution is associated with mortality, malformation, and abnormal chromosome division of fish embryos developing about the surface of the U.S. Atlantic coast. Embryo data are substantiated by the finding that adults of mackerel, windowpane flounder,Scophthalmus acquosus, and winter flounder,Pseudopleuronectes americanus, from more polluted coastal areas also have higher frequencies of mitotic abnormality than those from less polluted regions of the Mid- and North Atlantic. No ontogenetic interval escapes contamination. All are likely to be adversely influenced, resulting in considerable direct and indirect cumulative effect on total early-life survival. Development of genetic and epigenetic resistance to reproductively harmful influences of contaminants may interfere with other modifications in structure and function necessitated by natural environmental fluctuations, changes in climate, and by fishing itself.

Survival in early life of Atlantic salmon and rainbow trout: estimates of heritabilities and genetic correlations

Survival data obtained for offspring of 187 sires and 1404 dams of Atlantic salmon (eight year classes of data) and 213 sires and 1062 dams of rainbow trout (nine year classes) were analysed. Over year classes, average survival rates in the observation periods (during incubation and the early fresh water phase) ranged from 48% to 98%, being lowest in the period before the eyed-egg stage and during first feeding. In both species, heritabilities for survival derived from the sire components of variance were low (0.04–0.09). Heritabilities derived from the dam components of variance ranged from medium to high (0.31–0.87), indicating non-additive genetic and/or common environmental effects. Genetic correlations between survival in two succeeding periods were all, except one, positive and medium in magnitude (0.18–0.46). Genetic correlations between survival in non-succeeding periods were in general low and non-significant. Significant positive correlation between long-term survival and growth rate was found in Atlantic salmon (0.37). The corresponding correlation in rainbow trout was also positive (0.23), but not significantly different from zero.

Factors affecting culling and survival during rearing and first lactation in purebred and crossbred dairy cattle

ABSTRACTFactors affecting survival to first and second calving and successful completion of a > 168-day first lactation were assessed in 3075 purebred and crossbred dairy heifer calves. Growth, disease, frequency, reproduction, calving, udder and lactation traits were examined in females of a breeding project conducted jointly at five research stations (herds) of Agriculture Canada. Losses included mortalities and non-discretionary culling. About 0·23 of potential heifers were culled or died before first calving, and 0·25 of those calving once did not calve a second time. Results from retrospective selection index and stepwise linear logistic analyses showed that predictability of culling prior to 308 days post partum was poor. With few exceptions, survival rates from birth to 82 weeks varied among herds (P < 0·001) and among lines (P < 0·05). Heterosis for the probability of completing a lactation and of survival to second calving was significant (P < 0·05) and positive (0·05 to 0·09). Heavier heifers were more likely to survive to first calving. Sire's estimated breeding values (SEBV) for milk yield and fat, protein and lactose concentration were not important in predicting survival to first calving. SEBV lactose was negatively associated with survival after first calving as predicted from data available at most preceding stages of life. An age greater than 82 weeks at last insemination was associated with a lower probability of survival to first and second calving (P < 0·001). Cows which conceived for a second gestation and subsequently aborted had a lower probability of survival to second calving than cows which did not abort (0·57 v. 0·76, P < 0·01). The only continuous traits with large effects on survival or the probability of completing a first lactation were days to last insemination (a measure of fertility) and milk yield. It was concluded that (1) there is considerable scope for improved management to increase survival in early life by prevention of calfhood diseases; (2) losses in early life do not bias sire evaluation on first lactation records; (3) improved reproductive success would greatly enhance overall survival rates; and (4) crossbreeding could have a large impact on overall herd profitability through increased survival.

Tissue Glycogen Levels in Dams and Fetuses as Affected by Fasting and Refeeding Pregnant Sows1

Nineteen Landrace sows mated to Landrace boars were randomly assigned, on d 91 of pregnancy, to three groups: (1) control (six sows)--fed standard 13% protein corn-soybean meal gestation diet at 1.82 kg/d to d 112 of pregnancy; (2) 4-d fast (seven sows)--fed standard gestation diet to d 94 of pregnancy, fasted from d 95 to 98 of pregnancy and then refed a semipurified fat-free diet ad libitum until d 112 of pregnancy, and (3) 8-d fast (six sows)--treated the same as groups 2, except that the fast began on d 91 and extended through d 98 of pregnancy. The fat-free diet consisted of dextrose and soybean meal and was fortified with minerals and vitamins. On d 112 of pregnancy, all fetuses were removed by Caesarean section and determinations were made of fetal body and liver weights, fetal liver and gastrocnemius muscle glycogen concentrations, and maternal uterus and peritoneal adipose tissue glycogen levels. Sows in groups 2 and 3 consumed more (P less than .01) average daily feed during the refeeding period than did the control sows. Fasting and refeeding failed to affect maternal or fetal tissue glycogen concentration, or fetal body or liver weight. Average sow tissue glycogen concentrations were .23 and 3.0 mg/g tissue for peritoneal adipose tissue and uterus, respectively. Average fetal liver and gastrocnemius muscle glycogen concentrations were, 87 and 62 mg/g tissue, respectively. Average fetal body and liver weights were 1,287 and 39.5 g/fetus, respectively. We conclude that fasting followed by refeeding of a fat-free diet to pregnant sows during late gestation does not increase maternal or fetal tissue glycogen content and appears to be of no value in enhancing pig survival in early postnatal life.