Biological vulnerability of two exploited sharks of the genus Deania (Centrophoridae)

Life-history parameters of Deania calcea and Deania quadrispinosa suggested that their productivity was very low. Maturity (L_T50) occurs at c. 80% of maximum observed total lengths (L_T) for both species and sexes. A large proportion of mature females were neither pre-ovulatory nor pregnant, and the reproductive cycle included a distinct resting phase after pregnancy. For D. calcea, mean ovarian fecundity was 12 and maximum observed litter size was 10 (average of six); D. quadrispinosa averaged 17 pups per litter. Birth L_T was 28-33 cm for D. calcea and 23-25 cm for D. quadrispinosa. The male and female reproductive cycles were aseasonal, and consequently, the length of the reproductive cycle could not be determined. Preliminary ageing data from dorsal-spine growth bands suggested that female D. calcea lived to 31-36 years and males to 24-32 years. The L_T-at-age data using external bands on the spines showed maturity occurring at 15·5 years (males) and 21·5 years (females), whereas banding on the internal dentine indicated maturity at 10·5 and 17·5 years for males and females. Thus, a female lifetime of 31-36 years allowed for a maximum of 7 litters if a 2 year cycle is assumed or only five litters with a 3 year cycle, resulting in a lifetime fecundity of only 42 pups (2 year cycle) or even lower (3 year cycle).

The energetic and oxidative costs of reproduction in a free-ranging rodent

1. As understanding of the energetic costs of reproduction in birds and mammals continues to improve, oxidative stress is an increasingly cited example of a non-energetic cost of reproduction that may serve as a proximal physiological link underlying life-history trade-offs.

2. Here, we provide the first study to measure daily energy expenditure (DEE) and oxidative damage in a wild population. We measured both traits on eastern chipmunks (Tamias striatus) and assessed their relationships with age, reproductive status, litter size and environmental conditions.

3. We found that both physiological traits were correlated with environmental characteristics (e.g. temperature, seasons). DEE tended to increase with decreasing temperature, while oxidative damage was lower in spring, after a winter of torpor expression, than in autumn. We also found that DEE decreased with age, while oxidative damage was elevated in young individuals, reduced in animals of intermediate age and tended to increase at older age.

4. After controlling for age and environmental variables, we found that both female DEE and oxidative damage increased with litter size, although the latter increased weakly.

5. Our results corroborate findings from laboratory studies but highlight the importance of considering environmental conditions, age and reproductive status in broader analyses of the causes and consequences of physiological costs of reproduction in wild animals.

Regional differences in the reproductive parameters of the sparsely-spotted stingaree, Urolophus paucimaculatus, from South-Eastern Australia

Whether spatial variation occurs in the life-history traits of chondrichthyan species is important to fisheries modelling and assessments. A study on the reproductive parameters of Urolophus paucimaculatus from four separate regions across south-eastern Australia found regional differences in maximum total length (TL), size-at-maturity, size-at-maternity and litter sizes. Inshore embayments (Port Phillip Bay (PPB) and Corner Inlet (CI)) appear to allow for larger TLs (females and males) than do offshore areas (Lakes Entrance (LE) and Western Bass Strait (WBS)). Size-at-maturity and size-at-maternity decreased across longitude from west (PPB) to east (LE) and seasonality of parturition and ovulation occurred earlier in PPB (August-October) than in LE (September-December). Maximum litter size correlated with maximum TL (six in PPB, five in each of CI and LE, and four in WBS). There was uncertainty in classifying females for maternal condition because the reproductive cycle appears to range from a continuous annual cycle to a non-continuous biennial cycle. Much of the uncertainty arises from the ambiguity of observation of non-pregnant mature females, which have either aborted through capture and handling, or are in a 'resting year' between pregnancies. Most likely, the majority are reproducing annually with an unknown proportion of females non-continuous and resting between pregnancies.

Exercise as an intervention to improve metabolic outcomes after intrauterine growth restriction

Individuals born after intrauterine growth restriction (IUGR) are at an increased risk of developing diabetes in their adult life. IUGR impairs β-cell function and reduces β-cell mass, thereby diminishing insulin secretion. IUGR also induces insulin resistance, with impaired insulin signaling in muscle in adult humans who were small for gestational age (SGA) and in rodent models of IUGR. There is epidemiological evidence in humans that exercise in adults can reduce the risk of metabolic disease following IUGR. However, it is not clear whether adult IUGR individuals benefit to the same extent from exercise as do normal-birth-weight individuals, as our rat studies suggest less of a benefit in those born IUGR. Importantly, however, there is some evidence from studies in rats that exercise in early life might be able to reverse or reprogram the long-term metabolic effects of IUGR. Studies are needed to address gaps in current knowledge, including determining the mechanisms involved in the reprogramming effects of early exercise in rats, whether exercise early in life or in adulthood has similar beneficial metabolic effects in larger animal models in which insulin resistance develops after IUGR. Human studies are also needed to determine whether exercise training improves insulin secretion and insulin sensitivity to the same extent in IUGR adults as in control populations. Such investigations will have implications for customizing the recommended level and timing of exercise to improve metabolic health after IUGR.

Growth restriction in the rat alters expression of cardiac JAK/STAT genes in a sex-specific manner.

Uteroplacental insufficiency resulting in intrauterine growth restriction has been associated with the development of cardiovascular disease, coronary heart disease and increased blood pressure, particularly in males. The molecular mechanisms that result in the programming of these phenotypes are not clear. This study investigated the expression of cardiac JAK/STAT signalling genes in growth restricted offspring born small due to uteroplacental insufficiency. Bilateral uterine vessel ligation was performed on day 18 of pregnancy to induce growth restriction (Restricted) or sham surgery (Control). Cardiac tissue at embryonic day (E) 20, postnatal day (PN) 1, PN7 and PN35 in male and female Wistar (WKY) rats (n=7-10 per group per age) was isolated and mRNA extracted. In the heart, there was an effect of age for males for all genes examined there was a decrease in expression after PN1. With females, JAK2 expression was significantly reduced after E20, while PI3K in females was increased at E30 and PN35. Further, mRNA expression was significantly altered in JAK/STAT signalling targets in Restricteds in a sex-specific manner. Compared with Controls, in males, JAK2 and STAT3 were significantly reduced in the Restricted, while in females SOCS3 was significantly increased and PI3K significantly decreased in the Restricted offspring. Finally, there were specific differences in the levels of gene expression within the JAK/STAT pathway when comparing males to females. Thus, growth restriction alters specific targets in the JAK/STAT signalling pathway, with altered JAK2 and STAT3 potentially contributing to the increased risk of cardiovascular disease in the growth restricted males.

Asynchrony and regional differences in the reproductive cycle of the greenback stingaree Urolophus viridis from south-eastern Australia

Determining the periodicity of the reproductive cycle in chondrichthyan species when the population is recruiting asynchronously, as found for Urolopus viridis, can be problematic. The reproductive cycle generally requires distinguishable trends in reproductive indices across the population. The present study utilised other similar and sympatric urolophid species with synchronous reproductive cycles. Through data collected in the present study and comparisons of maximum total length (TL), periodicity of egg and embryo in utero, ovarian cycles, largest ovarian follicle diameter, and matrotrophic contribution (percentage increase from egg to embryo after maternal histotroph supplement) from similar studies, an annual reproductive cycle can be hypothesised. Sampling across two separate regions of Lakes Entrance (LE) and Western Bass Strait (WBS), U. viridis also showed regionality in several of the reproductive indices. Maximum TL and mass for females, mean size-at-birth, and female size-at-maturity and size-at-maternity in LE were markedly smaller than in WBS. In both regions litter size (1–2) increased with TL, with an exception of one female in WBS producing a litter of 3 which could be attributed to the larger TL. The implication of U. viridis producing such few young annually is they have the lowest biological productivity of any urolophid species in south-eastern Australia.

Uteroplacental insufficiency leads to hypertension, but not glucose intolerance or impaired skeletal muscle mitochondrial biogenesis, in 12-month-old rats

Growth restriction impacts on offspring development and increases their risk of disease in adulthood which is exacerbated with "second hits." The aim of this study was to investigate if blood pressure, glucose tolerance, and skeletal muscle mitochondrial biogenesis were altered in 12-month-old male and female offspring with prenatal or postnatal growth restriction. Bilateral uterine vessel ligation induced uteroplacental insufficiency and growth restriction in offspring (Restricted). A sham surgery was also performed during pregnancy (Control) and some litters from sham mothers had their litter size reduced (Reduced litter), which restricted postnatal growth. Growth-restricted females only developed hypertension at 12 months, which was not observed in males. In Restricted females only homeostasis model assessment for insulin resistance was decreased, indicating enhanced hepatic insulin sensitivity, which was not observed in males. Plasma leptin was increased only in the Reduced males at 12 months compared to Control and Restricted males, which was not observed in females. Compared to Controls, leptin, ghrelin, and adiponectin were unaltered in the Restricted males and females, suggesting that at 12 months of age the reduction in body weight in the Restricted offspring is not a consequence of circulating adipokines. Skeletal muscle PGC-1α levels were unaltered in 12-month-old male and female rats, which indicate improvements in lean muscle mass by 12 months of age. In summary, sex strongly impacts the cardiometabolic effects of growth restriction in 12-month-old rats and it is females who are at particular risk of developing long-term hypertension following growth restriction.

Endurance training in early life results in long-term programming of heart mass in rats

Being born small for gestational age increases the risk of developing adult cardiovascular and metabolic diseases. This study aimed to examine if early-life exercise could increase heart mass in the adult hearts from growth restricted rats. Bilateral uterine vessel ligation to induce uteroplacental insufficiency and fetal growth restriction in the offspring (Restricted) or sham surgery (Control) was performed on day 18 of gestation in WKY rats. A separate group of sham litters had litter size reduced to five pups at birth (Reduced litter), which restricted postnatal growth. Male offspring remained sedentary or underwent treadmill running from 5 to 9 weeks (early exercise) or 20 to 24 weeks of age (later exercise). Remarkably, in Control, Restricted, and Reduced litter groups, early exercise increased (P < 0.05) absolute and relative (to body mass) heart mass in adulthood. This was despite the animals being sedentary for ~4 months after exercise. Later exercise also increased adult absolute and relative heart mass (P < 0.05). Blood pressure was not significantly altered between groups or by early or later exercise. Phosphorylation of Akt Ser(473) in adulthood was increased in the early exercise groups but not the later exercise groups. Microarray gene analysis and validation by real-time PCR did not reveal any long-term effects of early exercise on the expression of any individual genes. In summary, early exercise programs the heart for increased mass into adulthood, perhaps by an upregulation of protein synthesis based on greater phosphorylation of Akt Ser(473).

Reproductive Patterns and Birth Seasonality in a South-American Breeding Colony of Common Marmosets, Callithrix jacchus

SOUSA,M.B.C. et al. Reproductive Patterns and Birth Seasonality in a South-American Breeding Colony of Common Marmosets, Callithrix jacchus. Primates, v.40, n.2, p. 327-336, Apr. 1999.

Fatores ambientais e estimativa de herdabilidade para o intervalo desmame-cio de fêmeas suínas

Este trabalho foi realizado com os objetivos de avaliar a influência de fatores ambientais e estimar a herdabilidade para a característica intervalo desmame-cio (IDC) de fêmeas suínas. Para isso, utilizaram-se 1.032 observações de 347 porcas Dalland (C-40), pertencentes a dois rebanhos. No modelo, incluíram-se como aleatórios os efeitos do pai e da mãe da porca e, como fixos, os efeitos do ano de parto, do rebanho e da estação de parição, bem como as co-variáveis idade da porca ao parto, tamanho da leitegada ao nascer e período de lactação. As estimativas dos componentes de variância e do parâmetro genético foram obtidas utilizando-se o aplicativo MTDFREML, que emprega a metodologia da máxima verossimilhança restrita livre de derivadas. A média foi de 5,3 dias, com um coeficiente de variação de 71,44%. O período de lactação teve influência linear sobre o IDC. do mesmo modo, a regressão quadrática do IDC em relação à idade da porca ao parto foi significativa. O pai e a mãe foram importantes fontes de variação no intervalo desmame-cio, que, provavelmente pelo fato de acontecer tardiamente na vida do animal, não foi influenciado pelo rebanho, pelo ano e pela estação. A estimativa de herdabilidade para o primeiro intervalo desmame-cio foi de 0,11, o que indica que esta característica não apresentaria ganho genético satisfatório como resposta à seleção individual.

Efeitos genéticos e não-genéticos sobre o intervalo de parto em fêmeas suínas no Sudeste do Brasil

The effect of environmental and genetic effects on the farrowing interval in Dalland (C-40) sows in the Southeast of Brazil was studied. Data consisting of 1,013 farrowing intervals recorded in two herds were analyzed, using a model that included the sire and the dam as random effects and the year of farrowing, the herd and the farrowing season as fixed effects, plus the covariables sow's age at farrowing, litter size at birth, lactation length and weaning-estrus interval. For the farrowing interval first only, variance components were estimated by REML, with an animal model that included, as fixed effect, a contemporary group and, as random effects, the additive genetic variance and the error. The mean farrowing interval was 140.9+5.7 days, with a 4.0% coefficient of variation. Variance analysis showed no effect of either year, season of farrowing or herd on the farrowing interval. The sire effect was not important for the farrowing interval, but the dam represented an important source of variation. The total number of piglets born and the sow's age at farrowing had no influence on the farrowing interval. The length of lactation exerted an influence on the farrowing interval, accounting for 19.4% of the total variation of this trait. Likewise, the linear regression of the weaning-estrus interval in relation to the farrowing interval was highly significant, accounting for 51.7% of the total variation. The heritability estimate was 0.00, suggesting that no genetic gain can be obtained by selection for a shorter farrowing interval.

Environmental and genetic factors affecting the weaning-estrus interval in sows

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Genetic and environmental effects on age at first farrowing in sows in southeastern Brazil

We evaluated genetic and environmental factors affecting age at first farrowing of sows in the Brazilian southeast. For this purpose, 466 observations regarding the age at first farrowing were made for Dalland-C40 (c) animals belonging to two herds. The effects of the environmental factors on this trait were assessed by means of a model that included, as random effects, the influence of the sow's father and mother and, as fixed effects, the influence the year of birth, the herd and the birth season, along with the covariable litter size at birth. The variance components were estimated using the derivative-free restricted maximum likelihood method. The estimated mean was 354.8 +/- 25.87 days, with a coefficient of variation of 7.29%. Significant effects on the trait were observed for the herd, the year and the season of birth; but a linear effect of litter size at birth on the age at first farrowing was not observed. The boar did not significantly contribute to the variation occurring among the sows, whereas the sow's mother caused significant variation. The heritability estimate for the age at first farrowing was 0.44 +/- 0.15, which is considered high. We concluded that herd effect and year and season of birth should be taken into consideration for an accurate genetic comparison; consequently, the animals should be joined into contemporary groups.

Effects of hypertension on maternal adaptations to pregnancy: experimental study on spontaneously hypertensive rats

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Impact of maternal mild hyperglycemia on maternal care and offspring development and behavior of Wistar rats

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)