Early Sexual Maturation Research Articles

The role of intragestational ghrelin on postnatal development and reproductive programming in mice

The purpose of this study was to evaluate the intragestational role of ghrelin in offspring development and reproductive programming in a mouse model of ghrelin imbalance during pregnancy. Female mice were injected with ghrelin (supraphysiological levels: 4 nmol/animal/day), antagonist (endogenous ghrelin inhibition with (D-Lys3)GHRP-6, 6 nmol/animal/day) or vehicle (control = normal ghrelin levels) throughout the pregnancy. Parameters evaluated in litters were growth, physical, neurobiological and sexual development and, at adulthood, reproductive function. Litter size and initial weight did not vary between treatments. Male pups from dams treated with ghrelin showed higher body weight increase until adulthood (31.7 ± 0.8 vs control = 29.7 ± 0.7, n = 11–14 litters/treatment; P < 0.05). Postnatal physical and neurobiological development was not modified by treatments. The antagonist accelerated male puberty onset, evidenced as earlier testis descent and increased relative testicular weight (antagonist = 0.5 ± 0.0% vs ghrelin = 0.4 ± 0.0% and control = 0.4 ± 0.0%, n = 5–10 litters/treatment; P < 0.05). At adulthood, these males exhibited lower relative testicular weight and reduced sperm motility (63.9 ± 3.6% vs control = 70.9 ± 3.3 and ghrelin = 75.6 ± 3.0, n = 13–15 animals; P < 0.05), without changes in plasma testosterone or fertility. Female pups intragestationally exposed to the antagonist showed earlier vaginal opening (statistically significant only at Day 25) and higher ovarian volume (antagonist = 1085.7 ± 64.0 mm3 vs ghrelin = 663.3 ± 102.8 mm3 and control = 512.3 ± 116.4 mm3; n = 4–6 animals/treatment; P < 0.05), indicating earlier sexual maturation. At adulthood, these females and those exposed to ghrelin showed a tendency to higher percentages of embryo loss and/or foetal atrophy. In conclusion, ghrelin participates in reproductive foetal programming: alterations in ghrelin activity during pregnancy modified body weight increase and anticipated puberty onset, exerting (or tending to) negative effects on adult reproductive function.

Dietary methoprene supplement promotes early sexual maturation of male Queensland fruit fly Bactrocera tryoni

Sterile insect technique (SIT) is an environmentally benign pest management technique that relies on released sterile male insects mating with, and curtailing reproduction of, wild females. However, for species with high mortality rates and long adult maturation phases, a large proportion of the released insects can die before maturing and so fail to contribute to SIT. To counter this problem, inclusion of yeast hydrolysate in pre-release diets and treatment of pupae or adults with methoprene, a juvenile hormone analogue, have been investigated as means of accelerating development of some fruit flies, including Queensland fruit fly, Bactrocera tryoni (Froggatt) (‘Q-fly’). Methoprene has most often been administered topically in acetone solution, which is toxic, flammable, and impractical for operational settings. As a practical alternative, we incorporated methoprene (0, 0.05, 0.1, and 0.5%) into Q-fly adult diet of sugar only or sugar mixed with yeast hydrolysate for 2 days, and then provided sugar only for the rest of the trial period. Mating performance of males and females was tested from 4 to 30 days of age. Flies provided sugar mixed with yeast hydrolysate had increased mating propensity in comparison with flies that were provided sugar only. At all ages and for both diets, all methoprene doses increased male mating probability. Methoprene treatment did not affect copula latency of males that received yeast hydrolysate, but males that received only sugar mated earlier if they had received 0.05% methoprene. Methoprene treatment of males was also associated with longer copulations, which may affect fertility of females that later remate. Females differed from males in that methoprene treatment did not significantly affect mating probability or latency, but resembled males in that methoprene treatment resulted in longer copulations. Sex differences in response to methoprene may lead to male-biased operational sex ratio when bisex Q-fly strains are used in SIT. Yeast hydrolysate increased longevity of both males and females, but methoprene treatment did not affect longevity. Overall, findings of the present study indicate that Q-fly sexual maturation can be accelerated, and SIT might hence be enhanced, by incorporation of methoprene and yeast hydrolysate in pre-release diet.

Analysis of alternative splicing events by RNA sequencing in the ovaries of Xiang pig at estrous and diestrous

Alternative splicing (AS) is an important mechanism for controlling gene expression, which regulates multiple biological processes in higher organisms. Chinese indigenous Xiang pig has distinctive biological characteristics, such as small size, early sexual maturity, lower litter size and not very clear exhibition of estrous behaviors. To further understand how AS responds to estrous cycles in Xiang pig, the genome-wide analysis of AS events was performed by RNA-seq method in Xiang pig ovaries at diestrous and estrous. Using ASprofile program, we analyzed twelve basic AS events in Xiang pig ovaries and identified 68,775 AS events in 15,142 genes from diestrous ovaries and 69,493 AS events in 15,291 genes from the estrous ovaries with average 4.54 splicing events. 94.4–95.5% of expressed genes underwent alternative splicing in this tissues. The frequencies of AS events were similar to each other at diestrous and estrous. Transcription start site (TSS) was the predominant type of AS events, followed by transcription terminal site (TTS), and skipped exon (SKIP). The remaining type of AS events, e.g., intron retention (IR) and alternative exon ends (AE), showed the lower frequencies. Further comparison analysis of gene expression indicated that 4,433 genes had at least one splice variant differentially expressed during estrous, whereas only 2,382 of them were differentially expressed at gene level. Numerous genes involved in gonad development and hormone metabolism were differentially regulated through AS. Twelve genes with different types of alternatively splicing were validated by using RT-PCR method. The GO annotation and KEGG pathway analysis clearly revealed that a lot of DEGs (differentially expressed genes) and DSGs (differentially spliced genes) were involved in follicular development and ovarian steroid biosynthesis. A large number of DSGs, although not differentially expressed, were enriched in circadian rhythm and several signaling pathways. These pathways potentially regulated the female animal reproductive function in gene and/or AS level. Our results suggested that alternative splicing play an essential role in regulation of gene expression in female pigs during estrous. Numerous genes involved in gonad development, hormone metabolism, circadian rhythm were differentially regulated through alternative splicing.

Life history of Subulina octona (Brugüière) (Gastropoda: Pulmonata: Subulinidae) based on four-year laboratory observations and a comparative histological analysis of egg-retaining and ovoviviparous subulinids

ABSTRACTIn the present study, we aimed to characterize the life history of the land snail Subulina octona integrating information on life-history traits and morphology. We also compared the histology of the free-oviduct and spermoviduct of ovoviviparous and egg-retaining species of subulinids. We considered as ovoviviparous the species in which the complete embryonic development as well as egg hatching occurs inside the parent’s body and, at the end of this process, the parent releases juveniles instead of eggs. We considered as egg-retaining the species in which a great part of the embryonic development takes place inside the parent’s body and the eggs laid contain well-developed embryos. The results showed that the free-oviduct of both ovoviviparous and egg-retaining species shows a histological arrangement that confers greater strength to its walls and is probably related to egg retention. The wall of the spermoviduct is formed by pseudostratified columnar epithelium, with cell apical processes (probably cilia), and by underlying secretory cells. In gravid egg-retaining snails, the eggshells appear in close contact with the secretory cells of the spermoviduct. This fact suggests that these cells play a role in eggshell formation. The present study is the first account for histological features of S. octona, Allopeas gracile and Allopeas micra. The life history of S. octona is a combination of long lifespan, early sexual maturity, indeterminate growth and egg retention. Egg retention limits the number of young that can be produced in one reproductive event. However, the reproductive strategy adopted by S. octona, associating egg retention and K-strategism, compensates this cost of retaining eggs, because the reproductive success may be enhanced as a result of the higher survival of juveniles and the possibility of performing several reproductive events during the year.

Genome-wide differential expression profiling of mRNAs and lncRNAs associated with prolificacy in Hu sheep.

Reproductive ability, especially prolificacy, impacts sheep profitability. Hu sheep, a unique Chinese breed, is recognized for its high prolificacy (HP), early sexual maturity, and year-round estrus. However, little is known about the molecular mechanisms underlying HP in Hu sheep. To explore the potential mRNAs and long non-coding RNAs (lncRNAs) involved in Hu sheep prolificacy, we performed an ovarian genome-wide analysis of mRNAs and lncRNAs during the follicular stage using Hu sheep of HP (litter size = 3; three consecutive lambings) and low prolificacy (LP, litter size = 1; three consecutive lambings). Plasma luteinizing hormone (LH) concentration was higher in the HP group than in the LP group (P<0.05) during the follicular stage. Subsequently, 76 differentially expressed mRNAs (DE-mRNAs) and five differentially expressed lncRNAs (DE-lncRNAs) were identified by pairwise comparison; quantitative real-time PCR (qRT-PCR) analysis of ten randomly selected DE genes (mRNA and lncRNA) were consistent with the sequencing results. Gene Ontology (GO) analysis of DE-mRNAs revealed significant enrichment in immune response components, actin filament severing and phagocytosis. Pathway enrichment analysis of DE-mRNAs indicated a predominance of immune function pathways, including phagosomes, lysosomes, and antigen processing. We constructed a co-expression network of DE-mRNAs and mRNA-lncRNAs, with C1qA, CD53, cathepsin B (CTSB), CTSS, TYROBP, and AIF1 as the hub genes. Finally, the expression of lysosomal protease cathepsin genes, CTSB and cathepsin D (CTSD), were significantly up-regulated in sheep ovaries in the HP group compared with the LP group (P<0.05). These differential mRNAs and lncRNAs may provide information on the molecular mechanisms underlying sheep prolificacy.

Life history traits of a poorly known pelagic fish, Aethotaxis mitopteryx (Perciformes, Notothenioidei) from the Weddell Sea

Amongst the nototheniid subfamily Pleuragramminae, Aethotaxis mitopteryx is an infrequently collected high Antarctic species with an array of morphological and physiological adaptations supporting an evolutionarily derived benthopelagic lifestyle. The present study deals with some poorly known life history traits of this species, counting on 79 specimens collected in the Weddell Sea during 2014 and 2015 austral summer. Annulation pattern in sagittal otoliths were used to assess population age structure and growth rate, while macroscopic and histological analyses of gonads were performed to estimate reproductive status and features of gametogenesis. The sex ratio of the sampled population was close to parity, with females significantly larger than males. Based on the von Bertalanffy growth model, females attained a larger maximum size (40 vs. 27 cm) at a lower rate (0.05 vs. 0.12 years−1) than males. Individual longevity was remarkable in both sexes, females and males attaining 62 and 32 years of age, respectively. Females showed group synchronous oocyte development and presumed high reproductive effort, as indicated by the large size of residual hydrated oocytes in regressing individuals (4.6–4.8 mm). Body sizes at sexual maturity were 33 and 19 cm in females and males, corresponding to 32 and 11 years of age, respectively. All specimens were caught far from the reproductive season. From an evolutionary perspective, it appears that the process of pelagization similarly influenced the life strategies of the species within the clade Pleuragramminae, which shared high reproductive effort linked to early sexual maturity, slow somatic growth and long life span.

Spolno sazrijevanje i neki aspekti socijalnog ponašanja adolescentica

In an investigation on 385 girl pupils of the eighth class in primary school from Zadar, Šibenik and Split, the hypothesis that breach of the usual rules of behaviour is determined, not only by the time of sexual maturity of adolescent girls, but the interaction of the time of sexual maturity and the order of birth was tested. Investigations were carried out to establish whether these girls, regarding the order of birth and the time of sexual maturity, differ in the expectancy of their parent’s sanctions for breach of rules.A two-way analysis of variance (2 X 4) was carried out on the frequency of the breach of the usual rules of behaviour. The results showed that the effects of the time of sexual maturity and the order of birth, very according to the nature of the breach; namely for the breach of smoking rules, the order of birth was the only significant variable. The rules of school diligence were affected only by the time of sexual maturity. The only significant effect of the interaction of the two variables was shown on the breach of parental prohibition.The results were interpreted in terms of learning according to the model. The interpretation that these adolescents imitated older brothers and sisters and/or peer groups seemed relevant because they did not differ in the expectancy of parental sanctions for the breach of the rules regarding the sequence of birth, or the time of sexual maturity.The results also indicated that it was not justifiable to generalise the results found in some other cultures (e g. on 14 yr. old Swedish girls), that the girls who sexually mature earlier, break the rules of behaviour signifi, cantly more than their peer groups who sexually mature later. It seems that they break the rules more when some intervening social wariables are present with their earlier sexual maturity.

Evaluation of productive and reproductive performances of local and crossbred cows in Manikgonj district of Bangladesh

A total of 90 lactating cows from twelve dairy farms were used to conduct this study in order to evaluate the productive and reproductive performance of crossbred and local cows at farmer’s level in Manikgong district. All cows were divided into three groups, according to their genetic composition as Local, Local x Friesian and Local x Friesian x Friesian cows. The results showed late sexual maturity (37.41±0.03 months), calving interval (481.86±0.33 days), shortest lactation period (198.46±2.36 days) and lowest average milk production (2.25±0.04 L/day) in local cows. On the contrary, longest lactation period (266.43±1.18 days) and highest average milk production (7.45±0.11 L/day) were observed in LFF cows, whereas early sexual maturity (30.58±0.02 months) was found in Local x Friesian cows. From the above perspective it could be concluded that LFF crossbred cows may be suitable for profitable dairy farming in Bangladesh but herd life and life time productivity is one of the most influential factor for profitable dairy farming. However, further study with larger sample sizes covering more different management systems would be required to describe a better inference in this consideration.Asian J. Med. Biol. Res. September 2017, 3(3): 330-334

Telomere length, sibling competition and development of antioxidant defense in wild house mice

Antioxidants and telomere length are potential biomarkers for individuals’ exposure and ability to cope with environmental stressors. However, intraspecific variations in antioxidant alterations due to natural, life cycle related stress, have been rarely estimated. We investigated those changes in wild-derived house mice in a longitudinal study with natural sibling competition as a stressor. Blood was used for telomere length measurements at 8-weeks age and for several selected antioxidants at 8-weeks and 6-months age. Our results show that most of the antioxidants increase during that time, indicating that antioxidant-system continues to develop after early development and sexual maturation. In addition females had higher antioxidant-levels than males. Mice with longer telomeres had also higher superoxide dismutase-activity and more glutathione than mice with shorter telomeres, meaning that long telomeres are associated with better antioxidant defense at maturation and during later life. Sibling competition at early age affected superoxide dismutase-levels at 6-months, but only in females. Females, which were lighter than the average of the litter had low superoxide dismutase –activity in later adulthood, indicating delayed negative effect of sibling competition on antioxidant defense. Our results highlight that sex and developmental stage are crucial in intraspecific comparisons of the antioxidant status and its alterations.

Genetic analysis of a red tilapia (Oreochromis spp.) population undergoing three generations of selection for increased body weight at harvest

Quantitative genetic analysis was performed on 10,919 data records collected over three generations from the selection programme for increased body weight at harvest in red tilapia (Oreochromis spp.). They were offspring of 224 sires and 226 dams (50 sires and 60 dams per generation, on average). Linear mixed models were used to analyse body traits (weight, length, width and depth), whereas threshold generalised models assuming probit distribution were employed to examine genetic inheritance of survival rate, sexual maturity and body colour. The estimates of heritability for traits studied (body weight, standard length, body width, body depth, body colour, early sexual maturation and survival) across statistical models were moderate to high (0.13-0.45). Genetic correlations among body traits and survival were high and positive (0.68-0.96). Body length and width exhibited negative genetic correlations with body colour (-0.47 to -0.25). Sexual maturity was genetically correlated positively with measurements of body traits (weight and length). Direct and correlated genetic responses to selection were measured as estimated breeding values in each generation and expressed in genetic standard deviation units (σG). The cumulative improvement achieved for harvest body weight was 1.72 σG after three generations or 12.5% per generation when the gain was expressed as a percentage of the base population. Selection for improved body weight also resulted in correlated increase in other body traits (length, width and depth) and survival rate (ranging from 0.25 to 0.81 genetic standard deviation units). Avoidance of black spot parent matings also improved the overall red colour of the selected population. It is concluded that the selective breeding programme for red tilapia has succeeded in achieving significant genetic improvement for a range of commercially important traits in this species, and the large genetic variation in body colour and survival also shows that there are prospects for future improvement of these traits in this population of red tilapia.

Differential proliferation and metabolic activity of Sertoli cells in the testes of broiler and layer breeder chickens

Decades of genetic selection have generated 2 different, highly specialized types of chickens in which 1 type, known as the layer-type chicken, expresses high laying performance while the other type, known as the broiler-type chicken, is dedicated to the production of fast-growing birds. Selected lines for the latter type often express disorders in their reproductive performance including early sexual maturation and accelerated, non-reversible seasonal decline of their semen production and mating behavior. The aim of the present study was to characterize some metabolic markers of the Sertoli cell populations. Sertoli cells are somatic cells known to support, coordinate, nourish, and protect the germ cell populations from onset to the end of their meiotic process. Comparisons of gonadal development between males of the 2 genetic types taken at their pre-pubertal period indicated that the testes of layer-type chickens are significantly less developed than in broiler-type males taken at the same age. In addition, cultures of purified Sertoli cells from the 2 types revealed in vitro a higher proliferative capacity when issued from layer compared to broiler-type chickens. This was associated with a higher expression of the genes involved in the beta-oxidation of fatty acids (CPT1; PPARβ) as well as a 4-fold increase in the Lactate Dehydrogenase-A expression and activity. In contrast, Sertoli cells from broiler-type chickens presented an elevated activity of citrate synthase and mitochondria, suggesting a better efficacy of aerobic metabolism in Sertoli cells from broiler compared to layer-type chickens. Moreover, the testis from broiler-type chickens seems to be more sensitive to oxidative stress due to the lower global antioxidant capacity compared to layer-type chickens.In conclusion, these results suggest that the metabolic activity of testicular tissues is different in the layer and broiler breeder chickens. The aerobic metabolism more prevalent in broiler-type chickens could be a factor to reduce the male fertility such as germ cell quality.

Implicaciones de la precipitación sobre la evolución del tamaño corporal y distancia interaxilar en el complejo Aspidoscelis gularis (Squamata: Teiidae)

Life history traits are highly variable attributes that maximize organisms’s adaptation. The relationship of weight and body size with environmental changes and habitat heterogeneity has been documented in previous reports; and size and body shapes are both considered life history attributes that are associated with rainfall, that boost available resources in the environment. While in Aspidoscelis genus, clutch size and relative mass are mainly associated with latitude and altitude, in Aspidoscelis gularis, winter rainfall favors two reproductive seasons, which may determine season variable clutch size. With the aim to study this, samplings were undertaken from May-July 2013, and May-September 2015. A total of 65 individuals lizards of the Southeast clade were obtained, and body length and interaxilar distance measurements were taken; furthermore, hepatic tissue samples were taken for DNA extraction, which allowed us to analyze phylogenetic relationships through a Bayesian Inference analysis, and subsequently, to apply Phylogenetic Comparative Methods (like phylogenetic signal, phylogenetically independent contrasts and reconstruction of ancestral character). Our results showed that there is a low phylogenetic signal regarding body size and shape, while the phylogenetically independent contrasts and reconstruction of ancestral characters suggest that small body sizes are associated to locations with highest rainfall. This can be associated to an establishment of an early sexual maturity, which reflects the maximum size of adults. Furthermore, according to an ANOVA and ANCOVA, there were statistically significant differences in body size and shape respectively, which promote a system for sexual competition for males and a system for fertility in females. These results were important to determine the effect of rainfall on some life history traits, pointing out that lizards of the Southeast clade, belonging to the A. gularis complex were able to face different selection pressures, determined by the environment.

Tropical anurans mature early and die young: Evidence from eight Afromontane Hyperolius species and a meta-analysis.

Age- and size-related life-history traits of anuran amphibians are thought to vary systematically with latitude and altitude. Because the available data base is strongly biased towards temperate-zone species, we provide new estimates on eight afrotropical Reed Frog species. A meta-analysis of the demographic traits in 44 tropical anuran species aims to test for the predicted clinal variation and to contrast results with variation detected in temperate-zone species. The small-sized reed frogs reach sexual maturity during the first or second year of life, but longevity does not exceed three to four years. Latitudinal effects on demographic life-history traits are not detectable in tropical anurans, and altitudinal effects are limited to a slight size reduction at higher elevations. Common features of anuran life-history in the tropics are early sexual maturation at small size and low longevity resulting in low lifetime fecundity. This pattern contrasts with that found in temperate-zone anurans which mature later at larger size and grow considerably older yielding greater lifetime fecundity than in the tropics. Latitudinal and altitudinal contraction of the yearly activity period shape the evolution of life-history traits in the temperate region, while trait variation in the tropics seems to be driven by distinct, not yet identified selective forces.

Assessment of lifetime performance of small ruminants under different feeding systems

Evaluation of lifetime productivity of individual animals in response to various interventions allows assessment of long-term investment opportunities for farmers. In order to gain a better understanding of promising feed interventions for improvement of small ruminant production in Southwestern Nigeria, a dynamic modelling approach was used to explore the effect of different feeding strategies on the lifetime productivity of West African Dwarf (WAD) goats. Modifications were made to the current version of Livestock Simulator developed for cattle production to simulate goat production systems particularly for WAD goats. Effects of changes in input parameters (quality of feed and potential adult weight) confirmed the sensitivity of the modelled weight development and reproductive performance. The values of simulated model outputs corresponded well with observed values for most of the variables, except for the pre-weaning mortality rate in the cut-and-carry system where a wide discrepancy between simulated (2.1%) and observed (23%) data was found. The scenario analysis showed that simulated goats in the free grazing system attained sexual maturity and kidded much later than those in the grazing with supplementation and the cut-and-carry systems. The simulated results suggested that goats require supplementation with protein and energy sources, in order to promote lifetime productivity, early sexual maturity and higher birth weight. In terms of economic returns based on feed cost alone, the moderately intense system produced the most profit. We therefore conclude that grazing with adequate supplementation using farm-generated feed resources offers an opportunity for improving smallholder goat production systems in West Africa.

Estrous Cycle, Fertilility and Fetal Development in Rats with Hyperbilirubinemia

Objective: Decreasing in reproductive capacity has been observed in jaundiced female rats. The animals with hyperbilirubinemia present early sexual maturation, late ovulation, reduced number of corpora lutea and precocious vaginal opening. The interaction with toxic agents leads to abnormal development of the embryos. The objective is to investigate the influence of jaundice on estrous cycle, fertility, ovaries and fetus development. Methods: 66 female rats were divided into two groups (n=33): group 1 - ligature of the biliopancreatic duct, group 2 - sham operation. These animals were paired with males. Vaginal smears were collected daily to verify pregnancy and the gestational period. The morphologic aspect of the ovaries and the corpus luteum were studied. The morphology of the fetuses were assessed. Serum bilirubins were recorded. 32 rats of the control group and 11 jaundiced rats became pregnant. Results: The 17 rats with hyperbilirubinemia that did not become pregnant presented involutive corpora lutea and modifications in their estrous cycles, remaining in pro-estrus or estrus. The pregnant rats with hyperbilirubinemia had fetuses with abnormal development. Conclusions: Fertilization occurs in jaundiced rats, but reproductive capacity is reduced, with irregular estrous cycles, involutive corpora lutea and abnormal fetal development.

Age structure, growth pattern, sexual maturity, and longevity of Leptodactylus latrans (Anura: Leptodactylidae) in temperate wetlands

We present the first data on age structure, growth pattern, and lines of arrested growth (LAG) forLeptodactylus latransin temperate wetlands. Based on these data, we estimate LAG periodicity, age, size at sexual maturity and longevity for this species. We also tested for differences of these parameters between sexes. The age was determined through skeletochronology. Female maturity was determined by presence of differentiated ova, while male maturity was assessed through histological analysis to evaluate spermatozoid production. To establish whether this species marks one LAG per year, eight individuals were kept one year in captivity. For each specimen, LAG was compared for different phalanges of the same toe clipped at start and end of captivity.Leptodactylus latransmarked one LAG per year, indicating a growth rhythm adjusted to a seasonal environment and mainly driven by genetic factors. Longevity was five years for both sexes and frogs reached sexual maturity during the first year, exhibiting a reproductive lifespan of four years. Sexual maturity was related to a minimal size of 60 mm or a body mass of around 33 g. There was no difference in either size or growth pattern between sexes. The von Bertalanffy growth model showed thatL. latransgrows fast after metamorphosis and their growth rate strongly decreases at about three years, probably due to the increased allocation of energy to reproduction. The high growth rates and early sexual maturation ofL. latranswould allow an elevated rate of population renewal.

Distinct effects of obesity and puberty on risk and age at onset of pediatric MS.

ObjectiveThe aim of this study was to examine the relative contributions of body mass index (BMI) and pubertal measures for risk and age of onset of pediatric MS.MethodsCase–control study of 254 (63% female) MS cases (onset<18 years of age) and 420 (49% female) controls conducted at 14 U.S. Pediatric MS Centers. Sex‐ and age‐stratified BMI percentiles were calculated using CDC growth charts from height and weight measured at enrollment for controls, and within 1 year of onset for MS cases. Sex‐stratified associations between MS risk and age at symptom onset with both BMI and pubertal factors were estimated controlling for race and ethnicity.ResultsOnly 11% of girls and 15% of boys were prepubertal (Tanner stage I) at MS onset. 80% of girls had onset of MS after menarche. BMI percentiles were higher in MS cases versus controls (girls: P < 0.001; boys: P = 0.018). BMI was associated with odds of MS in multivariate models in postpubertal girls (OR = 1.60, 95% confidence interval [CI]: 1.12, 2.27, P = 0.009) and boys (OR = 1.43, 95% CI: 1.08, 1.88, P = 0.011). In girls with MS onset after menarche, higher BMI was associated with younger age at first symptoms (P = 0.031). Younger menarche was associated with stronger effects of BMI through mediation and interaction analysis. In pubertal/postpubertal boys, 89% of whom were obese/overweight, earlier sexual maturity was associated with earlier onset of MS (P < 0.001).InterpretationHigher BMI in early adolescence is a risk factor for MS in girls and boys. Earlier age at sexual maturity contributes to earlier age at MS onset, particularly in association with obesity.

Marker assisted selection for spawning date and co-variation among economically important fitness traits in a commercial strain of rainbow trout (Oncorhynchus mykiss)

The effects of marker assisted selection for spawning date in males on embryonic developmental rate, growth related traits and precocious male maturation and phenotypic and genetic associations among traits were investigated in a commercial strain of rainbow trout (Oncorhynchus mykiss). The relationship between spawning date category of the sire (early or late) and developmental rate as measured by hatching time was inconsistent among families. However, two half-sib families produced by males with an allelic complement associated with late spawning date had higher rates of precocious male maturation and faster developmental rates than two families produced by males with earlier spawning date alleles. QTL analysis suggests that some of the co-variation between spawning date and developmental rate has a genetic basis as two QTL for developmental rate as measured by hatching time co-localized to the same markers known to be associated with spawning date in this strain. We observed no association between the spawning date category of the sire and progeny length at 61days post-fertilization (alevin stage), body weight at 381days (juveniles), body weight at 614days and specific growth rate, which suggests that selection for early or late spawning date alleles will have little effect on growth traits. Within families, faster developmental rates conferred a size advantage at 61days post-fertilization but not at 381 and 614days. Moreover, no correlation between developmental rate and the propensity of early male maturation was detected within families. Males that matured at 2years were significantly heavier at both 381 and 614days and had higher specific growth rates than immature males and females. Likewise, body weight at 614days and family were significant predictors for the propensity for early sexual maturation in males. This indicates that selection for greater body size will likely result in higher rates of unwanted precocious male maturation. Together, these results suggest that co-variation among economically important fitness traits may present potential trade-offs impacting selection goals. RelevanceAddresses feasibility of using molecular approaches in selective breeding programs.

Life history and reproductive dynamics of the cryptogenic calcareous sponge Sycettusa hastifera (Porifera, Calcarea) living in tropical rocky shores

Life history accounts for the chance of survival and reproductive success of a species, considering, for example, when, how often and how much a species reproduces. Consequently, it is directly related to the success or failure of bioinvasions. Here, we investigated some aspects of the life history of the cryptogenic calcareous sponge Sycettusa hastifera. A population from Arraial do Cabo, Brazil (south-western Atlantic) was investigated from September 2008 to December 2009 by monthly collections and histological analyses. We observed that S. hastifera reproduced continuously throughout the year without seasonality and presented high fecundity. The fecundity was not different depending on the sponge body part (top or base), but it was related to the wet weight of the sponge (although a minimum size was not required for reproduction). Reproduction could not be predicted by the seawater temperature. The reproductive characteristics of S. hastifera were similar to those of other previously studied calcareous sponges. Sycettusa hastifera shows traits of an invasive species, such as high fecundity, short life cycle, early sexual maturity and the ability to use pioneer habitats. Consequently, it possesses several characteristics that would allow it to invade new areas.

Performance of triploid Atlantic cod (Gadus morhua L.) in commercial aquaculture

The use of triploid fish can potentially reduce two of the major obstacles in Atlantic cod aquaculture; early sexual maturation that causes reduced profitability, and avoiding introgression between farmed cod and native populations, by preventing spawning in the netpens or that escapees reproduce.Cod eggs were pressure treated to produce triploid fish. However, we observed that the pressure treatment produced a mixture of triploid and diploid individuals. The diploid and triploid fish were reared together; in a seawater pond during their larval and juvenile period, and in a commercial cod farm from juveniles to slaughter. Two experiments were performed on two separate year-classes of cod: in the first experiment, fish were reared under artificial continuous light, while in the second experiment the fish were reared under ambient light conditions.Triploid cod had lower gonadosomatic index at all measurements compared to the diploids. However, from a production point of view, triploidisation alone only slightly reduced the gonadosomatic index and had to be combined with traditionally employed artificial light in order to be effective. Triploid fish were generally lighter than the diploids, but this difference disappeared towards time-of-harvest in the year-class without artificial light, possibly because of the lower maturation rate among the triploids. The triploid fish had a higher incidence of skeletal deformities compared to the diploids. Statement of RelevanceThe use of sterile fish by means of triploidisation is a promising method to reduce sexual maturation and the same time eliminate potential interbreeding of escaped cod with wild cod. In this paper we compare growth, maturation and deformities between triploid and diploid cod reared in common garden under commercial condition.