First is best

We experience the world serially rather than simultaneously. A century of research on human and nonhuman animals has suggested that the first experience in a series of two or more is cognitively privileged. We report three experiments designed to test the effect of first position on implicit preference and choice using targets that range from individual humans and social groups to consumer goods. Experiment 1 demonstrated an implicit preference to buy goods from the first salesperson encountered and to join teams encountered first, even when the difference in encounter is mere seconds. In Experiment 2 the first of two consumer items presented in quick succession was more likely to be chosen. In Experiment 3 an alternative hypothesis that first position merely accentuates the valence of options was ruled out by demonstrating that first position enhances preference for the first even when it is evaluatively negative in meaning (a criminal). Together, these experiments demonstrate a "first is best" effect and we offer possible interpretations based on evolutionary mechanisms of this "bound" on rational behavior and suggest that automaticity of judgment may be a helpful principle in clarifying previous inconsistencies in the empirical record on the effects of order on preference and choice.     

Does the first LH surge of the breeding season initiate the first full-length cycle in the ewe?

To determine whether the first LH surge of the breeding season initiates a transient rise in progesterone in most ewes, serum progesterone (daily) and LH (every 4 h) concentrations were measured in samples collected from 7 ewes between 19 July and first oestrus or 8 September, whichever came first. In 6 of the 7 ewes, the first LH surge of the breeding season was followed within 5 days by a transient, 2-day rise in progesterone. Within less than 5 (N = 4), or 9 (N = 1) or 10 (N = 1) days later, a second LH surge occurred, which was similar in maximum amplitude and duration to the first surge, and which initiated the first full-length luteal phase of the breeding season. In the remaining ewe, the first LH surge of the breeding season induced an abbreviated (9 days) and insufficient (maximum progesterone, 0.94 ng/ml) luteal phase. These results demonstrate that most ewes have more than one LH surge before the first full-length luteal phase, the first surge inducing a transient rise in progesterone. Therefore, although the seasonal decrease in response to oestradiol negative feedback is sufficient for initiation of the first LH surge of the breeding season, additional endocrine mechanisms may be necessary to induce the first full-length luteal phase.     

First Passage Time Analysis of Animal Movement and Insights into the Functional Response

Movement plays a role in structuring the interactions between individuals, their environment, and other species. Although movement models coupled with empirical data are widely used to study animal distribution, they have seldom been used to study search time. This paper proposes first passage time as a novel approach for understanding the effect of the landscape on animal movement and search time. In the context of animal movement, first passage time is the time taken for an animal to reach a specified site for the first time. We synthesize current first passage time theory and derive a general first passage time equation for animal movement. This equation is related to the Fokker–Planck equation, which is used to describe the distribution of animals in the landscape. We illustrate the first passage time method by analyzing the effect of territorial behavior on the time required for a red fox to locate prey throughout its home range. Using first passage time to compute search times, we consider the effect of two different searching modes on a functional response. We show that random searching leads to a Holling type III functional response. First passage time analysis provides a new tool for studying how animal movement may influence ecological processes.     

Why change mates?

In some wading birds (Charadrii) each adult rears a brood alone. The female leaves her first clutch with her first mate before herself rearing a clutch fertilized by a second male, who is already tending its first mate's first clutch. We here develop a simple model to account for the exchange of mates between clutches, and relate it to reported field studies. We suggest that females are attempting to be polygamous, rather than simply bigamous. Provided a female has a chance of obtaining a second, unmated male and that the costs of leaving the first male before remating are not high, matechanging will be favoured over monogamy. The implications of this model to the evolution of the more usual forms of polyandry and of male-like females are discussed.     

Redial generations of Fasciola gigantica in the pulmonate snail Lymnaea truncatula.

Lymnaea truncatula, 4 mm in height, were subjected to infection by a single miracidium of Fasciola gigantica, then raised at 23 degrees C until day 60 of the experiment. Histological study of these snails demonstrated a mean redial burden of 34 parasites at day 60, of which one third were degenerating forms. The mean number of living independent rediae did not exceed 5 for the first and second generations. Conversely, in subsequent generations there were as many as 18 rediae per snail at day 60. The first living redia of the first generation in particular gave rise to daughter rediae. Mature rediae appeared at day 35 and especially concerned the first and second generations at day 60. The authors conclude that development of the first and second redial generations occurs during the same period, and that the forms of the first cohort of the second generation are produced from the first redia of the first generation which originated from the sporocyst.     

An evolutionary model of stature, age at first birth and reproductive success in Gambian women

We have built a model to predict optimal age at first birth for women in a natural fertility population. The only existing fully evolutionary model, based on Ache hunter-gatherers, argues that as women gain weight, their fertility (rate of giving birth) increases-thus age at first birth represents a trade-off between time allocated to weight gain and greater fertility when mature. We identify the life-history implications of female age at first birth in a Gambian population, using uniquely detailed longitudinal data collected from 1950 to date. We use height rather than weight as an indicator of growth as it is more strongly correlated with age at first birth. Stature does not greatly influence fertility in this population but has a significant effect on offspring mortality. We model age at first reproduction as a trade-off between the time spent growing and reduced infant mortality after maturation. Parameters derived from this population are fitted to show that the predicted optimal mean age of first birth, which maximizes reproductive success, is 18 years, very close to that observed. The reaction norm associated with variation in growth rate during childhood also satisfactorily predicts the variation in age at first birth.     

Variation in probability of first reproduction of Weddell seals

1. For many species, when to begin reproduction is an important life-history decision that varies by individual and can have substantial implications for lifetime reproductive success and fitness. 2. We estimated age-specific probabilities of first-time breeding and modelled variation in these rates to determine age at first reproduction and understand why it varies in a population of Weddell seals in Erebus Bay, Antarctica. We used multistate mark-recapture modelling methods and encounter histories of 4965 known-age female seals to test predictions about age-related variation in probability of first reproduction and the effects of annual variation, cohort and population density. 3. Mean age at first reproduction in this southerly located study population (7.62 years of age, SD=1.71) was greater than age at first reproduction for a Weddell seal population at a more northerly and typical latitude for breeding Weddell seals (mean=4-5 years of age). This difference suggests that age at first reproduction may be influenced by whether a population inhabits the core or periphery of its range. 4. Age at first reproduction varied from 4 to 14 years, but there was no age by which all seals recruited to the breeding population, suggesting that individual heterogeneity exists among females in this population. 5. In the best model, the probability of breeding for the first time varied by age and year, and the amount of annual variation varied with age (average variance ratio for age-specific rates=4.3%). 6. Our results affirmed the predictions of life-history theory that age at first reproduction in long-lived mammals will be sensitive to environmental variation. In terms of life-history evolution, this variability suggests that Weddell seals display flexibility in age at first reproduction in order to maximize reproductive output under varying environmental conditions. Future analyses will attempt to test predictions regarding relationships between environmental covariates and annual variation in age at first reproduction and evaluate the relationship between age at first reproduction and lifetime reproductive success.     

Puerperal morbidity: A neglected area of maternal health in Sri Lanka

Abstract

Data on women with at least two children are used to examine how the breastfeeding experience with the first child affects whether subsequent children are breastfed. Our results indicate that women most often repeat with later children the feeding decision they made with their first child. That is, those who breastfed their first child are very likely to breastfeed a later child and those who did not breastfeed their firstborn are unlikely to breastfeed a later‐bom. Among those who did not breastfeed their first child, education beyond high school increases the likelihood that they will switch to breastfeeding with a later‐born. Those who breastfed their first child are less likely to breastfeed a later‐born if the first breastfeeding experience was of short duration or was perceived to be unsuccessful or unsatisfactory or if the woman had not gone beyond high school or received anesthesia at the later birth. Hence, educational differences are greater at higher parities than at first parity.     

北京动物园大熊猫繁殖记录

北京动物园在三十年中,共繁殖大熊猫28胎（其中双胎18次）,产仔46只,成活21只,成活率为45．65％,为大熊猫的迁地保护作出了杰出的贡献。1963年第一次在人工饲养下自然繁殖成功大熊猫“明明”;1978年第一次用人工授精方法繁殖成功大熊猫“元晶”;1980年第一次以纯超低温保存的大熊猫冷冻精液人工授精成功产下二仔;1987年第一次在人工饲养下繁殖出子三代;1990年第一次实现不同地理位置的大熊猫自然交配繁殖成功幼仔“亚庆”;1992年第一次繁殖成功大熊猫人工授精第三代幼仔“京京”;1992年第一次以人工授精繁殖长大的雄性大熊猫自然交配成功繁殖“永明”和“永亮”;1992～1993年第一次以人工哺育的方法使未食母乳的大熊猫幼仔“永亮”成活;1993年第一次达到1992年所产的3仔全部成活,成活率为100％。     

Effect of feeding program during rearing and age at first insemination on performances during subsequent reproduction in young rabbit does

An experiment was performed to study the effect of the feeding program and age at first mating on body growth, feed intake, reproductive performance, and culling of rabbit does over three parities, using 155 does of a strain of New Zealand white rabbits. Three treatments were applied. Ad libitum feeding until first insemination at 14.5 wk (AL-14.5) or 17.5 wk of age (AL-17.5), and restrictive feeding from five wk of age until first insemination at 17.5 wk of age (R-17.5). At first insemination, the BW of AL-14.5 and R-17.5 was similar (3 907 vs. 3 791 +/- 46 g, respectively), whereas AL-17.5 does were heavier (4 390 +/- 46 g, P < 0.001). During reproduction, performance of AL-17.5 was not improved compared to AL-14.5 and R-17.5 does. Al-17.5 does showed a lower feed intake during the first gestation (-25%) and first parity (-10%) than R- 17.5, resulting in weight loss (-6%) during the first gestation and decreased litter weights (-19%) and litter growth (-14%) in the first parity. Extended first mating by three wk (17.5 vs. 14.5 wk) but similar BW at first mating did not affect feed intake and BW development during the first three parities. However, the number of live born kits and weight at first kindling, and litter growth in the first parity were improved in R-17.5 (+23%, +18%, and +14%, respectively). Reproductive performance can be improved by restricted feeding during rearing and extended first insemination to 17.5 wk of age. However, the culling rate was not affected by the rearing strategy.     

Parental care trade‐offs in the inter‐brood phase in Barn Swallows Hirundo rustica

In seasonal environments with limited time and energy resources, double‐brooded birds face trade‐offs in the timing of their two reproductive attempts and in the effort allocated to the first and the second broods. In the Barn Swallow Hirundo rustica a long care period for the first brood enhances the survival of first‐brood chicks, but also delays the start of the second brood, which in turn reduces the survival prospects of second‐brood chicks. Probably as a response to this trade‐off, double‐brooded Barn Swallows reduce the period of post‐fledging care for first‐brood fledglings. By radiotracking whole families, we investigated the determinants of this behaviour and its consequences for the survival of the first‐brood fledglings. The end of the females’ investment in post‐fledging care of the first brood was related to the beginning of egg synthesis for the second clutch. With the start of egg synthesis, females significantly reduced provisioning rates to the first‐brood fledglings to less than one‐fifth of the previous rates, while the proportion of time they spent foraging remained high. Assuming that the females’ foraging success was constant, we conclude that their energy income was allocated to egg production rather than fledgling provision. Males did not compensate for the females’ reduced feeding rates. Thus the start of egg production for the second clutch had a marked effect on the quantity of food received by first‐brood fledglings. In parallel with the changes in parental behaviour and provisioning rates, we observed a marked drop in the daily survival rate of first‐brood chicks. These results support the hypothesis that females face a strong trade‐off in the allocation of energy to subsequent broods. Energy allocation to a second clutch involves a cost in terms of reduced provisioning, and as a result the survival of first‐brood chicks is compromised. This is probably outweighed by the improved success of an early second brood.     

Human ribosomal protein S26 inhibits splicing of its own pre-mRNA

In vitro splicing was studied for a human ribosomal protein (rp) S26 pre-mRNA fragment containing the first exon, first intron, and a part of the second exon. Splicing yielded two products, the first was corresponded to a fragment of the mature rpS26 mRNA and another was retained the 19 3'-terminal nucleotides of the first intron between the first and second exons. Recombinant rpS26 inhibites generation of both splicing products in vitro. The inhibition was specific, because another recombinant human rp, S19, had no effect on the splicing of the pre-mRNA fragment. Toe-printing was used to map the spS26-binding sites of the per-mRNA within the regions of the conventional and alternative 3' splicing sites of the first intron. On the strength of the rusults, rpS26 was assumed to regulate the expression of its own gene at the level of pre-mRNA splicing via a feedback mechanism.     

Vulnerability of larvae of two species of aphidophagous ladybirds, Adalia bipunctata Linnaeus and Harmonia axyridis Pallas, to cannibalism and intraguild predation

Vulnerability of larvae of two species of aphidophagous ladybirds, Adalia bipunctata Linnaeus and Harmonia axyridis Pallas, to cannibalism and intraguild predation was assessed in the laboratory. In the first experiment, a first instar of one of the two above species was kept with a fourth instar of the other species in a Petri dish. The number of times each first instar larva was encountered by the fourth instar larva and the fate of the first instar was determined over a period of 10 min. The fourth instar larvae captured and killed all the first instar larvae of their own species at the first encounter. However, when presented with fourth instar larvae of the other species the first instar larvae of A. bipunctata and H. axyridis were encountered 6.4 ± 1.3 ( n  = 10) and 19.4 ± 2.1 ( n  = 10), respectively. In this experiment no first instar larvae of H. axyridis , whereas all those of A. bipunctata , were killed.     

Factors associated with first service conception in artificially inseminated nulliparous Holstein heifers

Animal and management factors associated with first service conception in nulliparous dairy heifers were determined in 601 Holstein heifers from a dairy farm in north central Florida. Animal data collected included body weight, height at the withers and tail head, body condition score at 6 months of age and just prior to first artificial insemination (AI), and pelvimetry measurements taken just prior to first AI. Management data included season of first AI, inseminator, service sire, method of estrus detection, whether the estrus of first insemination was induced using prostaglandin F(2alpha) (PGF(2alpha)), and whether the heifer received a modified live virus (MLV) vaccine within 21 days of first insemination. Data were analyzed using multivariable logistic regression. Heifers inseminated in the summer were more than four times less likely to become pregnant to first insemination than heifers bred during the rest of the year (odds ratio (OR)=0.24; 95% CI=0.14, 0.41). Using secondary signs for estrus detection instead of standing estrus resulted in significantly reduced odds of conception to first service (OR=0.37; 95% CI 0.13, 1.02). Also, heifers inseminated at estrus induced by PGF(2alpha) were approximately one-third less likely to conceive than those heifers inseminated to a naturally occurring estrus (OR=0.66; 95% CI 0.46, 0.95). An interaction between pelvic size and breeding season was found indicating that large pelvic size had a significant positive effect on fertility in the summer, but was not associated with conception to first service in the winter.     

Allozyme heterozygosity, date of first feeding and life history strategy in Atlantic salmon

The relations between allozyme heterozygosity, relative date of first feeding and life history strategy in juvenile Atlantic salmon Salmo salar were examined using eggs obtained from a 400 family cross (20 male × 20 female adult Atlantic salmon). Multilocus heterozygosity, through its positive associations with the timing of first feeding and growth rate, was correlated with life history strategy in juvenile Atlantic salmon, albeit under genotype × environmental (temperature, food availability) regulation. Under hatchery conditions, a 10 day difference was observed in the relative date of first feeding between early and late first feeding Atlantic salmon. Early first feeding Atlantic salmon exhibited a significantly higher mean heterozygosity, grew faster at ambient water temperature (April to November) and a significantly higher proportion adopted the early freshwater maturation (age 0+ years, male fish) or early migrant (age 1+ years, mainly female fish) strategies compared to late first feeding Atlantic salmon. Elevated water temperatures over the winter (December to April, >10·5° C) provided additional growth opportunity allowing previously mature male parr (mainly early first feeders) and lower modal group parr (mainly late first feeders) to adopt the early migrant strategy by the following spring.     

Product limit estimation for infectious disease data when the diagnostic test for the outcome is measured with uncertainty

Low sensitivity and/or specificity of a diagnostic test for outcome results in biased estimates of the time to first event using product limit estimation. For example, if a test has low specificity, estimates of the cumulative distribution function (cdf) are biased towards time zero, while estimates of the cdf are biased away from time zero if a test has low sensitivity. In the context of discrete time survival analysis for infectious disease data, we develop self-consistent algorithms to obtain unbiased estimates of the time to first event when the sensitivity and/or specificity of the diagnostic test for the outcome is less than 100%. Two examples are presented. The first involves estimating time to first detection of HIV-1 infection in infants in a randomized clinical trial, and the second involves estimating time to first Neisseria gonorrhoeae infection in a cohort of Kenyan prostitutes.     

The morphogenetic significance of the first quartet micromeres for the development of the snailBithynia tentaculata

Summary The significance of the first quartet of micromeres for the morphogenesis ofBithynia — a polar lobe-forming gastropod-has been studied by deletion experiments. After removal of the whole first quartet at the 8-cell stage a dorsoventrally organized veliger larva is formed. Apparently, an interaction between the animal micromeres and a vegetal macromere, which is essential for the origin of a dorsoventral organization in equally cleaving gastropods, is not required in polar lobe forming eggs. It is concluded that in these eggs dorsoventrality is determined by segregation of the polar lobe. The embryos, in which the first quartet has been removed, never develop head structures. This indicates that the capacity to form head structures is restricted to the first quartet of micromeres. Deletion of a specific first quartet micromere (1a, 1b, 1c or 1d) showed, however, that the individual cells of this quartet are not strictly determined right from their origin. Frequently regulative development was observed after removal of individual first quartet cells.     

Infertility and age at first coitus: a possible relationship

Reported age at first coitus was shown to be associated with incidence and degree of infertility. Infertility patients reported later first coital ages than gynecological patients in a sample of 792 women seen in a major fertility service. Among the infertility patients, those who had never conceived presented a later first coital age than those who had previously conceived. Routine gynecological patients reported the youngest first coital age of the groups studied.     

Coerced first sexual intercourse and selected reproductive health outcomes among young women in KwaZulu-Natal, South Africa

Coercion may play an important role in compelling young women to engage in sexual intercourse at an early age. With a decline in age at first intercourse and increased reporting of coercive first sex, concerns of adverse reproductive health outcomes such as unintended pregnancy and sexually transmitted infections (STIs), including HIV, have become important issues, particularly in the context of a high HIV prevalence. This paper uses data collected in 2001 from the second round of a longitudinal study of 1130 sexually experienced young women in KwaZulu-Natal to investigate the relationship between coerced first intercourse and selected reproductive health outcomes and behaviours. Nearly 46% of all sexually experienced young women had reported that their first sexual encounter had been coerced. Young women who reported being coerced at first sex were significantly more likely to be Black and living in an urban area. Those who had been coerced at first sex were also more likely to report having had an STI and having experienced unintended pregnancy, than those who had not been coerced at first sex. Coercion at first sex is an important social and public health problem that has a serious impact on the reproductive health and behaviours of young women. Interventions should directly address the issue of sexual coercion by ensuring young women are aware of their reproductive rights.