Spatio-temporal variations in reproductive patterns and population structure of Pasiphaea multidentata (Decapoda: Caridea) in the Blanes canyon and adjacent margin, North-western Mediterranean Sea

The bathyal faunal communities of the NW Mediterranean slopes have been studied consistently in the last two decades, with a special focus on population structure, trophic dynamics and benthopelagic coupling of commercial deep-sea decapod crustaceans and fishes (reviewed in Sardà et al. 2004) and associated species (Cartes and Sardà, 1993; Company and Sardà, 1997, 2000; Cartes et al., 2001; Company et al., 2001, 2003, 2004). One of the major topographic features in the North-western Mediterranean slope is the presence of submarine canyons. Canyons play a major role in funnelling energy and organic matter from the shelf to bathyal and abyssal depths (Puig et al., 2000), but the implications of this enhanced organic supply in the deep-sea benthic communities is still mostly unknown. Trophic supply can follow two major pathways – vertical deposition in the water column (Billett et al., 1983; Baldwin et al., 1998; Lampitt et al., 2001) or down-slope advection on the margins (Puig et al., 2001; Bethoux et al., 2002; Canals et al., 2006) – and can be a limiting factor in the deep-sea, being especially important in the oligotrophic Mediterranean Sea (Sardà et al., 2004). Differences in the quantity, quality and timing of organic matter input to the deep seafloor have been used to explain patterns of biomass and abundance in benthic communities (Levin et al., 1994; Gooday & Turley, 1990; Billett et al., 2001; Galéron et al., 2001; Puig et al., 2001; Gage, 2003) as well as other biological process and in particular the existence of seasonal reproduction (Tyler et al., 1994; Company et al., 2004 (MEPS). Reproduction is a highly energetic process tightly linked to food availability and quality.

The reproductive cycle of the sea urchin Arbacia lixula in northwest mediterranean: potential influence of temperature and photoperiod

We studied the reproductive cycle of the sea urchin Arbacia lixula in a subtidal population from northeast Spain over four years using a gonadosomatic index (GSI) and gonad histology. Our results show that the GSI of A. lixula follows a seasonal cycle which peaks in May-July and attains its lowest values in October-November every year. The time course of the GSI matched closely the photoperiod cycle. We also found a remarkable inter-annual variability in the maximum value of GSI, which correlated with mean water temperature during the gonad growth period (winter and spring). Gonad histology was also in agreement with a single gametogenic cycle per year in this species. We explored the application of circular statistics to present and analyse gonadal development data, which allowed us to adequately handle the high intra-individual variability detected, with several developmental stages commonly found within the same gonad. The picture that emerged is one of a gametogenic timing driven by photoperiod, while the amount of reproductive output is determined by temperature. This is coherent with the tropical origin of the species and lends support to recent warnings about an increase in the abundance of this species in the Mediterranean as a result of global warming, with associated increased impact potential in sublittoral communities.

The Timing of labor demand

We examine the timing of firms' operations in a formal model of labor demand. Merging a variety of data sets from Portugal from 1995-2004, we describe temporal patterns of firms' demand for labor and estimate production-functions and relative labor-demand equations. The results demonstrate the existence of substitution of employment across times of the day/week and show that legislated penalties for work at irregular hours induce firms to alter their operating schedules. The results suggest a role for such penalties in an unregulated labor market, such as the United States, in which unusually large fractions of work are performed at night and on weekends.

Non-invasive monitoring of diaphragmatic timing by means of surface contact sensors: an experimental study in dogs

Background: Non-invasive monitoring of respiratory muscle function is an area of increasing research interest, resulting in the appearance of new monitoring devices, one of these being piezoelectric contact sensors. The present study was designed to test whether the use of piezoelectric contact (non-invasive) sensors could be useful in respiratory monitoring, in particular in measuring the timing of diaphragmatic contraction.Methods: Experiments were performed in an animal model: three pentobarbital anesthetized mongrel dogs. The motion of the thoracic cage was acquired by means of a piezoelectric contact sensor placed on the costal wall. This signal is compared with direct measurements of the diaphragmatic muscle length, made by sonomicrometry. Furthermore, to assess the diaphragmatic function other respiratory signals were acquired: respiratory airflow and transdiaphragmatic pressure. Diaphragm contraction time was estimated with these four signals. Using diaphragm length signal as reference, contraction times estimated with the other three signals were compared with the contraction time estimated with diaphragm length signal.Results: The contraction time estimated with the TM signal tends to give a reading 0.06 seconds lower than the measure made with the DL signal (-0.21 and 0.00 for FL and DP signals, respectively), with a standard deviation of 0.05 seconds (0.08 and 0.06 for FL and DP signals, respectively). Correlation coefficients indicated a close link between time contraction estimated with TM signal and contraction time estimated with DL signal (a Pearson correlation coefficient of 0.98, a reliability coefficient of 0.95, a slope of 1.01 and a Spearman's rank-order coefficient of 0.98). In general, correlation coefficients and mean and standard deviation of the difference were better in the inspiratory load respiratory test than in spontaneous ventilation tests.Conclusion: The technique presented in this work provides a non-invasive method to assess the timing of diaphragmatic contraction in canines, using a piezoelectric contact sensor placed on the costal wall.

Joint determinants of education enrolment and first birth timing in France and West Germany

We examined the reciprocal influence between educational decisions and the timing of first births, using the Family and Fertility Surveys of France and West Germany. Since these two processes are potentially endogenous, we modelled them jointly, using event history models. We hypothesise that the reciprocal impact of educational and fertility careers, as well as the impact of the common determinants of both processes, are gender specific and context specific.The results show a significant endogeneity for women and men in both countries. This endogeneity is stronger for women than for men, while no substantial differences are found between the two countries. Removing this shared and unobserved heterogeneity, the results show a stronger reciprocal impact between the processes for women than for men. A similar impact of being enrolled in education on first birth in both countries is found, while the effect of the birth (and especially of the pregnancy) of the first child on terminating one’s education appeared to be more marked in West Gernany than in France.

Weak and Strong Altruism in Trait Groups: Reproductive Suicide, Personal Fitness, and Expected Value

A simple variant of trait group selection, employing predators as the mechanism underlying group selection, supports contingent reproductive suicide as altruism (i.e., behavior lowering personal fitness while augmenting that of another) without kin assortment. The contingent suicidal type may either saturate the population or be polymorphic with a type avoiding suicide, depending on parameters. In addition to contingent suicide, this randomly assorting morph may also exhibit continuously expressed strong altruism (sensu Wilson 1979) usually thought restricted to kin selection. The model will not, however, support a sterile worker caste as such, where sterility occurs before life history events associated with effective altruism; reproductive suicide must remain fundamentally contingent (facultative sensu West Eberhard 1987; Myles 1988) under random assortment. The continuously expressed strong altruism supported by the model may be reinterpreted as probability of arbitrarily committing reproductive suicide, without benefit for another; such arbitrary suicide (a "load" on "adaptive" suicide) is viable only under a more restricted parameter space relative to the necessarily concomitant adaptive contingent suicide.

Timing of seasonal sales

We present a model of timing of seasonal sales where stores chooseseveral designs at the beginning of the season without knowingwich one, if any, will be fashionable. Fashionable designs have achance to fetch high prices in fashion markets while non-fashionableones must be sold in a discount market. In the beginning of theseason, stores charge high prices in the hope of capturing theirfashion market. As the end of the season approaches with goods stillon the shelves, stores adjust downward their expectations that theyare carrying a fashionable design, and may have sales to capture thediscount market. Having a greater number of designs induces a storeto put one of them on sales earlier to test the market. Moreover,price competition in the discount market induces stores to startsales earlier because of a greater perceived first-mover advantage incapturing the discount market. More competition, perhaps due todecreases in the cost of product innovation, makes sales occur evenearlier. These results are consistent with the observation that thetrend toward earlier sales since mid-1970's coincides with increasingproduct varieties in fashion good markets and increasing storecompetition.

On the timing of balance of payments crises: Disaggregated information and interest rate policy

This paper proposes a dynamic framework to study the timing of balance of paymentscrises. The model incorporates two main ingredients: (i) investors have private information; (ii)investors interact in a dynamic setting, weighing the high returns on domestic assets against the incentives to pull out before the devaluation. The model shows that the presence of disaggregated information delays the onset of BOP crises, giving rise to discrete devaluations. It also shows that high interest rates can be eective in delaying and possibly avoiding the abandonment of the peg. The optimal policy is to raise interest rates sharply as fundamentals become very weak. However, this policy is time inconsistent, suggesting a role for commitment devices such as currency boards or IMF pressure.

The timing of foreign direct investment under uncertainty: Evidence from the Spanish banking sector

This paper investigates the timing of foreign direct investment (FDI) in the banking sector. The importance of this issue would arise from the existence of differential benefits associated to be the first entrant in a foreign location. Nevertheless, when uncertainty is considered, the existence of some Ownership-Location-Internalization (OLI) advantages can make FDI less reversible and/or more delayable and therefore it may be optimal for the firm to delay the investment until the uncertainty is resolved. In this paper, the nature of OLI advantages in the banking sector has been examined in order to propose a prognostic model of the timing of foreign direct investment. The model is then tested for the Spanish case using duration analysis.

Weak and strong altruism in traitgGroups: Reproductive suicide, personal fitness and expected value

A simple variant of trait group selection, employing predators as themechanism underlying group selection, supports contingent reproductivesuicide as altruism (i.e., behavior lowering personal fitness whileaugmenting that of another) without kin assortment. The contingentsuicidal type may either saturate the population or be polymorphicwith a type avoiding suicide, depending on parameters. In addition tocontingent suicide, this randomly assorting morph may also exhibitcontinuously expressed strong altruism (sensu Wilson 1979) usuallythought restricted to kin selection. The model will not, however,support a sterile worker caste as such, where sterility occurs beforelife history events associated with effective altruism; reproductivesuicide must remain fundamentally contingent (facultative sensu WestEberhard 1987; Myles 1988) under random assortment. The continuouslyexpressed strong altruism supported by the model may be reinterpretedas probability of arbitrarily committing reproductive suicide, withoutbenefit for another; such arbitrary suicide (a "load" on "adaptive"suicide) is viable only under a more restricted parameter spacerelative to the necessarily concomitant adaptive contingent suicide.

Annual reproductive cycle and fecundity of Scorpaena notata (Teleostei, Scorpaenidae)

Scorpaena notata (Teleostei: Scorpaenidae) is an oviparous species with external fertilisation that shows some unusual features in its gonadal morphology and gametogenesis. In this work we analyse the annual reproductive cycle and the fecundity of this species by studying the monthly histological changes in the gonads and of various indices related to reproduction. Sexual dimorphism does not occur in the population we studied, which is clearly dominated by males. Multiple spawning takes place between July and October, consisting of between 6,000 and 33,000 eggs per female, each of about 500 µm in diameter. The fecundity of the species is determined by the size and weight of the individuals

The impact of eliminating a child benefit on birth timing and infant health

We study the effects of the cancellation of a sizeable child benefit in Spainon birth timing and neonatal health. In May 2010, the government announced that a2,500-euro universal "baby bonus" would stop being paid to babies born startingJanuary 1, 2011. We use detailed micro data from birth certificates from 2000 to 2011,and find that more than 2,000 families were able to anticipate the date of birth of theirbabies from (early) January 2011 to (late) December 2010 (for a total of about 10,000births a week nationally). This shifting took place in part via an increase as well as ananticipation of pre-programmed c-sections, seemingly mostly in private clinics. We findthat this shifting of birthdates resulted in a significant increase in the number ofborderline low birth weight babies, as well as a peak in neonatal mortality. The resultssuggest that announcement effects are important, and that families and healthprofessionals may face effective trade-offs when deciding on the timing (and method) ofbirth.

Experimental evidence that intra-specific competition in seagrass meadows reduces reproductive potential in the sea urchin Paracentrotus lividus (Lamarck)

To better understand the biological controls that regulate sea urchin dynamics, we studied the effects of potential inter- and intra-specific competition for food on several biological variables of the main sea urchin in the Mediterranean (Paracentrotus lividus). We carried out a caging experiment in which we manipulated sea urchin density (natural vs. high density) and herbivorous fish (Sarpa salpa) accessibility (free access vs. exclusion) in a Posidonia oceanica meadow. No evidence of competition between fish and urchins was detected. Neither density-dependent mortality nor changes in the somatic variables were found; however, we detected that intra-specific competition affected the reproductive potential of P. lividus. The gonad index of urchins at high population densities was ca. 30% lower than that of urchins at natural densities. As a spawning event had just occurred when urchins were collected, these differences probably reflect differences in reserve content, which may compromise the following reproductive period and decrease survival in the long term, as the gonads are also used as storage organs. For the time period studied, mortality rates appeared to be independent of local densities. The results indicate that a long-term negative feedback mechanism appears to take place in P. lividus in response to increased population density.

Educational attainment and timing of fertility decisions

This paper focuses on timing of fertility decisions, conditional on the level of educational attainment of parents. Timing of fertility and educational attainment of parents rationalize the negative relationship observed in the data between hourly wages and childbearing. It is shown how the recent evolution in total fertility rates observed in developed countries could be in part the result of a transition from an early childbearing regime to a late childbearing regime. I develop a general equilibrium overlapping generations model in order to understand the joint determination of timing of childbearing decisions together with other household economic decisions in a life cycle framework. I show how idiosyncratic uncertainty might have asymmetric efects on completed fertility depending on timing of childbearing, generating the diferences in completed fertility observed between households that difer in their level of educational attainment.

Educational attainment and timing of fertility decisions

This paper focuses on timing of fertility decisions, conditional on the level of educational attainment of parents. Timing of fertility and educational attainment of parents rationalize the negative relationship observed in the data between hourly wages and childbearing. It is shown how the recent evolution in total fertility rates observed in developed countries could be in part the result of a transition from an early childbearing regime to a late childbearing regime. I develop a general equilibrium overlapping generations model in order to understand the joint determination of timing of childbearing decisions together with other household economic decisions in a life cycle framework. I show how idiosyncratic uncertainty might have asymmetric efects on completed fertility depending on timing of childbearing, generating the diferences in completed fertility observed between households that difer in their level of educational attainment.