Hepatic Rupture Associated With HELLP (Hemolysis, Elevated Liver Enzymes, and Low Platelets) Syndrome: A Report of Two Cases and Literature Review.

Hepatic rupture is a rare complication of severe preeclampsia. A high index of suspicion is required in the presence of abdominal pain accompanied by hemodynamic decompensation in a pregnant woman. Hepatic rupture constitutes a medical emergency that demands immediate intervention, often with the support of other medical disciplines, in a highly specialized hospital setting. Unruptured hepatic hematomas can be managed conservatively. Immediate delivery and surgical repair of the liver are necessary for maternal survival. Spontaneous liver rupture in pregnancy is often unrecognized, highly lethal, and not completely understood with few cases having been reported in the literature. Therefore, we present two cases of HELLP (hemolysis, elevated liver enzymes, and low platelets) syndrome with hepatic rupture, emphasizing their clinical presentation and therapeutic approaches.

Influence of repulsion on entropy scaling and density scaling of monatomic fluids.

Entropy scaling is applied to the shear viscosity, self-diffusion coefficient, and thermal conductivity of simple monatomic fluids. An extensive molecular dynamics simulation series is performed to obtain these transport properties and the residual entropy of three potential model classes with variable repulsive exponents: n, 6 Mie (n = 9, 12, 15, and 18), Buckingham's exponential-six (α = 12, 14, 18, and 30), and Tang-Toennies (αT = 4.051, 4.275, and 4.600). A wide range of liquid and supercritical gas- and liquid-like states is covered with a total of 1120 state points. Comparisons to equations of state, literature data, and transport property correlations are made. Although the absolute transport property values within a given potential model class may strongly depend on the repulsive exponent, it is found that the repulsive steepness plays a negligible role when entropy scaling is applied. Hence, the plus-scaled transport properties of n, 6 Mie, exponential-six, and Tang-Toennies fluids lie basically on one master curve, which closely corresponds with entropy scaling correlations for the Lennard-Jones fluid. This trend is confirmed by literature data of n, 6 Mie, and exponential-six fluids. Furthermore, entropy scaling holds for state points where the Pearson correlation coefficient R is well below 0.9. The condition R > 0.9 for strongly correlating liquids is thus not necessary for the successful application of entropy scaling, pointing out that isomorph theory may be a part of a more general framework that is behind the success of entropy scaling. Density scaling reveals a strong influence of the repulsive exponent on this particular approach.

Diffusion of hydrocarbons diluted in supercritical carbon dioxide.

Mutual diffusion of six hydrocarbons (methane, ethane, isobutane, benzene, toluene or naphthalene) diluted in supercritical carbon dioxide ([Formula: see text]) is studied by molecular dynamics simulation near the Widom line, i.e., in the temperature range from 290 to 345 K along the isobar 9 MPa. The [Formula: see text] + aromatics mixtures are additionally sampled at 10 and 12 MPa and an experimental database with Fick diffusion coefficient data for those systems is provided. Taylor dispersion experiments of [Formula: see text] with benzene, toluene, n-dodecane and 1,2,3,4-tetrahydronaphthalene are conducted along the [Formula: see text] 10 MPa isobar. Maxwell-Stefan and Fick diffusion coefficients are analyzed, together with the thermodynamic factor that relates them. It is found that the peculiar behavior of the Fick diffusion coefficient of some [Formula: see text] mixtures in the extended critical region is a consequence of the thermodynamic factor minimum due to pronounced clustering on the molecular scale. Further, the strong dependence of the Fick diffusion coefficient on the molecular mass of the solute as well as the breakdown of the Stokes-Einstein relation near the Widom line are confirmed. Eleven correlations for the prediction of the Fick diffusion coefficient of [Formula: see text] mixtures are assessed. An alternative two-step approach for the prediction of the infinite dilution Fick diffusion coefficient of supercritical [Formula: see text] mixtures is proposed. It requires only the state point in terms of temperature and pressure (or density) as well as the molecular solute mass as input parameters. First, entropy scaling is applied to estimate the self-diffusion coefficient of [Formula: see text]. Subsequently, this coefficient is used to determine the infinite dilution Fick diffusion coefficient of the mixture, based on the finding that these two diffusion coefficients exhibit a linear relationship, where the slope depends only on the molecular solute mass.

Thermodynamics of supercritical carbon dioxide mixtures across the Widom line.

Supercritical carbon dioxide (scCO2) mixtures are essential for many industrial applications. However, the knowledge of their thermophysical properties in the extended critical region is insufficient. Here, supercritical liquid- and gas-like regions dominated by distinct dynamics and thermodynamics exist and are demarcated by the so-called Widom line. The nature of the anomalies observed for several thermophysical properties at the crossover between these two regions is the subject of a lively debate. Hence, the extended critical region of scCO2 and seven of its binary mixtures with hydrogen, methane, ethane, isobutane, benzene, toluene or naphthalene is studied with respect to thermodynamic, transport and structural properties on the basis of molecular dynamics simulations and equation of state calculations. The Widom line is evaluated employing five criteria and a new empirical equation is proposed for its prediction. Further, the crossover anomalies are investigated in the light of pseudo-boiling theory, diffusion and viscosity as well as structural characteristics given by the radial distribution function.

Sampling the Bulk Viscosity of Water with Molecular Dynamics Simulation in the Canonical Ensemble.

The bulk viscosity, a transport coefficient in the Navier-Stokes equation, is often neglected in the continuum mechanics of Newtonian fluids. Recently, however, the role of the bulk viscosity is highlighted in the area of surface and interface-related phenomena, in systematic model up-scaling and as an important quantity for the interpretation of acoustic sensor data. The prediction of the bulk viscosity usually employs molecular dynamics and the Green-Kubo linear response theory, which is used to sample transport properties in general from molecular trajectories. Since simulations are usually carried out at specified state points in concert with the evaluation of other thermodynamic properties, the role of thermostats in molecular dynamics needs to be explored systematically. In this work, we carefully investigate the role of thermostatting schemes and numerical implementations of the Green-Kubo formalism, in particular in the canonical ensemble, using two popular water force field models. It turns out that the sampling of the bulk and shear viscosities is a delicate challenge since details of thermostatting and numerical subtleties may have an influence on the results beyond statistical uncertainties. Based on the present findings, we conclude with hints on how to construct robust sampling in the canonical ensemble for the bulk viscosity.

Diffusion in multicomponent aqueous alcoholic mixtures.

The Fick diffusion coefficient matrix of the highly associating quaternary mixture water + methanol + ethanol + 2-propanol as well as its ternary and binary subsystems is analyzed with molecular dynamics simulation techniques. Three of the ternary subsystems are studied in this sense for the first time. The predictive capability of the employed force fields, which were sampled with the Green-Kubo formalism and Kirkwood-Buff integration, is confirmed by comparison with experimental literature data on vapor-liquid equilibrium, shear viscosity and Fick diffusion coefficient, wherever possible. A thorough analysis of the finite size effects on the simulative calculation of diffusion coefficients of multicomponent systems is carried out. Moreover, the dependence of the Fick diffusion coefficient matrix on the velocity reference frame and component order is analyzed. Their influence is found to be less significant for the main matrix elements, reaching a maximum variation of 19%. The large differences found for the cross elements upon variation of the reference frame hinder a straightforward interpretation of the Fick diffusion coefficient matrix with respect to the presence of diffusive coupling effects.

Diffusion of the carbon dioxide-ethanol mixture in the extended critical region.

The effect of traces of ethanol in supercritical carbon dioxide on the mixture's thermodynamic properties is studied by molecular simulations and Taylor dispersion measurements. This mixture is investigated along the isobar p = 10 MPa in the temperature range between T = 304 and 343 K. Along this path, the mixture undergoes two transitions: First, the Widom line is crossed, marking the transition from liquid-like to gas-like conditions. A second transition occurs from the supercritical gas-like domain to a subcritical gas. The Widom line crossover entails inflection points for most of the studied properties, i.e. density, enthalpy, shear viscosity, Maxwell-Stefan and intradiffusion coefficients. On the other hand, the transition between the super- and subcritical regions is found to be generally smooth, an observation that is qualitatively confirmed by experimental Taylor dispersion measurements. Dedicated atomistic simulations show the presence of microheterogeneities due to ethanol self-association along the investigated path, which lead to the mixture's anomalous behavior in its extended critical region.

Fick Diffusion Coefficient Matrix of a Quaternary Liquid Mixture by Molecular Dynamics.

For the first time, the Fick diffusion coefficient matrix of a quaternary liquid mixture is sampled consistently by means of molecular dynamics simulation. The required phenomenological diffusion coefficient and thermodynamic factor matrices of the mixture water + methanol + ethanol + 2-propanol are determined following the Green-Kubo formalism and Kirkwood-Buff theory. Further, a system size correction methodology for the Fick diffusion coefficient of multicomponent mixtures is proposed. Ten compositions are studied under ambient conditions and validated by analyzing the ternary limits of the quaternary Fick diffusion matrix. Because of complex intermolecular interactions due to the presence of hydrogen bonding, the elements of the Fick diffusion coefficient matrix exhibit a significant composition dependence. The magnitude of several cross coefficients indicates important coupling effects mainly affecting the diffusive flux of water. These effects are explained in the light of the structural information given by the radial distribution functions of the mixture. This work that solely rests on molecular dynamics simulation techniques to predict the Fick diffusion coefficient matrix of quaternary mixtures is expected to be a significant step forward for the understanding of multicomponent diffusion.

Diffusion of methane in supercritical carbon dioxide across the Widom line.

Diffusion of methane diluted in supercritical carbon dioxide is studied by experiment and molecular simulation in the temperature range from 292.55 to 332.85 K along the isobars 9.0, 12.5 and 14.7 MPa. Measurements of the Fick diffusion coefficient are carried out with the Taylor dispersion technique. Molecular dynamics simulation and the Green-Kubo formalism are employed to obtain Fick, Maxwell-Stefan and intradiffusion coefficients as well as shear viscosity. The obtained diffusion coefficients are on the order of 10-8 m2/s. The composition, temperature and density dependence of diffusion is analyzed. The Fick diffusion coefficient of methane in carbon dioxide shows an anomaly in the near-critical region. This behavior can be attributed to the crossing of the so-called Widom line, where the supercritical fluid goes through a transition between liquid-like and gas-like states. Further, several classical equations are tested on their ability to predict this behavior and it is found that equations that explicitly include the density are better suited to predict the sharp variation of the diffusion coefficient near the critical region predicted by molecular simulation.

Herpes zóster tras primera dosis de vacuna de varicela en paciente inmunocompetente / Herpes zoster after first dose of varicella vaccine in an immunocompetent patient

La varicela es una enfermedad de distribución universal. La vacunación universal ha disminuido la incidencia de varicela en los últimos años. El herpes zóster en los vacunados es posible, pero su incidencia es entre 4 y 12 veces menor que entre los no vacunados. En la infancia, el herpes zóster suele ser leve, autolimitado, bien tolerado y habitualmente solo requiere tratamiento sintomático. Se presenta un caso de herpes zóster en una niña vacunada cinco meses antes, con buena evolución

Chickenpox is a disease of universal distribution. Universal vaccination has decreased the incidence of varicella in recent years. Herpes zoster after vaccination is possible but its incidence is between 4 to 12 times lower than among the unvaccinated. In childhood, herpes zoster is usually mild, self-limiting, well tolerated and usually only requires symptomatic treatment. We present a case of herpes zoster in a child vaccinated five months earlier, with good evolution

Interplay of structure and diffusion in ternary liquid mixtures of benzene + acetone + varying alcohols.

The Fick diffusion coefficient matrix of ternary mixtures containing benzene + acetone + three different alcohols, i.e., methanol, ethanol, and 2-propanol, is studied by molecular dynamics simulation and Taylor dispersion experiments. Aiming to identify common features of these mixtures, it is found that one of the main diffusion coefficients and the smaller eigenvalue do not depend on the type of alcohol along the studied composition path. Two mechanisms that are responsible for this invariant behavior are discussed in detail, i.e., the interplay between kinetic and thermodynamic contributions to Fick diffusion coefficients and the presence of microscopic heterogeneities caused by hydrogen bonding. Experimental work alone cannot explain these mechanisms, while present simulations on the molecular level indicate structural changes and uniform intermolecular interactions between benzene and acetone molecules in the three ternary mixtures. The main diffusion coefficients of these ternary mixtures exhibit similarities with their binary subsystems. Analyses of radial distribution functions and hydrogen bonding statistics quantitatively evidence alcohol self-association and cluster formation, as well as component segregation. Furthermore, the excess volume of the mixtures is analyzed in the light of intermolecular interactions, further demonstrating the benefits of the simultaneous use of experiment and simulation. The proposed framework for studying diffusion coefficients of a set of ternary mixtures, where only one component varies, opens the way for further investigations and a better understanding of multicomponent diffusion. The presented numerical results may also give an impulse to the development of predictive approaches for multicomponent diffusion.

Molecular Insight into the Liquid Propan-2-ol + Water Mixture.

The hydrogen bonding structure of the mixture propan-2-ol + water is analyzed at ambient conditions of temperature and pressure with molecular modeling and simulation techniques. A new force field for propan-2-ol is developed for this purpose on the basis of quantum chemical calculations and validated for a wide range of macroscopic properties. The basic mixing properties, excess volume and excess enthalpy, as well as the most important transport properties, that is, diffusion coefficients and shear viscosity, are considered to verify the suitability of the employed force fields for studying the complex behavior of this aqueous alcoholic mixture. Radial distribution functions and hydrogen bonding statistics are employed to characterize the hydrogen bond network and molecular clustering. Inhomogeneous mixing on the microscopic level, given by the presence of segregation pockets, is identified. The interrelation between the intriguing macroscopic behavior of this binary mixture and its microscopic structure is revealed.

The effect of alcohols as the third component on diffusion in mixtures of aromatics and ketones.

With laboratory and numerical work, we demonstrate that one of the main diffusion coefficients and the smaller eigenvalue of the Fick diffusion matrix are invariant to the number of methylene groups of the alcohol in ternary mixtures composed of an aromatic (benzene), a ketone (acetone) and one of three different alcohols (methanol, ethanol or 2-propanol). A critical analysis of the relationship between the kinetic and thermodynamic contributions to the diffusion coefficients allows us to explain this intriguing behaviour of this class of mixture. These findings are reflected by the diffusive behaviour of the according binary subsystems. Our approach provides a promising systematic framework for future investigations into the important and challenging problem of transport diffusion in multicomponent liquids.

Mutual diffusion governed by kinetics and thermodynamics in the partially miscible mixture methanol + cyclohexane.

To gain an understanding of the transport and thermodynamic behavior of the highly non-ideal mixture methanol + cyclohexane, three complementary approaches, i.e. experiment, molecular simulation and predictive equations, are employed. The temperature and composition dependence of different diffusion coefficients is studied around the miscibility gap at ambient pressure. On the one hand Fick diffusion coefficients are measured experimentally by interferometric probing and on the other hand Maxwell-Stefan diffusion coefficients and intradiffusion coefficients are sampled by equilibrium molecular dynamics simulation at five temperatures below the upper critical temperature of ∼319 K. The spinodal curve is determined from extrapolation of the experimental Fick diffusion coefficient data and compared to predictions from excess Gibbs energy models. It is found that these models are not capable to correctly describe the activity coefficients over the whole composition range of the studied mixture. Thus, different parameter sets for a modified Wilson model are used for calculations of the thermodynamic factor, which is needed to transform Maxwell-Stefan into Fick diffusion coefficients and vice versa. Further, predictive equations for the Maxwell-Stefan diffusion coefficient, which are based on intradiffusion coefficients, are compared to simulation results. Using different approaches provides a clearer understanding of the relations between kinetic and thermodynamic properties contributing to the diffusion behavior of partially miscible mixtures.

Mutual diffusion of binary liquid mixtures containing methanol, ethanol, acetone, benzene, cyclohexane, toluene, and carbon tetrachloride.

Mutual diffusion coefficients of all 20 binary liquid mixtures that can be formed out of methanol, ethanol, acetone, benzene, cyclohexane, toluene, and carbon tetrachloride without a miscibility gap are studied at ambient conditions of temperature and pressure in the entire composition range. The considered mixtures show a varying mixing behavior from almost ideal to strongly non-ideal. Predictive molecular dynamics simulations employing the Green-Kubo formalism are carried out. Radial distribution functions are analyzed to gain an understanding of the liquid structure influencing the diffusion processes. It is shown that cluster formation in mixtures containing one alcoholic component has a significant impact on the diffusion process. The estimation of the thermodynamic factor from experimental vapor-liquid equilibrium data is investigated, considering three excess Gibbs energy models, i.e., Wilson, NRTL, and UNIQUAC. It is found that the Wilson model yields the thermodynamic factor that best suits the simulation results for the prediction of the Fick diffusion coefficient. Four semi-empirical methods for the prediction of the self-diffusion coefficients and nine predictive equations for the Fick diffusion coefficient are assessed and it is found that methods based on local composition models are more reliable. Finally, the shear viscosity and thermal conductivity are predicted and in most cases favorably compared with experimental literature values.

Adolescencia e hipertensión arterial / Adolescence and high blood pressure

Introducción: se desconocen las características demográficas y clínicas de la hipertensión arterial en niños y adolescentes en Guane. Objetivo: caracterizar la hipertensión arterial en adolescentes de 10-15 años en Guane en el año 2013. Material y método: se realizó una investigación observacional, descriptiva, transversal, con componente analítico en 360 niños de las edades mencionadas, en los que se comprobó: tensión arterial, índice de masa corporal, circunferencia de la cintura, tabaquismo y actividad física, todos con referencia a la edad y al sexo. Se resumieron las variables cualitativas en frecuencias absolutas y relativas porcentuales, y la asociación entre las mismas se midió mediante las pruebas de X² y Odds Ratio al 95 % de certeza. Resultados: hubo 175 normotensos en las edades 10-12 años, 8 pre-hipertensos y 9 hipertensos en el grupo de 13-15 años. Hubo prevalencia estadísticamente significativa (x²) de normotensos en el sexo femenino (p = 0.008). La obesidad estaba incrementada más de 5 veces en los varones (p = 0,002) y en edades de 13-15 años. Existió un incremento significativo de hipertensos en el grupo de 13-15 años con aumento de la circunferencia abdominal (p<0,001). El tabaquismo estuvo significativamente aumentado entre los varones del grupo de 13-15 años, mientras que entre las niñas predominaba la actividad física ligera (p = 0.03). Conclusiones: la hipertensión arterial en niños aun con baja frecuencia de presentación muestra diferencias en cuanto a la edad y el sexo, con predominio en varones y en el grupo de 13-15 años.

Introduction: the demographic and clinical characteristics of high blood pressure in Guane children and adolescents are unknown. Objective: to characterize high blood pressure in Guane 10-15-year-old adolescents, 2013. Material and method: an observational, descriptive, cross-sectional research was carried out, with an analytical component, on 360 children of the mentioned ages, in which we analyzed: blood pressure, body mass index, waist circumference, smoking and physical activity, all of which with reference to age and sex. The quantitative variants were defined in percentage absolute and relative frequencies, while association among them was measured by chi-square and Odds Ratio tests at 95% of certitude. Results: there were 175 with normal blood pressure between 10-12 years old, 8 pre-hypertensives aged 13-15 years old. There was a statistically significant prevalence of female patients with normal blood pressure (p=0.008). Obesity increased five times in male patients (p=0.002) and in ages 13-15 years old. There was a significant increase in hypertensive patients aged 13-15 years old, with increase in the waist circumference (p<0.001). Smoking was significantly increased among male patients aged 13-15 years old, while in girls there was a predominance of subtle physical activity (p=0.03). Conclusions: high blood pressure in children with low frequency of presentation shows differences regarding age and sex, with a predominance in male patients and the groups aged 13-15 years old.

Adolescencia e hipertensión arterial / Adolescence and high blood pressure

Se desconocen las características demográficas y clínicas de la hipertensión arterial en niños y adolescentes en Guane. El objetivo fue caracterizar la hipertensión arterial en adolescentes de 10-15 años en Guane en el año 2013. Se realizó una investigación observacional, descriptiva, transversal, con componente analítico en 360 niños de las edades mencionadas, en los que se comprobó: tensión arterial, índice de masa corporal, circunferencia de la cintura, tabaquismo y actividad física, todos con referencia a la edad y al sexo. Se resumieron las variables cualitativas en frecuencias absolutas y relativas porcentuales, y la asociación entre las mismas se midió mediante las pruebas de X2 y Odds Ratio al 95 por ciento de certeza. Hubo 175 normotensos en las edades 10-12 años, 8 pre-hipertensos y 9 hipertensos en el grupo de 13-15 años. Hubo prevalencia estadísticamente significativa (x2) de normotensos en el sexo femenino (p = 0.008). La obesidad estaba incrementada más de 5 veces en los varones (p = 0,002) y en edades de 13-15 años. Existió un incremento significativo de hipertensos en el grupo de 13-15 años con aumento de la circunferencia abdominal (p<0,001). El tabaquismo estuvo significativamente aumentado entre los varones del grupo de 13-15 años, mientras que entre las niñas predominaba la actividad física ligera (p = 0.03). La hipertensión arterial en niños aun con baja frecuencia de presentación muestra diferencias en cuanto a la edad y el sexo, con predominio en varones y en el grupo de 13-15 años(AU)

The demographic and clinical characteristics of high blood pressure in Guane children and adolescents are unknown. The objective was to characterize high blood pressure in Guane 10-15-year-old adolescents, 2013. An observational, descriptive, cross-sectional research was carried out, with an analytical component, on 360 children of the mentioned ages, in which we analyzed: blood pressure, body mass index, waist circumference, smoking and physical activity, all of which with reference to age and sex. The quantitative variants were defined in percentage absolute and relative frequencies, while association among them was measured by chi-square and Odds Ratio tests at 95 per cent of certitude. There were 175 with normal blood pressure between 10-12 years old, 8 pre-hypertensives aged 13-15 years old. There was a statistically significant prevalence of female patients with normal blood pressure (p=0.008). Obesity increased five times in male patients (p=0.002) and in ages 13-15 years old. There was a significant increase in hypertensive patients aged 13-15 years old, with increase in the waist circumference (p<0.001). Smoking was significantly increased among male patients aged 13-15 years old, while in girls there was a predominance of subtle physical activity (p=0.03). High blood pressure in children with low frequency of presentation shows differences regarding age and sex, with a predominance in male patients and the groups aged 13-15 years old(AU)

Mutual diffusion in the ternary mixture of water + methanol + ethanol and its binary subsystems.

Mutual diffusion is investigated by means of experiment and molecular simulation for liquid mixtures containing water + methanol + ethanol. The Fick diffusion coefficient is measured by Taylor dispersion as a function of composition for all three binary subsystems under ambient conditions. For the aqueous systems, these data compare well with literature values. In the case of methanol + ethanol, experimental measurements of the Fick diffusion coefficient are presented for the first time. The Maxwell-Stefan diffusion coefficient and the thermodynamic factor are predicted for the ternary mixture as well as its binary subsystems by molecular simulation in a consistent manner. The resulting Fick diffusion coefficient is compared to present measurements and that obtained from the classical simulation approach, which requires experimental vapor-liquid equilibrium or excess enthalpy data. Moreover, the self-diffusion coefficients and the shear viscosity are predicted by molecular dynamics and are favorably compared to experimental literature values. The presented ternary diffusion data should facilitate the development of aggregated predictive models for diffusion coefficients of polar and hydrogen-bonding systems.

Thermodynamic properties for applications in chemical industry via classical force fields.

Thermodynamic properties of fluids are of key importance for the chemical industry. Presently, the fluid property models used in process design and optimization are mostly equations of state or G (E) models, which are parameterized using experimental data. Molecular modeling and simulation based on classical force fields is a promising alternative route, which in many cases reasonably complements the well established methods. This chapter gives an introduction to the state-of-the-art in this field regarding molecular models, simulation methods, and tools. Attention is given to the way modeling and simulation on the scale of molecular force fields interact with other scales, which is mainly by parameter inheritance. Parameters for molecular force fields are determined both bottom-up from quantum chemistry and top-down from experimental data. Commonly used functional forms for describing the intra- and intermolecular interactions are presented. Several approaches for ab initio to empirical force field parameterization are discussed. Some transferable force field families, which are frequently used in chemical engineering applications, are described. Furthermore, some examples of force fields that were parameterized for specific molecules are given. Molecular dynamics and Monte Carlo methods for the calculation of transport properties and vapor-liquid equilibria are introduced. Two case studies are presented. First, using liquid ammonia as an example, the capabilities of semi-empirical force fields, parameterized on the basis of quantum chemical information and experimental data, are discussed with respect to thermodynamic properties that are relevant for the chemical industry. Second, the ability of molecular simulation methods to describe accurately vapor-liquid equilibrium properties of binary mixtures containing CO(2) is shown.

Geographical variation in the genetic diversity and composition of the endangered queen conch Strombus gigas (Mesogastropoda: Strombidae) from Yucatán, México.

In Mexico and elsewhere in the Caribbean, the queen conch Strombus gigas is an endangered species. Understanding the genetic connectivity of their populations will support management strategies for long-term conservation of the species. Genetic diversity and population differentiation was assessed from samples collected at Banco Chinchorro and Isla Cozumel in the Mexican Caribbean and at Arrecife Alacranes in the Gulf of Mexico. Samples were obtained from the commercial capture at Banco Chinchorro (n = 50) and Isla Cozumel (n = 40) on March 2004. On November 2004, a non-invasive method for the Arrecife Alacranes sampling was applied, taking the hemolymph of live animals (n = 65) and releasing them to the wild. The mitochondrial DNA variation at two genes (COI and Cyt-b) was analyzed. Genetic diversity at the three locations ranged between 0.55-0.65 in COI and 0.87-0.94 in Cyt-b, showing no bottleneck evidences. A non-significant fixation index (F(ST) = 0.019, p = 0.161) and a Maximum Parsimony Network tree that did not show particular clades associated with any of the geographical locations, suggested a lack of statistically significant genetic differentiation among populations. Nevertheless, the cline patterns observed in both genetic diversity and haplotypic frequencies from Banco Chinchorro through Arrecife Alacranes, and the larger genetic distance between these locations from those between Isla Cozumel, Banco Chinchorro and Arrecife Alacranes, suggest the possibility of a pattern of isolation-by distance. The role of the main current systems over the potential genetic differences in S. gigas populations along the Mexican Caribbean, and the conservation management of S. gigas at these locations as discrete units is discussed.