Phase Behavior of Aqueous Na-K-Mg-Ca-CI-NO3 Mixtures: Isopiestic Measurements and Thermodynamic Modeling

A comprehensive model has been established for calculating thermodynamic properties of multicomponent aqueous systems containing the Na{sup +}, K{sup +}, Mg{sup 2+}, Ca{sup 2+}, Cl{sup -}, and NO{sub 3}{sup -} ions. The thermodynamic framework is based on a previously developed model for mixed-solvent electrolyte solutions. The framework has been designed to reproduce the properties of salt solutions at temperatures ranging from the freezing point to 300 C and concentrations ranging from infinite dilution to the fused salt limit. The model has been parameterized using a combination of an extensive literature database and new isopiestic measurements for thirteen salt mixtures at 140 C. The measurements have been performed using Oak Ridge National Laboratory's (ORNL) previously designed gravimetric isopiestic apparatus, which makes it possible to detect solid phase precipitation. Water activities are reported for mixtures with a fixed ratio of salts as a function of the total apparent salt mole fraction. The isopiestic measurements reported here simultaneously reflect two fundamental properties of the system, i.e., the activity of water as a function of solution concentration and the occurrence of solid-liquid transitions. The thermodynamic model accurately reproduces the new isopiestic data as well as literature data for binary, ternary and higher-order subsystems. Because of its high accuracy in calculating vapor-liquid and solid-liquid equilibria, the model is suitable for studying deliquescence behavior of multicomponent salt systems

Seasonal variation in sonic muscles in the fawn cusk-eel Lepophidium profundorum

The fawn cusk-eel Lepophidium profundorum (Ophidiidae) has an unusual sound-producing system with sexually dimorphic sets of antagonistic muscles. Outside the mating season, the dorsal and ventral muscles are well developed and larger in males than in females, but the tiny intermediate muscles are smaller, suggesting a minor role, if any, in male advertisement call production. We examined summer individuals with more developed gonads and find a fourfold hypertrophy of the intermediate but not the other muscles. This result suggests androgen dependence and an important role in sound production for the intermediate muscle. Even though both sexes gain weight in the summer, the ventral and dorsal muscles in females lose weight, suggesting that sound production is less important in females and that muscle mass may be used to support egg growth

Relating endocrinology, physiology and behaviour using species with alternative mating strategies

1. Recent reviews demonstrate that genetically determined alternative mating strategies (AMS) are widespread and typically consist of morphs that are recognized by morphological or colour traits. Despite well-established behavioural differences associated with each morph, and evidence that androgens are involved in the induction of morphs, few studies have examined whether morphs also vary in whole-organismal performance traits, which may affect dominance status, resource holding potential (RHP) or mate attraction. 2. Our survey revealed a link between androgens and physiological performance traits that are associated with territorial or courtship displays across vertebrate taxa, although the number of species in the sample is limited. Experimental elevation of testosterone alters muscular contractile properties, swimming performance, sprint speed and endurance in males. Whether morphs differ in physiological capacities is relatively unexplored, although recent studies have found that males with high dominance status also exhibit greater physiological capacities (locomotor performance, call duration). 3. Multiple studies support the hypothesis that elevated testosterone results in fitness trade-offs. Potential costs of testosterone include impaired immune function, higher parasite loads, greater energetic requirements and ultimately reduced survival. Long term studies of Uta stansburiana highlight the trade-offs among life-history traits induced by variation in testosterone. Circumstantial evidence suggests a role of testosterone in depressing immune function in species with AMS. 4. We argue that hypotheses regarding the role of trade-offs in shaping selection on functional modules, which are involved in sexual selection, are best developed by manipulative studies on discrete morphs. Our review highlights the need to measure multiple traits to provide additional insights into the roles of sexual selection and physiological epistasis in maintaining intraspecific variation in reproductive phenotypes. The integration of endocrine control of behaviour, physiology and performance is rarely attempted in most studies and may be facilitated by analyses that focus on estimating correlational selection