Showing papers in "Physiological and Biochemical Zoology in 2006"
TL;DR: This effort illustrates the need for an overarching concept of thermal adaptation that encompasses molecular, organellar, cellular, and whole‐organism information as well as the mechanistic links between fitness, ecological success, and organismal physiology.
Abstract: Through functional analyses, integrative physiology is able to link molecular biology with ecology as well as evolutionary biology and is thereby expected to provide access to the evolution of molecular, cellular, and organismic functions; the genetic basis of adaptability; and the shaping of ecological patterns. This paper compiles several exemplary studies of thermal physiology and ecology, carried out at various levels of biological organization from single genes (proteins) to ecosystems. In each of those examples, trade-offs and constraints in thermal adaptation are addressed; these trade-offs and constraints may limit species' distribution and define their level of fitness. For a more comprehensive understanding, the paper sets out to elaborate the functional and conceptual connections among these independent studies and the various organizational levels addressed. This effort illustrates the need for an overarching concept of thermal adaptation that encompasses molecular, organellar, cellular, and whole-organism information as well as the mechanistic links between fitness, ecological success, and organismal physiology. For this data, the hypothesis of oxygen- and capacity-limited thermal tolerance in animals provides such a conceptual framework and allows interpreting the mechanisms of thermal limitation of animals as relevant at the ecological level. While, ideally, evolutionary studies over multiple generations, illustrated by an example study in bacteria, are necessary to test the validity of such complex concepts and underlying hypotheses, animal physiology frequently is constrained to functional studies within one generation. Comparisons of populations in a latitudinal cline, closely related species from different climates, and ontogenetic stages from riverine clines illustrate how evolutionary information can still be gained. An understanding of temperature-dependent shifts in energy turnover, associated with adjustments in aerobic scope and performance, will result. This understanding builds on a mechanistic analysis of the width and location of thermal windows on the temperature scale and also on study of the functional properties of relevant proteins and associated gene expression mechanisms.
337 citations
TL;DR: It is argued that major advances will require a quantitative theory of coadaptation that predicts which strategies should evolve in specific thermal environments and must also consider the biotic interactions that influence the net benefits of behavioral and physiological strategies.
Abstract: Over the last 50 yr, thermal biology has shifted from a largely physiological science to a more integrated science of behavior, physiology, ecology, and evolution. Today, the mechanisms that underlie responses to environmental temperature are being scrutinized at levels ranging from genes to organisms. From these investigations, a theory of thermal adaptation has emerged that describes the evolution of thermoregulation, thermal sensitivity, and thermal acclimation. We review and integrate current models to form a conceptual model of coadaptation. We argue that major advances will require a quantitative theory of coadaptation that predicts which strategies should evolve in specific thermal environments. Simply combining current models, however, is insufficient to understand the responses of organisms to thermal heterogeneity; a theory of coadaptation must also consider the biotic interactions that influence the net benefits of behavioral and physiological strategies. Such a theory will be challenging to develop because each organism's perception of and response to thermal heterogeneity depends on its size, mobility, and life span. Despite the challenges facing thermal biologists, we have never been more pressed to explain the diversity of strategies that organisms use to cope with thermal heterogeneity and to predict the consequences of thermal change for the diversity of communities.
285 citations
TL;DR: A recent theoretical model used to predict hatchling sex of reptiles with temperature‐dependent sex determination predicts that sex ratios will be fairly robust to moderate global warming as long as eggs experience substantial daily cyclic fluctuations in incubation temperatures.
Abstract: Incubation temperature influences hatchling phenotypes such as sex, size, shape, color, behavior, and locomotor performance in many reptiles, and there is growing concern that global warming might adversely affect reptile populations by altering frequencies of hatchling phenotypes. Here I overview a recent theoretical model used to predict hatchling sex of reptiles with temperature-dependent sex determination. This model predicts that sex ratios will be fairly robust to moderate global warming as long as eggs experience substantial daily cyclic fluctuations in incubation temperatures so that embryos are exposed to temperatures that inhibit embryonic development for part of the day. I also review studies that examine the influence of incubation temperature on posthatch locomotion performance and growth because these are the traits that are likely to have the greatest effect on hatchling fitness. The majority of these studies used artificial constant-temperature incubation, but some have addressed fluctuating incubation temperature regimes. Although the number of studies is small, it appears that fluctuating temperatures may enhance hatchling locomotor performance. This finding should not be surprising, given that the majority of natural reptile nests are relatively shallow and therefore experience daily fluctuations in incubation temperature.
226 citations
TL;DR: A novel application of an in vitro technique that measures the intrinsic bacteria‐killing abilities of blood and assesses the capacities of whole blood and plasma from free‐living individuals of five tropical bird species to kill a nonpathogenic strain of E. coli before and after the birds experienced an acute stress.
Abstract: In wild birds, relatively little is known about intra- or interspecific variation in immunological capabilities, and even less is known about the effects of stress on immune function. Immunological assays adaptable to field settings and suitable for a wide variety of taxa will prove most useful for addressing these issues. We describe a novel application of an in vitro technique that measures the intrinsic bacteria-killing abilities of blood. We assessed the capacities of whole blood and plasma from free-living individuals of five tropical bird species to kill a nonpathogenic strain of E. coli before and after the birds experienced an acute stress. Killing invasive bacteria is a fundamental immune function, and the bacteria-killing assay measures constitutive, innate immunity integrated across circulating cell and protein components. Killing ability varied significantly across species, with common ground doves exhibiting the lowest levels and blue-crowned motmots exhibiting the highest levels. Across species, plasma killed bacteria as effectively as whole blood, and higher concentrations of plasma killed significantly better. One hour of acute stress reduced killing ability by up to 40%. This assay is expected to be useful in evolutionary and ecological studies dealing with physiological and immunological differences in birds.
203 citations
TL;DR: After 12 d of incubation, embryo mass and yolk reserves were less in eggs that experienced periodic cooling than in controls incubated constantly at 37.5°C, adding a new dimension to the fitness consequences of variation in adult nest attentiveness.
Abstract: For many bird embryos, periodic cooling occurs when the incubating adult leaves the nest to forage, but the effects of periodic cooling on embryo growth, yolk use, and metabolism are poorly known. To address this question, we conducted incubation experiments on eggs of zebra finches (Taeniopygia guttata) that were frequently cooled and then rewarmed or were allowed to develop at a constant temperature. After 12 d of incubation, embryo mass and yolk reserves were less in eggs that experienced periodic cooling than in controls incubated constantly at 37.5°C. Embryos that regularly cooled to 20°C had higher mass‐specific metabolic rates than embryos incubated constantly at 37.5°C. Periodic cooling delayed development and increased metabolic costs, reducing the efficiency with which egg nutrients were converted into embryo tissue. Avian embryos can tolerate periodic cooling, possibly by adjusting their physiology to variable thermal conditions, but at a cost to growth efficiency as well as rate of de...
186 citations
TL;DR: The main theories for the evolutionary genesis of the DGC are summarized, including reduction in respiratory water loss (the hygric hypothesis), optimizing gas exchange in hypoxic and hypercapnic environments (the chthonic hypothesis), and protection against parasitic invaders (the strolling arthropods hypothesis).
Abstract: Many adult and diapausing pupal insects exchange respiratory gases discontinuously in a three‐phase discontinuous gas exchange cycle (DGC). We summarize the known biophysical characteristics of the DGC and describe current research on the role of convection and diffusion in the DGC, emphasizing control of respiratory water loss. We summarize the main theories for the evolutionary genesis (or, alternatively, nonadaptive genesis) of the DGC: reduction in respiratory water loss (the hygric hypothesis), optimizing gas exchange in hypoxic and hypercapnic environments (the chthonic hypothesis), the hybrid of these two (the chthonic‐hygric hypothesis), reducing the toxic properties of oxygen (the oxidative damage hypothesis), the outcome of interactions between O2 and CO2 control set points (the emergent property hypothesis), and protection against parasitic invaders (the strolling arthropods hypothesis). We describe specific techniques that are being employed to measure respiratory water loss in the pr...
176 citations
TL;DR: There is little evidence for compensation in traits associated with feeding and foraging in ectothermic vertebrates, and it is suggested that this difference may be due to different selective regimes operating on locomotor versus feeding traits.
Abstract: When competing for food or other resources, or when confronted with predators, young animals may be at a disadvantage relative to adults because of their smaller size. Additionally, the ongoing differentiation and growth of tissues and the development of sensory-motor integration during early ontogeny may constrain performance. Because ectothermic vertebrates show different growth regimes and energetic requirements when compared to endothermic vertebrates, differences in the ontogenetic trajectories of performance traits in these two groups might be expected. However, both groups of vertebrates show similar patterns of changes in performance with ontogeny. Evidence for compensation, resulting in relatively high levels of performance in juveniles relative to adults, appears common for traits related to locomotor and defensive behaviors. However, there is little evidence for compensation in traits associated with feeding and foraging. We suggest that this difference may be due to different selective regimes operating on locomotor versus feeding traits. As a result, relatively high levels of locomotor performance in juveniles and relatively high levels of feeding performance in adults are observed across a wide range of vertebrate groups.
166 citations
TL;DR: Both lizards and turtles display positive allometric scaling of bite force relative to some measures of head size throughout ontogeny, suggesting (1) strong selection for increased relative bite performance with increasing head size and (2) intrinsic changes in the geometry and/or mass of the jaw adductors during growth.
Abstract: Because selection on juvenile life‐history stages is likely strong, disproportionately high levels of performance (eg, sprint speed, endurance, etc) might be expected Whereas this phenomenon has been demonstrated with respect to locomotor performance, data for feeding are scarce Here, we investigate the relationships among body dimensions, head dimensions, and bite force during growth in lizards and turtles We also investigate whether ontogenetic changes in bite performance are related to changes in diet Our analyses show that, for turtles, head dimensions generally increase with negative allometry For lizards, heads scale as expected for geometrically growing systems Bite force generally increased isometrically with carapace length in turtles but showed significant positive allometry relative to body dimensions in lizards However, both lizards and turtles display positive allometric scaling of bite force relative to some measures of head size throughout ontogeny, suggesting (1) strong
138 citations
TL;DR: The data support a regulated, reversible decrease of liver (but not muscle) mitochondrial oxidative phosphorylation in hibernating ground squirrels.
Abstract: We compared liver and skeletal muscle mitochondrial function among activity states to characterize regulated reversible metabolic suppression in the mammalian hibernator Spermophilus tridecemlineatus. At 37°C, succinate oxidation was 70% lower in the liver mitochondria from torpid animals than in those from summer‐active animals or in animals arousing from torpor. Respiration was very sensitive to temperature (Q10 5.8–9.8), and when measured at 25° or 5°C there was no difference among the three states. Liver mitochondria from summer‐active animals oxidized pyruvate and β‐hydroxybutyrate at higher rates than those from torpid animals, and flux through complex 4 of the electron transport chain was about three‐ and fivefold higher than flux through complexes 2–4 and complexes 1–4, respectively. In the hibernating and arousing animals there was no difference in flux through complexes 2–4 and complex 4, suggesting a downregulation of cytochrome c oxidase in liver mitochondria during the hibernation se...
113 citations
TL;DR: It is estimated that δ15N of tissues collected from wild animals that consume high‐quality diets may reliably indicate the dietary protein source, whereas δ13C of these same tissues is likely the product of metabolic routing of carbon from several macronutrients.
Abstract: During fall migration many songbirds switch from consuming primarily insects to consuming mostly fruit. Fruits with more carbohydrates and less protein may be sufficient to rebuild expended fat stores, but such fruits may be inadequate to replace catabolized protein. We manipulated the concentrations and isotopic signatures of macronutrients in diets fed to birds to study the effects of diet quality on metabolic routing of dietary nutrients. We estimated that approximately 45% and 75%, respectively, of the carbon in proteinaceous tissue of birds switched to high‐ or low‐protein diets came from nonprotein dietary sources. In contrast, we estimated that approximately 100% and 20%–80%, respectively, of the nitrogen in proteinaceous tissues of birds switched to high‐ or low‐protein diets was attributable to dietary protein. Thus, the routing and assimilation of dietary carbon and nitrogen differed depending on diet composition. As a result, δ15N of tissues collected from wild animals that consume hig...
109 citations
TL;DR: The ability of salmonids to maintain feeding metabolism during prolonged swimming performance is discussed, and it is suggested that reduced swimming performance may be due to postprandial sparing of intestinal blood to support digestion, thereby limiting the allocation of blood flow to locomotory muscles.
Abstract: Following a relatively large meal (2% body mass of dry pellets), intestinal blood flow in chinook salmon (Oncorhynchus tshawytscha) increased significantly, up to 81%, between 14 and 29 h postprandially. Also, 15 h postprandially, oxygen consumption ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc}
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TL;DR: Residuals were consistently related to distribution aridity and rainfall variability, with species from arid and variable rainfall habitats having a low BMR, presumably to conserve energy in a low‐productivity environment and facilitating maintenance of water balance during dry periods.
Abstract: We analyzed body temperature (Tb), basal metabolic rate (BMR), wet thermal conductance (Cwet), and evaporative water loss (EWL) of marsupials by conventional and phylogenetically corrected regression. Allometric effects were substantial for BMR, Cwet, and EWL but not Tb. There was a strong phylogenetic signal for mass and all physiological traits. A significant phylogenetic signal remained for BMR, Cwet, and EWL even after accounting for the highly significant phylogenetic signal of mass. Tb, BMR, Cwet, and EWL allometric residuals were correlated with some diet, distribution, and climatic variables before and after correction for phylogeny. Tb residuals were higher for marsupials from arid environments (high Ta and more variable rainfall). The fossorial marsupial mole had a lower‐than‐expected Tb residual. The allometric slope for BMR was 0.72–0.75. Residuals were consistently related to distribution aridity and rainfall variability, with species from arid and variable rainfall habitats having a...
TL;DR: Female reindeer lost body fat but gained body fat when ambient temperatures were low and nitrogen demand for fetal growth is highest in pregnant females.
Abstract: We studied bred and unbred female reindeer (Rangifer tarandus tarandus) during 12 wk of winter when ambient temperatures were low and nitrogen (N) demand for fetal growth is highest in pregnant females. Animals were fed a complete pelleted diet ad lib. that contained 2.54% N in dry matter that was \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc}
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TL;DR: Overall, the observations show that when food resources are abundant, testosterone stimulates both early growth and immunity in developing house finches.
Abstract: Female birds deposit variable amounts of androgens, such as testosterone, into the yolks of their eggs. Evidence suggests that yolk androgens play an important role in the determination of offspring phenotype. While androgens are generally regarded as anabolic and immunosuppressive, studies of the behavioral and physiological effects of yolk androgens on offspring of several avian species have been conflicting, leaving the adaptive significance associated with deposition patterns of yolk androgens unclear. We injected either a physiological dose of testosterone or a control vehicle into house finch (Carpodacus mexicanus) eggs and examined the effects of these injections on offspring growth and immunity. Two days after hatching, nestlings from eggs treated with testosterone were significantly larger than nestlings from eggs treated with a control injection, suggesting a stimulatory effect of yolk androgens in early development. By 8 d after hatching, however, this effect disappeared, and chicks from the two treatment groups were similar in size. Nestlings in the testosterone treatment group showed a significantly larger swelling response to phytohemagglutinin than control nestlings 15 d after hatching, which is close to fledging. Overall, our observations show that when food resources are abundant, testosterone stimulates both early growth and immunity in developing house finches.
TL;DR: It is suggested that lower COT may have coadapted in response to selection for higher running distances in these lines and the sex‐specific responses to selection may in part be consequences of sex differences in body mass and running style.
Abstract: Selective breeding for over 35 generations has led to four replicate (S) lines of laboratory house mice (Mus domesticus) that run voluntarily on wheels about 170% more than four random‐bred control (C) lines. We tested whether S lines have evolved higher running performance by increasing running economy (i.e., decreasing energy spent per unit of distance) as a correlated response to selection, using a recently developed method that allows for nearly continuous measurements of oxygen consumption ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc}
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TL;DR: It is suggested that N conservation is a high priority in this elasmobranch and that feeding promotes ureogenesis and growth.
Abstract: Urea not only is utilized as a major osmolyte in marine elasmobranchs but also constitutes their main nitrogenous waste. This study investigated the effect of feeding, and thus elevated nitrogen intake, on nitrogen metabolism in the Pacific spiny dogfish Squalus acanthias. We determined the activities of ornithine urea cycle (O‐UC) and related enzymes in liver and nonhepatic tissues. Carbamoyl phosphate synthetase III (the rate‐limiting enzyme of the O‐UC) activity in muscle is high compared with liver, and the activities in both tissues increased after feeding. The contribution of muscle to urea synthesis in the dogfish body appears to be much larger than that of liver when body mass is considered. Furthermore, enhanced activities of the O‐UC and related enzymes (glutamine synthetase, ornithine transcarbamoylase, arginase) were seen after feeding in both liver and muscle and were accompanied by delayed increases in plasma urea, trimethylamine oxide, total free amino acids, alanine, and chloride ...
TL;DR: Biologists, including ecological and evolutionary physiologists, should exercise care when using allometric equations to make predictions, particularly given that methods to adjust for bias are easily implemented.
Abstract: Biologists often use allometric equations that take the form of power functions (e.g., \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc}
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ormalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $Y=aM^{b}$ \end{document} , where M stands for mass and a and b are empirically fitted constants). Typically, these allometric equations are fitted by taking the antilog of log‐log regressions. Predictions from these allometric equations are biased, and the bias my be appreciable. Methods for making predictions that correct for the bias are available, but they have rarely, if ever, been u...
TL;DR: Together, the three‐dimensional data of the cardiac and vascular systems have shown that the most profound physiological and developmental changes occur in days 5 and 6, which corresponds with the appearance of the adult form of the heart and the transition from diffusive to convective O2 supply to internal tissues.
Abstract: There has been considerable recent interest in the development of the circulation in the zebrafish. Optical techniques typically used to visualize changes in heart size allow measurement of stroke volume during early vertebrate development, but this approach is complicated in zebrafish larvae because of the heart’s irregular shape and its significant change in morphology during the first 6 d of development. By use of a threedimensional integration of the early zebrafish heart and vessels, we have greatly reduced measurement error of stroke volume and cardiac output and have determined the cross‐sectional growth of major vessels in the developing zebrafish larvae. A dramatic 500%–600% increase in cardiac output (from 10 to 50–60 nL min−1) occurs on days 5 and 6 postfertilization in Danio rerio. Cross‐sectional area of key vessels (dorsal artery, caudal artery, dorsal vein) as well as between‐individual variation significantly decreased over the first 6 d of development. Associated with the decreas...
TL;DR: It is concluded that better immunological state and lower stress in great tits during breeding were positively related to their survival probability, compared to nonsurvivors.
Abstract: In birds, it has been shown that reproductive effort may impair parental condition, while the relation of different condition indices to subsequent survival is still poorly understood. In this study, we measured body mass and various hematological condition indices in breeding great tits in relation to local survival. Number and quality of nestlings and the occurrence of second broods, potentially reflecting parents’ breeding effort, were also considered in analyses. The great tits, both male and female, that returned the following year had had a higher albumin/globulin ratio, lower plasma globulin concentration, and a lower heterophile/lymphocyte ratio during breeding in the preceding year, compared to those who did not return. Surviving males (but not females) also had had a higher level of circulating lymphocytes, compared to nonsurvivors. There was no correlation between breeding effort and survival. We conclude that better immunological state and lower stress in great tits during breeding we...
TL;DR: A new model for Cl− uptake in FW fish is proposed whereby the combined action of an apical anion exchanger, cytoplasmic carbonic anhydrase, and basolateral V‐type H+‐ATPase creates a local environment high enough to energize Cl − uptake.
Abstract: Despite all the efforts and technological advances during the last few decades, the cellular mechanisms for branchial chloride uptake in freshwater (FW) fish are still unclear Although a tight 1:1 link with \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc}
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TL;DR: The hypothesis that changes in metabolism, beyond those elicited by low food consumption, may be responsible at least in part for the low growth rates typical of subordinate fish is supported and that these changes may be related specifically to circulating cortisol levels in subordinate fish.
Abstract: To assess the effects of subordinate social status on digestive function, metabolism, and enzyme activity in salmonid fish, juvenile rainbow trout Oncorhynchus mykiss were paired with size‐matched conspecifics (<1.5% difference in fork length) for 5 d. Fish that were fasted for 5 d and fish sampled directly from the holding tank were used as control groups. Both subordinate and fasted fish experienced significant decreases in intestine mass ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc}
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ormalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $P=0.043$ \end{document} ), and...
TL;DR: The combination of respirometry and carbon isotope analysis revealed that hummingbirds initially oxidized endogenous fat following a fast and then progressively oxidized proportionately more carbohydrates, providing an example of evolutionary convergence in physiological and biochemical traits among unrelated nectar‐feeding animals.
Abstract: We sought to characterize the ability of hummingbirds to fuel their energetically expensive hovering flight using dietary sugar by a combination of respirometry and stable carbon isotope techniques. Broadtailed hummingbirds (Selasphorus platycercus) were maintained on a diet containing beet sugar with an isotopic composition characteristic of C3 plants. Hummingbirds were fasted and then offered a solution containing cane sugar with an isotopic composition characteristic of C4 plants. By monitoring the rates of CO2 production and O2 consumption, as well as the stable carbon isotope composition of expired CO2, we were able to estimate the relative contributions of carbohydrate and fat, as well as the absolute rate at which dietary sucrose was oxidized during hovering. The combination of respirometry and carbon isotope analysis revealed that hummingbirds initially oxidized endogenous fat following a fast and then progressively oxidized proportionately more carbohydrates. The contribution from dietar...
TL;DR: It is shown that prehatching and posthatching temperatures can interact to affect various phenotypic traits and Tadpoles may be able to alter the long‐term effects of incubation temperature by choosing particular larval developmental temperatures.
Abstract: In many oviparous vertebrates, hatchling phenotypes are influenced by egg incubation temperature. Many of those phenotypic traits can also acclimate to long‐term thermal conditions of juveniles and adults, yet the interactive effects of prehatching and posthatching temperatures on phenotypes have not been studied. To address such interaction, we incubated eggs of wood frogs (Rana sylvatica) at two temperatures and subsequently reared larvae at three temperatures in a fully factorial design. We measured body size, size‐independent morphology, and burst swimming speed at one developmental stage. Body size was independent of egg temperature but decreased significantly with increasing larval temperature. Size‐independent morphology depended in complex ways on both temperature treatments directly and on their interaction. Burst speed was not influenced directly by egg temperature but was influenced by larval temperature and by the interactions among egg temperature, larval temperature, and test temper...
TL;DR: It is suggested that yolk antioxidants are deposited according to a compensatory deposition strategy, enabling females to improve the quality of young produced with less attractive males.
Abstract: The manipulation of egg content is one of the few ways by which female birds can alter offspring quality before hatch. Lipid‐soluble vitamins and carotenoids are potent antioxidants. Female birds deposit these antioxidants into eggs in variable amounts according to environmental and social conditions, and the quantities deposited into eggs can have effects on offspring health and immunological condition. Allocation theory posits that females will alter the distribution of resources according to mate quality, sometimes allocating resources according to the differential allocation hypothesis (DAH), investing more in offspring sired by better‐quality males, and other times allocating resources according to a compensatory strategy, enhancing the quality of offspring sired by lower‐quality males. It is unknown, however, whether antioxidants are deposited into eggs according to the DAH or a compensatory strategy. We examined deposition patterns of yolk antioxidants (including vitamin E and three carote...
TL;DR: It is concluded that although juveniles can process plant material, an animal diet allows for greater juvenile growth, which in turtles is linked to higher survivorship and increased future reproductive success.
Abstract: Many reptiles undergo an ontogenetic diet shift from carnivory to herbivory. In this study, we used the yellow‐bellied slider turtle, Trachemys scripta, as a model to evaluate whether juvenile turtles are carnivorous because physiological constraints preclude herbivory. We conducted feeding trials in which we fed juvenile and adult turtles a duckweed plant, Lemna valdiviana, or a freshwater grass shrimp, Palaemontes paludosus, for 5 wk. During the trials, we measured mass‐specific intake, digestibility, and digestible intake for both size classes, as well as juvenile growth. At the end of the trials, we measured the nutrient composition of the juvenile turtles. Juveniles fed shrimp grew 3.2 times faster than those fed duckweed and had equivalent lipid stores. Digestive processing in juveniles was extremely efficient on the shrimp diet, with higher mass‐specific intakes than adults and very high digestibilities (97%). Juveniles digested duckweed as well as adults did; however, their intake of this...
TL;DR: This work analyzes audio and video recordings of calling túngara frogs to suggest that the vocal sac not only increases call rate but also allows males to produce more calls of increased attractiveness to females.
Abstract: In most anurans, the production of advertisement calls is ac- companied by the inflation of a vocal sac. Current functions of the vocal sac, however, are not fully understood, although several hypotheses have been proposed. One hypothesis sug- gests that the vocal sac decreases the intercall interval (i.e., increases call rate) by reinflating the lungs more rapidly than is possible with the buccal pump. We investigate this hypothesis by analyzing audio and video recordings of calling tungara frogs. We compare the first two call bouts emitted by an orig- inally uninflated male. The first call bout requires lung inflation via buccal pumping, but in the second, the male is already inflated because of capture of air and reinflation of the lungs by the vocal sac. Lung inflation to typical field levels requires 26-51 buccal pumps, which takes at least 4.4 s. This estimate is more than 2.5 times the typical intercall interval with lung reinflation via a vocal sac (ca. 1.7 s). Evidence from phonotaxis tests demonstrates that these differences in intercall intervals are salient to females and that female Physalaemus pustulosus prefer the shorter intercall interval/higher call rate. Acoustic analyses demonstrate that the first call of bout 1, which requires buccal pumping, is usually shorter, of lower amplitude, and spans a smaller frequency range than the first call of bout 2, which does not require buccal pumping. Because females prefer longer, more intense calls, these results suggest that the vocal sac not only increases call rate but also allows males to produce more calls of increased attractiveness to females.
TL;DR: Some of the metabolic costs involved during the migration of adult salmon from seawater to freshwater are elucidated, which may have applications for fisheries conservation and management models of energy use.
Abstract: We present the first data on the differences in routine and active metabolic rates for sexually maturing migratory adult sockeye salmon (Oncorhynchus nerka) that were intercepted in the ocean and then held in either seawater or freshwater. Routine and active oxygen uptake rates (Mo2) were significantly higher (27%–72%) in seawater than in freshwater at all swimming speeds except those approaching critical swimming speed. During a 45‐min recovery period, the declining postexercise oxygen uptake remained 58%–73% higher in seawater than in freshwater. When fish performed a second swim test, active metabolic rates again remained 28%–81% higher for fish in seawater except at the critical swimming speed. Despite their differences in metabolic rates, fish in both seawater and freshwater could repeat the swim test and reach a similar maximum oxygen uptake and critical swimming speed as in the first swim test, even without restoring routine metabolic rate between swim tests. Thus, elevated Mo2 related to either being in seawater as opposed to freshwater or not being fully recovered from previous exhaustive exercise did not present itself as a metabolic loading that limited either critical swimming performance or maximum Mo2. The basis for the difference in metabolic rates of migratory sockeye salmon held in seawater and freshwater is uncertain, but it could include differences in states of nutrition, reproduction, and restlessness, as well as ionic differences. Regardless, this study elucidates some of the metabolic costs involved during the migration of adult salmon from seawater to freshwater, which may have application
TL;DR: This work investigated the effects of meal size, meal type, and body temperature on the postprandial metabolic responses and the SDA of the tiger salamander (Ambystoma tigr inum tigrinum) and compared the Sda responses among six species of Ambystomas salamanders representing the breadth of Am bystoma phylogeny.
Abstract: The past decade has witnessed a dramatic increase in studies of amphibian and reptile specific dynamic action (SDA). These studies have demonstrated that SDA, the summed energy expended on meal digestion and assimilation, is affected significantly by meal size, meal type, and body size and to some extent by body temperature. While much of this attention has been directed at anuran and reptile SDA, we investigated the effects of meal size, meal type, and body temperature on the postprandial metabolic responses and the SDA of the tiger salamander (Ambystoma tigrinum tigrinum). We also compared the SDA responses among six species of Ambystoma salamanders representing the breadth of Ambystoma phylogeny. Postprandial peaks in \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc}
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TL;DR: The contrast between equatorial and northern congeners indicates factors such as breeding environment and life‐history strategy may play important roles in shaping stress response in these species.
Abstract: Seasonal modulation of the adrenocortical response appears to be ubiquitous in mid‐ to high‐latitude vertebrates but has not been investigated in tropical vertebrates. Previous studies demonstrate that temperate passerines show seasonality in corticosterone secretion and corticosteroid binding globulin capacities. We examined seasonal and sex differences in the stress response in an equatorial population of Zonotrichia capensis, the only Zonotrichia that breeds in the tropics, and compared the results with those of northern Zonotrichia. Seasonal differences in tropical Zonotrichia would presumably be independent of photoperiod and thus directly related to such activities as reproduction and feather molt. In addition, we investigated the possible role of binding globulin as a sex steroid binding globulin, as suggested for temperate passerines. Similar to northern congeners, Z. capensis show seasonal modulation in total corticosterone and binding globulin capacity with higher levels during breeding...
TL;DR: It is suggested that formation of the caudal fin improves energy transfer to the water and therefore increases thrust production and swimming velocity and changes to the axial skeleton during the larval period produce increased axial stiffness, which allows the production of a more rapid and effective escape response.
Abstract: Teleost fishes typically first encounter the environment as free-swimming embryos or larvae. Larvae are morphologically distinct from adults, and major anatomical structures are unformed. Thus, larvae undergo a series of dramatic morphological changes until they reach adult morphology (but are reproductively immature) and are considered juveniles. Free-swimming embryos and larvae are able to perform a C-start, an effective escape response that is used evade predators. However, escape response performance improves during early development: as young fish grow, they swim faster (length-specific maximum velocity increases) and perform the escape more rapidly (time to complete the behavior decreases). These improvements cease when fish become juveniles, although absolute swimming velocity (m s(-1)) continues to increase. We use studies of escape behavior and ontogeny in California halibut (Paralichthys californicus), rainbow trout (Oncorhynchus mykiss), and razorback suckers (Xyrauchen texanus) to test the hypothesis that specific morphological changes improve escape performance. We suggest that formation of the caudal fin improves energy transfer to the water and therefore increases thrust production and swimming velocity. In addition, changes to the axial skeleton during the larval period produce increased axial stiffness, which in turn allows the production of a more rapid and effective escape response. Because escape performance improves as adult morphology develops, fish that enter the environment in an advanced stage of development (i.e., those with direct development) should have a greater ability to evade predators than do fish that enter the environment at an early stage of development (i.e., those with indirect development).