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The polysaccharide glycogen is an evolutionarily conserved storage form of glucose. However, the physiological significance of glycogen metabolism on homeostatic control throughout the animal life cycle remains incomplete. Here, we describe Drosophila mutants that have defective glycogen metabolism. Null mutants of glycogen synthase (GlyS) and glycogen phosphorylase (GlyP) displayed growth defects and larval lethality, indicating that glycogen plays a crucial role in larval development. Unexpectedly, however, a certain population of larvae developed into adults with normal morphology. Semi-lethality in glycogen mutants during the larval period can be attributed to the presence of circulating sugar trehalose. Homozygous glycogen mutants produced offspring, indicating that glycogen stored in oocytes is dispensable for embryogenesis. GlyS and GlyP mutants showed distinct metabolic defects in the levels of circulating sugars and triglycerides in a life stage-specific manner. In adults, glycogen as an energy reserve is not crucial for physical fitness and lifespan under nourished conditions, but glycogen becomes important under energy stress conditions. This study provides a fundamental understanding of the stage-specific requirements for glycogen metabolismin the fruit fly. [ABSTRACT FROM AUTHOR]

While swimming in their natural environment, marine organisms must successfully forage, escape from predation, and search for mates to reproduce. In the process, planktonic organisms interact with their fluid environment, generating fluid signatures around their body and in their downstream wake through ontogeny. In the early stages of their life cycle, marine organisms operate in environments where viscous effects dominate and govern physical processes. Ontogenetic propulsive transitions in swimming organisms often involve dramatic changes in morphology and swimming behavior. However, for organisms that do not undergo significant changes in morphology, swimming behavior or propulsive mode, how is their swimming performance affected? We investigated the ontogenetic propulsive transitions of the hydromedusa Sarsia tubulosa, which utilizes jet propulsion and possesses a similar bell morphology throughout its life cycle. We used digital particle image velocimetry and high-speed imaging to measure the body kinematics, velocity fields and wake structures induced by swimming S. tubulosa with bell exit diameters from 1 to 10 mm. Our experimental observations revealed three distinct classes of hydrodynamic wakes: elongated vortex rings for 1030 (larger than 2 mm bell exit diameter) and elliptical vortex rings (or leading vortex rings) followed by trailing jets for most instances where Re>100 (larger than 4 or 5 mm bell exit diameter). The relative travel distance and propulsive efficiency remained unchanged throughout ontogeny, and the swimming proficiency and hydrodynamic cost of transport decreased non-linearly. [ABSTRACT FROM AUTHOR]

The new technology of next-generation sequencing is changing our perceptions of the form and function of the biological world. The emerging data reveal an array of microbes that is more vast and more central to all biological processes than previously appreciated. Further, evidence is accumulating that the alliances of microbes with one another and with constituents of the macrobiological world are critical for the health of the biosphere. This contribution summarizes the basic arguments as to why, when considering the biochemical adaptations of animals, we should integrate the roles of their microbial partners. [ABSTRACT FROM AUTHOR]

Within its life cycle, a copepod goes through drastic changes in size, shape and swimming mode. In particular, there is a stark difference between the early (nauplius) and later (copepodid) stages. Copepods inhabit an intermediate Reynolds number regime (between ∼1 and 100) where both viscosity and inertia are potentially important, and the Reynolds number changes by an order of magnitude during growth. Thus we expect the life stage related changes experienced by a copepod to result in hydrodynamic and energetic differences, ultimately affecting the fitness. To quantify these differences, we measured the swimming kinematics and fluid flow around jumping Acartia tonsa at different stages of its life cycle, using particle image velocimetry and particle tracking velocimetry. We found that the flow structures around nauplii and copepodids are topologically different, with one and two vortex rings, respectively. Our measurements suggest that copepodids cover a larger distance compared to their body size in each jump and are also hydrodynamically quieter, as the flow disturbance they create attenuates faster with distance. Also, copepodids are energetically more efficient than nauplii, presumably due to the change in hydrodynamic regime accompanied with a welladapted body form and swimming stroke. [ABSTRACT FROM AUTHOR]

Parrots rely heavily on vocal signals to maintain their social and mobile lifestyles. We studied vocal ontogeny in nests of wild green-rumped parrotlets (Forpus passerinus) in Venezuela. We identified three successive phases of vocal signaling that corresponded closely to three independently derived phases of physiological development. For each ontogenetic phase, we characterized the relative importance of anatomical constraints, motor skills necessary for responding to specific contexts of the immediate environment, and the learning of signals that are necessary for adult forms of communication. We observed shifts in the relative importance of these three factors as individuals progressed from one stage to the next; there was no single fixed ratio of factors that applied across the entire ontogenetic sequence. The earliest vocalizations were short In duration, as predicted from physical constraints and under-developed motor control. Calls became longer and frequency modulated during intermediate nestling ages in line with motor skills required for competitive begging. In the week before fledging, calls drastically shortened in accordance with the flight-constrained short durations of adult contact calls. The latter constraints were made evident by the demonstrated links between wing-assisted incline running, a widespread prelude to avian flight, just before the shift from long- duration begging calls to short-duration contact calls. At least in this species, the shifting emphases of factors at different ontogenetic stages precluded the morphing of intermediate-stage begging calls into adult contact calls; as shown previously, the latter are influenced by sample templates provided by parents. [ABSTRACT FROM AUTHOR]

The timing of dormancy is a rapidly evolving life-history trait playing a crucial role in the synchronization of seasonal life cycles and adaptation to environmental change. But the physiological mechanisms regulating dormancy in animals remain poorly understood. In insects, dormancy (diapause) is a developmentally dynamic state, and the mechanisms that control diapause transitions affect seasonal timing. Here we used microarrays to examine patterns of gene expression during dormancy termination: a crucial life-history transition in the apple maggot fly Rhagoletis pomonella (Walsh). This species is a model system for host race formation and ecological speciation via changes in diapause regulation of seasonality. Our goal was to pinpoint the timing of the transition from diapause to post-diapause development and to identify candidate genes and pathways for regulation of diapause termination. Samples were taken at six metabolically defined developmental landmarks, and time-series analysis suggests that release from metabolic depression coincides with preparation for or resumption of active cell cycling and morphogenesis, defining the 'end' of diapause. However, marked changes in expression, including members of pathways such as Wnt and TOR signaling, also occur prior to the metabolic rate increase, electing these pathways as candidates for early regulation of diapause termination. We discuss these results with respect to generalities in insect diapause physiology and to our long-term goal of identifying mechanisms of diapause adaptation in the Rhagoletis system. [ABSTRACT FROM AUTHOR]

The traditional view of the cnidarian nervous system is of a diffuse nerve net that functions as both a conducting and an integrating system; this is considered an indicator of a primitive condition. Yet, in medusoid members, varying degrees of nerve net compression and neuronal condensation into ganglion-like structures represent more centralized integrating centers. In some jellyfish, this relegates nerve nets to motor distribution systems. The neuronal condensation follows a precept of neuronal organization of higher animals with a relatively close association with the development and elaboration of sensory structures. Nerve nets still represent an efficient system for diffuse, non-directional activation of broad, two-dimensional effector sheets, as required by the radial, non-cephalized body construction. However, in most jellyfish, an argument can be made for the presence of centralized nervous systems that interact with the more diffuse nerve nets. [ABSTRACT FROM AUTHOR]

One of the more common patterns of offspring size variation is that mothers tend to produce larger offspring at lower temperatures. Whether such variation is adaptive remains unclear. Determining whether optimal offspring size differs between thermal environments provides a direct way of assessing the adaptive significance of temperature-driven variation in egg size. Here, we examined the relationship between offspring size and performance at three temperatures for several important fitness components in the zebra fish, Danio rerio. The effects of egg size on performance were highly variable among life-history stages (i.e. pre- and post-hatching) and dependent on the thermal environment; offspring size positively affected performance at some temperatures but negatively affected performance at others. When we used these data to generatea simple optimality model, the model predicted that mothers should produce the largest size offspring at the lowest temperature, offspring of intermediate size at the highest temperature and the smallest offspring at the intermediate temperature. An experimental test of these predictions showed that the rank order of observed offspring sizes produced by mothers matched our predictions. Our results suggest that mothers adaptively manipulate the size of their offspring in response to thermally driven changes in offspring performance and highlight the utility of optimality approaches for understanding offspring size variation. [ABSTRACT FROM AUTHOR]

Saips are barrel-shaped marine invertebrates that swim by jet propulsion. Morphological variations among species and life-cycle stages are accompanied by differences in swimming mode. The goal of this investigation was to compare propulsive jet wakes and swimming performance variables among morphologically distinct salp species (Pegea con foederata, Weelia (Salpa) cylindrica, Cyclosalpa sp.) and relate swimming patterns to ecological function. Using a combination of in situ dye visualization and particle image velocimetry (PIV) measurements, we describe properties of the jet wake and swimming performance variables including thrust, drag and propulsive efficiency. Locomotion by all species investigated was achieved via vortex ring propulsion. The slow-swimming P. confoederata produced the highest weight-specific thrust (T=53N kg-1) and swam with the highest whole- cycle propulsive efficiency (ηwc=55%). The fast-swimming W. cylindrica had the most streamlined body shape but produced an intermediate weight-specific thrust (T=30 N kg -1) and swam with an intermediate whole-cycle propulsive efficiency (ηwc=52%). Weak swimming performance variables in the slow-swimming C. affinis, including the lowest weight-specific thrust (T=25Nkg1) and lowest whole-cycle propulsive efficiency (i=47%), may be compensated by low energetic requirements. Swimming performance variables are considered in the context of ecological roles and evolutionary relationships. [ABSTRACT FROM AUTHOR]

As juvenile life-history stages are subjected to strong selection, these stages often show levels of performance approaching those of adults, or show a disproportionately rapid increase of performance with age. Although testing performance capacity in aquatic suction feeders is often problematic, in pivot feeders such as seahorses models have been proposed to estimate whether snout length is optimal to minimise the time needed to reach the prey. Here, we investigate whether the same model can also explain the snout lengths in an ontogenetic series of seahorses, explore how pivot feeding kinematics change during ontogeny, and test whether juveniles show disproportionate levels of performance. Our analysis shows that the dimensions of the snout change during ontogeny from short and broad to long and narrow. Model calculations show that the snout lengths of newborn and juvenile seahorses are nearly optimal for minimising prey reach time. However, in juveniles the centre of head rotation in the earth-bound frame of reference is located near the posterior end of the head, whereas in adults it is shifted forward and is located approximately above the eye. Modelling shows that this forward shift in the centre of rotation has the advantage of decreasing the moment of inertia and the torque required to rotate the head, but has the disadvantage of slightly increasing the time needed to reach the prey. Thus, the snout lengths of juvenile seahorses appear to be close to optimal, suggesting that they reach levels of performance close to adult levels, which illustrates the pervasive nature of selection on performance in juveniles. [ABSTRACT FROM AUTHOR]

Multiple freeze-thaw cycles are common in alpine, polar and temperate habitats. We investigated the effects of five consecutive cycles of approx. -5°C on the freeze-tolerant larvae of Pringleophaga marini Viette (Lepidoptera: Tineidae) on sub-Antarctic Marion Island. The likelihood of freezing was positively correlated with body mass, and decreased from 70% of caterpillars that froze on initial exposure to 55 % of caterpillars that froze on subsequent exposures; however, caterpillars retained their freeze tolerance and did not appear to switch to a freeze-avoiding strategy. Apart from an increase in gut water, there was no difference in body composition of caterpillars frozen 0 to 5 times, suggesting that the observed effects were not due to freezing, but rather to exposure to cold per se. Repeated cold exposure did not result in mortality, but led to decreased mass, largely accounted for by a decreased gut mass caused by cessation of feeding by caterpillars. Treatment caterpillars had fragile guts with increased lipid content, suggesting damage to the gut epithelium. These effects persisted for 5 days after the final exposure to cold, and after 30 days, treatment caterpillars had regained their pre-exposure mass, whereas their control counterparts had significantly gained mass. We show that repeated cold exposure does occur in the field, and suggest that this may be responsible for the long life cycle in P. marioni. Although mean temperatures are increasing on Marion Island, several climate change scenarios predict an increase in exposures to sub-zero temperatures, which would result in an increased generation time for P. marioni. Coupled with increased predation from introduced house mice on Marion Island, this could have severe consequences for the P. marioni population. [ABSTRACT FROM AUTHOR]

Lampreys, one of the only two surviving groups of agnathan (jawless) vertebrates, contain several anadromous species that, during their life cycle, thus migrate from fresh to seawater and back to freshwater. Lampreys have independently evolved the same overall osmoregulatory mechanisms as the gnathostomatous (jawed) and distantly related teleost fishes. Lamprey gills thus likewise play a central role in taking up and secreting monovalent ions. However, the ultrastructural characteristics and distribution of their epithelial cell types [ammocoete mitochondria-rich (MR) cell, intercalated MR cell, chloride cell and pavement cell] differ in several respects from those of teleosts. The ultrastructural characteristics of these cells are distinctive and closely resemble those of certain ion-transporting epithelia in other vertebrates, for which the function has been determined. The data on each cell type, together with the stage in the life cycle at which it is found, i.e. whether in fresh or seawater, enable the following proposals to be made regarding the ways in which lampreys use their gill epithelial cells for osmoregulating in hypo- and hypertonic environments. In freshwater, the intercalated MR cell takes up Cl- and secretes H+, thereby facilitating the uptake of Na+ through pavement cells. In seawater, the chloride cell uses a secondarily active transcellular transport of Cl- to provide the driving force for the passive movement of Na+ through leaky paracellular pathways between these cells. [ABSTRACT FROM AUTHOR]

The article focuses on a study by Jens De Meyer related to changes occurred in head of eel fishes after consumption of food. Topics discussed include life-cycle of eel fishes on their transformation into a transparent glass eel when they leave the sea, dividing the eels into three groups and putting them on different diets, and concern towards welfare of eel population in European rivers.

The article focuses on the research paper "Correlated Changes in Life History Traits in Response to Selection for Faster Pre-Adult Development in the Fruitfly Drosophila melanogaster," by P. Yadav and colleagues, published in the "Journal of Experimental Biology." It focuses on how shortened pre-adult development in fast-developing fruit flies affect their ability to survive preadult development, their adult lifespan, fecundity, size and ability to tolerate starvation and desiccation.

The article discusses the study conducted by Colin Selman and colleagues that examines the link between physiological mechanisms and oxidative stress on the lifespan of species. The study found no evidence of increased oxidative damage relative on lymphocyte and hepatocyte DNA and lipids. The researchers conclude that the increase in energy expenditure does not influence oxidative damage or shorten the lifespan of animals.