A pilot study of the performance of captive-reared delta smelt Hypomesus transpacificus in a semi-natural environment

A captive breeding programme was developed in 2008 for delta smelt Hypomesus transpacificus in reaction to dramatic population decline over several decades. We took 526 sub-adult captive-reared delta smelt and cultured them for 200 days without providing artificial food or water quality management to assess their performance once released in the wild. The results indicated captive-reared sub-adult delta smelt could survive in a semi-natural environment with uncontrolled water quality and naturally produced wild prey through spawning and into their post spawning phase.     

Ecophysiological traits of terrestrial and aquatic carnivorous plants: are the costs and benefits the same?

Identification of tradeoffs among physiological and morphological traits and their use in cost–benefit models and ecological or evolutionary optimization arguments have been hallmarks of ecological analysis for at least 50 years. Carnivorous plants are model systems for studying a wide range of ecophysiological and ecological processes and the application of a cost–benefit model for the evolution of carnivory by plants has provided many novel insights into trait‐based cost–benefit models. Central to the cost–benefit model for the evolution of botanical carnivory is the relationship between nutrients and photosynthesis; of primary interest is how carnivorous plants efficiently obtain scarce nutrients that are supplied primarily in organic form as prey, digest and mineralize them so that they can be readily used, and allocate them to immediate versus future needs. Most carnivorous plants are terrestrial – they are rooted in sandy or peaty wetland soils – and most studies of cost–benefit tradeoffs in carnivorous plants are based on terrestrial carnivorous plants. However approximately 10% of carnivorous plants are unrooted aquatic plants. Here we ask whether the cost–benefit model applies equally well to aquatic carnivorous plants and what general insights into tradeoff models are gained by this comparison. Nutrient limitation is more pronounced in terrestrial carnivorous plants, which also have much lower growth rates and much higher ratios of dark respiration to photosynthetic rates than aquatic carnivorous plants. Phylogenetic constraints on ecophysiological tradeoffs among carnivorous plants remain unexplored. Despite differences in detail, the general cost–benefit framework continues to be of great utility in understanding the evolutionary ecology of carnivorous plants. We provide a research agenda that if implemented would further our understanding of ecophysiological tradeoffs in carnivorous plants and also would provide broader insights into similarities and differences between aquatic and terrestrial plants of all types.     

Apparatus for long-term ventricular access in the awake canine

An apparatus is described that permits lateral ventricular cerebrospinal fluid (CSF) to be sampled or an infusion to be performed into the ventricular system in the awake canine. The device has been used in 25 dogs. CSF was sampled, and experiments involving infusions into the lateral ventricle were performed over a 6- to 24-mo period. The maximum frequency of ventricular cannulation using the apparatus was once per week. Complications occurred in 10 dogs, all of which were successfully treated, permitting experiments to continue. Three fatal complications included meningitis in one animal at 24 mo and seizures in two animals, causing death at 12 and 18 mo. Administration of peptides, bombesin, and somatostatin into the ventricular system was followed by prompt rises in bombesin and somatostatin radioimmunoactivity in the CSF. There were no parallel increases of these peptides in the peripheral blood levels up to 2 h after infusion. Peptides of this molecular weight infused with this apparatus do not seem to leak into peripheral blood. The apparatus permits repeated ventricular cannulation in the awake canine for sampling of CSF and administration of biological substances to determine specific central nervous system action.     

The Cultural Evolution of Human Communication Systems in Different Sized Populations: Usability Trumps Learnability

This study examines the intergenerational transfer of human communication systems. It tests if human communication systems evolve to be easy to learn or easy to use (or both), and how population size affects learnability and usability. Using an experimental-semiotic task, we find that human communication systems evolve to be easier to use (production efficiency and reproduction fidelity), but harder to learn (identification accuracy) for a second generation of naïve participants. Thus, usability trumps learnability. In addition, the communication systems that evolve in larger populations exhibit distinct advantages over those that evolve in smaller populations: the learnability loss (from the Initial signs) is more muted and the usability benefits are more pronounced. The usability benefits for human communication systems that evolve in a small and large population is explained through guided variation reducing sign complexity. The enhanced performance of the communication systems that evolve in larger populations is explained by the operation of a content bias acting on the larger pool of competing signs. The content bias selects for information-efficient iconic signs that aid learnability and enhance usability.     

Pooled energy budgets: Resituating human energy ‐allocation trade‐offs

Across taxa, many life‐history traits vary as a function of differences in body size. 1 - 5 Among primates, including humans, allometric relationships explain many trends in metabolic, growth, reproductive, and mortality rates. 6 - 8 But humans also deviate from nonhuman primates with respect to other developmental, reproductive, and parenting characteristics. 9 - 13 Broad relationships between life‐history traits and body size assume that energy expended in activity (foraging effort) is proportional to body size, and that energy available for growth and reproduction are equivalent. Because human subsistence and parenting are based on food sharing, and cooperation in labor and childrearing, the ways by which energy is acquired and allocated to alternate expenditures are expanded. We present a modification of the general allocation model to include a mechanism for these energy transfers. Our goal is to develop a framework that incorporates this mechanism and can explain the human life‐history paradox; that is, slow juvenile growth and rapid reproduction. We suggest that the central characteristics of human subsistence and energy transfer need to be accounted for in order to more fully appreciate human life‐history variability.