Conserving large carnivores: dollars and fence

Conservationists often advocate for landscape approaches to wildlife management while others argue for physical separation between protected species and human communities, but direct empirical comparisons of these alternatives are scarce. We relate African lion population densities and population trends to contrasting management practices across 42 sites in 11 countries. Lion populations in fenced reserves are significantly closer to their estimated carrying capacities than unfenced populations. Whereas fenced reserves can maintain lions at 80% of their potential densities on annual management budgets of $500 km⁻², unfenced populations require budgets in excess of $2000 km⁻² to attain half their potential densities. Lions in fenced reserves are primarily limited by density dependence, but lions in unfenced reserves are highly sensitive to human population densities in surrounding communities, and unfenced populations are frequently subjected to density‐independent factors. Nearly half the unfenced lion populations may decline to near extinction over the next 20–40 years.     

Hydrodynamic analysis of feeding in sand dollars

Summary Subtidal sand dollars, Dendraster excentricus, assume an inclined posture under conditions of moderate water flow (10 cm s^-1 to 2 m s^-1). In this posture, when the test is in the usual position parallel to the water flow, the test acts as a lifting body. Analysis of the hydrodynamic characteristics of the sand dollar test was accomplished by slender body theory. Streamline curvature due to lift moves food particles in the direction of the feeding surface and enhances feeding efficiency. The position parallel to water flow is most advantageous to sand dollars in reversing flows, such as wave surge, whereas sand dollars in unidirectional flows can place the test at a slight angle to the water flow to increase lift. The high camber of sand dollars from a bay habitat characterized by low water velocities was interpreted as an adaptation allowing efficient lift production in low velocity flows; sand dollars from a protected outer coast location characterized by higher water velocities were significantly less cambered.Within sand dollar beds, the animals alter their spacing as a function of the water velocity. This movement is construed as a method for maintaining the optimal gap between sand dollars. Sand dollar tests induce mutual interference effects which vary with the configuration of the animals. In the prevalent configuration, sand dollars are able to take advantage of the streamline curvature induced by neighboring animals. The optimal gap increases as the square of the water velocity. At distances grater than or less than the optimal gap, feeding efficiency was shown to decrease from that at the optimal gap.     

Turning biodefense dollars into products

Five years after the US anthrax attacks, and more than two years after BioShield legislation was ratified, a survey reveals that biodefense funding has thus far produced only a handful of products for clinical development.     

Extinct and extant sand dollars (Clypeasteroida: Echinoidea) from Uruguay

We summarize information concerning Recent and Pleistocene-Holocene Uruguayan sand dollars (Mellitidae), as well as Miocene taxa (Monophorasteridae). Recent and Pleistocene-Holocene species (Encope emarginata, Mellita quinquiesperforata, and Leodia sexisperforata) are at their southernmost limits of distribution, with only E. emarginata recorded further south than Uruguay. Lower temperatures to the south, and/or the Rio de la Plata salinity barrier are suggested as controlling factors of these distributions. During the Miocene, the sea temperatures were notably higher than at present, and it was at this time that the extinct genera Monophoraster and Amplaster reached their maximum diversity in Uruguay. The family Monophorasteridae is the basal sister group of the Mellitidae.     

Red-carpet rodent care: making the most of dollars and sense in the animal facility

Cutting-edge biomedical research programs have entered an era in which phenotypic characterizations for genetically altered rodents can facilitate appropriate care. The veterinary care requirements necessary to support such animal models can include the procedures already adapted as standard practice in companion animal hospitals, and can decrease data variability while increasing survival rates.     

New private facility woos public dollars in Calgary

The opening of a private wing in an old hospital has caused consternation in Calgary because some people consider it a beachhead for private medicine.     

Thyroid hormones determine developmental mode in sand dollars (Echinodermata: Echinoidea)

Evolutionary transitions in larval nutritional mode have occurred on numerous occasions independently in many marine invertebrate phyla. Although the evolutionary transition from feeding to nonfeeding development has received considerable attention through both experimental and theoretical studies, mechanisms underlying the change in life history remain poorly understood. Facultative feeding larvae (larvae that can feed but will complete metamorphosis without food) presumably represent an intermediate developmental mode between obligate feeding and nonfeeding. Here we show that an obligatorily feeding larva can be transformed into a facultative feeding larva when exposed to the thyroid hormone thyroxine. We report that larvae of the subtropical sand dollar Leodia sexiesperforata (Echinodermata: Echinoidea) completed metamorphosis without exogenous food when treated with thyroxine, whereas the starved controls (no thyroxine added) did not. Leodia sexiesperforata juveniles from the thyroxine treatment were viable after metamorphosis but were significantly smaller and contained less energy than sibling juveniles reared with exogenous food. In a second starvation experiment, using an L. sexiesperforata female whose eggs were substantially larger than in the first experiment (202+/-5 vs. 187+/-5 microm), a small percentage of starved L. sexiesperforata larvae completed metamorphosis in the absence of food. Still, thyroxine-treated larvae in this experiment completed metamorphosis faster and in much higher numbers than in the starved controls. Furthermore, starved larvae of the sand dollar Mellita tenuis, which developed from much smaller eggs (100+/-2 microm), did not complete metamorphosis either with or without excess thyroxine. Based on these data, and from recent experiments with other echinoids, we hypothesize that thyroxine plays a major role in echinoderm metamorphosis and the evolution of life history transitions in this group. We discuss our results in the context of current life history models for marine invertebrates, emphasizing the role of egg size, juvenile size, and endogenous hormone production for the evolution of nonfeeding larval development.     

Muscles advance the teeth in sand dollars and other sea urchins

We demonstrate the action of the dental promoter muscles in advancing the continuously growing teeth of sand dollars and sea urchins. Teeth wear at the occlusal end, while new calcite is added to the opposite end. Dental ligaments rigidly hold teeth during chewing, but soften and reform during advancement. The source of forces that advance the teeth was unknown until our discovery of the dental promoter muscles. The muscles, which underly the tooth, attach centrally to the stereom of the pyramid of the Aristotle''s lantern (jaw) and peripherally to a membrane that covers the distal end of the tooth. The muscles shorten along an axis nearly parallel to the long axis of the tooth. We stimulated contraction by addition of acetylcholine, with increasing concentrations of acetylcholine generating higher forces. Forces exerted by this muscle are appropriate for its size and are 1000 times lower than forces exerted by interpyramidal muscles that generate chewing forces. In sand dollars, a single muscle contraction of the dental promoter muscle can account for half the mean daily advancement of the teeth.