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In many ectotherms, incubation temperature has profound effects on the timing of hatching and size of hatchlings, but the mechanisms underlying these effects are poorly understood. We studied the energetics of embryonic development and growth in the lizard Sceloporus undulatus. Eggs were incubated at six constant temperatures, ranging from 28 degrees to 38 degrees C, and embryonic metabolism, incubation period, and body size at hatching were determined. The duration of embryonic development decreased significantly from 55 d at 28 degrees to 40 d at 32 degrees C but did not differ significantly between 32 degrees and 34 degrees C. Embryos incubated at temperatures above 34 degrees C did not survive to hatching. Metabolic rate at specific stages of development (percentage of total incubation period) did not differ among embryos incubated at 28 degrees, 30 degrees, and 34 degrees C. As a result, the total amount of energy expended during the incubation period at 28 degrees C (2.0 kJ) was greater than that at 30 degrees - 34 degrees C (1.7-1.8 kJ). However, the difference in energy expenditure did not affect body size at hatching; neither snout-vent length nor body mass varied significantly with incubation temperature, and both were the same as those of hatchlings collected in the field. Thus, there was no apparent trade-off between hatching date and body size of lizards at hatching. In a natural population in New Jersey, USA, we quantified soil temperatures at potential nesting sites and studied the thermoregulatory behavior of gravid females to examine the possible consequences of female behavior for hatchling phenotypes. In females and at potential nest sites, embryos would experience temperatures that resulted in high mortality in the laboratory experiment (>32 degrees C). Gravid females had a field body temperature of 33.9 degrees C (95% CI = 0.8 degrees C) and selected a body temperature of 33.3 degrees C (95% CI = 1.0 degrees C) when placed in thermal gradients in the laboratory. Soil temperatures rose above 32 degrees C for several hours each day. Embryos must be able to survive intermittent exposure to temperatures that were lethal under conditions of chronic exposure in the laboratory. Selection of relatively high body temperatures by gravid females, coupled with tolerance of acute exposure to relatively high soil temperatures, would reduce the incubation period without a concomitant reduction in body size at hatching. Keywords: body size; embryo energetics; hatchling size; incubation temperature; incubation period; metabolic rate; nest site choice; preferred body temperature; reptiles; Sceloporus undulatus; temperature effects; thermoregulation by gravid females.

A DNA binding protein interacting with nonalternating oligo (A). oligo(T) tracts (A.T tracts) is encoded by the DAT 1 gene of the Saccharomyces cerevisiae. The amino-terminal 36 residues were found to be adequate for specific DNA binding activity. Data obtained revealed that the pentad arginines interact in a cooperative manner with a repeated minor groove characteristic of A.T tract DNA to reach high-affinity recognition.

William Hodges 1744-1797 The Art of Exploration Geoff Quilley, Curator Organized by the National Maritime Museum, Greenwich, UK, and the Yale Center for British Art, New Haven, CT. At the [...]

Gene(sis) Contemporary Art Explores Human Genomics Robin Held, curator Organized by the Henry Art Gallery, the University of Washington, Seattle, WA, in affiliation with the Berkeley Art Museum, Berkeley, CA. [...]