Lawrence E. Licht

Genome size and metabolic rate in salamanders

Abstract 1. 1. The relationship between genome size (C-value) and metabolic rate in salamanders was examined by correlation analyses. 2. 2. The C-values of 48 species of salamanders were determined by flow cytometry measurement of DNA quantity in erythrocyte nuclei; C-values of 88 species were taken from the literature. 3. 3. Standard metabolic rates for salamanders at 5, 15, 20 and 25°C were taken from the literature. 4. 4. Only at 25°C is there a robust, significant correlation between C-value and metabolic rate, and the hypothesis of a frugal metabolic strategy and genome size effect on metabolic rates in salamanders is discussed.

Shedding Light on Ultraviolet Radiation and Amphibian Embryos

Abstract The hypothesis that increasing ultraviolet-B (UVB) radiation is a causal factor in the decline of amphibian populations has received considerable attention in the scientific and public media. To evaluate the validity of this hypothesis, it is necessary to examine the natural environmental factors and biological traits of amphibians that protect them from UVB radiation. A careful reading of the literature reveals that most published studies on the effects of ambient UVB radiation on amphibian embryos have found no increased mortality. Those few reports that show harmful effects employ experimental methods that do not place enough importance on the natural abiotic and biotic factors that provide UVB protection. In the laboratory, amphibian embryos are resistant to doses of UVB radiation far higher than those they would normally receive from ambient sunlight. The jelly surrounding amphibian eggs absorbs UVB radiation, as revealed by spectral measurements of absorbance; after UVB exposure, embryos with their jelly capsules removed show significantly higher mortality than those with the jelly intact. In light of this and other factors mitigating UVB absorption, the hypothesis that ambient UVB radiation causes amphibian mortality and population declines is without support.

Acid tolerance of anuran embryos and larvae from Central Ontario

Acid tolerance of embryos and larvae was determined for three species of anurans (Rana sylvatica, Rana catesbeiana and Hyla versicolor) from an acid-sensitive area in central Ontario. The lethal pH for embryos of R. sylvatica was 3.5-4.0 and the critical pH, that pH at which survivorship decreases to levels below that found for neutral water, was 4.0-4.5. The lethal pH for larvae was 3.5 and the critical pH was 3.5-3.8. For both embryos and larvae of R. catesbeiana, the lethal pH was 3.5-3.8; the critical pH was 4.0-4.5 for embryos and 4.0 for larvae. Embryos of H. versicolor were relatively acid-tolerant. The lethal pH of embryos was 3.5 and the critical pH 3.8. The lethal pH of larval H. versicolor was 3.8-4.0 and the critical pH 3.5-3.8

Why rattle snake

Etude des caracteristiques acoustiques du bruit de crecelle produit par 13 serpents a sonnette representant 6 especes afin de determiner sa fonction

Comparative Size of Epidermal Cell Nuclei from Shed Skin of Diploid, Triploid and Tetraploid Salamanders (Genus Ambystoma)

A comparison was made of the sizes of the nucleus within epidermal cells from the shed skin of six species of mole salamanders (genus Ambystoma), and three different hybrid complexes including diploid, triploid, and tetraploid animals. The shed skin cells of diploids have smaller nuclei than those of polyploid animals. Nuclei of tetraploid cells are largest but their dimensions overlap those of triploid cells. Nuclei of shed skin cells can be measured to accurately distinguish diploids from polyploids in mixed populations without injury of any kind to the animals.

Uptake of 14C DDT by wood frog embryos after short term exposure

Wood frog embryos at four different developmental stages and three temperatures were subjected to 0.025 ppm 14C DDT for 24 hr. Embryos within jelly capsules at stages 13, 16 and 18 accumulated about 0.16 ppm at 9, 15 and 21 degrees C. The protective jelly envelopes around embryos in stages 13, 16 and 18 contained about 0.014 ppm at all temperatures. Jelly-free hatching embryos in stage 20 accumulated about 6-10 times the level of earlier stages and showed effects of DDT poisoning. Jelly capsules around amphibian eggs restrict DDT uptake.

Comparative rates of oxygen consumption and water loss in diploid and polyploid salamanders (genus Ambystoma)

Abstract 1. 1. The mole salamanders Ambystoma laterale and Ambystoma texanum coexist with their fertile diploid and polyploid hybrids on Pelee Island, Ontario. 2. 2. Rates of oxygen consumption and water loss of diploid A. laterale do not diner from those of diploid, triploid or tetraploid hybrids. 3. 3. Potential benefits of polyploidy may be from indirect effects of adult body size on rates of metabolism and water loss.

PLOIDY AND DEVELOPMENTAL RATE IN A SALAMANDER HYBRID COMPLEX (GENUS AMBYSTOMA)

In contrast to higher plants, in which polyploidy is widespread (Stebbins, 1970), animal polyploids are rare. The major barriers for animals apparently result from problems in meiosis, which lead to offspring inviability, sterility, or imbalance of the sex-determination system (White, 1973). Fertile diploid (2n = 28), triploid, and tetraploid salamanders (genus Ambystoma) coexist on Pelee Island, Lake Erie, Ontario (Bogart et al., 1985; Bogart and Licht, 1986). We have examined the eggsofdiploid and polyploid Ambystoma from Pelee Island to ascertain the effects of ploidy on embryonic development. Because these salamanders belong to a hybrid complex (A. laterale-A. texanum), we also have gained insight into the effects of hybridization on development and hatching success.

Courtship Behavior of Ambystoma texanum on Pelee Island, Ontario

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Postmetamorphic retention of C14DDT by wood frog tadpoles.

Abstract 1. Rana sylvatica tadpoles were treated with either 0.001 or 0.003 ppm C14 DDT and after metamorphosis isolated tissues from the young frogs were examined for DDT content. 2. DDT-treated tadpoles retained the chemical after transformation. Heart, head, gut, and lungs contained only trace quantities of DDT, but the liver and fat concentrated high levels, as much as 60 ppm for fat. 3. Newly transformed frogs, which had been treated with DDT as tadpoles, lost DDT much more slowly while living a terrestial existence, than did tadpoles still living an aquatic life.