Population structure of nuclear and mitochondrial DNA variation among humpback whales in the North Pacific

The population structure of variation in a nuclear actin intron and the control region of mitochondrial DNA is described for humpback whales from eight regions in the North Pacific Ocean: central California, Baja Peninsula, nearshore Mexico (Bahia Banderas), offshore Mexico (Socorro Island), southeastern Alaska, central Alaska (Prince Williams Sound), Hawaii and Japan (Ogasawara Islands). Primary mtDNA haplotypes and intron alleles were identified using selected restriction fragment length polymorphisms of target sequences amplified by the polymerase chain reaction (PCR–RFLP). There was little evidence of heterogeneity in the frequencies of mtDNA haplotypes or actin intron alleles due to the year or sex composition of the sample. However, frequencies of four mtDNA haplotypes showed marked regional differences in their distributions (Φ_ST = 0.277; P < 0.001; n = 205 individuals) while the two alleles showed significant, but less marked, regional differences (Φ_ST = 0.033; P < 0.013; n = 400 chromosomes). An hierarchical analysis of variance in frequencies of haplotypes and alleles supported the grouping of six regions into a central and eastern stock with further partitioning of variance among regions within stocks for haplotypes but not for alleles. Based on available genetic and demographic evidence, the southeastern Alaska and central California feeding grounds were selected for additional analyses of nuclear differentiation using allelic variation at four microsatellite loci. All four loci showed significant differences in allele frequencies (overall F_ST = 0.043; P < 0.001; average n = 139 chromosomes per locus), indicating at least partial reproductive isolation between the two regions as well as the segregation of mtDNA lineages. Although the two feeding grounds were not panmictic for nuclear or mitochondrial loci, estimates of long-term migration rates suggested that male-mediated gene flow was several-fold greater than female gene flow. These results include and extend the range and sample size of previously published work, providing additional evidence for the significance of genetic management units within oceanic populations of humpback whales.     

The Induction of a Phospholipid Requirement and Morphological Abnormalities in Tetrahymena pyriformis by Growth at Supraoptimal Temperatures*†

SYNOPSIS. Supplementation of a chemically-defined medium that supported excellent axenic growth of Tetrahymena pyriformis, mating type II, variety 1, at 35 C, with nucleic acid derivatives allowed full growth at 37, and further addition of phospholipids permitted equivalent growth at 39 and 1/3 of that at 40. No other nutrients tested were active at 40. Population growth could be sustained continuously by serial sub-culture every 48 hr at 40 only if the medium contained synthetic phospholipids or phospholipids isolated from natural sources. The requirement was specific for phosphatidyl choline and phosphatidyl ethanolamine. Phospholipids which contained only saturated fatty acids, and ones which contained unsaturated acids were active. Phospholipids and neutral lipids isolated from 35-grown T. pyriformis were also effective. Phospholipid precursors, sterols, neutral lipids and fatty acids were not. A 48–72 hr exposure to 40 in either the unsupplemented medium or the nucleic acid derivatives-phospholipid-supplemented medium caused extreme variation in size and shape, fractured and displaced kineties, and abnormalities of karyokinesis. The frequency and degree of teratology was greater in the unsupplemented medium, but not markedly so. A possible metabolic basis for the temperature-induced phospholipid requirement and the morphological abnormalities is discussed.     

Amino Acid Activation in Subcellular Fractions of Tetrahymena pyriformis*

SYNOPSIS. The presence of amino acid activating enzymes was demonstrated in the ciliated protozoan Tetrahymena pyriformis. By employing a sensitive hydroxamate assay procedure, the activation of L-valine was assayed in various subcellular fractions of the ciliate, and some characteristics of the enzyme activity in the most active fraction were determined. Most of the activity resided in pH 5 fractions isolated from high speed supernatants of ciliates disrupted by various physical and chemical methods. No activity could be demonstrated in isolated cilia, in pellicles with attached kinetosomes, in microsomes or in macronuclei, providing these organelles were thoroughly washed. A washed mitochondrial preparation isolated by the Mager and Lipmann procedure activated L-valine; mitochondria isolated by the procedure of Hogg and Kornberg did not. The pH 5 fraction isolated from the 102,000 X g supernatant of digitonin-lysed ciliates was stable for several weeks when stored in 0.1 M Tris buffer, pH 7.6 at – 25 C. The activity of this fraction with respect to L-valine activation was dependent on the presence of ATP¹ and magnesium in the reaction mixture. The optimal concentrations of these components and of L-valine and hydroxylamine were determined, and the linearity of activity with time and enzyme concentration was demonstrated. Valine activation was not modified by dialysis of the pH 5 fraction, or treatment with RNase, or the addition of boiled pH 5 fraction.