Hostile encounters among spruce-woods warblers (Dendroica: Parulidae)

Intraspecific interactions were initiated with high frequency by four species of sympatric warblers (Dendroica: Parulidae) early in the breeding season. They declined during the incubation and nestling stages and then increased during the fledging stage in two species, the black-throated green (Dendroica virens) and yellow-rumped (D. coronata) warblers. Interspecific interactions occurred infrequently early in the season, but increased during the incubation and nestling stages in the black-throated green and blackburnian (D. fusca) warblers and during the fledging stage in the magnolia warbler (D. magnolia). Fights and chases predominated over supplanting attacks in both intraspecific and interspecific encounters. Male black-throated green and yellow-rumped warblers initiated hostile encounters more frequently than did their females, but male and female blackburnian and magnolia warblers did not differ in this regard. A somewhat equivocal interspecific social dominance hierarchy occurred: magnolia > black-throated green > yellow-rumped > blackburnian. Reversals to this trend were frequent and may have resulted from the strong defences initiated by these species in certain parts of their territories, particularly about their nests.     

Rapid identification of sex in birds by flow cytometry

A rapid method to identify sex in birds is described. The method requires microliter volumes of blood, and, under appropriate conditions, results can be available within an hour of sample collection. Samples can be stored at 4 degrees C or -20 degrees C without sacrificing the ability to discriminate sex differences in DNA content. The assay will find utility in laboratory, field, and applied studies, in other classes of vertebrates, and in studies on the dynamics of genome size within and among populations.     

Uncoupling by proteolysis of alpha-adrenergic receptor-mediated inhibition of adenylate cyclase in human platelets

Ethyl 2{5(4-chlorophenyl)pentyl}oxiran-2-carboxylate (POCA) is a new hypoglycaemic compound. The POCA-CoA ester strongly inhibits β-oxidation at carnitine palmitoyltransferase I. Chronic administration of POCA to rats decreases plasma concentrations of cholesterol and triacylglycerol and increases the number of hepatic peroxisomes similarly to hypolipidaemic drugs related to clofibrate. Peroxisomal fractions from rats fed a diet containing 0.2% of POCA for 4 weeks were prepared on self-generated Percoll gradients. POCA induced a 4-fold increase in catalase activity and peroxisomal β-oxidation, agreeing with the morphological data. The increase in peroxisomal β-oxidation caused by POCA feeding does not prevent accumulation of lipid following the inhibition of mitochondrial β-oxidation.     

ZZW autotriploidy in a Blue-and-Yellow Macaw

We describe genome size (nuclear DNA content), and cellular and nuclear dimensions of erythrocytes in a triploid Blue-and-Yellow Macaw (Ara ararauna) and its diploid parents. The genome size of the triploid (4.23 pg) was 1.5 times greater than the genome size of the mother (2.80 pg) and the father (2.89 pg). The sex chromosome composition was ZZW, and was predicted correctly based on the genome size of the parents. Erythrocytes of the triploid were significantly larger than the erythrocytes of the parents. Because polyploidy has been reported only in one other family of birds (Phasianidae), the parrots and their relatives might prove to be useful in the study of avian triploidy.     

Somatic embryogenesis on various potato tissues from a range of genotypes and ploidy levels

Somatic embryos (SEs) formed on in vitro-cultured stem internodes, leaves, microtubers and roots of 18 tetraploid potato (Solanum tuberosum L.) cultivars, diploid and monoploid germplasm and three wild Solanum species. A two-step protocol with 6-benzylaminopurine or thidiazuron in the first medium, and zeatin, indoleacetic acid and gibberellic acid in the second medium produced SEs within 14-28 days. SEs developed through the globular, heart and torpedo stages to produce thin-stemmed plantlets resembling potato seedlings. Plantlets transferred to the greenhouse produced greenhouse tubers. Secondary SEs were observed at the base of germinating torpedo-stage SEs in culture. SEs formed on stem internode sections, leaves and microtuber slices of in vitro-grown plants. Genotypic differences in regenerative capacity were clearly evident.     

Notes and lectotypification of some type specimens of Sisyrinchium (Iridaceae)

Type specimens of Hydastylus borealis, H. brachypus, Olsynium inflatum, Sisyrinchium inalatum, and S. sarmentosum have been located and are discussed; lectotypes are selected.