The lampbrush chromosomes of Xenopus laevis: preparation,identification, and distribution of 5S DNA sequences

Details are given of a technique for making permanent preparations of the lampbrush chromosomes of Xenopus laevis. Stained preparations allow all 18 bivalent chromosomes to be identified, and a working map showing the major features has been constructed. Fifteen of the Xenopus chromosomes have one telomere conspicuously larger than the other; the two smallest chromosomes, and one other, lack large telomeres. Similar preparations, extracted with RNase and denatured, have been hybridized in situ with a ³H-labelled 5S cRNA probe. Chromosomes can be identified in the resulting autoradiographs. 5S DNA sequences are present at all the larger telomeres and at three of the smaller ones, but are absent from the telomeres at both ends of the two smallest chromosomes. There are also five interstitial sites of hybridization. At one of these, label is on the chromosome axis; at the other four, label extends well away from the axis.     

A Test of Local Enhancement in Amphibians

Local enhancement is an underexplored social learning mechanism that is often observed in organisms that live in groups. This mechanism occurs when individuals are attracted to areas where conspecifics have previously been, but which are not present when the animal actually moves into the area. We tested for local enhancement in wood frog tadpoles (Lithobates sylvatica) and spotted salamander larvae (Ambystoma maculatum) in three experiments that exposed individuals to one side of a test chamber which was empty and another that contained a group of three conspecifics. Side preference of the focal individual was recorded once the conspecifics were removed. Tadpoles showed a clear preference for moving to areas where a group of tadpoles had previously been located. Conversely, this preference was not observed in salamander larvae. In addition, salamander larvae took significantly more time to initially choose a side. These results indicate that tadpoles exhibit local enhancement, whereas aquatic salamander larvae do not. This difference in social learning could be largely due to differences in aquatic ecology between tadpoles and salamander larvae.     

Chromatin and epigenetics in all their states: Meeting report of the first conference on Epigenetic and Chromatin Regulation of Plant Traits - January 14 – 15, 2016 - Strasbourg,France

In January 2016, the first Epigenetic and Chromatin Regulation of Plant Traits conference was held in Strasbourg, France. An all-star lineup of speakers, a packed audience of 130 participants from over 20 countries, and a friendly scientific atmosphere contributed to make this conference a meeting to remember. In this article we summarize some of the new insights into chromatin, epigenetics, and epigenomics research and highlight nascent ideas and emerging concepts in this exciting area of research.     

Properdin factor B (Bf) polymorphism: Subtyping of SS phenotypes

The authors have studied the genetic polymorphism of the properdin factor B (Bf) by the isoelectrofocusing technique. The SS phenotypes, all similar on agarose gel electrophoresis, were shown to be heterogeneous after isoelectrofocusing; this heterogeneity corresponds to the expression of two new suballeles SA and SB, inherited in a codominant manner. Gene frequencies for 121 individuals with SS phenotype are 0.57 for SA, and 0.43 for SB.     

Systems of mate selection in a cockroach species with male dominance hierarchies

The system of mate selection in the cockroach, Nauphoeta cinerea, was studied experimentally. The dominant male in a group mates more often than expected if random mating were occurring. The presence of a female usually does not result in changes in the dominance hierarchy, but the frequency of certain behavioural patterns in intermale interactions changes after introduction of the female. Females can discriminate between dominant and non-dominant males on the basis of odour. The experimental approach to this question is somewhat confounded by turning tendencies of the females; data are presented relating female choice to turning tendency.