The grasshopper Dichroplus pratensis Bruner is polymorphic and polytypic for a complex Robertsonian system. In this species, centric fusions induce changes in number and position of chiasmata, and thus potentially affect intrachromosomal genetic recombination and genetic variability. Males and females, from 23 populations covering most of the geographic range of the species and spanning 22 degrees of latitude, were studied. We analyzed chiasma frequency in relation to variability in six exomorphological characters. The chromosomal polymorphisms of D. pratensis are widely geographically distributed, and show a central-marginal pattern, in which the central populations (those occupying the ecologically optimal habitats) have high mean frequencies of different fusions per individual (F) of up to F = 3.00 and total chiasma frequencies as low as XT = 8.98 per cell, while those near the margins of the distribution (central Patagonia and the Andes) have very low levels of chromosomal polymorphisms [down to F = 0.00 in most geographically marginal locations), monomorphic karyotypes and high chiasma frequencies (XT = 11.66, in the southernmost (Rada Tilly, 45°57´S) and XT = 12.01 in the northernmost population (Volcán, 23°55´S)]. Increasing chiasma frequencies towards the margins of the range are positively and significantly correlated with increasing levels of morphological variability. The decrease in fusion polymorphism and the consequent increase in genetic recombination (both inter- and intrachromosomal) in the marginal areas, is a result of natural selection favouring higher levels of variability, which could be adaptive in ecologically harsher and changing environments.
The craniometric variability of skulls of the common hamster (Cricetus cricetus) from different countries (Belgium, the Netherlands, Austria, Germany) and different regions within Germany was studied. The aim was to study the variability in different regions and to see if differences between populations exist now and might have existed in former times also. The discriminant analyses were performed for females and males separately. The material was assigned to three different age classes and tests were attempted with all age classes. For the largest sample from Saxony-Anhalt, differences could also be observed between the three selected time periods (1900-1930, 1931-1960 and 1961-1990). Discriminant analyses were performed by keeping the sexes, age classes, and time periods separate
wherever the material allowed for it. Regional samples differed to some degree (depending on the set of samples used). Particularly the
samples from Austria, Belgium, and the Netherlands were more offset from the German samples; nevertheless, some overlap existed for the males of the third time period. The position of the small sample from the Rhineland was ambiguous in the different discriminant analyses but seemed rather to fall within the range of other German samples and not clearly in-between the German and the Dutch/Belgian samples. Overall variability, changes with time, and possible yearly fluctuations, as described in the literature, influenced the results and overlaid existing regional differences. The existence of a western subspecies could not be supported. The lack of substantial numbers of specimens illustrated the importance of collecting even the common species at all times for future research.
The morphometrical variability of Zonorchis clalhraium (Deslongschamps, 1824) from Apus apus in the Czech Republic, Z. rutshurensis (Baer, 1959) from Apus cajffer streubeli and Z. dureni Vercammen-Grandjean, 1960 from Hirundo ni-grita in Congo was studied. Zonorchis rulshurensis and Z dureni are considered to be synonyms of Z. clathratum. Lyperosomum oswuldoi Travassos, 1919 sensu Jaroń, 1969 is considered to beZ. clathratum, and L. clathratum (Deslongschamps, 1824) sensu Jaroń, 1969 is considered to be Stromitremu koschewnikovi (Skryabin et Massino, 1925).
The aim of this study was to obtain information on the karyotypes, testes and ovaries of three fulgoroid families, mainly in the Issidae but also in the Caliscelidae and Acanaloniidae. For the Issidae, the data is for 19 species belonging to 11 genera of the subtribes Issina (2 species, 1 genus), Hysteropterina (14 species, 9 genera) and Agalmatiina (3 species, 2 genera) of the tribe Issini. The male karyotypes are shown to be quite uniform across the tribe, with 2n = 26 + X in all species studied except Latilica maculipes (Melichar, 1906) with 2n = 24 + X. The modal karyotype, 2n = 26 + X, matches the most probable ancestral state in the Fulgoroidea. In the majority of cases the number of seminal follicles in males and ovarioles in females are stable within but fairly variable among the species, the modal value of the follicle number is 10 per testis. Contrary to what might be expected from other fulgoroid families, such as the Dictyopharidae and Delphacidae, the variability in these characters revealed neither regular trends nor evident correspondence with the taxonomy of Issidae. In the Caliscelidae, all species studied had testes consisting of 6 follicles each and karyotypes of 2n = 24 + X and 26 + XY, respectively, in 3 and 1 species. The only representative studied of the Acanaloniidae, Acanalonia bivittata (Say, 1825), had 2n = 24 + X and 13 follicles in its testis. The variability in all the characters investigated is discussed and compared to other fulgoroid families, primarily to the most extensively studied families, Delphacidae and Dictyopharidae.
It is important to determine and clarify the variability of mammary carcinogenesis induction in animal experimental studies particularly in connection with chemoprevention projects. The circannual seasonal rhythms of hormone levels or various parameters within the immune system may involve factors participating in mammary gland carcinogenesis. In our study, 19 experiments were conducted and all of them lasted for about 25 weeks after chemical carcinogen administration (DMBA or NMU) under standard laboratory conditions. Females of two rat strains - a medium susceptible Sprague-Dawley strain and a very low susceptible Wistar:Han were used. We observed not only the effect of seasonal changes but also the effect of age after single or repeated carcinogen administration. The seasonal dependence of mammary carcinogenesis with higher tumor incidence during long days in comparison with winter short days has been demonstrated in Sprague-Dawley rats. In experiments on the Wistar:Han strain, certain features of seasonal character were recorded, although the very low susceptibility of this strain to mammary carcinogenesis might have influenced the results. A limited period of carcinogen administration in early puberty around postnatal days 43-46 (higher susceptibility), when compared to the period after postnatal day 50, is the factor significantly increasing incidence and frequency of mammary carcinogenesis in the Sprague-Dawley strain. Our results indicate the need to consider the effect of season and age of animals at the time of carcinogen administration on rat mammary carcinogenesis induction. However, the application of the results obtained in one strain of experimental animals may only lead to misleading conclusions., P. Kubatka, E. Ahlersová, I. Ahlers, B. Bojková, K. Kalická, E. Adámeková, M. Marková, M. Chamilová, M. Čermáková., and Obsahuje bibliografii