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In experimental crosses between A. tubaeform and A caninum the worms failed to produce progeny in dual-strain combinations. Even though these two strains did not fail to copulate. Egg production was observed only in identical single-strain combinations. This supports the assumption that the two species are genetically separate and valid.
The offspring from hybridization experiments between Schistosoma intercalatum, Cameroun (intermediate host Bulinus forskalii) and S. intercalatum, Zaïre (intermediate host B. globosus) was investigated. Reciprocal crosses between the two forms were performed. F1- and F2-miracidia developed in both parental intermediate hosts. The minimum prepatent period was 24 days at 26 degrees C, an average of the prepatent periods for the two parental strains. The total cercariae production per 100 exposed snails decreased sharply from 121 000 for the parental strain from Cameroun in B. forskalii to 21 000 and 5000 from the F1- and F2-generations, respectively. The figures for S. intercalatum, Zaïre in B. globosus were 270 000, 134 000 and 3000, respectively. F1- and F2-generations were from the cross between males from Cameroun and females from Zaïre. The viablility of the four cross-breeding experiments carried out (two with each combinations of the parental strains) were low. It was only possible to obtain F2-cercariae. No miracidia were hatched from eggs produced by the F2-gerneation.
Q- and G-banding studies of Aotus trivigatus trivirgatus and Aotus trivirgatus griseimembra are presented. After the analysis of 8 specimens, 2 A.t. trivirgatus and 6 A.t. griseimembra and the review of the literature on the field we state the existence of two different karyotypes, 2n = 54 and 2n = 50, for A.t. trivirgatus and three different karyotypes, 2n = 54, 2n = 52 and 2n = 50, for A.t. griseimembra. It was found that Robertsonian translocations were the mechanism involved in the numerical reduction of the chromosomes. The data presented include the statement of two natural hybrids and the cross-breedings which originated them.
The influence of the increase of the degree of homozygosity, obtained by successive consanguine cross-breeding, on the mean weights and the variability of the weights of twelve muscles of the Japanese quail (Coturnix c. japonica) was studied in four generations of females and two generations of males. It was found that the mean weights of the twelve muscles in both sexes showed a progressive reduction in the consecutive generations of consanguine crosses, this reduction being more marked in the males than in the females. These results support the hypotheses of Haldane and Lerner that heterozygotes are at an advantage, having a more active metabolism and a greater rate of growth, because their richer biochemical system and greater number of alleles coding the enzymes enables them to benefit from their environment to a greater extent and within wider limits. The rates of decrease vary from one muscle to the other within the limits of 5.3 and 16.6%. For certain muscles there are also notable differences between males and females. Contrary to the hypothesis that could be formed at first sight, the variability in weight increases considerably, in almost all cases, when the degree of homozygosity increases. Here again quite considerable differences are found in the evolution of the variability with the degree of homozygosity, from one muscle to the other and also between the two sexes. Comparison of the mean weight of the left and right elements of the bilateral muscles shows no significant preponderance. It was found, however, that slight asymmetries observed in the different groups of different consanguinity tend to be in the same direction for a given muscle. The variability of the weights of the left and right elements does not seem to be influenced by the degree of homozygosity in the females; in the males, however, an increase in homozygosity increases the variability of the weights of the left and right elements in certain cases. The mean degree of humidity and the variability of the ratio wet weight/dry weight are not changed significantly by the degree of consanguinity in females. In the males, the variability in the degree of humidity is less in heterozygotes, an indication of their better capacity for homeostatic regulation. The reduction in the mean weights and the increase in variability as the degree of homozygosity increases shows the importance of the advantage of heterozygotes, which has a bearing on theories of the genetics of populations and their application in rearing, and particularly to selection techniques.
Occasionally the hedgehog (Erinaceus europaeus) is infected by Trichophyton mentagrophytes (Robin) Blanchard var. erinacei. This zoophilic dermatophyte may cause a difficult human phlegmatic trichophytia infection. The thread-fungus grows on the usual culture-medium with a clear-white surface without radius-folding. The lower surface of the culture shows a typical brillant-yellow colour. Microscopically the fungus presents abundant microconidia formation and a few distinct macroconidia. Cross-breeding with the tester strain Arthroderma simii "+" was negative, with "-" showed an increased growth and a formation of cleistothecium-primordia in the combination zone.
When Royal College of Surgeons (RCS) rats are bred with Wistar albinos the offspring are deeply pigmented and have normally functioning retinas. From this second generation, various breeding possibilities exist. In the course of successive cross-breedings one can obtain albinos, tan striped (RCS type) or pigmented animals, any one of which may be normal, carrier or affected. The skin pigmentation trait and that of retinal degeneration are independently inherited and follow autosomal recessive Mendelian laws. However normals for ERG studies vary with skin pigmentation. It is suggested that only one group should be chosen and preferably the pigmented variety.
This study was designed as an exploratory analysis to compare carcass performance, meat quality traits, and gut microbiota of Neijiang pigs (NN), Yorkshire pigs (YY), and Yorkshire × Neijiang hybrid pigs (YN), with the goal of generating testable hypotheses regarding potential links between gut microbial composition and production phenotypes. Compared with NN pigs, YN hybrids exhibited improved carcass performance while inheriting the favorable meat quality characteristics of Neijiang pigs. The results of 16S rRNA sequencing analysis showed that the relative abundance of the microbiota was similar to that of NN pigs. LDA effect size (LEfSe) results showed that Streptococcus, Treponema, probable_genus_10 and Fibrobacter were the differentially enriched taxa in YN pigs (p < 0.05). Correlation analysis was performed on carcass, meat quality and intestinal microbiota screened out by LEfSe. The results showed that Akkermansia tended to positively associate with body length and oblique length in YN pigs; Dialister correlated positively with dressing rate and pH45min; Treponema showed positive trends with a*45min and a*24h (p < 0.05). Finally, the correlation network model preliminarily mapped associations among production traits, gut microbiota, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways for exploratory screening. Nine core microbial taxa exhibited close correlations with phenotypic indicators, which implied that these microbes might modulate metabolic pathways to shape pig performance. Overall, hybrids inherited superior parental carcass and meat quality but harbored unique gut microbial communities relative to purebreds-these preliminary correlative observations generate new hypotheses that gut microbiota may contribute to heterosis-associated phenotypic advantages, which require further targeted validation.