Comparative studies on the karyotype of Ascaris suum and "Ascaris ovis"

The mitochondrial genome of the sheep roundworm Ascaris ovis (Ascaridida: Nematoda) from Southwest China

The Ascaris roundworms (Ascaridida: Nematoda), one of the commonest soil-transmitted helminths (STHs), can cause ascariasis with significant socioeconomic and public health impact. In this study, the mitochondrial genome of Ascaris ovis, a representative of this genus from the sheep in Southwest China was determined using Illumina sequencing technology. The assembled genome was 14,205 bp in size and encoded 36 genes, including 12 protein-coding genes, 22 transfer RNA genes, and two ribosomal RNA genes. Phylogenetic analysis showed that A. ovis grouped with the congeneric Ascaris lumbricoides of humans, Ascaris spp. of non-human primates and Ascaris suum of pigs and together formed a monophyletic group relationship with either species of Baylisascaris/Toxascaris/Parascaris, species of Toxocara, species of Anisakis/Pseudoterranova or species of Ascaridia/Heterakis in the order Ascaridida, supporting its genetic similarity with A. lumbricoides, A. suum, and other congeneric species. The cumulative mitochondrial DNA data of this genus should contribute to a better understanding of the phylogenetic relationships among these roundworms.

Development of SYBR Green real-time PCR for diagnosis of fasciolosis in sheep

Fasciolosis is commonly diagnosed by microscopic detection of egg following sedimentation. However, this technique is time-consuming when a large number of samples must be processed and requires sufficient experience. Quantitative real-time PCR based on the detection of liver fluke ribosomal DNA in feces has been introduced, which is more accurate and liable to reflect the presence of flukes in hosts. This study aimed to develop an efficient molecular detection method in laboratory diagnosis. A cross-sectional study of 250 sheep was performed to detect Fasciola hepatica infections using gold standard microscopic detection, conventional PCR and real-time PCR. Both conventional and real-time PCRs targeted the internal transcribed spacer 2 (ITS-2). A composite reference standard(CRS) was used to analyze the sensitivity and specificity of three methods. Furthermore, the minimal amount of plasmid DNA detected by the real-time PCR was 1.67 pg plasmid DNA (equivalent to 1.1 × 10⁶ copies). In conclusion, a highly sensitive and specific method for fasciolosis in sheep was developed.

Meiosis and some aspects of cytological mechanisms of chromosomal sex determination in nematode species

Meiotic division in Toxascaris leonina, Baylisascaris transfuga, Hexametra sp., Toxocara canis, T. cati, Heterakis gallinarum and Physaloptera clausa of the class Nematoda were studied. Chromosomal sex determination type in different taxa is described. The XX-XO type of sex determination predominates in the species examined. A Y chromosome occurs only in B. transfuga. A correlation between the number and length of sex chromosomes and autosomes in the different taxa was established.

Karyotype analysis of Ascaris lumbricoides var. suum. Male and female pachytene nuclei by 3-D reconstruction from electron microscopy of serial sections

Twelve synaptonemal complexes are present in both oocyte and spermatocyte pachytene nuclei of Ascaris lumbricoides var. suum, as determined by 3-D reconstruction of the nuclear contents from electron microscropy of serial sections and therefore, n=12 in the strain of Ascaris described here. In the female the heterochromatic end of each synaptonemal complex is attached to the nuclear envelope and the other end is free in the nucleoplasm. In the male neither end of the synaptonemal complex is attached, but there is a heterochromatic knob at one end of each complex. Five additional large heterochromatic masses are present in the spermatocyte nucleus and these may be the sex chromosomes described by earlier workers.

Comparative cytological studies of mitotic and male meiotic karyotype of Ascaridia dissimilis (Vigueras, 1931) and Ascaridia galli (Schrank, 1788)

Gametogony and spermatogenesis of A. dissimilis and A. galli were studied. It was found that the chromosome number of A. dissimilis is 2n = 10 for female specimens and 2n = 9 for male ones. The chromosome number of A. galli is also 2n = 10 for female specimens and 2n = 9 for males ones. Comparison of the relative length of chromosomes in the chromosome set, expressed in percentages, shows nearly equal magnitudes for both species. Spermatogenesis processes were studied. It was found that they run a similar course in both species. In the following stages of gametogony and spermatogenesis differences between the two species are not discovered.

Morphology and behaviour of sex chromosomes during meiosis in Ascaris suum

The morphology and behaviour of sex chromosomes was studied in A. suum during meiosis. It was found that the five sex chromosomes have their proper characteristic. The largest is submetacentric, of 2 microns mean length. The second largest is acrocentric, mean length of 1.4 mu. The third largest is metacentric, 1.2 mu mean length. The fourth and the fifth are metacentric, of mean length of 1 mu. In primary and secondary spermatocyte cells the sex chromosomes are close to each other, most often in the peripheral part of the cell. During anaphase I the pentad sex chromosomes lie freely between the two sister cells. It is assumed that in anaphase II the five sex chromosomes divide equally and are regularly distributed in the daughter cells. It was found that the chromosomes set of female Ascaris in metaphase I contains 24 bivalent chromosomes n = 24 and of male Ascaris 19 bivalents and 5 univalents. It is assumed that the univalent chromosomes, found in spermatocyte cells, determine sex.