First Report on Karyotypic, Morphometric and Meiotic Analysis of a Predatory Bombardier Beetle Pherosophus catoirai (Coleoptera: Carabidae) from Jammu region of Outer Himalayas, India

Chromosomal studies and manual karyotyping are the aged techniques for determining the identity of a species on evolutionary scale; however, these techniques are simple, reliable and inexpensive to authenticate the existence of a particular species. In the present work, the chromosome complement and meiotic processes of a predatory bombardier beetle Pherosophus catoirai were investigated. This species presented 2n=35 as diploid chromosome number and the chromosomal formula was found to be 12m+8sm+12st+X0. Sex mechanism was X0 type with metacentric X chromosome. Y chromosome was absent in this species. Karyotype revealed small chromosomes except X chromosome which is found to be largest in the spermatogonial metaphase stage. Meiotic stages were pachytene, diplotene, diakinesis and metaphase-I. Present study may find importance to analyse evolution of chromosomes in order Coleoptera particularly in family Carabidae.

Cytogenetics of chromosome rearrangements in Tribolium castaneum

The karyotype of the red flour beetle, Tribolium castaneum, was reexamined and improved by restriction enzyme banding with HpaII. After this treatment, each of the 10 chromosomes were identified in spermatogonial metaphase cells and 3 of the 8 autosomal bivalents and the XY pair were identified in spermatocyte metaphase I nuclei. Based on centromere position, relative length, and banding pattern, probable correlations between some of the mitotic chromosomes and some of the metaphase I bivalents were ascertained. Thus improved, the karyotypes of beetles harboring genetically defined translocations were investigated. Spermatocyte metaphase I nuclei were most informative, as normal chromosome pairing was visibly disrupted by rearrangements. Bivalents associated with each rearrangement were identified. Results demonstrated that each of the five best defined T. castaneum linkage groups corresponds to a different chromosome and established correspondence between bivalents and linkage groups 1–4. The relevance of these findings is discussed with regard to Tribolium genetics and evolution.Key words: beetles, red flour beetle, Coleoptera, linkage groups, chromosome banding.

Visualization of kinetochores in mammalian meiotic preparations and observations of argentophilic differences between mitotic and meiotic kinetochores

Brief staining with AgNO3 was found to differentially stain the kinetochores of chromosomes from diakinesis – metaphase I and metaphase II nuclei of mammals. The results differ from those of Giemsa-stained or C-banded preparations as the silver-stained meiotic kinetochores are clearly distinguishable from both constitutive heterochromatin and euchromatin. Silver-staining is presented as a valuable method for the staining of meiotic material because it allows for the positive identification of centromeric position and orientation with respect to chiasmata. The nonargentophilic nature of the centromere (kinetochore) region of spermatogonial metaphase chromosomes in some species suggests a fundamental structural difference between mitotic and meiotic kinetochores.Key words: kinetochore, meiosis, mammal.

HUMAN MALE MEIOSIS: CHROMOSOME BEHAVIOUR AT PRE-MEIOTIC AND MEIOTIC STAGES OF SPERMATOGENESIS

Normal testicular material was obtained from 53 men. The morphology and behaviour of the chromosomes during pre-meiotic and meiotic stages of spermatogenesis are described in detail. Three types of spermatogonial metaphase chromosome have been identified; they are thought to be from spermatogonia of different generations. Homologous chromosomes appear to be paired at the beginning of spermatogonial prophase, and at the onset of the meiotic prophase (leptotene). Bivalents assume a "lampbrush" appearance during mid- to late pachytene.

CYTOLOGY AND PARTHENOGENESIS OF THE WHEAT STEM SAWFLY, CEPHUS CINCTUS NORT. (HYMENOPTERA: CEPHIDAE)

A chromosome complement of 18 was established for the female of Cephus cinctus Nort. by counts of 18 elements at oogonial metaphase and nine bivalents at pachytene. The male has a haploid set of nine chromosomes on the basis of counts at spermatogonial metaphase and at meiotic metaphases I and II. Male haploidy was confirmed by the fact that the male karyotype comprises one member of each morphologically identifiable pair present in the female. Spermatogenesis is characterized by lack of synapsis and complete abortion of the first meiotic division. Formation of a monopolar spindle at first meiotic metaphase is discussed. A cytological comparison of thelyotokous and arrhenotokous strains of C. cinctus failed to reveal any difference in chromosome number or in chromosome morphology. Cephus cinctus reproduces largely by arrhenotoky, the population normally being bisexual; the males develop from unfertilized eggs, most of the females arising from fertilized eggs; azygous, or impaternate, females occur sporadically. From the bisexual population a thelyotokous strain has arisen that is not distinguishable by cytological comparison; the females of both arrhenotokous and thelyotokous races are diploid; no diploid males were found. The haplo-diploid relationship of male to female was confirmed; male haploidy has become established by adaptive modifications in meiosis, as indicated in the cytological details given.

Memoirs: The Male Meiotic Phase in Two Genera of Marsupials (Macropus and Petauroides)

Macropus ualabatus has twelve chromosomes, namely 10 + XY in the male and 10 + XX in the female. In Petauroides the number is almost certainly twenty-two, the male being of the formula 20 + XY. No female counts were obtained for this animal. In the male Macropus Xis generally attached to one of the autosomes in spermatogonial mitoses. Y, which is exceedingly minute, is free. During the pachytene stage, while the autosomes are still elongated, X and Y condense into a bivalent. In the first meiotic division this bivalent is attached to an autosome. As a result of the first meiotic division the usual two classes of secondary spermatocytes are formed one with X and the other with Y. In the second meiotic division, those with X show only five separate chromosomes, showing that X, as usual, is fused with an autosome. The other class of second divisions shows five autosomes and the minute Y. In the female Macropus the sex chromosomes were never found free from the autosomes in the ovarian follicle cells, which therefore show only ten separate chromosomes. In Petauroides the sex chromosomes cannot be distinguished with certainty from the autosomes. An unequal pair of small chromosomes usually situated in the centre of the spermatogonial metaphase plates probably, however, are X and Y. Early pachytene nuclei show two compact bodies which unite into one, presumably the sex bivalent. The second reduction of the chromosome number to onequarter of the diploid total in the second meiotic division, which has been described for several species of birds and mammals, does not take place either in Macropus or Petauroides. Chromomeres are very prominent in Petauroides in the zygotene and diplotene stages. Probably in Macropus, and more convincingly in Petauroides, the cytological conditions to permit of ‘crossing over’ are present in the male. The plasmosome which appears in the pachytene stage is probably formed from the plastin or linin basis of the contracting sex chromosomes.