Mosome Number Research Articles

Chromosomal analysis and nors polymorphism of bagarius suchus (Siluriformes: Sisoridae) by conventional banding and fish techniques

In the present study, conventional staining and NORs banding as well as Fluorescence in situ hybridizat ion (FISH) using the 18S rDNA and telomeric (TTA GGG)n probes were applied to stain the chromosomes of crocodile catfish, Bagariussuchus (Siluriformes, Sisoridae) fro m the Chao Praya River, Thailand. Kidney cells of 6 male and 6 female crocodile catfishes were used as a sample. The mitotic chro mosome preparations were done directly fro m kidney cells. The results showed that the diploid chro mosome number of B. suchus was 2n=56, the fundamental numbers (NF) were 102 in both male and female. The karyotype comprises 17m+17sm+12a+10t. The nucleo lar organizer reg ions (NORs) were detected by Ag -NORs banding and 18S rDNA probe mapping. The 18S rDNA are terminally located on the short arm adjacent to the telomere of the single pair of the 1st chromosome pair whereas NOR-bearing chro mosome is only one chromosome of the 1st chromosome pair (1a 1b, poly morphic characteristic) at the subtelomeric region of the short arm. Moreover, FISH with telomeric probe showed hybridizat ion signals on each telomere of all chro mosomes and interstitial telomeric sites were not detected. There were variations in signals of FISH and their position in the karyotype along with variat ion in DNA sequences. These markers are useful for future discrimination of population of closely related species and their poly morphis m.

Comparative karyo-morphology of the two endemic and critically-endangered species of Mantisia (Zingiberaceae)

Karyo-morphological studies have been carried out in two critically rare, endangered and endemic rhizoma- tous, horticulturally important species of genus Mantisia (Zingiberaceae) from North-East India. The somatic chro- mosome number (2n020) has been recorded in both M. spathulata and M. wengeri with distinct inter-specific variation in the arm ratio of homologous pairs in the comple- ments. All the chromosomes were sub-metacentric in nature (20 L) and more or less symmetrical karyotypes in both the species indicating stabilized genomic pattern. In M. wengeri two chromosome pairs exhibited heteromorphy. Nucleolar organizing region (NOR) and meta-, telo-, and sub- telocentric chromosomes were absolutely lacking. Chromo- some class based on total length of each chromosome as well as its designation through centromeric position was deter- mined. This karyo-morpological study provides valuable baseline genetic data for clearly distinguishing Mantisia (x010) from its phenotypically very similar allied genus Globba L. (x08). Thus, present investigation provides valu- able insight on karyotypic variation, speciation and evolution of the genus Mantisia and also addresses the conservation concerns.

Karyotype characterization of planthopper species Hysteropterum albaceticum Dlabola, 1983 and Agalmatium bilobum (Fieber, 1877) (Homoptera: Auchenorrhyncha: Issidae) using AgNOR-, C- and DAPI/CMA3 -banding techniques

Males of Hysteropterum albaceticum Dlabola, 1983 and Agalmatium bi- lobum (Fieber, 1877) display a chromosomal complement of 2n = 26 + X, which is a basic one of the tribe Issini (Issidae). In the present study, silver staining, C-banding and a base specifi c CMA 3 -and DAPI-banding were used with the aim of identifying pos- sible cytogenetic markers and distinguishing between karyotypes with the same chro- mosome number and no detectable inter-species differences in karyotype structure. We characterized the species studied in terms of the distribution and molecular structure of C-heterochromatin regions and the location of nucleolus organizer regions (NORs). The species are shown to differ considerably in the amount of heterochromatin, its distribution pattern along the karyotypes and its stain ability with DAPI and CMA 3 .

Direction of karyotype evolution in the bug family Nabidae (Heteroptera): New evidence from 18S rDNA analysis

The bug family Nabidae (Heteroptera) includes taxa showing either a low chromosome number 2n = 16 + XY or high chromosome numbers 2n = 26 or 32 + XY. In order to reveal the direction of karyotype evolution in the family, a molecular phy- logeny of the family was created to reveal the taxon closest to the ancestral type and hence the ancestral karyotype. The phylogeny was based on a partial sequence of the 18S rDNA gene of both high and low chromosome number species belonging to the subfami- lies Prostemmatinae and Nabinae. Phylogeny created by the Neighbour Joining method separated the subfamilies, Prostemmatinae and Nabinae, which form sister groups at the base of this phylogenetic tree, as well as within the Nabinae, tribes Nabini and Arach- nocorini. Combining karyosystematic data with the phylogeny of the family indicated that the ancestral karyotype was a high chro- mosome number, consisting of 2n = 32 + XY. During the course of evolution changes have occurred both in meiotic behaviour of the sex chromosomes and in the number of autosomes. The direction of karyotype evolution was from a high to low autosome number. Abrupt decreases in the number of autosomes have occurred twice; firstly when the tribe Arachnocorini differentiated from the main stem in the subfamily Nabinae and secondly within the tribe Nabini, when within the genus Nabis 2n = 16 + XY species diverged from the 2n = 32 + XY species. A scheme of the sequence of events in karyotype evolution during the evolution of the Nabidae is presented.

A cytological and molecular study of the generaScorzoneraL. andPodospermum(L.) DC (Asteraceae)

The genus Scorzonera L. s.l. encompasses enormous morphological variation and has created problems for taxonomists. Podospermum has been treated as either a section of a broadly defined Scorzonera or as an independ- ent genus. In Italy, there are twelve Scorzonera species and three Podospermum species. The relationship between these species is not at all clear. To clarify these relationships, a survey, including thirteen of the fifteen taxa found in Italy, was carried out using: i) sequence analysis of ribosomal internal transcribed spacer (ITS) and external tran- scribed spacer (ETS) regions; ii) analysis of Amplified Fragment Length Polymorphisms (AFLPs); iii) chromosome counts. In addition, to broaden the scope of the work and allow taxonomically significant interpretation of the data to be made, sequences from a range of related species were obtained from the EMBL nucleotide sequence database. Our analyses clearly indicate that Scorzonera s.l. is a polyphyletic grouping. The three approaches used were consist- ent with each other although showing different levels of resolution. There was broad division, on the basis of chro- mosome number, either 2n = 12 or 14. This was supported by PCO analysis of AFLP fragments which indicate three groups. Finally, phylogenetic analysis of sequence data produced four to six highly supported clades that might ap- propriately be given independent taxonomic status.

Karyotypic study in some Iranian species and populations of Tulipa L. (Liliaceae)

Karyotypic studies were performed on 12 species/ populations of Iran- ian tulips for the first time. The species/ populations possessed 2n = 2x = 24 chro- mosome number but varied in details of karyotype including type of chromo- somes, karyotype symmetry and number of SAT-chromosomes and differed sig- nificantly in total chromatin length as well as length of chromosome arms. A pair of heteromorph chromosomes occurred in T. humilis. The use of karyotypic da- ta in taxonomy of the genus Tulipa L. is discussed.

Experimental Taxonomy of Weissia controversa and W. sharpii (Musci: Pottiaceae)

Weissia sharpii Anders. & Lemmon is a recently described species endemic to the Southern Appalachian-Ozarkian region. It was distinguished from the more widespread species, W. controversa Hedw., on the basis of its diploid gametophytes, restricted habitat in cedar glades, and several morphological features of the gametophytes. An experiment was performed in which two populations each of W. sharpii and W. controversa were grown reciprocally on soil from each other's native habitats, and twelve morphological characters were measured. Soil type had virtually no effect on the expression of any of the characters. An analysis of variance indicates that the species differ significantly in leaf length-width ratio, upper leaf width, and in the width of the gap between involuted leaf margins. These morphological discontinuities, combined with differences in chro- mosome number and ecology, indicate that W. sharpii and W. controversa should be treated as separate species. Weissia controversa exhibited a greater degree of variation between populations than did W. sharpii when both were grown experimentally. This is in agreement with the relative variability of W. controversa in nature. Experimental studies on the plasticity of morphological characters in mosses and liverworts are reviewed. Weissia Hedw. is one of about sixty-five gen- era in the moss family, Pottiaceae. In their checklist of North American mosses, Crum et al. (1973) credited eight species of Weissia as occurring on this continent, but only one, W.

Chromosomal studies in the Egyptian flora. II. Karyotype studies in the genus Plantaga L.

The first reliable chromosome counts in species of the genus Plantago L. was made by McCullagh (1934). Later more detailed cytological investigations were carried out on more than half of the species in this genus. Some of these investigations were made in connection with taxonomic studies in order to elucidate the relationships in particular groups of related species (Bocher et al. 1955, Rahn 1957, Cartier 1971, 1973, Sopova and Rizova 1975, Zemskova 1977). Other studies were concerned with investigating the cytology of Plantago species in certain floras or phytogeographic regions (Gregor 1939, Runemark 1967, Briggs 1973, Favarger and Vasudevan 1972, Fernandes and Franca 1973). The cytology of the genus Plantago in Egypt has not been a subject of a study. The chro mosome number of only three species was reported by Badr (1980). The numbers of some other species which grow in Egypt are also known from chromosome counts in plants from near floras particularly that of Europe. The present study is therefore conducted to investigate the cyto logical features in species of the genus Plantago from Egypt. This investigation deals not only with chromosome numbers but also with detailed karyotype features such as chromosome length and centromere position. The impact of karyotype features in the taxonomic relationships of the studied species is also elucidated.

Gouldochloa, a New Genus of Centothecoid Grasses from Tamaulipas, Mexico

A new genus and species, Gouldochloa curvifolia, is described from Tamaulipas, Mexico. Features of its spikelet morphology, leaf anatomy, embryo structure, and cytology indicate that Gouldochloa is allied to the centothecoid grasses. The embryo formula is P+PP and the chro- mosome number is 2n = 24. Gouldochloa is most closely related to Chasmanthium. A key to the genera of the Centotheceae in the New World is presented.

Pohlidium petiolatum (Poaceae: Centotheceae), a New Genus and Species from Panama

Pohlidium petiolatum is described as a new genus and species based on collections made along the Rio Tife in Panama. It belongs to the Centotheceae on the basis of its petiolate, tessellately veined blades, two truncate, glabrous lodicules, laterally compressed caryopsis, chro- mosome number of n = 12, and anatomical characteristics. It differs most prominently from other genera in the tribe in its unisexual spikelets, absence of both glumes in the female spikelet and reduction to one or no glumes in the male spikelet, adaxially projecting midrib, and papillate abaxial epidermis. Its closest affinity appears to be with Calderonella and Zeugites.

Karyotypic Analysis of Plasmodiophora Diplantherae

Synaptonemal complexes (SCs) in nuclei of transitional plasmodia of Plasmodiophora diplantherae were counted through serial section analysis. On this basis the haploid chro? mosome number was nine, the lowest haploid number known for Plasmodiophoromycetes. Total length (TL) of SCs per nucleus (approx. 39 /nm) was similar to that of P. brassicae (n = 20, TL = approx. 47 jim, vol. = approx. 15 ixm3), but nuclear volume (approx. 28 /um3) was similar to those of Polymyxa betae (n = 30, TL = approx. 73 /um, vol. = approx. 26 ^m3), P. graminis (n = 30, TL = approx. 70 jim, vol. = approx. 24 /um3), and Sorosphaera veronicae (n = 33, TL = approx. 76 /ttm, vol. = approx. 25 Mm3).

Variation Patterns in Crataegus series Pruinosae (Rosaceae) in Southern Ontario

Numerical analyses (principal components analysis, multidimensional scaling, and clustering of Euclidean distances) of 120 individuals representing eleven morphotypes of Crataegus series Pruinosae in southern Ontario consistently divided the data (based on 24 morphological characters) into three major groups. The results show various correlations with phenology, chro- mosome number, and apomixis. A common hypothesis for the evolution of Crataegus is that the complex variation patterns found today are the result of commingling and hybridization between a few distinct species in response to European settlement and forestry practices. Our results are conformable to this hypothesis but there are suggestions from related genera that some of the present variation may be of a more ancient origin.

Chromosomes of the Townsend Pocket Gopher, Thomomys Townsendii

Animals were collected, subjected to in vivo colchicine treatment and red bone marrow cells were stained with giemsa. Photomicrographs and karyo- grams were prepared for all seven subspecies of the Townsend pocket gopher, Thomomys townsendii. A diploid chromosome number of 76 was found for six subspecies, T. t. bachman,i T. t. elkoensis, T. t. nevadensis, T. t. owyhensis, T. t. relictus and T. t. townsendii. The seventh subspecies, T. t. similis, has a 2n chromo- some number of 40 which, along with other unique morphological traits, indicates either confusion with the Thomomys talpoides complex or consideration of taxo- nomic revision to Thomomys similis. METHODS AND MATERIALS. Chromosome preparations were made from 54 specimens of personally collected Thomomys townsendii and one specimen of Thomomys talpoides, using an in vivo colchicine treatment, femoral marrow cells and giemsa stain (Kiossoglou et al., 1964). All of the currently recognized subspecies (Hall and Kelson, 1959) were examined. Photomicrographs were made of well-spread metaphase cells, the chromosomes were cut out and hypothetically homologous pairs were matched according to size and centromere position. Accepted techniques were used to deternine chromosome number and morphology and fundamental number (Bender and Chu, 1963; Nadler and Block, 1962; Patton, 1967; Matthey, 1951). DISCUSSION. The following six subspecies, T. t. bachmani, T. t. elkoensis, T. t. nevadensis, T. t. owyhensis, T. t. relictus and T. t. townsendii, were found to have similar karyotypes and a diploid chro- mosome number of 76 as illustrated in Figures 1 and 2. In all of these the 12 metacentric chromosome pairs in Group I range uniformly from large to small, with pair number 12 relatively quite small; the 22 sub- metacentric chromosome pairs in Group II range from large to medium size, and the 3 pairs of acrocentric chromosomes in Group III range from medium-large to small size. The X chromosome is a large sub- metacentric and the Y is a small acrocenrtic (tending toward subtelo- centric in T. t. bachmani and T. t. relictus). Each of these animals has an autosomal fundamental number 142.