Trends of karyological evolution in Pelobatoid frogs

Summary The Pelobatids have a basal karyotype of 26 chromosomes, with 6 pairs of large and 7 of small chromosomes (6+7). From this karyotype, shown byLeptobrachium, Pelobates andScaphiopus, those ofMegophrys andSpea (5+8) may be derived, as well as that ofL. pelodytoides, with only 24 chromosomes.Pelodytes has 24 chromosomes and a karyotype 7+5 differing from that of typical Pelobatids under several respects.Research supported by a contribution from the Italian C. N. R.     

Feulgen-DNA amounts and karyotype lengths of three planarian species of the genusDugesia

Summary Genome sizes of the planariansD. lugubris (2n=8),D. polychroa (2n=8) andD. benazzii (2n=16) were evaluated on metaphase plates by measuring both the Feulgen-DNA contents and the karyotype lengths. In the three species, genome sizes are significantly different; this finding rules out the possibility of a karyotype evolution through simple chromosome rearrangements betweenD. lugubris andD. polychroa. A different Feulgen-DNA content per unit length of karyotype in the three species studied was also found, which suggests that DNA could be differently packed along metaphase chromosomes.     

Karyotype and DNA content ofPhractolaemus ansorgei Blgr. (Teleostei: Gonorynchiformes)

Summary The diploid DNA content ofPhractolaemus ansorgei spinosus (Phractolaemidae) is estimated by Feulgen cytophotometry at 3 pg. The karyotype has 28 chromosomes and 54 chromosome arms; it significantly resembles the karyotype ofChanos chanos (Chanidae).Research supported by the Division of Human Genetics, K. U. Leuven, Belgium. The Zairian ONRD permitted a stay at IRSAC-Mabali. The Department of Human Genetics, University of Amsterdam, Netherlands, provided laboratorium facilities for cytophotometric analysis. I thank J. Bylsma, M. Kibishwa, F. Koperdraad and H. Van den Berghe for advice.     

The largest known chromosome number for a mammal,in a South American desert rodent

Summary Tympanoctomys barrerae, a desert specialist member of the family Octodontidae, until now thought to be conservative, and ancestral to South American hystricognath rodents, presents the highest diploid chromosome number (2n=102) known in a mammal. Unexpectedly, its karyotype was found to be composed mainly of metacentric to sub-metacentric chromosomes. Mechanisms by which such a karyotype may have been derived are discussed.     

Supernumerary chromosomes in Drosophila nasuta albomicana

Supernumerary chromosomes have been detected in the karyotype of D.n.albomicana. Their number varies from one to three. They are the smallest elements in the karyotype. Karyotypes of D.n.albomicana with and without supernumerary chromosomes have been presented.     

Karyotype of Geomys pinetis (Mammalia: Geomyidae), with a discussion of the chromosomal relationships within the genus.

4 of the 5 subspecies of Geomys pinetis were karyotyped. All specimens examined had a diploid number of 42 and a fundamental number of 80. This karyotype was compared with the described karyotypes of other species of Geomys and was considered to be derived from an ancestoral form having a karyotype of about 70 acrocentric elements.     

Supernumerary chromosomes inDrosophila nasuta albomicana

Summary Supernumerary chromosomes have been detected in the karyotype ofD.n. albomicana. Their number varies from one to three. They are the smallest elements in the karyotype. Karyotypes ofD.n. albomicana with and without supernumerary chromosomes have been presented.     

A model for determination of the expected numbers of chromosome alterations and break points]

The assumption that the expected number of chromosome break points is simple and directly proportional to the length of chromosomes is criticized. Translocations and inversions imply two dependent break points in relation to their distribution on the whole karyotype, that is why, this assumption should be modified. A model is presented which takes the dependence into account and which provides the formulas for the calculations of probabilities of binary rearrangements and of their respectives break points. We apply the model to the human karyotype.     

Somatic chromosomes of black-headed oriole,Oriolus xanthornus (Linn.): A probable case of translocation heterozygosity

Summary 2n=80. There are 7 pairs of macrochromosomes in the male karyotype. In 2 females, besides the sex chromosomes, chromosome 3 and the largest microchromosome are unpaired and there is an additional large unpaired macrochromosome. This aberrant karyotype is best interpreted in terms of a reciprocal translocation heterozygosity, in all likelihood, at the population level.Acknowledgment. We thank Prof. U.S. Srivastava, Zoology Department, Allahabad University, for providing facilities. Financial assistance from CSIR, India in the form of a Senior Research Fellowship to one of us (H.A.A.) is thankfully acknowledged.     

I cromosomi di alcuniPipidae (Amphibia Salientia)

Summary The karyotype of the African PipidHymenochirus boettgeri (2n=24, all meta- or submetacentric chromosomes) is different from the one of the African PipidXenopus laevis (2n=36). The karyotype of the American PipidPipa (Protopipa)parva (2n=30, all acrocentric chromosomes) is very primitive and different from the karyotypes of the African Pipids and from that ofPipa pipa; the male meiotic chromosomes ofP. parva, usually with 1 procentric chiasma, show a clear difference from the male bivalents of the other Pipids, all with 2 terminal chiasmata.     

Chromosomal homology in southern Akodon

Summary Differential staining (G and C) of southern South AmericanAkodon are presented.A. olivaceus, A. longipilis andA. sanborni all have the same karyotype (2n=52, NF=58). A virtually identical band sequence is observed. This situation is interpreted using the canalization model of chromosomal evolution which stresses an optimum karyotype for each adaptive zone. Despite the high degree of conservation of the chromosome structures, the specific status of these species is supported by maintenance of distinctness when they occur in areas of sympatry.The research was partially supported by Proyecto de Investigación I-78-86, Dirección de Investigación, Universidad Austral de Chile and Programa Especial de Citogenética, U. de Chile sede Norte, Santiago, Chile.     

New robertsonian metacentrics in another 22-chromosome mouse population in Central Apennines

Summary New centric fusions (Rb 8-14 Rma) have been described in a 22-chromosome karyotype from a Mus musculus population in southern Central Italy. The diakinesis of hybrids obtained by crossing mice with different 22-chromosome complements show a ring-multivalent made up 16 metacentrics pairing arm-to-arm.     

Karyotypes and nuclear DNA contents of Polypteridae (Osteichthyes)

Summary Calamoichthys calabaricus, Polypterus palmas, P. weeksii, P. delhezi andP. ornatipinnis have the same amount of DNA per erythrocyte nucleus. The karyotype ofP. weeksii has 38 chromosomes and differs from the karyotypes of the other species, all with 36 chromosomes, by a Robertsonian chromosomal rearrangement. The karyotype condition is regarded as derived for vertebrates.Research supported by the Division of Human Genetics, K.U. Leuven, Belgium and the UNAZA, campus Kinshasa, Zaire. The Department of Human Genetics, University of Amsterdam, Netherlands, provided facilities for cytophotometry.     

New observations on the karyotype of the Djungarian hamster,Phodopus sungorus

Summary In this paper, the C-banding pattern of the karyotype of Phodopus sungorus is presented and polymorphism is taken into consideration.     

Chromosome banding patterns and the nucleolar organizer region of the eastern mole (Scalopus aquaticus)

Summary The C and G chromosome banding patterns and the AgAS positive sites (NOR regions) of cultured lung cells of the Eastern mole (Scalopus aquaticus) are presented. A distinctive secondary constriction is found on a pair of autosomes instead of on the X-chromosome as previously believed. The presence of a heterochromatic heteromorphism is noted and a large amount of constitutive heterochromatin is present in the karyotype.     

Nuclear projections in tumour cells and large chromosome markers

Summary The application of banding techniques on cytological smears from pleural effusion in a case of histiocytic sarcoma has provided direct evidence for correspondence between nuclear projections in tumor cells and extra large chromosome markers observed in the neoplastic karyotype obtained by direct preparations.     

Chromosomal abnormalities in an anholocyclic biotype ofMyzus persicae (sulzer)

Résumé Le karyotype normal deMyzus persicae (Sulzer) provenant de diverses sources fut de 2n=12. Une forme anholocyclique verte de cette espèce possède un karyotype de 2n=13 ou 2n=14, avec 1 ou 2 autosomes non appariés. Une comparaison des dimensions relatives des chromosomes des karyotypes normaux et anormaux suggère que ces derniers dérivent des chromosomes par fragmentation.

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The work is sponsored by a British Science Research Council grant for research on variation inM. persicae, as part of the United Kingdom contribution to the International Biological Programme project on biological control of aphids.     

The karyotype ofOxymycterus sp (Cricetidae,Rodentia) from Central Brazil

Cytogenetical data, including G-, C-bands and NORs distribution ofOxymycterus sp (2n=54; FN=64) captured in Distrito Federal, state of Goiás, Central Brazil are presented. Our results are compared to the karyotype information already available on this genus.     

The karyotype,C-bands and AgNO3-bands of a lungless salamander from Korea:Onychodactylus fischeri (Boulenger) (Amphibia,Urodela)

The karyotype of a lungless salamander,Onychodactylus fischeri, from Korea was analyzed and compared with that of the Japanese congeneric species,O. japonicus. In both species the diploid karyotype consists of78 chromosomes, including 6 pairs of large chromosomes, 6 pairs of medium-sized ones, and the remaining 27 pairs of microchromosomes. The chromosome number ofO. fischeri, 2n=78, is, like that ofO. japonicus, the largest so far reported in the order Urodela. C-banding showed that constitutive heterochromatin inO. fischeri was mainly in the centromeric regions and near the secondary constrictions of the large chromosomes. AgNO₃-bands were located in the secondary constrictions associated with C-band heterochromatin.     

Remarks on the karyotype of the polypteriformes. The chromosomes ofPolypterus delhezi,P. endlicheri congicus andP. palmas

Summary The chromosomes of 3 species of bikirs (Polypterus delhezi, P. endlicheri congicus andP. palmas) were studied in somatic metaphases. The diploid number was found to be 2 n=36 in all the species and a basic morphological identity of the karyotype emerges from karyogram comparison not only in the 3 species described herein, but also in the other Polypteriformes already studied.