A frog with highly evolved sex chromosomes

Summary Highly differentiated ZZ/ZW sex chromosomes and an exceptionally low genome, size were found in the karyotypes ofPyxicephalus adspersus (Anura, Ranidae). The W-chromosome is considerably smaller than the Z-chromosome and consists to a very great proportion of constitutive heterochromatin. The DNA content of this species and the chromosome length have the lowest values determined in the Ranidae to date.This study was supported by a grant from the Deutsche Forschungsgemeinschaft. We thank Professor W. Engel for his support and interest.     

The chromosomes of four species of Falconiformes

Summary Leucocyte cultures were used in four species of Falconiformes for the purpose of karyotypic sex determination and the establishment of a breeding pair. The Andean condor has 80 Guiana eagle 54, Crane hawk 66, and Turkey vulture 76 chromosomes with readily distinguished ZW elements in the female.Our cordial thanks are extended toA. Risser, Ph. D. Assistant Curator of Birds, San Diego Zoo;Warren Thomas, D.V.M., Director, Los Angeles Zoo for their cooperation and assistance in the collection of blood samples for chromosome study. We are also grateful toK. Benirschke, M.D., Director of Research, San Diego Zoo for his kind assistance.     

G-banding patterns of the housefly,Musca domestica,autosomes and sex chromosomes

Summary G-banding patterns were found on the X-chromosomes of the housefly. This indicates the presence of major gene loci on these chromosomes, i.e. sex-linked genes. G-banding patterns were also found on the Y-chromosome of 2 preparations. The first polyploid cell (a tetraploid, 2n=24) forMusca domestica was observed in one of the banding preparations.     

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.     

The somatic chromosomes of 3 lizard species:Gekko gecko,Iguana iguana,andCrotaphytus collaris

Zusammenfassung Die somatischen Chromosomen der 3 EidechsenartenGekko gecko (2N=38),Iguana iguana (2N=34) undCrotophytus collaris (2N=36), werden dargestellt.G. gecko besitzt metazentrische, subteleozentrische und teleozentrische Elemente, aber keine Mikrochromosomen.I. iguana undC. collaris besitzen Makrochromosomen (6 Paare) und Mikrochromosomen. Bei den ArtenG. gecko undI. iguana waren in keinen von beiden Geschlechtern heteromorphische Chromosomenpaare nach zuweisen.

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Supported by Project No. 417 from the U.S. Children's Bureau and Grant No. 08737 from the National Cancer Institute.     

The chromosomes of two species of the genusOryzomys (rodentia-cricetidae)

Resumen Oryzomys es un género altamente politípico y primitivo que ocupa un área geográfica que se extiende por todo el continente Sudamericano y el sur de Norteamérica. De este género se describen los cromosomas de dos especies pertenecientes al subgéneroOryzomys. O. albigularis (posiblementeO. a. camcolus) (2N=66) yO. delicatus (2N=60) cuyos cromosomas son fundamentalmente del tipo acrocéntrico o subtelocéntrico con algunos pares matacéntricos o submetacéntricos.     

The chromosomes ofBufo rubropunctatus andBufo chilensis (Anura,Bufonidae) and other species of thespinolosus group

Summary The chromosomes ofBufo rubropunctatus andB. chilensis (on basis of adults) are described for the first time. These chromosomic sets are compared with the karyotypes ofB. spinolosus andB. variegatus and other species ofspinolosus group. The importance of the secondary constrictions applied to the phylogeny ofBufo are discussed.Supported by Proyecto N⁰ S-77-47, Dirección de Investigación, Universidad Austral de Chile.I would like to thank Dr J. M. Cei for collecting the Argentinian toads. Mr N. Diaz collected the specimens from Santiago, Chile.The technical assistence of Sonia Lacrampe is acknowledged with appreciation.     

RNA synthesis in the sex chromosomes of the opossum,Didelphis virginiana. I. Female

Résumé Pour une étude quantitative de la synthèse du RNA, nous avons utilisé des chromosomes sexuels d'Opossum, morphologiquement faciles à distinguer en prophase et possédant des caractères cytogénétiques inusuels. Les résultats suggèrent que les deux chromosomesX des lymphocytes femelles sont actifs génétiquement (quoique l'un d'eux le soit moins que l'autre) pendant une courte période du cycle de la cellule.     

The chromosomes ofCalamoichthys calabaricus (Pisces,Polypteriformes)

Riassunto È stato descritto il cariotipo di un Polypteriforme,Calamoichthys calabaricus, Smith. Il numero diploide, 2n=26, le dimensioni dei cromosomi e la stessa morfologia del cariotipo mettono in evidenza le affinità filetiche intercorrenti tra Polypteriformi e Dipnoi e la linea evolutiva tetrapoda, diversificandoli, al contrario, dagli altri primitivi Attinopterigi, Holostei e Chondrostei.