DNA replication,G- and C-bands and meiotic behaviour of supernumerary chromosomes of Rattus rattus (Linn.)

Supernumerary chromosomes have been observed in a few individuals of three subspecies of Rattus rattus from India and Nepal. The supernumerary chromosomes are late replicating and positively heteropycnotic during meiosis which characterize their heterochromatic nature. Their G-banding patterns do not exactly resemble the patterns exhibited by the chromosomes of similar size and morphology of the normal complement. The supernumerary chromosomes become conspicuous for the lack of a centromeric C-band in them as compared to the prominent C-bands in other chromosomes of the complement.     

Karyologic diversification and phylogenetic relationships of the genus<Emphasis Type="Italic">Thalpomys</Emphasis> (Rodentia,Sigmodontinae)

We describe the karyotype ofThalpomys species, from different Brazilian localities of the Cerrado.Thalpomys cerradensis Herskovitz, 1990 showed 2n=36, FN=34 andT. lasiotis Thomas, 1916 2n=38, FN=38. Comparisons of G-band karyotypes showed evident inter-specific homologies indicating that their chromosome complements could be derived from one another by two presumed rearrangements. Both species showed pericentromeric C-band regions in almost all chromosomes but a comparison with CMA3/DA/DAPI staining indicated that the molecular content of heterochromatic regions was different.T. lasiotis specimens from two different localities differed in the morphology of the X chromosome due to the presence of a short heterochromatic arm. These chromosome types are apparently fixed in each population rather than maintained as a polymorphic variation. Phylogenetic analyses supported the monophyly of the genusThalpomys but was not capable of elucidating its phylogenetic relationship to other Akodontini rodents. These analyses also showed inter-individual variation inT. lasiotis, even within a given population. Phylogenetic analyses placedT. lasiotis specimens with different karyotypes in different monophyletic branches. Molecular and karyologic data confirmed the identity of the genusThalpomys.     

Chromosome markers in Mus musculus: Differences in C-banding between the subspecies M. m. musculus and M. m. molossinus

Quinacrine (Q-band) and centromeric heterochromatin (C-band) patterns of metaphase chromosomes of two subspecies of Mus musculus were compared. M. m. musculus (the laboratory mouse) and M. m. molossinus (a subspecies from Southeast Asia) had similar Q-band patterns along the length of the chromosomes, but differences were observed in the centromeric region of some chromosomes. The two subspecies had very different distributions of C-band material. Antibodies to 5-methylcytosine were bound to regions of the chromosome corresponding to the C-bands in each animal. These findings support the idea that satellite DNA, which is concentrated in the C-band region, changes more quickly than bulk DNA. The interfertility of these two subspecies permits the development of a musculus strain carrying normal marker chromosomes for genetic studies.     

Highly repeated DNA analysis and systematics of the Lemuridae,a family of Malagasy prosimians

Hybridization of highly repeated DNA sequences ofEulemur fulvus mayottensis, Lemur catta, andVarecia has been performed on blots of different species of Lemuridae (L. catta, Hapalemur griseus, Varecia variegata variegata, V. v. rubra, E. macaco macaco, E. coronatus, E. mongoz, andE. rubriventer). The probe ofE. fulvus only hybridized with the differentEulemur species, whereas that ofVarecia hybridized with the two subspecies ofVarecia and that ofL. catta with bothL. catta andHapalemur. These results were used to confirm the classification ofVarecia in a separate genus and to review the separation of theL. catta/Hapalemur group from the other species ofEulemur. Comparison of the migration patterns from DNA fragments of these different species has been used to propose a cladogram of the differentEulemur species.     

Chromosome homology in the climbing rats,genus tylomys (Rodentia: Cricetidae)

The climbing rats (Tylomys spp.) have diploid numbers of 52 (T. panamensis), 42 (T. nudicaudus), 40 (T. n. gymnurus) and 36 (T. n. villai). Using G-band analysis we found that the variations are mainly of the Bobertsonian type, and practically all changes can be traced. G-banding also revealed that biarmed chromosomes with similar morphology may be composed of different components. Such conclusions were verified also by analysis of the chromosomes of interspecific hybrids. C-band staining showed that the constitutive heterochromatin of Tylomys is mainly located in the centromeric regions and the sex chromosomes, a situation similar to that of Microtus agrestis. In one specimen of T. panamensis, however, an additional terminal heterochromatic segment was found in one member of the large metacentric pair. Our data underline that in mammalian cytotaxonomy studies both C- and G-band (or C- and Q-band) techniques must be applied to gain maximal information.     

Synaptonemal complex analysis of heteromorphic trivalents in Lemur hybrids

Synaptonemal complexes (SCs) in surface spread pachytene spermatocytes of Lemur resemble those in other mammals and are of two types: metacentric (or submetacentric) and acrocentric, with a very short second arm. In autosomal SC and mitotic karyotypes of Lemur fulvus (2n=60) a 11 proportionality in relative length is observed as in other mammals. In an intraspecific lemur hybrid (2n=55) obtained by mating L. fulvus rufus (2n=60) x L. fulvus collaris (2n=51), G-band patterns show that 10 single acrocentric mitotic chromosomes correspond to the arms of 5 single metacentrics, implying homology. It is inferred that the metacentrics have evolved by centric (Robertsonian) fusion of the acrocentrics. In the SC karyotype of the hybrid all SCs are normal except for five which have the configurations expected of metacentric-acrocentric trivalents. Similarly, in L. f. collaris (2n= 51), with one unpaired metacentric and two unpaired acrocentrics, one such SC trivalent is present in the complement. In an SC trivalent, each of the acrocentric long axes is synapsed with an arm of the metacentric axis, confirming the homology predicted from banding similarities. At late zygotene, the acrocentric short arms, which are non-homologous, are the last to pair, demonstrating that synapsis of the homologous arms occurs first. At later pachytene the acrocentric short arms are fully synapsed, producing a short SC side arm. This subsequent non-homologous synapsis is taken to be an instance of the synaptic adjustment phenomenon which has been shown to lead to non-homologous synapsis in a duplication and several inversions in the mouse. The kinetochore of the metacentric is the same size as those of the acrocentrics, and thus is unlikely to have arisen by true centromeric fusion, but rather by a translocation. The kinetochores of the acrocentrics always lie together on the same side of the metacentric kinetochore (cis configuration), implying a single pairing face on the metacentric axis. The observed trivalent configuration may well constitute a prerequisite for proper meiotic disjunction in metacentric-acrocentric heterozygotes. Such a mechanism is consistent with fertility regularly observed in such hybrid lemurs.     

Precise karyotyping of carrot mitotic chromosomes using multicolour-FISH with repetitive DNA

Carrot (Daucus carota L.) chromosomes are small and uniform in shape and length. Here, mitotic chromosomes were subjected to multicolour fluorescence in situ hybridization (mFISH) with probes derived from conserved plant repetitive DNA (18-25S and 5S rDNA, telomeres), a carrot-specific centromeric repeat (Cent-Dc), carrot-specific repetitive elements (DCREs), and miniature inverted-repeat transposable elements (MITEs). A set of major chromosomal landmarks comprising rDNA and telomeric and centromeric sequences in combination with chromosomal measurements enabled discrimination of carrot chromosomes. In addition, reproducible and unique FISH patterns generated by three carrot genome-specific repeats (DCRE22, DCRE16, and DCRE9) and two transposon families (DcSto and Krak) in combination with telomeric and centromeric reference probes allowed identification of chromosome pairs and construction of detailed carrot karyotypes. Hybridization patterns for DCREs were observed as pericentromeric and interstitial dotted tracks (DCRE22), signals in pericentromeric regions (DCRE16), or scattered signals (DCRE9) along chromosomes similar to those observed for both MITE families.     

Karyotype of the rare Johnston’s genet<Emphasis Type="Italic">Genetta johnstoni</Emphasis> (Viverridae) and a reassessment of chromosomal characterization among congeneric species

We present herein new data on karyotypes of members of the genusGenetta. G- and C-banded chromosomes of the Johnston’s genetGenetta johnstoni Pocock, 1908 (2n = 50 / FNa = 92) are described for the first time, and compared with those ofG. genetta (2n = 54 / FNa = 92). In addition, the standard karyotype ofG. maculata (2n = 52 / FNa = 96) was studied. A reassessment of taxonomic attribution of previously published material allowed us to characterize (2n, FNa, and chromosome morphology) the karyotypes of three genets, previously unknown (G. pardina, G. letabae andG. tigrina). Our results show that despite a rather low interspecific variability in 2n and FNa, all the species of genets (exceptG. pardina andG. maculata) appear differentiated when chromosomal morphology is taken into account. Although chromosomal banding data are limited, confrontation of G-band karyotypes with preliminary molecular phylogenetic results reveals that karyotypic evolution within the genusGenetta might involve various rearrangements like Robertsonian and tandem translocations, pericentric inversions, and centromere fissions; thus providing at least for some taxa a solid postzygotic isolation. Finally, our study suggests that cytogenetic analyses might constitute a useful tool for questioning interspecific boundaries, especially within the taxonomically debated complex of large-spotted genets.     

Karyotypic conservation in the mammalian order monotremata (subclass Prototheria)

The order Monotremata, comprising the platypus and two species of echidna (Australian and Nuigini) is the only extant representative of the mammalian subclass Prototheria, which diverged from subclass Theria (marsupials and placental mammals) 150–200 million years ago. The 2n=63, 64 karyotype (newly described here) of the Nuigini echidna is almost identical in morphology and G-band pattern to that of the Australian echidna, from which it diverged about a million years ago. The karyotype of the platypus (2n=52) has several features in common with those of the echidna species; six pairs of large autosomes, many pairs of small (but not micro-) chromosomes, and a series of small unpaired chromosomes which form a multivalent at meiosis. Comparison of the G-band patterns of platypus and echidna autosomes reveals considerable homology. Chromomycin banding demonstrates GC-rich heterochromatin at the centromeres of many platypus and echidna chromosomes, and at the nucleolar organizing regions; some of this heterochromatin C-bands weakly in platypus (but not echidna) spreads. Late replication banding patterns resemble G-banding patterns and confirm the homologies between the species. Striking heteromorphism between chromosomes of some of the large autosomal pairs can be accounted for in the echidna by differences in amount of chromomycin-bright, late replicating heterochromatin. The sex chromosomes in all three species also bear striking homology, despite the difference in sex determination mechanism between platypus (XX/XY) and the echidna species (X₁X₁X₂X₂/X₁X₂Y). The platypus X and echidna X₁ each represent about 5.8% of haploid chromosome length, and are G-band identical. Y chromosomes are similar between species, and are largely homologous to the X (or X₁).     

Feeding behavior ofLemur catta andLemur fulvus

The feeding behavior of two sympatric species of lemurs, Lemur cattaand Lemur fulvus,was studied in an enclosure simulating a natural habitat at the Duke University Primate Center. L. fulvusspent less time feeding during the day than L. catta.But the former species ate more fruit and had longer feeding bouts on preferred food items than L. catta.They also had a shorter food passage time than L. cattaand their choice of resting places was more influenced by food distribution. Furthermore, the two lemur species ate parts of different plant species and showed different reactions to chemical plant components. According to these results, L. fulvusis a more conservative feeder than L. catta.These interspecific differences in feeding behavior may be one of a number of differences that allow the two species to coexist. In allopatry, however, L. fulvusmay also adopt feeding patterns similar to those of L. catta.But L. cattawas never found to change its feeding strategies in different areas. It may be this option of L. fulvusto adopt different feeding strategies in different situations that allows this species to have the widest range of all Malagasy lemurs. Duke University Primate Center Publication No. 259.     

Structural organization of the heterochromatic region of human chromosome 9

Giemsa-11, G-banding and Lateral Asymmetry staining techniques were used to define the substructure of the C-band heterochromatin of human chromosome 9, in a sample of 108 different chromosomes 9, from 54 individuals. In this sample, the juxtacentromeric portion of the C-band region stained positive by the G-banding technique while Giemsa-11 delineated a more distally located block. Examination of the pericentric inversions generally revealed that the entire C-band region is changed with the substructural organization left intact; i.e. the G-band is proximal, the G-11 distal to the centromere. The partial pericentric inversions were found to have larger than average amounts of G-band heterochromatin on the short arm. The G-11 staining was in its usual position on the long arm with none on the short arm. Such apparent inversions therefore may not represent true inversions. — Long heterochromatic regions frequently had a segmented appearance when stained with G-11; there was a dark G-band within the pale heterochromatic region when stained with the G-banding technique which corresponded in location to the achromatic gap produced by G-11. This extra G-band may have been derived from the juxtacentromeric G-band by processes analogous to unequal crossing over. — Simple lateral asymmetry was consistently present only in the G-band heterochromatin of those chromosomes 9 containing large blocks of G-band positive material. Examination of the portion of the C-band which would correspond to the G-11 positive material revealed no consistent patterns of asymmetry. Usually both strands were heavily stained and symmetrical but occasionally there were light areas present on one strand suggestive of compound lateral asymmetry.     

Weitere Untersuchungen über Chromosomenverhältnisse und DNS-Gehalt bei Anuren (Amphibia)

The karyotypes of the toad Bufo marinus L. (2n=22) and the frogs Limnodynastes tasmaniensis Gthr. (2n=24), Rana temporaria L., R. esculenta L. (both 2n=26) and R. arvalis Nills. (2n=24) were analysed in colchicine treated leukocyte and spermatogonial metaphases and/or embryonic and larval mitoses. The DNA content of Feulgen stained erythrocyte nuclei was measured microspectrophotometrically. Heteromorphic sex chromosomes are absent in all species. L. tasmaniensis has the lowest DNA content among these species. The south American toad B. marinus shows a karyotype similar to the other known toad species and contains the same amount of DNA as the European species B. calamita with the lowest DNA amount among the European toads. In southern German populations of R. temporaria besides animals with the “standard”-karyotype (2n=26) individuals with 1 or 2, in rare cases with 3 or 4 supernumerary chromosomes have been found. The supernumeraries are heterochromatic and smaller than the smallest chromosome of the “standard”-karyotype. If only 1 or 2 supernumerary chromosomes are present, they seem to show normal mendelian inheritance as a rule. The observation of a few tadpoles with intraindividual different numbers of supernumeraries points to the occurrence of unequal distribution of these chromosomes in individuals containing a higher number of supernumerary chromosomes. The karyotype of R. esculenta is very similar to the “standard”-karyotype of R. temporaria, but the chromosomes of R. esculenta are somewhat longer than those of R. temporaria. R. esculenta contains about 54% more DNA than R. temporaria in the erythrocyte nuclei, so that it must be assumed that all chromosomes of R. esculenta contain more DNA than their homologues in R. temporaria. R. arvalis possesses about 28% more DNA than R. temporaria. It is supposed that these interspecific differences in DNA content of the Rana species — as observed earlier in Bufo species — are not a consequence of differential polyteny but are caused during evolutionary processes by local increase in DNA in the chromosomes of R. esculenta and R. arvalis.     

Constitutive heterochromatin,G-bands and nucleolus-organizer regions in four species of Didelphidae (Marsupialia)

Chromosomes of Didelphis albiventris, D. marsupialis, Philander opossum and Lutreolina crassicaudata, four species of marsupials with very similar karyotypes and 2n=22 were studied. All the chromosomes were acrocentrics except the X in L. crassicaudata, which is a metacentric.The G-band patterns of these species are similar but the distribution of constitutive heterochromatin differs among them as shown by C-banding. The hypothesis that the X in L. crassicaudata might be an isochromosome derived from the acrocentric X in the other species is discarded since G-and C-banding patterns differ in the two arms.In D. marsupialis the Ag-NORs are terminal and located in both arms of one pair and in the long arms of two pairs of medium-sized autosomes. In P. opossum the NOR-bearing chromosomes could be precisely identified through simultaneous silver staining and G-banding. The Ag-NORs are terminal and located at the short arm of pair 5 and the long arm of pair 7.     

Chromosome banding study of the golden loach,Sabanejewia aurata balcanica from Slovakia (Cobitidae)

The karyotype of a subspecies of the golden loach,Sabanejewia aurata balcanica from eastern Slovakia was studied by conventional Giemsa staining, Ag-NOR staining, and C-banding. The diploid chromosome number was 2n = 50. The karyotype comprised 2 pairs of metacentric, 6 pairs of submetacentric and 17 pairs of subtelocentric to acrocentric chromosomes. Both metacentric pairs and 2 large subtelocentric pairs had massive pericentromeric blocks, while all other elements had only weak blocks of heterochromatin. The NORs were localized on the short arms of one middle-sized subtelocentric pair. The karyotype ofS. a. balcanica differs from that ofS. aurata kubanica, suggesting chromosomal polymorphism of this widely distributed, polytypic cobitid species. The polymorphic karyotypes of the golden loach may thus demonstrate transient stages, linking primitive and advanced cobitid karyotypes.     

Comparative karyology of species of the genera <Emphasis Type="Italic">Misgurnus</Emphasis> and <Emphasis Type="Italic">Cobitis</Emphasis> (Cobitidae) from the Amur River Basin in connection with their taxonomic relations and the evolution of karyotypes

Data are first provided on karyotypes of four species of Cobitidae from the Amur Basin: Misgurnus nikolskyi (2n = 50 = 10m + 4 sm + 36sta, NF = 64), Cobitis lutheri, (2n = 50 = 12m + 8sm + 30sta, NF = 70), C. choii (2n = 50 = 8m + 10sm + 8st + 24a, NF = 68), and C. melanoleuca (2n = 50 = 6m + 16sm + 28sta, NF = 72), and number of chromosomes in M. mohoity (2n = 50) and karyotypes of C. melanoleuca from the basin of the Don, Malyi and Bol’shoi Uzen rivers, and Selenga. These data are discussed in connection with problems of taxonomy of the studied genera, as well as the evolutionary relations of their karyotypes. On the basis of karyological differences between the populations of C. melanoleuca from different parts of the range, a new subspecies C. melanoleuca gladkovi subsp. nov. that inhabits waters of Europe is described.     

Codominant autosomal inheritance of polymorphic red cell acid phosphatases of lemurs and some properties of the enzymes

Red cell acid phosphatase phenotypes of 207 captive animals of the genera Lemur, Hapalemur, and Propithecus were determined by starch gel electrophoresis and phosphatase-specific staining. In Lemur fulvus, three phenotypes, designated A, B, and AB, were observed. In each of the species L. catta, L. macaco, L. mongoz, and L. variegatus, a single phenotype was observed. In Hapalemur griseus, three phenotypes were found: A, B, and AB. In Propithecus verreauxi, a single phenotype was found. Examination of breeding records in conjunction with the results of the electrophoretic analyses supports the conclusion that the erythrocytic acid phosphatases in this group of nonhuman primates are the products of at least two codominant autosomal alleles. There is a wide range of specific activities of the acid phosphatases as determined by colorimetric assays. The values range from 60.6 moles of p-nitrophenol released per gram of hemoglobin per 30 min in Lemur catta to 429.1 moles in Propithecus verreauxi. The enzymes of L. fulvus and P. verreauxi were purified approximately 400-fold, and Michaelis-Menten constants were determined on the purified preparations. For L. fulvus phenotype A, K _m =0.8 mM; for L. fulvus phenotype B, K _m =0.8 mM; and for P. verreauxi, K _m =0.6 mM; the substrate in each case was p-nitrophenylphosphate.The work reported here was taken in part from a doctoral dissertation submitted by G.A.M. to the Graduate School of Duke University in partial fulfillment of the requirements for the Doctor of Philosophy degree. This work was supported by grants from the National Science Foundation (Nos. GS 39635X and BNS-74-02504), the USPHS (fellowship to G.A.M., No. GM-02007), and the Wenner-Gren Foundation (No. 2697).     

C-banding patterns in the AustralianBulbine (Liliaceae): The perennial group,B. bulbosa s. lato

C-banding studies support earlier evidence thatB. bulbosa, as a previously circumscribed, is heterogeneous, consisting of three distinct entities: (1) theB. bulbosa complex (B. bulbosa s. str.) at 4x (2n = 24), 8x (2n = 48) and 12x (2n = 72) ploidy levels, (2) the rock lily and (3) the Kroombit population (both 2n = 46). Each of these three main groups has a distinctive banding profile, though centromeric and telomeric dot bands, variably expressed, are common to all. In theB. bulbosa complex, substantial heterochromatin development, apart from bands associated with the NORs on chromosomes 1 L, 2 S and 3 L, occurs only at the terminal regions of the short arms of the large and middlesized acrocentric chromosomes, with considerable polymorphic and polytypic variation in the number and size of the heterochromatic blocks, especially at the 4x level. Queensland 8xB. bulbosa populations differ in having terminal heterochromatin, probably associated with NORs, on 11 S and 12 S, and in having some strong interstitial bands. The differences appear to correlate with attributes relating to flower morphology, and may have systematic significance. The karyotypes of rock lily and Kroombit are somewhat similar but the former has a characteristic C-band profile with multiple interstitial bands on chromosomes 1–5 and 7–9, whereas the latter has only one interstitial band on chromosome 9.First contribution of a series on cytoevolution in the AustralianBulbine. Two introductory papers in Austral. J. Bot.34 (2)     

Cytogenetic analysis of four species of the genus Alsodes (Anura: Leptodactylidae) with comments about the karyological evolution of the genus

A comparative cytogenetic analysis of Alsodes pehuenche, A. vanzolinii, A. verrucosus and A. aff. vittatus show that all four species share the same diploid number 2n = 26; the fundamental number is 50 in A. vanzolinii and 52 in A. aff. vittatus, A. pehuenche and A. verrucosus. The karyotypes of A. pehuenche and A. aff. vittatus are described for the first time; the C-band patterns, the NOR locations and Q-band patterns are also described for the first time for the four species. C-band patterns are species specific and useful to identify the taxa. The usefulness of the chromosomal data in taxonomy and systematics of Alsodes species is discussed. Transformation of euchromatin into heterochromatin and centric fissions and translocations are proposed as the main mechanisms that govern the chromosomal evolution of the frog genus Alsodes.