Karyotype of Callithrix mauesi (Callitrichidae,Primates) and its relations with those of C. emiliae and C. jacchus

A study was conducted on the most recently described marmoset species, Callithrix mauesi, and the results obtained were compared to those previously reported for the karyotypes of C. jacchus and C. emiliae. No mechanism of chromosome rearrangement differentiates the karyotypes of C. mauesi (2n = 44) and C. emiliae (2n = 44), which diverge from C. jacchus (2n = 46) by a Robertsonian translocation and a paracentric inversion. C. mauesi, like C. emiliae, presents telomeric constitutive heterochromatin in various chromosomes, forming large heterochromatic blocks in some. This does not occur in C. jacchus, which basically presents centromeric constitutive heterochromatin. The karyotype of C. mauesi differs from that of C. emiliae only by the amount and distribution of this telomeric constitutive heterochromatin. One of the chromosomes presenting a heterochromatic block in C. mauesi is chromosome X, a fact not previously reported in the Order Primates. The present chromosome data show that C. mauesi is closer to C. emiliae than to C. jacchus, in agreement with its inclusion in the C. argentata group. In the present paper, we describe for the first time, at the chromosome level, chimerism between fraternal twins of the same sex (XY/XY), with the heterochromatic block of pair 2 being the marker. © 1994 Wiley-Liss, Inc.     

Chromosomal evolution inCallithrix emiliae

We studied the karyotype of specimens ofCallithrix emiliae (Callithricidae, Primates) from Rondonia, Brazil. Comparison with the karyotype ofCallithrix jacchus showed that, even though these two species show many karyotypic similarities, they differ by a Robertsonian translocation, a paracentric inversion and large-scale addition of heterochromatin. TheC. emiliae species appears to be in an active phase of chromosome evolution by the addition of constitutive heterochromatin.     

Chromosome studies of Saguinus midas niger (Callithricidae,Primates) from Tucurui,Para, Brazil: Comparison with the karyotype of Callithrix jacchus

The karotype of Saguinus midas niger was studied by G-, C-, and nuclear organizer region (NOR)-banding techniques. Variations in C-banding patterns were observed in some chromosomes. The banding patterns obtained were compared with those previously described for Callithrix jacchus. The two species differ by a reciprocal translocation involving pairs 9 and 16; by a paracentric inversion in chromosomes 1, 13, 14, 18, and 22; and by a pericentric inversion in at least four subtelocentric pairs (chromosomes 19, 20, 21, and 22), dislocating the nucleolar organizer region from the small short arm in C. jacchus to the proximal segment of the long arm in S. m. niger (or vice versa). The amount of constitutive heterochromatin is greater in S. m. niger than in C. jacchus, especially in chromosomes 4, 7, and 14. The Y chromosome is smaller in C. jacchus than in S. m. niger.     

Comparative chromosomal study of five taxa of genus Callithrix,group Jacchus (Platyrrhini,primates)

The karyotypes of four marmoset species of the Callithrix jacchus group (C. aurita, C. kuhlii, C. geoffroyi, and C. penicillata) were investigated. The patterns of G-, C-, and NOR-bands of these karyotypes were compared with those of C. jacchus, previously described, in order to clarify the taxonomic relationships of this species group. All species present 2n = 46, 14 uni- and 30 biarmed autosomes, a median size submetacentric X chromosome, and the same NOR-band patterns. No rearrangement or constitutive heterochromatic variation differentiate these species, which differ only in the morphology of the Y chromosome. The data obtained indicate that, from the chromosomal point stand, the marmoset species of C. jacchus group constitute a homogeneous clade. Am J Primatol 41:53–60, 1997. © 1997 Wiley-Liss, Inc.     

Chromosome Studies in Callitrichidae (Platyrrhini): A Comparison Between Callithrix and Leontopithecus

Chromosome studies in 20 Callithrix jacchus, 1 Callithrix flaviceps, and 1 Leontopithecus rosalia chrysomelas revealed evidence of chimerism in C. jacchus and L.r. chrysomelas, and the existence of a variant Y chromosome type in C. jacchus. Constitutive heterochromatin in C. jacchus was limited to the centromere region of the chromosome complement, and only in small amounts. A comparison between the G-band karyotypes of C. jacchus and L.r. chrysomelas showed clear similarities between species. Three structural rearrangements have probably occurred during phylogeny in the common ancestor from which these extant species later derived. The chromosome number of C. flaviceps was found to be 46.     

Chromosome comparison among five species of platyrrhini (Alouatta caraya,Aotus azarae,Callithrix jacchus,Cebus apella,andSaimiri sciureus)

Karyotypes of 82 individuals from five Platyrrhini species (Alouatta caraya, Aotus azarae, Callithrix jacchus, Cebus apella, andSaimiri sciureus) were studied and compared using a G-banding technique. Cytogenetic analysis showed full chromosome or full arm homologies among these geographically neighbouring species. A small number of chromosomal rearrangements (inversions, deletions, and translocations) could be detected among these taxa. These five species are closely related in chromosomal evolution. An interesting correspondance was found betweenCebus apella chromosomes and those of the other four species.Alouatta caraya andCebus apella are the closest species.Callithrix jacchus andAotus azarae would have the most separated karyotypes.     

Social implications of gummivory in marmosets

Gummivory or exudate feeding is a major dietary specialization which has received relatively little attention in the literature. While plant exudates contribute to the diet of many primate species, we suggest that the callitrichid species Cebuella pygmaea and Callithrix jacchus are obligate exudate feeders under free-ranging conditions. Callithrix jacchus provides an excellent model for examining the effects of exudate feeding and foraging upon social behavior, since other callitrichid species of similar body size do not share this dietary specialization. We review the effects of exudate foraging on specific social behaviors observed both in field and laboratory populations of C. jacchus. By comparing this species to closely related species, exudate foraging is seen to (1) be retained under laboratory conditions, (2) increase the frequency of territorial marking behavior while decreasing the frequency of overt aggression in males, (3) decrease the duration of infant care, and (4) increase the number of nonadults in social groups but not affect group size. The evidence presented supports the hypothesis that the consequences of exudate foraging in C. jacchus are fundamental and socially complex. © 1994 Wiley-Liss, Inc.     

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.     

Proposed chromosomal phylogeny for the South American primates of the Callitrichidae family (Platyrrhini)

Cytogenetic and cytotaxonomic studies (G, C, sequential G/C, and NOR banding) were performed on 110 specimens representing the four genera of South American primates of the family Callitrichidae: Cebuella (C. pygmaea), Callithrix, groups argentata (C. argentata, C. emiliae, C. chrysoleuca, C. humeralifera, C. mauesi), and jacchus (C. aurita, C. geoffroyi, C. jacchus, C. kuhli, C. penicillata), Leontopithecus (L. chrysomelas, L. rosalia), and Saguinus (S. midas midas, S. m. niger). Mitotic chromosomes are characterized, and the rearrangements distinguishing the karyotypes of the taxa are inferred from arm homologies. The results were then converted into numerical data and submitted to cladistic analysis. The following conclusions were achieved: 1) Five karyotypic classes were observed, which correspond to the five taxa studied. Differences between them are as follows: a) Cebuella (2n = 44, 10 acrocentrics, A + 32 bi‐armed autosomes, bi) and the argentata group (2n = 44, 10A + 32bi) are different from each other due to a reciprocal translocation; b) both can be distinguished from the jacchus group (2n = 46, 14A + 30bi) by a centric fusion/fission rearrangement and a paracentric inversion; c) Leontopithecus (2n = 46, 14A + 30bi) and Saguinus (2n = 46, 14A + 30bi) differ from the jacchus group by a reciprocal translocation and three paracentric inversions; and d) Saguinus is different from the others by one paracentric inversion and pericentric inversions in at least four pairs of acrocentric autosomes. 2) The cladistic analysis separates Cebus (used as an outgroup) from the Callitrichidae groups, which forms a clade. Among the Callitrichidae, marmosets (Cebuella and Callithrix) form a sub‐clade, Cebuella and the argentata group being more closely related to each other than both are to the jacchus group. Tamarins (Leontopithecus and Saguinus) are also quite close, so that if one was not derived from the other, they with the marmosets share a common ancestor. Among the tamarins, Leontopithecus is karyotypically closest to the marmosets, specifically to the jacchus group. 3) Based on the chromosome information and considering the possible direction of the evolutionary changes (primitivity or phyletic dwarfism hypothesis, previously advanced by other authors), it was possible to propose the ancestral karyotypes and to develop two alternatives for the origin, differentiation and dispersion of the callitrichid. Both proposals are plausible, but when the geographical distribution is considered, the phyletic dwarfism hypothesis seems to be the most probable. Am. J. Primatol. 49:133–152, 1999. © 1999 Wiley‐Liss, Inc.     

Cold-sensitive chromosome regions and heterochromatin inCestrum (Solanaceae):C. strigillatum,C. fasciculatum,andC. elegans

Cold-induced mitotic under-condensation of certain chromosome segments is a rare phenomenon in plants. There are about 11 genera of monocotyledons and only 3 of dicotyledons, where species are known to have such cold-sensitive regions (CSRs). The molecular causes of cold-induced undercondensation are not clear, and no consistent cytochemical characteristics of CSRs are known. Recently we have presented a chromosome banding analysis on CSRs and their relation to constitutive heterochromatin inCestrum parqui (Solanaceae), a species of sect.Cestrum. The present study is concerned with a similar analysis inC. strigillatum of sect.Cestrum, and inC. fasciculatum andC. elegans of sect.Habrothamnus. Chromomycin/DAPI fluorescent double staining, sequential C-banding, and sequential silver impregnation were applied. The species differ in detail but are similar qualitatively. Four classes of heterochromatin can be discriminated. (1) CSRs, with banding properties indicating AT-rich constitutive heterochromatin. After cold-treatment CSR heterochromatin can be silver-impregnated from interphase, as chromocentres, to metaphase, as undercondensed segments. CSRs are subject to frequent heteromorphy. (2) Nucleolar organizers. Two pairs were identified in the karyotypes. Banding properties indicate GC-rich heterochromatin. The nucleolar organizing regions are less evident and their silver-reducing capability reduces during metaphase. (3) Non-nucleolar CMA-positively fluorescing bands. These are minute, polymorphic, positively C-stained, and restricted to one or a few sites in the karyotypes. (4) Indifferently fluorescing, positively C-stained bands. They occur on centromeres, some chromosome ends, and clustered over the chromosome arms. They are mostly very delicate and do not resist harsh banding treatments. — The species investigated here andC. parqui resemble each other qualitatively in heterochromatin classes (1), (2), and (3), but differ much in banding properties of class (4). Therefore, heterochromatin characteristics in the genus are not so uniform as the present results inC. strigillatum, C. fasciculatum, andC. elegans appear to show.     

Characterization of constitutive heterochromatin of Callithrix geoffroyi (Callitrichidae, Primates) by restriction enzymes and fluorochrome bands

The neotropical primate genus Callithrix comprises two groups of species, jacchus and argentata, which inhabit distinct geographical regions and manifest different fur coloration and constitutive heterochromatin (CH) markers in their karyotypes. In this investigation the CH of a representative of the jacchus group, Callithrix geoffroyi, was analysed using fluorochromes and restriction enzymes in situ. To clarify the source of the constitutive heterochromatin of both groups, the data obtained in the jacchus group were compared with those published in the argentata group obtained by the same techniques. The C-bands of C. geoffroyi (four specimens, 2n = 46) were centromeric in all chromosomes, and distally located in pairs 6 and 22. The Alu I, Hae III, Hin fI, Rsa I, Dde I, Mbo I, and Msp I restriction endonucleases and CMA3 and DAPI fluorochromes produced different bands, which allowed the characterization of four distinct types of constitutive heterochromatin in the C. geoffroyi genome. Several of these types of heterochromatin were present in the ancestor of the two groups of species, jacchus and argentata, while others originated after their cladogenesis.     

Cytogenetic studies of two land-planarian species from Brazil: Geoplana marginata and Issoca rezendei (Tricladida,Terricola)

The chromosome complement and the C-banded karyotypes of specimens of Geoplana marginata auct. and of Issoca rezendei (Schirch) were investigated. The diploid and fundamental numbers of the two species were identical (2n = 14; FN = 28). Their karyotypes were similar except for the morphology of chromosome pair 6. Their C-banding patterns differed in quantity and localization of the constitutive heterochromatin. The similarity in karyotypes of these species support the hypothesis, proposed earlier on morphological grounds, that the genera Geoplana Stimpson and Issoca Froehlich are closely related. G. marginata and I. rezendei are the first land planarian species of the Neotropical Region to have their karyotypes described.     

Comparison of infant care in family groups of the common marmoset (Callithrix jacchus) and the cotton-top tamarin (Saguinus oedipus)

The involvement of parents and siblings in infant care in similarly composed groups of common marmosets (Callithrix jacchus) and cotton-top tamarins (Saguinus oedipus) was compared during the infants' first 8 weeks of life. The results indicate an earlier infant independence in C. jacchus than in S. oedipus due primarily to a more frequent rejection of carried infants in C. jacchus. There was no species difference in extent of maternal involvment in carrying infants. However, S. oedipus fathers carried infants significantly more often during weeks 5–8 than did C. jacchus fathers. Siblings were generally more involved in infant care at an earlier infant age in C. jacchus than in S. oedipus.     

The functional correlates of jaw‐muscle fiber architecture in tree‐gouging and nongouging callitrichid monkeys

Common (Callithrix jacchus) and pygmy (Cebuella pygmaea) marmosets and cotton‐top tamarins (Saguinus oedipus) share broadly similar diets of fruits, insects, and tree exudates. Marmosets, however, differ from tamarins in actively gouging trees with their anterior dentition to elicit tree exudates flow. Tree gouging in common marmosets involves the generation of relatively wide jaw gapes, but not necessarily relatively large bite forces. We compared fiber architecture of the masseter and temporalis muscles in C. jacchus (N = 18), C. pygmaea (N = 5), and S. oedipus (N = 13). We tested the hypothesis that tree‐gouging marmosets would exhibit relatively longer fibers and other architectural variables that facilitate muscle stretch. As an architectural trade‐off between maximizing muscle excursion/contraction velocity and muscle force, we also tested the hypothesis that marmosets would exhibit relatively less pinnate fibers, smaller physiologic cross‐sectional areas (PCSA), and lower priority indices (I) for force. As predicted, marmosets display relatively longer‐fibered muscles, a higher ratio of fiber length to muscle mass, and a relatively greater potential excursion of the distal tendon attachments, all of which favor muscle stretch. Marmosets further display relatively smaller PCSAs and other features that reflect a reduced capacity for force generation. The longer fibers and attendant higher contraction velocities likely facilitate the production of relatively wide jaw gapes and the capacity to generate more power from their jaw muscles during gouging. The observed functional trade‐off between muscle excursion/contraction velocity and muscle force suggests that primate jaw‐muscle architecture reflects evolutionary changes related to jaw movements as one of a number of functional demands imposed on the masticatory apparatus. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc.     

Protein variation,taxonomy and differentiation in five species of marmosets (genusCallithrix Erxleben, 1777)

The electrophoretic patterns of 15 protein systems codified for 20 genetic loci were investigated using horizontal electrophoresis. A total of 150 blood samples, from five species of the genusCallithrix were analyzed. Polymorphic variation was observed in 10 out 20 loci analyzed. The genotypic distributions are in Hardy-Weinberg equilibrium. The average heterozygosity (H) varied from 1% to 5%, similar to those observed for other Neotropical primates. The genetic distance coefficients revealed a phylogenetic separation of these species into two groups: (1) “argentata” (C. humeralifer andC. emiliae); (2) “jacchus” (C. jacchus, C. penicillata, andC. geoffroyi). This arrangement is according to the taxonomic arrangement proposed byHershkovitz (1977),de Vivo (1988), andMittermeier et al. (1988). The results in each group are compatible with the subspecies values recorded for the Platyrrhini. These values showed that:C. humeralifer andC. emiliae are subspecies ofC. argentata;C. jacchus, C. penicillata, andC. geoffroyi are subspecies ofC. jacchus. These results also suggest thatC. j. geoffroyi is the “jacchus” group taxon, most similar genetically to the “argentata” group.     

Differential response of constitutive and facultative heterochromatin in the manifestation of mitomycin induced chromosome aberrations in Chinese hamster cells in vitro

The distribution of chromatid aberrations induced by mitomycin C among the individual chromosomes of female and male Chinese hamster cells in vitro was studied. The aberrations were found to be non-randomly distributed. Among the autosomes, the chromosomes possessing constitutive heterochromatin were more often involved in aberrations as well as in homologous exchanges. The inactivated X chromosomes in the female cells offer a situation where the short arm is facultatively heterochromatic and the long arm constitutively heterochromatic, thus enabling an analysis of their response for aberration formation. The short arm was seldom found to be involved in the aberration. The long arm of the inactivated X was more often affected (5 to 10 times) than the long arm of the functional X though both are constitutively heterochromatic. The possible role of (a) structure of heterochromatin, (b) the chromocenter formation and their association, (c) allocycly, and (d) the qualitative differences in the DNA of different types of heterochromatin are discussed in relation to the formation of chromatid aberrations.     

Chromosome plasticity in Ctenomys (Rodentia Octodontidae): chromosome 1 evolution and heterochromatin variation

A chromosome 1 (Cr1) pericentric inversion is described in six of seven species in the genus Ctenomys (tuco-tucos) from Uruguay. The inversion was inferred from G-band analyses of subtelocentric Cr1 hypothesised to be derived from the ancestral metacentric condition. Cr1 varies across species in heterochromatin amount and localisation including a metacentric chromosome without positive C-bands in C. torquatus, a subtelocentric chromosome with heterochromatic short arms in C. rionegrensis, and a subtelocentric chromosome negative after C-banding in five of the species analysed here. Pachytene chromosomes from C. rionegrensis, a species with the highest heterochromatin content, and C. torquatus, one of the species with the lowest heterochromatin content, were analysed in order to assess possible mechanisms of heterochromatin evolution. This analysis revealed the presence of three heterochromatic chromocenters in C. rionegrensis where bivalents converge, while in C. torquatus only one chromocenter was observed. In both species, highly repetitive DNA was observed, localised in chromocenters after “in situ” hybridisation. Heterochromatin associated protein M31 was localised in chromocenters of both species after immuno-detection. The spread of heterochromatin in Ctenomys chromosomes could be produced by chromatin exchanges at the chromocenter level. We propose the exchange of this DNA associated proteins between non-homologous chromosomes in pachytene to be the responsible for the spread of heterochromatin through the karyotypes of species like C. rionegrensis     

Effects of sibling-rearing experience on future reproductive success in two species of callitrichidae

The survival rate for offspring of mothers who either had or did not have previous experience rearing younger siblings was compared in two callitrichid species, Callithrix jacchus and Saguinus oedipus. Offspring of mothers with sibling-rearing experience had a higher survival percentage than offspring of inexperienced mothers in both species. While 50–60% of offspring of inexperienced C. jacchus mothers survived, no offspring of inexperienced S. oedipus mothers survived. The results suggest that sibling-rearing experience is necessary for adequate maternal behavior in S. oedipus, but not necessary to the development of maternal behavior in C. jacchus. Effects of previous sibling-rearing experience of S. oedipus fathers on offspring survival were also examined. Whether the father had rearing experience was not related to the survival of their offspring.     

Structural variability of human chromosome 9 in relation to its evolution

Summary Human chromosome 9 shows a high susceptibility for structural rearrangements, particularly pericentric inversions, which often are transmitted. Three types of pericentric inversions can be observed on No. 9: 1) Type I, showing the total constitutive heterochromatin in the short arm. 2) Type II with part of the C heterochromatin on the short arm, the rest located on the long arm proximal to the centromere. 3) Type III: a subtelocentric chromosome with part of the C heterochromatin in the very short arm and the rest located interstitially on the long arm. With these inversions as well as with other structural rearrangements, e.g. translocations, the break-points are located preferentially within the C heterochromatin or close to the heterochromatic-euchromatic junctions. These findings are in contrast to the findings in lymphocytes from 5 patients with Fanconi's anemia and after irradiation in vitro, reported in the literature. In lymphocytes break-points seem to be distributed more or less by chance. These observations together led us to speculate that human chromosome 9 primarily was an acrocentric chromosome; in morphology and at least in some functions similar to D-and G-group chromosomes. During evolution this acrocentric chromosome changed to a submetacentric one due to a pericentric inversion.The author is sponsored by the Deutsche Forschungsgemeinschaft.     

Constitutive heterochromatin variation in two species of rattus with apparently similar karyotypes

Rattus blanfordi and R. cutchicus medius both have a chromosome complement of 2n=36 and all chromosomes except the submetacentric Y of R. blanfordi are acrocentric. The apparently similar karyotypes of the two species, however, show variations in the nature and quantity of C-band-positive constitutive heterochromatin (C-heterochromatin) as revealed by C- and G-banding and Hoechst 33258 fluorescence. R. blanfordi with large-sized X and Y chromosomes and conspicuously larger centromeric heterochromatin in all the autosomes as compared to that of R. cutchicus medius has much more C-heterochromatin in its genome than the latter. The variation in the quantity of C-heterochromatin has been accomplished without altering the morphology of the acrocentric chromosomes unlike other mammals in which variations have been reported to result generally in the addition or deletion of a totally heterochromatic second arm.