A PCR-based marker to simply identify Saimiri sciureus and S. boliviensis boliviensis

Squirrel monkeys, mainly Saimiri sciureus and S. boliviensis, are common in zoos and widely used in biomedical research. However, an exact species identification based on morphological characteristics is difficult. Hence, several molecular methods were proposed, but all of them are expensive and require extensive laboratory work. In contrast, we describe an Alu integration, which is present in S. boliviensis boliviensis and absent in S. sciureus. Among analyzed S. b. peruviensis specimens various presence/absence patterns of the integration were detected indicating that this study population might have originated from a natural hybrid zone. Based on the size of the Alu element ( approximately 300 bp), the presence/absence pattern of the integration can easily be traced by PCR and followed by agarose gel electrophoresis.     

Disparate Data Sets Resolve Squirrel Monkey (Saimiri) Taxonomy: Implications for Behavioral Ecology and Biomedical Usage

Squirrel monkeys (Saimiri spp.) are the most commonly used neotropical (platyrrhine) monkeys in biomedical research; however, no consensus exists as to the phylogenetic relationships amongst geographic variants or whether these variants represent species or subspecies. Here we report a strongly supported squirrel monkey phylogeny, congruent across multiple data sets, including new field data and the first molecular (mtDNA) cladogram. These data support species-level classification for the three major groups in this study. Approximately the same amount of molecular divergence exists among Saimiri oerstedii, S. sciureus, and S. boliviensis. The S. sciureus/S. oerstedii ancestor diverged from S. boliviensis and shortly thereafter S. sciureus and S. oerstedii diverged. Until now, lack of a robust taxonomy has hindered exploitation of the massive potential of Saimiri for comparative studies. No other primate genus displays such widely divergent, genetically-based social behaviors. Our taxonomy also provides robust support for previous warnings against the widespread use of hybrid squirrel monkeys as research models.     

Pleistocene diversification of living squirrel monkeys (Saimiri spp.) inferred from complete mitochondrial genome sequences

In order to enhance our understanding of the evolutionary history of squirrel monkeys (Saimiri spp.), we newly sequenced and analyzed data from seven complete mitochondrial genomes representing six squirrel monkey taxa. While previous studies have lent insights into the taxonomy and phylogeny of the genus, phylogenetic relationships and divergence date estimates among major squirrel monkey clades remain unclear. Using maximum likelihood and Bayesian procedures, we inferred a highly resolved phylogenetic tree with strong support for a sister relationship between Saimiri boliviensis and all other Saimiri, for monophyly of Saimiri oerstedii and Saimiri sciureus sciureus, and for Saimiri sciureus macrodon as the sister lineage to the S. oerstedii/S. s. sciureus clade. We inferred that crown lineages for extant squirrel monkeys diverged around 1.5 million years ago (MYA) in the Pleistocene Epoch, with other major clades diverging between 0.9 and 1.1 MYA. Our results suggest a relatively recent timeline of squirrel monkey evolution and challenge previous conceptions about the diversification of the genus and its expansion into Central America.     

A survey for helminth parasites in feral New World non-human primate populations and its comparison with parasitological data from man in the region

A survey for helminth parasites in feral New World non-human primates was conducted and compared with parasitological data from man in the region. A total of 835 fecal samples were collected from feral Aotus nancymae, A. vociferans, Saguinus labiatus, S. mystax, Saimiri boliviensis peruviensis, S. sciureus macrodon, Lagothrix lagotricha and Cacajao calvus rubicundus. In addition, adult parasites were collected from necropsies performed on monkeys that died during quarantine and in captivity. Helminth parasites shared by non-human primates and man in Peru were Ancylostoma braziliensis and Ascaris lumbricoides, found in a captive L. lagotricha; Necator americanus, found in a captive C. calvus rubicundus; Hymenolepis diminuta, found in feral Aotus spp. and S. mystax; and a single Trichuris spp. specimen found in a feral S. sciureus macrodon.     

The mobile nature of acrocentric elements illustrated by three unusual chromosome variants

Variant chromosomes are polymorphic in areas that are rich in repeat sequences such as the pericentromeric regions or in the acrocentric short arm regions. The dynamic nature of these regions is evident in the polymorphisms they exhibit. In this paper three unusual variants are described: a chromosome 21 with additional material on its short arm, a chromosome 7 with an insertion in the short arm and a chromosome 2 with satellites at the end of the long arm. All three variants were shown to involve acrocentric elements using special banding techniques and fluorescence in situ hybridization. The 21 variant was found to be a tricentric with a 21 and two 15 alpha-, two classical and three acrocentric beta-satellite signals interspersed by AgNOR-positive regions. The telomeres were present at the two terminal ends. The insertion on chromosome 7 was found to be C-band positive and to contain acrocentric beta-satellite DNA. However, acrocentric alpha-satellite, classical satellite, whole-chromosome-painting or all-telomeres sequence probes did not hybridize to the insertion. The satellited region of chromosome 2 had two C-bands, a small positive all-centromeres probe signal, and two signals for the beta-satellite probe. Sandwiched between the beta-satellite sequences was an AgNOR-positive region. The telomeres were present at the two ends of the satellited chromosome 2. Chromosome 2 subtelomeric probes hybridized to the terminal ends of the short and long arm of chromosome 2. The common thread in these three variants is the involvement of acrocentric short arm elements. The acrocentric short arm elements are shown to move to other acrocentric or nonacrocentric chromosomes and relocate to both terminal and interstitial positions. The integrations are stable and heritable. Received: 23 September 1997 / Accepted: 23 February 1998     

Fluorescence in situ hybridization (FISH) maps chromosomal homologies between the dusky titi and squirrel monkey

The Platyrrhini are one of the most karyologically derived groups of primates and the evolution of their karyotypes is far from understood. The identification of the origin and direction of chromosome rearrangements will contribute to a better understanding of New World monkey phylogeny, taxonomy, and evolution. We mapped homology and identified translocations in the chromosomes of the dusky titi monkey (Callicebus moloch, 2n = 50) and the squirrel monkey (Saimiri sciureus, 2n = 44) by fluorescence in situ hybridization (FISH) of human chromosome paints. The hybridization results established chromosomal homologies between these New World primates, humans, other primates, and more distantly related mammalian species and show that both species have highly rearranged karyotypes. The total number of hybridization signals was 37 in C. moloch and 40 in S. sciureus, which is in the range of most comparisons of human chromosomes with phylogenetically more distant species outside of the primate order. Parsimony analyses of outgroup painting patterns allowed us to propose an ancestral karyotype for New World monkeys consisting of 2n = 56 with homologs to the following human chromosomes or chromosome segments: 1b; 1c; 2a; 2b; 3a; 3b; 3/21; 4; 5; 6; 7; 8a; 8/18; 9; 10a; 10/16; 11; 12; 13; 14/15; 15a; 16a; 17; 19; 20; 22; X; Y. Associations 8/18 and 10/16 are derived ancestral associations for all Platyrrhini. A 2/16 association found in S. sciureus and C. moloch was also seen in Ateles geoffroyi and Cebus capucinus; a 5/7 association in S. sciureus was present in A. geoffroyi, C. capucinus, and Alouatta belzebul. Other associations seen in the dusky titi monkey or the squirrel monkey are probably automorphisms. Comparison with chromosome phylogenies based on R-banding [Dutrillaux et al., 1986] showed that there were many errors in assigning homology with human chromosomes. The chromosomal phylogeny of New World monkeys based on banding patterns is in need of revision using modern molecular methods.     

Protein electrophoretic variability in Saimiri and the question of its species status

An electrophoretic survey of 15 protein systems (22 loci) was employed to determine the genetic relationships among 9 populations (441 individuals) of South American squirrel monkeys (Saimiri sciureus sciureus, S. sciureus boliviensis, and S. sciureus ustus). Genetic markers capable of differentiating the second from the two other taxa were observed mainly in the ADA and GPI systems. Heterogeneity for ADA and CA2 between populations from opposite banks of the Jamari river was verified in S. sciureus ustus. The average heterozygosities ranged from 3% to 5%, the lowest being in S. sciureus sciureus and the highest in S. sciureus boliviensis. Low genetic distances (D = 0.001?0.057) were observed between populations within taxa or between S. sciureus sciureus and S. sciureus ustus. But both differed to a larger extent from S. sciureus boliviensis (D = 0.11 in both comparisons). There is a positive correlation between the genetic and geographic distance matrices. The three taxa are more clearly separated (D = 0.76–0.77) from the outgroup used for comparison (Cebus apella). Our data suggest that there is only one large, polytypic species of squirrel monkeys in South America, S. sciureus, forming a contiguous ring of geographical races or subspecies. Two of the most differentiated forms meet at the Peruvian Amazonia where natural hybrids and secondary intergradation have been reported. © 1993 Wiley-Liss, Inc.     

Karyological evidence for interspecific hybridization between Cichla monoculus and C. temensis (Perciformes, Cichlidae) in the Amazon

Cichla monoculus, Cichla temensis (peacock bass or tucunare), and its presumed hybrids, were cytogenetically analyzed. The fish were collected at three distinct sites in the central Amazon basin, namely in the Uatuma (C. monoculus, C. temensis and their natural hybrid), Jau (C. temensis), and Solimoes rivers (C. monoculus). The two species and the natural hybrid showed the same diploid number, 2n=48 acrocentric chromosomes. Single NORs were detected in the distal region of the long arm in all three species. However, in C. monoculus, the NOR was found on the second pair of the complement, in C. temensis, on the third pair and in the hybrid two NOR patterns were found, one on the second pair and the other on the third pair of chromosomes. The two species and the hybrid have their constitutive heterochromatin located in the pericentromeric region of all chromosomes and an interstitial C-band located on the largest chromosome pair. The great similarity in the chromosome number and morphology, chromosome size class differences, the NOR patterns and C-banding suggested chromosomal stasis during speciation and hybridization of Cichla.     

Neonatal activity and state control differences among three squirrel monkey subspecies (Saimiri sciureus sciureus,S. boliviensis boliviensis,and S. boliviensis peruviensis)

Squirrel monkeys are a long-standing biomedical model, with multiple species and subspecies housed in research facilities. Few studies have examined the developmental differences between these subspecies, which may affect research outcomes. The primate neonatal neurobehavioral assessment was completed at 2 weeks of age with 279 dam-reared squirrel monkeys (188 Saimiri boliviensis boliviensis, 45 S. b. peruviensis, and 46 Saimiri. sciureus sciureus). Activity, orientation to stimuli, state control, and motor maturity scores, as well as startle responses and number of vocalizations were compared across subspecies and sex using factorial analysis of covariance (ANCOVAs) controlling for birthweight. There were no differences in orientation or motor maturity scores (p > .05) among the three subspecies or between sexes; however, there were significant subspecies differences in motor activity and state control scores. Of the three subspecies, S. s. sciureus has the lowest state control and activity scores (p < .05). They also had the most exaggerated startle response/aversion to a sudden loud noise, vocalized significantly less, and were less likely to resist restraint during the assessment (p < .05). The three subspecies of squirrel monkeys did not differ in motor development and attention to external stimuli but were significantly different in state control and activity levels. Overall S. s. sciureus were less active, agitated, irritable, and easier to console compared to S. b. boliviensis and S. b. peruviensis. This supports field research on socioecology which documented different social structure and behavior in wild populations of S. s. sciureus compared to S. b. boliviensis and S. b. peruviensis.     

New insights into the effects of extra nucleolus organizer regions

Summary Chromosome studies were carried out in four members of a sibship with a 15p+chromosome. Two carriers had normal offspring, one was unmarried, and the index case had three abortions and no live children. By means of different banding techniques, up to four satellites and four stalks could be observed on the abnormal chromosome. The Ag-I method showed from zero to four silver precipitates on the 15p+marker. Mean Ag-staining for 15p+and the ten acrocentric chromosomes were obtained in the carriers. Statistically significant differences between sibs were found. These results suggest the existence of: (a) An interindividual and intercellular variation of nucleolus organizer region (NOR) activity in man. (b) An optimal threshold of NOR activity, so that disturbances at the meiotic level could occur when it is exceeded. Our conclusions lead us to advise analysis of NOR activity in individuals with extra nucleolus organizer regions.     

Karyotypes of squirrel monkeys (Saimiri sciureus) from different geographic regions

Three different karyotypes have been found so far among Saimiri originating from five different South American localities. All animals examined have the same diploid number (44) of chromosomes but the number of acrocentric and submetacentric chromosomes varies, presumably as a result of pericentric inversions. Saimiri originating from Iquitos, Peru, consistently have ten acrocentric chromosomes; animals originating from Leticia, Colombia, have 12 acrocentric chromosomes. Hybrids produced in our laboratory have the expected 11 acrocentrics and one unpaired submetacentric chromosome. Animals originating from Guyana have fourteen acrocentric chromosomes and the expected two fewer submetacentric chromosomes. Squirrel monkeys from Costa Rica, Panama, and Pucallpa, Peru, studied to this date conform to the Iquitos type with ten acrocentric chromosomes. These findings point to genetic differences which may result in variable responses to laboratory situations. The evolutionary factors involved in this rearrangement of chromosomes and possible influences on phenotypes are subjects of interest for future study. The importance of identifying the source of squirrel monkeys used in biomedical research is apparent if results from different laboratories are to be repeated or compared.     

Development of a polymorphic strain of Plasmodium vivax in monkeys.

A strain of Plasmodium vivax from Thailand with a polymorphic repeat unit of the circumsporozoite protein was established in Saimiri sciureus boliviensis and 3 species of Aotus monkeys. All 11 attempts to transmit infection via sporozoite inoculation, 4 times to splenectomized S. sciureus boliviensis, 2 times to splenectomized Aotus nancymai, and 5 times to intact Saimiri monkeys, were successful. Anopheles freeborni, Anopheles stephensi, Anopheles dirus, and Anopheles gambiae mosquitoes were infected by feeding on parasitemic blood from a chimpanzee and an Aotus azarae boliviensis monkey. Our results indicate that this strain may be useful in antisporozoite vaccine trials.     

Chromosome banding studies in an Indian mullet: evidence of structural rearrangements from NOR locations

C-, G- and NOR bands have been studied in the female sex of Rhinomugil corsula. (Mugilidae, Pisces) by deploying the conventional methodologies with suitable modifications of minor nature. The diploid metaphase complements contained 48 acrocentric chromosomes. The localization of C-band heterochromatin was found to be mostly at or near the centromeric regions of the acrocentric chromosomes. The G-type bands were not so well defined, but some of the G-banded chromosomes also contained C-bands. Interestingly, silver-positive NORs were found at the telomeric ends of five acrocentric chromosomes, including one homologous pair having NORs in both chromatids, while one chromosome showed NORs in both of its chromatids and the other two had only one NOR localized at one of its chromatids. This would suggest that one homologue of the second pair of NOR-bearing chromosomes possibly underwent a chromatid exchange with a non-NOR bearing chromosome. This is quite a unique situation not reported earlier in any species of fish., though some other form of NOR-polymorphism/heteromorphism has rarely been reported. Therefore, further exploration in natural populations of this species to examine the other sex and to verify if there also exists other chromosomally polymorphic races (in respect of NOR-polymorphism) of this species, would be rewarding.     

Physical mapping of the 5S ribosomal RNA genes in Arabidopsis thaliana by multi-color fluorescence in situ hybridization with cosmid clones

The 5S ribosomal RNA genes were mapped to mitotic chromosomes of Arabidopsis thaliana by fluorescence in situ hybridization (FISH). In the ecotype Landsberg erecta, hybridization signals appeared on three pairs of chromosomes, two of which were metacentric and the other acrocentric. Hybridization signals on one pair of metacentric chromosomes were much stronger than those on the acrocentric and the other pair of metacentric chromosomes, probably reflecting the number of copies of the genes on the chromosomes. Other ecotypes, Columbia and Wassilewskija, had similar chromosomal distribution of the genes, but the hybridization signals on one pair of metacentric chromosomes were very weak, and detectable only in chromosomes prepared from young flower buds. The chromosomes and arms carrying the 5S rDNA were identified by multi-color FISH with cosmid clones and a centromeric 180 bp repeat as co-probes. The metacentric chromosome 5 and its L arm carries the largest cluster of the genes, and the short arm of acrocentric chromosome 4 carries a small cluster in all three ecotypes. Chromosome 3 had another small cluster of 5S rRNA genes on its L arm. Chromosomes 1 and 2 had no 5S rDNA cluster, but they are morphologically distinguishable; chromosome 1 is metacentric and 2 acrocentric. Using the 5S rDNA as a probe, therefore, all chromosomes of A. thaliana could be identified by FISH. Chromosome 1 is large and metacentric; chromosome 2 is acrocentric carrying 18S-5.8S-25S rDNA clusters on its short arm; chromosome 3 is metacentric carrying a small cluster of 5S rDNA genes on its L arm; chromosome 4 is acrocentric carrying both 18S-5.8S-25S and 5S rDNAs on its short (L) arm; and chromosome 5 is metacentric carrying a large cluster of 5S rDNA on its L arm.     

Taxonomy of squirrel monkeys genus Saimiri (Cebidae,platyrrhini): A preliminary report with description of a hitherto unnamed form

Two groups of squirrel monkeys, genus Saimiri, are distinguished by external characters. The first, or Roman type, contains Saimiri boliviensis of upper Amazonia south of the Rio Marañón-Amazonas, with two subspecies of which S. boliviensis peruviensis is described as new. The second group, or Gothic type, contains three species: Saimiri sciureus with four subspecies distributed over much of tropical South America, Saimiri ustus of Brazil between the south bank Amazonian Rios Purús and Xingu, and S. oerstedi isolated on a Pacific coastal area straddling Costa Rica and Panamá. The geographic range of S. sciureus overlaps parts of those of S. ustus and S. boliviensis. Incomplete karyotypic data indicate that the diploid number of chromosomes for the genus is 44. Geographic variation is characterized by reduction from seven to six or five paired acrocentric autosomes through pericentric inversion with reciprocal increase in number of paired submetacentric or subtelocentric autosomes. Geographic distribution, behavior, sexual dimorphism including dichromatism, and hybridization are discussed. Ventral guide hairs for orientation of subprecocial newborn toward the maternal mammae are described. Distinguishing characters of species and subspecies are provided in a key. The taxons are listed with the taxonomy of each discussed, their geographic distribution plotted and mapped.     

Impaired transactivation of the glucocorticoid receptor cloned from the Guyanese squirrel monkey

Squirrel monkeys are among a diverse group of New World primates that demonstrate unusually high levels of circulating corticosteroids and glucocorticoid receptor (GR) insensitivity. Recent evidence suggests that overexpression of an immunophilin impairs dexamethasone binding to GR in the Bolivian squirrel monkey (Saimiri boliviensis). Here we describe the cloning, expression, and functional characterization of GR from the closely related Guyanese squirrel monkey (S. sciureus). The cloned Guyanese squirrel monkey GR (gsmGR) cDNA closely resembles human GR (hGR) cDNA, and yields a high affinity dexamethasone binding receptor when expressed in COS-1 cells. Transactivation analysis of hGR and gsmGR expressed in CV-1 cells and cultured squirrel monkey kidney (SMK) cells indicates that: (1) SMK cells elaborate a functional high activity GR from human GR cDNA; (2) gsmGR is an order of magnitude less efficient than hGR at transactivation in CV-1 and SMK cells; and (3) maximal transactivation by gsmGR is attenuated in both cell lines. Glucocorticoid resistance in S. sciureus is at least partly attributable to a naturally occurring mutation in the GR gene that results in impaired GR transactivation.     

Cytogenetic analysis of some Brazilian marsupials (Didelphidae: Marsupialia)

Three species of marsupials from the Amazon region (Marmosa cinerea, Caluromys lanatus, and Didelphis marsupialis) and two from the region of S?o Paulo (Didelphis marsupialis and Didelphis albiventris) were studied. The G-banding pattern of the species with 2n = 14 (M. cinerea and C. lanatus) was very similar, as well as the pattern of G-bands in the species with 22 chromosomes (Didelphis). All of the autosomes of M. cinerea and D. albiventris have centromeric C-bands and the Y chromosome is totally C-band positive. The long arm of the M. cinerea X chromosome is completely C-band positive except for a negative band close to the centromeric region. In D. albiventris the long arm of the X chromosome is C-band positive except for a negative band close to the telomeric region. In M. cinerea the silver-stained nucleolar organizer regions (Ag-NORs) are found in the acrocentric chromosomes, being located in the telomeric region of one pair and in the centromeric region of the other pair. Caluromys lanatus has centromeric Ag-NORs in one acrocentric and in one submetacentric chromosome pairs. Didelphis marsupialis has three chromosome pairs with telomeric Ag-NORs. In D. albiventris the Ag-NORs are terminal and located in both arms of one pair and in the long arm of two pairs of chromosomes.     

Chromosome analysis of 82 species of Scarabaeoidea (Coleoptera), with special focus on NOR localization

The aim of this study was the identification of the ancestral location of the nucleolus organizer region (NOR) in the Scarabaeoidea superfamily, and its evolutive trends in the karyotypes. For this purpose, the mitotic and meiotic chromosomes at pachynema of 82 species belonging to 4 families and 8 subfamilies, including 49 species without any published data, were examined after Giemsa staining, C-banding and NOR staining. It could be perceived that most karyotypes are composed of 18 nonacrocentric autosomes, an acrocentric X and a punctiform Y. NORs are frequently located on the X independent of its morphology. In contrast, autosomal NORs are frequently on the rare acrocentric short arms. Thus, it could be shown that the ancestral karyotype was very probably composed of 18 metacentric/submetacentric autosomes, an NOR carrier acrocentric X and a punctiform Y. The NOR translocation on autosomes parallels the passage to their acrocentric morphology. It is proposed that the frequent location of the NOR on the X of beetles, and possibly other insects, is made possible by their mode of dosage compensation of the X chromosome, consisting in the overexpression of the unique X of the males.     

Chromosomes of Australian lygosomine skinks (Lacertilia: Scincidae)

The karyotypes of 25 species from the scincid genera Egernia, Corucia and Tiliqua have been investigated using C-banding, silver staining of nucleolar organiser regions (NORs) and Hoechst 33258 induced condensation inhibition. At least one member from each of the species groups of Egernia recognised by Storr et al. (1981) was studied. The three genera have very similar conventionally stained karyotypes of 32 chromosomes. Some species show departures from this basic karyotype but these are due to additions of C-band positive material. Silver stained. NOR patterns are variable but most species have a silver staining site on a pair of larger microchromosomes. All specimens studied except one have a proximal C-band on the acrocentric ninth pair, which shows failure to condense following treatment with the fluorochrome Hoechst 33258. Heterogamety was not observed in any species. Mabuya multifasciata, proposed as a relative of the Egernia group, while having 32 chromosomes does not share the C-band marker on pair nine, unique to the Egernia group. Tribolonotus gracilis, sometimes allied with the Egernia group, has 32 chromosomes and a similiar karyotype, but prominent procentric C-bands on all chromosome pairs obscure the detection of the proximal C-band marker on pair nine.