Chromosome painting of the pygmy tree shrew shows that no derived cytogenetic traits link primates and scandentia.

We hybridized human chromosome paints on metaphases of the pygmy tree shrew (Tupaia minor, Scandentia). The lack of the ancestral mammalian 4/8 association in both Primates and Scandentia was long considered a cytogenetic landmark that phylogenetically linked these mammalian orders. However, our results show that the association 4/8 is present in Tupaia along with not previously reported associations for 1/18 and 7/10. Altogether there are 11 syntenic associations of human chromosome segments in the pygmy tree shrew karyotype: 1/18, 2/21, 3/21, 4/8, 7/10, 7/16, 11/20, 12/22 (twice), 14/15 and 16/19. Our data remove any cytogenetic evidence that Scandentia has a preferential phylogenetic relationship with Primates.

Disorders of sexual development in wild and captive exotic animals.

Disorders of sexual development (DSDs) are an increasing concern in both captive and free-ranging wildlife species. Partial or complete reduction in fertility that results from intersex conditions or gonadal dysgenesis is detrimental to the reproductive potential of wildlife populations, and consequently, to their long-term survival. Compared to the wealth of information available on humans and domestic species, a better understanding of the factors influencing sexual development in wildlife is essential for developing and improving population management or conservation plans. This review attempts to bring together the different facets of DSDs as studied in the fields of reproductive physiology, endocrinology, ecotoxicology, wildlife biology, and environmental health.

Homologous fission event(s) implicated for chromosomal polymorphisms among five species in the genus Equus.

The genus Equus is unusual in that five of the ten extant species have documented centric fission (Robertsonian translocation) polymorphisms within their populations, namely E. hemionus onager, E. hemionus kulan, E. kiang, E. africanus somaliensis, and E. quagga burchelli. Here we report evidence that the polymorphism involves the same homologous chromosome segments in each species, and that these chromosome segments have homology to human chromosome 4 (HSA4). Bacterial artificial chromosome clones containing equine genes SMARCA5 (ECA2q21 homologue to HSA4q31. 21) and UCHL1 (ECA3q22 homologue to HSA4p13) were mapped to a single metacentric chromosome and two unpaired acrocentrics by FISH mapping for individuals possessing odd numbers of chromosomes. These data suggest that the polymorphism is either ancient and conserved within the genus or has occurred recently and independently within each species. Since these species are separated by 1-3 million years of evolution, this polymorphism is remarkable and worthy of further investigations.

FISH analysis comparing genome organization in the domestic horse (Equus caballus) to that of the Mongolian wild horse (E. przewalskii).

Przewalski's wild horse (E. przewalskii, EPR) has a diploid chromosome number of 2n = 66 while the domestic horse (E. caballus, ECA) has a diploid chromosome number of 2n = 64. Discussions about their phylogenetic relationship and taxonomic classification have hinged on comparisons of their skeletal morphology, protein and mitochondrial DNA similarities, their ability to produce fertile hybrid offspring, and on comparison of their chromosome morphology and banding patterns. Previous studies of GTG-banded karyotypes suggested that the chromosomes of both equids were homologous and the difference in chromosome number was due to a Robertsonian event involving two pairs of acrocentric chromosomes in EPR and one pair of metacentric chromosomes in ECA (ECA5). To determine which EPR chromosomes were homologous to ECA5 and to confirm the predicted chromosome homologies based on GTG banding, we constructed a comparative gene map between ECA and EPR by FISH mapping 46 domestic horse-derived BAC clones containing genes previously mapped to ECA chromosomes. The results indicated that all ECA and EPR chromosomes were homologous as predicted by GTG banding, but provide new information in that the EPR acrocentric chromosomes EPR23 and EPR24 were shown to be homologues of the ECA metacentric chromosome ECA5.

Cytogenetic analysis of California condor (Gymnogyps californianus) chromosomes: comparison with chicken (Gallus gallus) macrochromosomes.

The California condor is the largest flying bird in North America and belongs to a group of New World vultures. Recovering from a near fatal population decline, and currently with only 197 extant individuals, the species remains listed as endangered. Very little genetic information exists for this species, although sexing methods employing chromosome analysis or W-chromosome specific amplification is routinely applied for the management of this monomorphic species. Keeping in mind that genetic conditions like chondrodystrophy have been identified, preliminary steps were undertaken in this study to understand the genome organization of the condor. This included an extensive cytogenetic analysis that provided (i) a chromosome number of 80 (with a likelihood of an extra pair of microchromosomes), and (ii) information on the centromeres, telomeres and nucleolus organizer regions. Further, a comparison between condor and chicken macrochromosomes was obtained by using individual chicken chromosome specific paints 1-9 and Z and W on condor metaphase spreads. Except for chromosomes 4 and Z, each of the chicken (GGA) macrochromosomes painted a single condor (GCA) macrochromosome. GGA4 paint detected complete homology with two condor chromosomes, viz., GCA4 and GCA9 providing additional proof that the latter are ancestral chromosomes in the birds. The chicken Z chromosome showed correspondence with both Z and W in the condor. The homology suggests that the condor sex chromosomes have not completely differentiated during evolution, which is unlike the majority of the non-ratites studied up till now. Overall, the study provides detailed cytogenetic and basic comparative information on condor chromosomes. These findings significantly advance the effort to study the chondrodystrophy that is responsible for over ten percent mortality in the condor.

Comparative cytogenetics of the African elephant (Loxodonta africana) and Asiatic elephant (Elephas maximus).

G- and C-banded karyotypes of the two extant species of the mammalian order Proboscidea are presented for the first time. Chromosome complements were 2n = 56 in both Loxodonta africana and Elephas maximus. Comparisons between the species demonstrated a high level of chromosome band homology, with 26 conserved autosomal pairs. The normal diploid karyotype of L. africana had 25 acrocentric/telocentric and two metacentric/submetacentric autosomal pairs. E. maximus differed by having one less acrocentric and one additional submetacentric pair due to either a heterochromatic arm addition or deletion involving autosomal pair 27. Several acrocentric autosomes of L. africana exhibited small short arms that were absent in homologous chromosomes of E. maximus. The X chromosomes in both species were large submetacentric elements and were homologous. However, the small acrocentric Y chromosomes differed; in E. maximus it was slightly larger and had more distinct G-bands than its counterpart in L. africana. Extant Elephantidae appear to be relatively conservative in their rates of chromosomal change compared to some other mammalian families. The high-quality banded karyotypes presented here should prove useful as references in future chromosome analyses of elephant populations and in comparative cytogenetic studies with other ungulate orders.

Trisomy 17 in a bonobo (Pan paniscus) and deletion of 3q in a lowland gorilla (Gorilla gorilla gorilla): comparison with human trisomy 18 and human deletion 4q syndrome.

A female bonobo (Pan paniscus) born at the San Diego Zoo exhibited inability to nurse and progressive weakness plus multiple congenital abnormalities including aural canal atresia and stenosis, malformed auricles, clenched hands, lordosis, agenesis of the caudal vertebra and cardiac abnormalities. Chromosome analysis identified the bonobo as being trisomic for chromosome 17, the homolog of human chromosome 18. Genotyping with human microsatellites suggested the extra chromosome was maternal in origin. In addition, a male lowland gorilla (Gorilla gorilla gorilla), also born at the zoo, exhibited postnatal growth retardation, facial dysmorphisms and small hands with short fingers. Karyotype analysis revealed the gorilla carried a deletion of the distal q arm of chromosome 3, the homolog of human chromosome 4. The phenotypic and karyotypic abnormalities found in the bonobo and gorilla were consistent with the characteristics of human trisomy 18 and human deletion 4q syndrome, respectively.

Cytogenetic identification of a hybrid owl monkey, Aotus nancymaae x Aotus lemurinus griseimembra.

A neonate male owl monkey (Aotus sp.) was identified cytogenetically as a hybrid after it failed to nurse and died. Phenotypically, the male parent possessed characteristics of the "gray-neck group," and G-banded karyotypes identified him as Aotus lemurinus griseimembra (2n = 53), heterozygous for the centric fusion of chromosomes 13 and 14. The female parent belonged to the "red-neck group" and was identified cytogenetically as Aotus nancymaae (2n = 54). The neonate hybrid had 2n = 54 chromosomes with 13 homologous pairs of autosomes, 26 nonhomologous autosomes, and XY sex chromosomes. Thirteen of the nonhomologous chromosomes represented the paternal complement, and 13 were from the maternal complement. Chromosomal rearrangements occurring between the karyotypes of A. l. griseimembra and A. nancymaae were believed to include two paracentric inversions, a reciprocal translocation, and two complex rearrangements involving pericentric inversion, telocentromeric fusion, and centromeric adjustment. Cytogenetic analyses are necessary to identify most Aotus taxa and thus should be utilized to pair chromosomally compatible animals and avoid interspecies hybridization.

Comparative cytogenetics of tapirs, genus tapirus (Perissodactyla, tapiridae).

Chromosomes of the four species of Tapirus were 2n = 52 in T. indicus, 2n = 76 in T. pinchaque, 2n = 80 in T. bairdii, and 2n = 80 in T. terrestris. The number of autosomal arms was 80-94. G-banded karyotypes indicated that a heterochromatic addition/deletion distinguished chromosomes 2 and 3 of T. bairdii and T. pinchaque, respectively. There were at least 13 conserved autosomes between the karyotypes of T. bairdii and T. terrestris, and at least 15 were conserved between T. bairdii and T. pinchaque. In G- and C-banded preparations, the X chromosomes of T. bairdii, T. indicus, and T. terrestris were identical, whereas the X chromosome of T. pinchaque differed from the X of the other species by a heterochromatic addition/deletion. The Y chromosome was a medium-sized to small acrocentric in T. bairdii, T. indicus, and T. pinchaque, but it was not positively identified in T. terrestris. There appeared to be fewer homologies between T. indicus and the three species occurring in Central and South America. Future cytogenetic studies of tapirs from the entire range of each of the four species might provide additional insight into their evolutionary biology and aid wildlife conservation efforts aimed at these threatened mammals.

Chromosomes of the antelope genus Kobus (Artiodactyla, Bovidae): karyotypic divergence by centric fusion rearrangements.

G- and C-banded karyotypes of four species of the genus Kobus were compared using the standard karyotype of Bos taurus. Chromosomal complements were 2n = 50-54 in K. ellipsiprymnus, 2n = 50 in K. kob, 2n = 48 in K. leche, and 2n = 52 in K. megaceros. The number of autosomal arms in all karyotypes was 58. Fifteen autosomal pairs were conserved among these four species, including the 1;19 and 2;25 centric fusions, and autosomal differences involved eight centric fusion rearrangements. Five centric fusions were each unique to a particular taxon: 3;10 (K. leche), 3;11 and 6;29 (K. kob), and 5;17 and 7;11 (K. ellipsiprymnus). The 4;7 fusion occurred in K. leche and K. megaceros, whereas the 5;13 fusion occurred in K. kob and K. leche; the 6;18 fusion was found in three species but was absent in K. kob. Differences between the X chromosomes of the four Kobus species were attributed to heterochromatic additions or deletions, and Y-chromosome differences may have been the result of pericentric inversion. G-banded karyotypes of putative K. l. leche and K. l. kafuensis appeared identical, as did C-banded karyotypes of the two subspecies. Karyotypes of K. e. ellipsiprymnus and K. e. defassa differed as a result of the 6;18 centric fusion, which was polymorphic in K. e. defassa, and the 7;11 centric fusion, which was polymorphic in K. e. ellipsiprymnus but absent in K. e. defassa. Several centric fusions were related by monobrachial chain-IV complexes; however, records of hybridization indicate that reproductive isolation between at least certain species of Kobus is incomplete. Karyotypic differences between K. ellipsiprymnus (including K. e. ellipsiprymnus and K. e. defassa), K. kob, K. leche, and K. megaceros support the validity of these taxa, as well as the need to manage them as separate populations.

Chromosomal rearrangements in a Somali wild ass pedigree, Equus africanus somaliensis (Perissodactyla, Equidae).

Chromosome analyses were conducted on 15 animals in a pedigree of Somali wild ass, Equus africanus somaliensis. G- and C-banded karyotypes are presented for the first time on this endangered species. The diploid number ranged from 62 to 64. Numerical chromosomal variation was the result of a centric fission which was accompanied by a heterochromatic deletion. The fission polymorphism involved acrocentric elements 19 and 21 as determined by G-banding. These autosomes are homologous to those involved in centric fission/fusion polymorphisms in other equids: E. asinus (domestic donkey), E. hemionus (onager), E. kiang (kiang), and E. burchelli (common zebra). Banding analyses also revealed a paracentric inversion polymorphism in submetacentric chromosome pair 2 of E. a. somaliensis. Both the centric fission and paracentric inversion polymorphisms involved heterochromatic regions. One individual was found to be heterozygous for two de novo chromosomal rearrangements: a centric fission (involving acrocentric elements 19 and 21) and a heterochromatic deletion of chromosome 2.

Chromosomes of Damaliscus (Artiodactyla, Bovidae): simple and complex centric fusion rearrangements.

G- and C-banded karyotypes of Damaliscus hunteri, D. lunatus and D. pygargus were compared using the standard karyotype of Bos taurus. Chromosomal complements were 2n = 36 in D. lunatus jimela, 2n = 38 in D. pygargus phillipsi and D. p. pygargus, and 2n = 44 in D. hunteri. The fundamental number in all karyotypes was 60. Among the three species of Damaliscus, seven autosomal pairs and the X chromosomes were conserved. Y-chromosome differences were attributed to heterochromatic additions or deletions. Banded karyotypes of the two subspecies of D. pygargus exhibited complete homology. Chromosomal complements of D. pygargus and D. lunatus differed by a simple centric fusion. However, karyotypes of D. pygargus and D. lunatus differed from D. hunteri by numerous centric fusions, several of which were related by monobrachial chain complexes. Between the karyotypes of D. hunteri and D. pygargus or D. lunatus, there were two chain complexes, one involving five chromosomes (chain V) and the other involving 12 in pygargus (chain XII) or 13 in lunatus (chain XIII). There were also two simple centric fusions between D. hunteri and D. lunatus/D. pygargus; acrocentric chromosomes 13, 15, 20 and 22 in D hunteri were fused as 13;15 and 20;22 in D. lunatus and D. pygargus.

A karyotypic analysis of the lesser Malay chevrotain, Tragulus javanicus (Artiodactyla: Tragulidae).

Chevrotains are small forest-dwelling ruminants of the family Tragulidae. The chromosome number of the lesser Malay chevrotain was determined to be 2n = 32, NF = 64, G- and Q-banding allowed the identification of homologous chromosomes, and C-banding demonstrated the presence of pericentromeric, telomeric and interstitial constitutive heterochromatin. Q-band comparisons with domestic cattle revealed relatively few monobrachial chromosome band homologies. However, the smallest biarmed autosome of the chevrotain, chromosome 15, was determined to be cytogenetically homologus with the acrocentric chromosome 19 of cattle. A molecular cytogenetic analysis confirmed this putative chromosomal homology. In fact, molecular cytogenetic analyses indicate complete conservation of synteny among mouse deer chromosome 15, domestic cattle chromosome 19, domestic pig chromosome 12 and human chromosome 17. In the light of these molecular cytogenetic data and since mouse deer chromosome 15 is submetacentric and appears homologous in banding to submetacentric chromosome 12 of the domestic pig, these outgroup comparisons indicate that the acrocentric condition of cattle chromosome 19 has been derived by inversion. Since this derivative condition is present in the Antilocapridae, Bovidae, Cervidae and Giraffidae, it is a chromosomal synapomorphy that unites these advance ruminant families within the Artiodactyla.

Diploid chromosome number and chromosomal variation in the white rhinoceros (Ceratotherium simum).

Chromosomal studies were conducted on 38 white rhinoceroses representing both the northern and southern subspecies and one subspecies hybrid. Improvements in tissue culture methods and harvesting techniques have made it possible to obtain a highly repeatable diploid number of 82 chromosomes for both subspecies. Comparison of G-banded karyotypes from the two subspecies failed to indicate a difference in banding pattern, but did reveal size polymorphisms involving short arm additions in five individuals. Chromosomal polymorphism, resulting in three individuals with a diploid number of 2n = 81, was noted in northern white rhinoceroses.