Biomedical Engineering Reference
In-Depth Information
be the most primitive of the primates, exhibiting no
opposable thumb, claws on all digits except the thumb, no
prehensile tail or wisdom teeth, an unstable body temper-
ature, and the use of scent to mark their territories.
The squirrel monkey has short, thick fur that is olive on
the shoulder and yellow on the back and limbs. Its mouth is
black and its ears, throat, and region around its eyes are
white. The black and white markings on its face resemble
a skull that differs between the taxa's two species most
important to biomedical research. S. sciureus exhibits
a sharply rising “gothic arch” above its eyes with the black
fur descending down from the brow ridge forming a “V”
shape. In contrast, S. boliviensis sports a more rounded
“Roman arch” of white above its eyes and males and
females have black and gray bodies, respectively. The
squirrel monkey's tail is typically longer than its body, has
a black tip and, in S. boliviensis, is very thin.
The owl monkey has pale yellow fur on its stomach,
underarms, and inner legs, light gray fur above and below
its eyes, and three black stripes running from the top of its
head to either eye and between the eyes. It has unusually
large (brown) eyes and large olfactory lobes, reflecting its
status as the only nocturnal New World primate, hence its
moniker, the night monkey. It exhibits little to no sexual
dimorphism. Red-necked owl monkeys (those living south
of the Amazon River), including A. nancymaae, are
distinguished from grey-necked owl monkeys (living north
of the Amazon River) by the red bands (rather than gray
bands) around their necks and the two exhibit reciprocally
monophyletic karyotypes.
marmosets (
Nievergelt et al., 1998
). These loci exhibited
from two to 12 alleles per locus and a range of gene
diversity from 0.38 to 0.94. Four of the loci identified with
the nine species-specific primers were also polymorphic,
but, as expected due to the ascertainment bias, exhibited
much less genetic diversity in a sample of 10 cotton-top
tamarins (Saguinus oedipus). Earlier studies of genetic
diversity in Callitrichids produced ambiguous results
(e.g.
Dixson et al., 1992
) because they employed DNA
extracted from blood, which almost always exhibits
chimerism. Recent studies have shown that somatic and
germ cell tissue of marmosets also exhibit chimerism,
albeit less frequently, confounding estimates of genetic
relationships among animals (
Ross et al., 2007
). The
pending availability of a draft sequence for marmosets will
make possible the detection of SNPs in this species that can
be used to preclude the influence of ascertainment bias in
studies of genetic diversity.
Most of the few population studies of New World
monkeys have used microsatellite (STR) loci to charac-
terize endangered species, such as the Leonopithecus
species of black lion tamarin (
Perez-Sweeney et al., 2005
),
the golden lion tamarin (
Grativol et al., 2001
), and the
golden headed tamarin (
Galbusera and Gillemot, 2008
)to
assess levels of genetic diversity or genetic subdivision to
inform conservation efforts. Relatively low levels of gene
diversity and numbers of STR alleles have been reported
for these callitrichid species compared to the study of
common marmosets by
Nievergelt et al. (1998)
and might
reflect genetic bottlenecks in the endangered Callitrichids.
Relatively few STRs (either human-specific or species-
specific) that are informative in species of Old World
monkeys have proved to be informative in New World
monkeys. However, studies such as those cited above have
led to the discovery of polymorphic STRs in these species
that have been tested and found to be informative in other
species and genera of New World Monkeys, notwith-
standing the ascertainment biased introduced which
compromises inter-species comparisons. For example,
Bohle and Zischler (2002)
isolated 10 polymorphic STRs in
the mustashed tamarin (Saguinus mystax) and found that
six of them also identified polymorphism in Saimiri
sciureus and S. boliviensis.
Lau et al. (2004)
screened 215
human microsatellite primer pairs and six that had been
identified as polymorphic in Saimiri boliviensis or Cebus
capella and found 20 (18 of which were identified with
human primers) that were polymorphic in 39 samples
representing three different species of Aotus (A. azarai,
A. lemurinus, and A. nancymaae). The number of alleles
per locus and observed level of heterozygosity ranged from
4.0 (in A. a.) to 6.1 (in A. n.) and from 0.39 (in A. a.) to 0.60
(in A. n.), respectively.
Lavergne et al. (2003)
studied
a 1140 bp sequence of the cytochrome b gene of mito-
chondrial DNA and three of 11 STR loci found to be
Genetic Diversity
Fewer studies of New World than Old World primate
species have been conducted, and most such studies have
focused on phylogeny rather than population comparisons
and, consequently, have employed very small samples. The
ABO blood group polymorphism is widespread among
New World monkeys. Aotus infulatus appears mono-
morphic, or nearly so, for the B antigen, while Saimiri
sciureus exhibits predominantly the A phenotype with
a low frequency of B, and Cebus apella exhibits all four
phenotypes (
Corvelo et al., 2002
). Though molecular
sequencing of the corresponding alleles has not been done,
the sequences are unlikely to be orthologous to those of Old
World Monkeys, as even the sequences of the latter differ
significantly among members of the same phenotype. For
example, the O allele in rhesus macaques derives from
mutations of the B allele while it derives from mutations of
the A allele in longtail macaques (
Kermarrec et al., 1999
).
One exception to the small sample sizes of New World
Monkeys typically studied is a report of genotypes for nine
species-specific and four human STRs (D5s111, D5s117,
D8s165 and D14s51)
in 98 free-ranging common
