Biomedical Engineering Reference
In-Depth Information
2001
). However,
Steiper and Ruvolo (2002)
have argued
that the owl monkey and squirrel monkey belong to sister
taxa and, therefore, are more closely related to each other
than either is to either Callitrichid species (marmosets and
tamarins). A study of 13 polymorphic electrophoretically
defined polymorphisms in relatively small samples of four
Callitrichid species (
Meireles et al., 1998
) supported
a subdivision into two clades, one containing Saguinus
together with Leontopithecus species (e.g. lion tail tamarin)
and another containing genus Callithrix together with
Cebuella pygmaea, the pygmy marmoset.
Thus, all four of the New World primates most
commonly used in biomedical research in the USA belong
to the same family of New World monkeys, Cebidae, and
each of the three subfamilies of Cebidae contains at least
one primate species employed in biomedical research,
namely two species of the subfamily Callitrichinae,
Saguinus oedipus (the cotton top tamarin) and Callithrix
jacchus (the common marmoset), one species of the
subfamily Cebinae, Saimiri sciurius (squirrel monkeys),
and one species of the subfamily Aotinae, Aotus nancy-
maae (the night or owl monkey).
northern Peru and northwestern Brazil that straddles the
Peru/Brazil border. It is the only species of owl monkey that
straddles the ranges of both the gray-necked and red-
necked owl monkeys.
NewWorld Monkeys are less expensive to purchase and
maintain in captivity, and their size and short generation
span provide both advantages and limitations on their use in
biomedical research. Nevertheless, they are less frequently
used as animal models due to their lack of availability since
no countries in their natural ranges currently allow their
export. The NCRR supports colonies of several hundred
squirrel (Saimiri boliviensis and S. sciureus) and owl
monkeys (Aotis nancymaae), each at the Michale
E. Keeling Center for Comparative Medicine and Research
of the University of Texas MD Anderson Cancer Center
located near Bastrop, and a population of cotton-top
tamarins (Saguinus oedipus) at the New England National
Primate Research Center, the largest colony of tamarins in
the USA. Colonies of common marmosets (Callithrix jac-
chus) are maintained at the New England, Wisconsin, and
Southwest National Primate Research Centers, and colo-
nies of squirrel monkeys are housed at four of the National
Primate Research Centers: New England, Yerkes, South-
west, and Tulane.
Phylogeography
While marmosets and tamarins inhabit Brazil, Peru,
Colombia, and Panama, the two species most commonly
used in biomedical research, the cotton-top tamarin
(Saguinus oedipus) and the common marmoset (Callithrix
jacchus), are native to northwestern Colombia and north-
eastern Brazil, respectively. Fewer cotton-top tamarins are
estimated to remain in the wild (about 1000), predomi-
nantly in a few fragmented reserves and parks, than are
currently in captivity, predominantly in research labs.
Squirrel monkeys are found from southern Central America
(Costa Rica and Panama) to the northern part of South
America. They are the most commonly used of the New
World primates in biomedical research and perhaps the
third most frequently used of all primates (
Abee, 2000
).
The squirrel monkeys have been subdivided into two
groups of species/subspecies of which one each is the most
commonly used species in biomedical research, Saimiri
boliviensis and S. sciureus. S. boliviensis is found in Brazil
and Bolivia while S. sciureus is found in Brazil, Colombia,
French Guiana, Guyana, Suriname, and Venezuela.
The owl (or night) monkey, once considered a single
species, is now regarded as eight species subdivided into
two groups of species by the Amazon River. Species of
gray-necked and red-necked owl monkeys live north and
south of the Amazon River, respectively. It is the group
south of the Amazon of which the most commonly used
owl monkey in biomedical research, Aotus nancymaae,is
a member. A. nancymaae, also known as the Peruvian red-
necked owl monkey, is restricted to a small region of
Phenotypic Diversity
Platyrrhines differ from catarrhines by their broad flat noses
with widely separated nostrils that open from side to side,
a 2.1.3.2 or 2.1.3.3 dental formula (in contrast to the 2.1.2.3
dental formula of catarrhine primates), the absence of ishial
callosities on the rump (that are found in catarrhine
primates), and the presence of a prehensile tail with hair-
less, tactile pads on its underside. New World primates are
also smaller than Old World primates, exhibit less sexual
dimorphism, are arboreal rather than predominantly
terrestrial like the catarrhines, and have a tympanic ring,
rather than a tube, connecting the tympanic membrane to
the external ear.
Marmosets and tamarins are the smallest of all primates
and resemble each other, with the principal difference
being the larger incisors of the marmoset, adapted for
extracting sap from trees, and the correspondingly longer
canines of the tamarin (
Haig, 1999
). Otherwise, the colors
and patterns of species of both taxa are species-specific as
are their characteristic tuffs, manes, and mustaches. For
example, the cotton-top tamarin, the tamarin species most
often used in biomedical research, gets its name from
a white fan of long white hair on its head. Its fur is grey-
brown at the shoulders, back, rump, and most of its tail,
reddish brown on the backs of its thighs and base of its tail,
and white on its stomach and limbs. Tamarins and
marmosets are the only primates that regularly produce
more than a single offspring at a time. They are regarded to
