NONHUMAN PRIMATES: Taxonomy and Use in Research

There is disagreement among taxonomists as to the classification of nonhuman primates. However, depending on the classification system used, there are two -- and sometimes three -- principal suborders recognized in the order Primates. Using Kavanagh’s classification, the prosimians are of the suborder Strepsirhini, and the simians are of the suborder Haplorhini. The Napiers classification add a third suborder, Tarsioidea, for the group of tiny insectivorous primates known as the tarsier

We will primarily use the Napiers’ system of classification in this course, which includes three suborders, Prosimii, Tarsioidea, and Anthropoidea. The anthropoideans are very important to use in research and will be covered in the most detail.

Don't panic over all these suborders, infraorders and superfamilies Don't panic over all these suborders, infraorders and superfamilies!  DON'T memorize this information.  This taxonomic breakdown is intended to give you an idea of the relationship of the different primates, nonhuman and human.

Prosimians Suborder Prosimians The first of the three suborders is the prosimians. Prosimians, or strepsirhines, differ from the simians, or haplorhines, in several ways.

Prosimian characteristics Prosimians have a wet patch of skin around the nostrils, which is joined to the upper lip. They have an anatomical characteristic called a dental “comb” — made up of the lower incisors, which project forward horizontally and in parallel, like a comb. They also have a horny structure under the tongue known as the sublingula, which is used for cleaning debris off the dental comb. Most of them are nocturnal and all possess a tapetum lucidum, a crystalline shield that lies behind the eye’s light-sensitive retina and reflects light back onto the retina, thus improving vision under poor light conditions

Prosimians/ Varecia variegata This is a photo of a prosimian, a ruffed lemur (Varecia variegata) from Madagascar. Prosimians rely primarily on their sense of smell. They can detect and interpret smells expertly, and they leave smell messages of various kinds for each other. In addition to the lemurs, lorises, galagos, indriids and aye-ayes are also prosimians

Tarsioids Suborder Tarsioidea The second suborder is the tarsioids, which have characteristics of both the prosimians and anthropoiedeans. The suborder Tarsioidea contains one family, Tarsiidae. There are three species of tarsiers, Tarsius syrichta (Philippines tarsier), Tarsius bancanus (Horsfield’s tarsier), and Tarsius spectrum (spectral tarsier).

Tarsius syrichta Tarsiers have an average weight of only 120 grams (or 4.25 ounces), and are nocturnal animals. Because they are not heavily used for research purposes, we will not focus on the tarsioids, but move on to the simians

Simian Suborder Anthropoidea We will now move away from the prosimians and tarsioids, and will be considering the third and final suborder, Anthropoidea, known as the simian primates.

Simian characteristics Whereas the prosimians (or strepsirhines) have a wet patch of skin around the nostrils, the simians (or haplorhines) have hairy skin between the nostrils and the upper lip. They do not have a dental comb or sublingula and most have poor night vision. They have a poorly developed sense of smell compared to prosimians and most are diurnal. Note the map in the background, indicating that the simians originate from both the “new world” and the “old world”. This map will vary as we proceed to discuss simians from around the globe. Old world New world

Simians The suborder Anthropoidea is categorized into New World monkeys (of the infraorder Platyrrhini) and Old World monkeys and apes (of the infraorder Catarrhini).

New World monkeys We will talk in some detail about the New World and Old World families. But for now, compare some of the features of the New World monkeys shown on this image Saimiri sciureus Cebus albitrons

Old World monkeys with those of these Old World monkeys. Erythrocebus patas Macaca nemestrina

New World monkeys Infraorder Platyrrhini The two families of New World monkeys (infraorder Platyrrhini) are the Cebidae and the Callitrichidae, both of which include genera which are quite useful in biomedical research.

New World monkeys New World monkeys, originating in South and Central America, are known as platyrrhine monkeys because of their widely separated nostrils, which usually open to the side having a broad (flat) nose”

New World characteristics. None of this group has cheek pouches or rump callosities. The thumb is semi-opposable and the great toe is opposable. Males of most species have an os penis or baculum, but it is lacking in Aotus, Ateles, and Lagothrix. Some New World monkeys are known to possess color vision and some have prehensile tails also “a slender bone reinforcing the penis in some mammals” “adapted for grasping or seizing”

Family Cebidae The family Cebidae includes several genera which are important in biomedical research: Saimiri spp squirrel monkeys Aotus spp owl monkeys Cebus spp capuchins Ateles spp spider monkeys Lagothrix spp woolly monkeys

Squirrel monkeys Saimiri sciureus, or squirrel monkeys, are small in size, diurnal, and arboreal. They normally have only one offspring and males are polygamous

They are used in dental, cancer, vision, cardiovascular, and infectious disease research. They were recently shown to be susceptible to Plasmodium falciparum, making them extremely valuable for malaria research.

Owl monkeys The Aotus spp, or “owl monkeys” – also known as douroucouli monkeys or night monkeys – are small, nocturnal and arboreal.

Owl monkeys/use in research Owl monkeys have long been valuable models of human malarias, other infectious diseases, and models for vision research

Capuchins Cebus spp, or capuchins, are larger than squirrel and owl monkeys. Also known as ringtail monkeys, the capuchins are diurnal and both arboreal and terrestrial.

Capuchins/use in research & non-research use They are used in pharmacologic, infectious disease, and behavioral research. These highly intelligent primates are tractable; in fact, many have been used as “organ-grinder” monkeys. Recently they have made valuable contributions as helping hands for the physically handicapped.

Spider & woolly monkeys Other platyrrhines of the family Cebidae – such as Ateles spp, or spider monkeys, and Lagothrica spp, or woolly monkeys – are used in research. These platyrrhines are relatively large, have prehensile tails, and are diurnal and arboreal animals.

Spider & woolly monkeys/use in research Spider monkeys and woolly monkeys are used in studies of the cardiovascular system and in studies of infectious diseases. One particular species of woolly monkeys, Lagothrix lagothrica, is used in research.

Marmosets & tamarins Marmosets (Callithrix spp) and tamarins (Saguinus spp) are from the family Callitrichidae. Callitrichids are small in size, diurnal, frequently have twin births, and males assist in caring for the young

Marmosets & tamarins/use in research Marmosets and tamarins are used for cancer and hepatitis research, and also for a variety of other studies.

Old World monkeys & apes We now move along the taxonomic chart from the New World (infraorder Platyrrhini) to the Old World (Infraorder Catarrhini). We will be addressing both the Old World monkeys (of the Cercopithecoidea superfamily) and the Old World apes (of the Hominoidea superfamily).

Old World monkeys & apes These primates have catarrhine noses (so-called because their nostrils are separated by a narrow nasal septum) and are hence from the infraorder named Catarrhini. The narrow downward nostrils of the catarrhines help distinguish these Old World monkeys from the platyrrhines

Old World characteristics Old World monkeys usually rest in a sitting position and accordingly are equipped with ischial callosities, which are tough pads of cornified skin located over the bony prominances of the buttocks. Ischial callosities are not present in New World monkeys, making this feature an important identifier

Old World characteristics Some Old World monkeys are arboreal or terrestrial, some both. Scent marking and smells are of little importance compared with prosimians or New World monkeys. They have nails rather than claws on all digits, similar to humans or apes. Their thumbs are truly opposable. All species are diurnal. None has a truly prehensile tail.

Cercopithecidae Family The Old World monkeys (superfamily Cercopitchecoidea) are all represented within the single family Cercopithecidae. Taxonomically, the family Cercopithecidae is divided into two distinct subfamilies: the Colobinae and the Cercopithecinae. monkeys with tails”

Subfamily Colobinae The colobine monkeys include the genera Colobus, Procolobus, Presbytis, Pygathrix, Rhinopithecus, Nasalis, and Simias. These monkeys are rarely used, and generally only in biological research. The Old World colobine monkeys are leaf-eaters.

Subfamily Cercopithecinae Several genera of the Cercopithecinae subfamily are valuable for biomedical studies. Most of the cercopithecines are omnivorous. The Old World cercopithecine monkeys include the genera Macaca, Cercocebus, Papio, Mandrillus, Theropithecus, Cercopithecus, Miopithecus, Allenopithecus, and Erythrocebus.

Tail length Within the subfamily Cercopithecinae all species have tails, but two groups are known by common names as “long-tailed” or “short-tailed” monkeys.

Long-tailed monkeys “Long-tailed” monkeys include: Cercopithecus spp-(guenons) Erythrocebus patas-(patas) Cercocebus spp (mangabeys)

Guenons The long-tailed Cercopithecus includes 20 species of guenons, including the African “green” or “savannah” monkeys.

Green monkey The African green reproduces prolifically and is said to be perhaps the world’s most common species of monkey. Adults weigh 5 - 7 kg, and males are larger than females. Cercopithecus aethiops (the African green monkey) naturally occurs in that part of Africa between the desert fringe and the forest of subsaharan Africa.

Green monkey/use in research African green monkeys are used regularly for physiological, neurobiological, immunological, cardiovascular and other research studies.

Patas The second group of long-tailed monkeys is the Erythrocebus patas, or patas monkeys, also commonly known as the red, hussar, or military monkey

Patas Patas are mainly terrestrial and they range within the drier, more open regions of Africa’s savannahs and semi-deserts in the sub-saharan region. They are large with females about 7 kg and males over 10 kg. They are used mainly in infectious disease research

Mangabeys The third long-tailed cercopithecine monkey group is the Cercocebus spp. (or mangabey). Mangabeys are mild-mannered and arboreal, although some are arboreal-terrestrial. They are diurnal central African forest dwellers.

Mangabeys Adult mangabeys reach a weight of 7 - 11 kg. Males are larger than females. Mangabeys are valued in biomedical research for neurobiological, cardiovascular and other studies.

Short-tailed monkeys The so-called “short-tailed” monkeys include the several species of the genus Macaca — that is, the macaques. Tail length, however, is not a consistent criterion. For example, within the macaques, tail lengths vary from quite long as for M. fascicularis (known as the long-tailed macaque), to short as for M. arctoides (known as the stump-tailed macaque), to almost absent in M. sylvana (once, because of the lack of a tail

Macaques Macaques, subfamily Cercopithecinae, are arboreal-terrestrial. They live in habitats varying from tropical flatlands to frigid mountains, and all have dominance hierarchies in their social systems. The young weigh about 450 g at birth, nurse approximately a year, mature at around 3-4 years, and live up to about 30 years. They are large (about 2.5 - 15 kg) as adults

Rhesus & long-tailed/use in research Several species of this group are valuable biomedical research models. The Rhesus (Macaca mulatta) and Cynomolgus also called long-tailed macaque or crab-eating macaque (Macaca fascicularis) are useful in physiology, hematology, reproduction, cardiovascular, infectious disease, and behavioral research.

Rhesus & long-tailed/use in research They have been used in vaccine development and drug testing for many years.

Other macaques/use in research Other macaques used in research include: Macaca arctoides (stump-tailed macaque) Macaca nemistrina (pig-tailed macaque)

Other macaques/use in research Macaca radiata, or the bonnet macaque Macaca nigra, or the Celebes black macaque

Baboons The last genus of the subfamily Cercopithecinae which is the Papio, or baboons. Baboons were once known as Cynopithecoids or “dog-monkeys” because of their elongated faces

Baboons The Papio spp. live outside the closed-canopy forests of Africa except the deserts and are mainly terrestrial. Inherently ferocious, they are tractable and readily learn a variety of tasks. Adults weigh 18 - 30 kg, males larger than females.

Baboons/characteristics and use in research They travel in troops, and males form harems of 6-10 females. Baboons are valuable research animals and are used in a variety of studies in dentistry and medicine. They have been useful in immunology, cardiovascular, reproduction and transplantation research.

Hominoidea The last catarrhine group which we will consider is the Hominoidea. This superfamily of Old World apes includes both the lesser apes, the great apes and the human primate, man. These animals are infrequently used in research because they are generally either on threatened or endangered status. The lesser apes are classified as the Hylobatidae family. The great apes are classified as the Pongidae family.

The apes are the tailless nonhuman primates native to Africa and the southern portions of Burma, the Malay peninsula, Indonesia, Java, Borneo, and other islands of that region.

Siamang The Hylobatidae Family includes the gibbons and siamangs

Orangutan The Pongidae Family includes the orangutans

Gorilla

Chimpanzees Chimps are native to Central Africa. The Pan spp. are threatened but, nevertheless, are important to biomedical research. Importation is prohibited and domestic breeding programs produce those that are being used

Chimpanzees are used in behavioral, infectious disease, and other studies. They play a particularly important role in research on hepatitis and AIDS. Adult females weigh 35-45 kg, males 40-50 kg.

Restrictions on importations in the 1970s and concerns over endangered primate populations led to the establishment of eight  primate centers in the United States for captive breeding of nonhuman primates.  This has reduced laboratory demand on wild nonhuman primate populations.  The centers also coordinate increased sharing of animals in studies to decrease the number of primates needed.  The primary species bred at these centers are rhesus macaques, squirrel monkeys and chimpanzees

Approximately 15,000 wild-caught primates continued to imported into the United States annually.  Most of these are rhesus, cynomologus, squirrel and owl monkeys from the Philippines, China and Peru.

In December 0f 2000, President Clinton signed the Chimp Sanctuary Bill (Chimpanzee Health Improvement, Maintenance and Protection).  This established a "retirement" facility called Chimp Haven for chimpanzees no longer needed for research.  

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