Introduction to squirrel monkey issue. ILAR 41 (1): 001.
The squirrel monkey (Saimiri sciureus) is a small South American primate that is recognized as an important animal model in
biomedical research. Because of their status near the middle of the primate evolutionary scale, complex behavioral tasks are within their
capabilities. Their physiological functioning is also at a level at which significant comparative work may be done. Similarities in diseases,
endocrine function, and physiologic responses exist between humans and squirrel monkeys. Some research areas in which the use of
squirrel monkey has contributed significantly include neurosciences, reproductive biology, and behavioral pharmacology. An unusual
biologic phenomenon of neotropical primates like the squirrel monkey is glucocorticoid resistance. There are two definitive texts devoted to
this primate as a research animals. The first is The Squirrel Monkey (Rosenblum and Cooper, 1968) and the other is the Handbook of
Squirrel Monkey Research (Rosenblum and Coe, 1985). The literature on the squirrel monkey continues to grow steadily.
Questions:
1. Which of the following primates have a lissencephalic brain?
a. Rhesus macaque
b. Squirrel monkey
c. Baboon
d. Marmosets
e. A and C
f. B and D
g. None of the above
2. What are the two families of the infraorder Platyrrhini? To which family do squirrel monkeys belong? To which subfamily do squirrel
monkeys belong?
3. Which of the following statements are FALSE with respect to squirrel monkeys?
a. Have high blood cortisol concentration
b. Readily develop atherosclerosis when fed dietary cholesterol
c. Have caniniform incisors
d. Have a high requirement for folic acid
e. Males exhibit "fatted male phenomenon" during breeding season
Answers:
1. F.
2. Cebidae and Callitrichidae. Squirrel monkeys belong to the family Cebidae and the subfamily Saimiriinae.
3. D. Marmosets have caniniform incisors.

 Squirrel monkey (Saimiri spp) research and resources. ILAR 41 (1): 002.
Advantages of Squirrel monkeys as Research Subjects
Squirrel monkeys are the most common neotropical primates used in biomedical research due to their small size and ease of handling, weighing less than 1 kg compared to 4 to 5 kg of the female rhesus monkey.
No B virus.
Taxonomy: Genotypic and Phenotypic Characteristics
All squirrel monkeys were thought to be of the same single species with several geographically separated subspecies. Karyotypic and phenotypic characteristics have led to the fact that squirrel monkeys are classified as a single genus with four species and nine subspecies. The most common used phenotypic characteristic for identification of squirrel monkeys is the shape of nonpigmented hair above the eyes. The "gothic arch" possessing a pointed arch of whitish hair above each eye is seen in S. sciureus while a "roman arch" is seen in S. boliviensis characterized by more shallow semicircular patterns above the eyes. Squirrel monkeys of the roman arch usually have black hair crowning their heads and gothic arch squirrel monkeys have gray green agouti coloration. The Guyanese squirrel monkey possesses a pattern of pigmented hairs within the patch of whitish hairs above each eye, which resembles an eyebrow.
All squirrel monkeys examined have 44 diploid chromosomes and more certain identification can be made of the acrocentric autosomes and observing periocular patches. There is sexual dimorphism in squirrel monkeys with males 25 to 30 % heavier than females and males also have longer canines than females. These differences are more subtle than in many old world primates. It is very important to identify the three different species to prevent in breeding. Colonies that have interbreeding can lead to pericentric inversions, which can lead to nonviable gametes due to crossovers at the inversion loop during meiosis. Furthermore, mixing of the species and subspecies within experimental groups may create confounding variables caused by different responses to experimental manipulation.
Sources of Squirrel Monkeys for Research
The exportation of the Bolivian squirrel monkey S. boliviensis boliviensis was banned by the Bolivian government in 1983 and by the late 1980s only Peruvian squirrel monkeys were available from the wild. In the past 2 years fewer than 100 Peruvian squirrel monkeys have been exported from Peru through the Peruvian Primatology Project administered through the Pan American Health Organization and 719 Guyanese squirrel monkeys from Suriname were exported in the late 1990s. Feral-origin squirrel monkeys share similar weaknesses with unknown medical histories, frequent parasitic infections and the possibility of natural malarial infections.
Domestic Squirrel monkeys
There were three federally supported breeding colonies in the US. One was located at the U. of South Alabama consisting of 271 squirrel monkeys supported by the United States Agency for International Development used for testing the efficiency of potential malarial vaccines. This program expired in 1994 and the animals were donated to the CDC for its malarial program. Later, these animals were transferred back to the U. of South Alabama. A second colony of 150 Peruvian maintained by NASA at the U. of Wisconsin was maintained for aerospace research. The Wisconsin colony was transferred to Mannheimer Foundation, a private colony in south Florida. The SMBRR Squirrel Monkey Breeding Research and Resource at the U. of South Alabama is now the only breeding colony in the US.
South American Squirrel Monkey Breeding Resources
There are two colonies is South America, one in French Guiana, the larger facility located at the Pasteur Institute which maintains 1000 animals at two sites in indoor or semi-free ranging on an island. The other breeding colony is located at Centro Argentina De Primares (CARPRIM) in Corrientes Argentino and is composed of Bolivian monkeys that are no longer available from other sources.
Usefulness Squirrel Monkey Research Areas
Their small size, ease of handling and ability to tolerate high gravitational forces made the squirrel monkey ideal for physiological studies of the effects of space flight. Squirrel monkeys maintained under laboratory conditions and also in captivity were found to have fatty plaques in their aortas resembling human atherosclerosis and were used to describe the pathogenesis of atherosclerosis. Animals were fed experimental diets high in fat trying to produce atherosclerosis. They developed cholelithiasis and were used in describing the experimental induction of cholelithiasis. Squirrel monkeys were also used for parenteral hormone administration and artificial insemination to successfully induce ovulation and artificial insemination in a nonhuman primate.
Research Using the Squirrel monkey at the SMBRR
The squirrel monkey is an important animal model for malaria vaccine development studies because Plasmodium spp. which cause malaria are host specific animals for studies of human malaria. The Bolivian squirrel monkey is shown to be a superior model P falciparum Indochina I and produces lesions similar to those reported in humans. The Guyanese squirrel monkey experimentally is found to be a less suitable model.
A new variant of Creutzfeldt-Jakob Disease (CJD), a fatal spongiform encephalopathy of humans which is thought to be transmitted to humans by consumption of contaminated beef. The squirrel monkey has been recognized as one of the nonhuman primates most susceptible to experimental infection of CJD and other transmissible spongiform encephalopathies. The susceptibility of the squirrel monkey is believed to be genetic which is 93.8% homologous to the human PrP sequence that is associated to infection in humans.
The squirrel monkey was chosen to understand the biomechanics of labor and delivery in nonhuman primates. In women, the flexed position of the fetus and its rotating fetus is well documented in humans but is unknown in primates. Data consisted of a series of radiographs taken in a specially designed cage during labor and delivery in the Bolivian squirrel monkey. Fetal rotation in squirrel monkey during labor and delivery was similar to that in humans. A lesion, Pelvic Organ Prolapse (POP), observed in labor and delivery of humans has been reported in older squirrel monkeys. This has been observed in female squirrel monkeys three years and older. The incidence and severity changed depending whether evaluation was made in the breeding season spring or nonbreeding season (early fall).
Squirrel monkeys were chosen to determine whether elastase-induced emphysema would abrogate emphysema with new alveoli production after treatment with retinoic acid. Their small size would reduce the amount of elastase needed.
Questions:
1. What are the three primary species of squirrel monkeys used in research?
2. What is the primary phenotypic characteristic used to identify the squirrel monkey?
3. What are three primary uses of squirrel monkeys in research?
Answers:
1. Bolivian-Saimiri boliviensis boliviensis, Peruvian-Saimiri boliviensis peruviensis, Guyanese-Saimiri sciureus sciureus
2. The shape of the nonpigmented hair above the eyes.
3. Atherosclerosis, Creutzfeldt-Jakob Disease, and Pelvic Organ Prolapse

 Research techniques for the squirrel monkey (Saimiri sp.). ILAR 41 (1): 010.
Basic biology and husbandry ­ Are arboreal. Live in large groups in the wild. Do not spend much time on floor of cages, rather prefer multiple levels of perches. Differences between squirrel monkeys and macaques = squirrel monkeys have absolute nutritional requirement of Vit D3, females lack mensus, show marked seasonality in reproduction (males often gain significant weight (fattening) during mating season. Normal hematological and blood chemistry values can be found on the web (http://www.saimiri.usouthal.edu/prl).
Biosafety ­ Squirrel monkeys are carriers of: 1) Herpesvirus saimiri ­ is oncogenic in other primates and can infect and transform human T lymphocytes in vitro and 2) Herpesvirus tamarinus ­ can cause fatal disease in Aotus and some other New World primates. Whenever working with squirrel monkey or their tissues or body fluids, humans should follow recommendations outlined in the Universal Precautions for Workers Handling Human Blood, Body Fluids and Tissue in the Workplace (CDC 1988).
Squirrel monkeys are NOT known carriers of Cercopithecine herpes virus 1. They are also more resistant to tuberculosis infection than are macaques.
Taxonomy ­ Saimiri are generally grouped into 4 species and 9 subspecies. Those commonly used in biomedical research usually only include 2 species (Saimiri sciureus and S. boliviensis) which are divided among 3 subspecies.
Biochemical markers should be used in pedigree validation for many reasons including the fact that infants will often be carried by females in a group who are not their dams (allomaternal behavior).
Identification of animals ­ Many methods have been used including tattoos, neck tags (nice for group-housed animals, can come in multiple colors, but have to be careful not to injure the animal with inappropriately sized collar), and implantable microchip transponders. Can approximately determine an animals age through examination of dentition.
Hypothermia and Hypoglycemia ­ Squirrel monkeys experience rapid heat loss when they are anesthetized or debilitated due to their small size, low body fat, and long extremities. Awake, restrained animals normal body temperature = 38-39.5 degree C. Healthy, active, struggling animals temp may quickly increase to 41 degrees C. A seriously ill animals temperature may be less than 37.7 degrees C.
Electronic thermometers, designed for human use, can be used in squirrel monkeys of all ages. Tympanic membrane thermometers can be used in adult squirrel monkeys. However, they do not work well with infant or small juveniles.
Hypothermic animals can be supplied with supplemental heat via incubator-type cages, re-circulating pads (water blankets), or heat packs that use a controlled exothermic chemical reaction. Electrical heating pads should not be used.
Squirrel monkeys are predisposed to hypoglycemia. Normal blood glucose concentration = 80 +/- 28 mg/dl. Hypoglycemic animals that are still conscious can be given oral glucose or sucrose. Unconscious animals should be given sterile 20% dextrose via stomach tube (infants ­ 1ml, juveniles ­ 3-5ml. and adults ­ 10ml). Concentrated IV glucose solutions are not recommended.
Restraint ­ Methods of restraint = manual restraint, chair restraint, and pole-and-collar methods.
Physiological responses shown to be caused by methods of restraint: capture and chain restraint can cause adrenal cortical activation and growth hormone release. Manual restraint can cause elevation in glucagons. General anesthesia with ether can cause growth hormone release in squirrel monkeys. Ketamine anesthesia MAY cause changes in glucose tolerance tests. Sodium thiopental can cause PVCs.
Clinical Techniques ­
Orogastric or nasogastric intubation ­ use a number 5 French infant feeding tube. Technique is the same as for other species.
Blood sampling and injections ­ The volume of blood that can be safely collected from a squirrel monkey is directly proportional to its body weight. In general, no more than 10 ml of blood/kg body weight should be collected at one time. Large samples (>0.25 ml) are best taken from the femoral vein or the lateral tail vein. Small samples can be taken from the saphenous veins. All three sites can be used for injections.
Subcutaneous injections can be administered between the scapulae. Intramuscular injections can be administered in the rear leg, but care must be taken to avoid the ischiatic nerve.
Anesthesia and Analgesia ­ Many of the methods and drugs used in other species can also be used in squirrel monkeys. However, long-acting barbiturates (ex. sodium pentobarbital) should only be used for terminal procedures due to their tendency to cause respiratory depression and prolonged recovery in squirrel monkeys.
Isoflurane is a very well tolerated inhalation anesthetic. Use of a non-rebreathing anesthesia circuit (such as a Bain Coaxial Circuit) is recommended.
Analgesics should be used after survival, surgical procedures. Buprenorphine (0.01mg/kg IM or IV q 12 hrs) is effective and causes little sedation.
Digestive System ­ Since squirrel monkeys are omnivores, they should be given supplemental food items (such as vegetables, fruit, mealworms, etc) in addition to a high quality New World biscuit. Lack of Vit C can result in scurvy which may present in unique ways including formation of cranial hematomas (cephalhematomas) in advanced stages.
Cardiovascular System ­ Squirrel monkeys were one of the first primate models of human atherosclerosis. Monkeys fed atherogenic diets are prone to gallstones. Since squirrel monkeys have been used as models of human heart disease, many studies have been conducted to determine Œnormal cardiovascular values in these animals.
Semen Collection and Preservation ­ Semen can be collected by 1) training the animals to masturbate, 2) electroejaculation, and 3) vibrostimulation. Vibrostumulation is recommended due to increased sample quality and decreased effort on the part of the researcher (no anesthesia or training of animals required). Care must be taken to avoid thermal burns to the rectum if electroejaculation is utilized.
Female Urogenital System ­ A radiographic technique has been developed to evaluate the patency of squirrel monkey oviducts. This is done by clamping off the cervix, injecting contrast media into the uterus, and then visualizing media within the abdominal cavity.
Ovulation can be induced by an injection regime using follicle-stimulating hormone and human chorionic gonadotropin hormone.
The gestation period of a squirrel monkey is 148 to 160 days (ave = 150 days). Pregnancy can be determined by manual palpation at 28-35 days. Alternatively, gestational stage can be determined by measuring the fundal height from the cranial symphyseal border to the highest point of the convexity of the gravid uterus. Ultrasonic imaging studies of the developing fetus have also been performed.
Dystocia is relatively common. This is likely partially due to the fetus large head size. Also, infants may have large birth weights. The average birth weight is approximately 105-120g which is about 15-17% of the dams weight in a males birth or 5-8% in a females birth. Dams receiving c-sections often reject their infants. Therefore, fostering or nursery rearing ins required. Fostering is far preferable. When nursery rearing is required, the infant must be fed hourly, 15hr/day.
Endocrine System ­ Squirrel monkeys have a high resistance to glucocorticoids. Their cortisol levels are 12 times higher than those of humans or other nonhuman primates.
Nervous System ­ Small volumes (0.1 ­ 0.2 ml) of cerebrospinal fluid can be collected at the atlanto-occipital junction.
Special Senses ­ Squirrel monkeys are often used in studies of vestibular function. The rail test is used to assess balance while a stabilimetry technique is used to assess postural ataxia.
Necropsy and Perfusion ­ An animal may be perfused after placing it in a surgical plane of anesthesia. After the heart is exposed, a needle is used to introduce saline into the left ventricle. The right atrium is cut to allow blood and saline to escape. After fluid emptying from the right atrium has become clear, the fixative solution is administered through the needle placed in the left ventricle.
Additional info ­ Age at sexual maturity = 2.5 ­ 3.5 years. Life span = approx 21 years. See article for dosages of recommended sedation and anesthetic agents.
Questions:
1. To what genus do squirrel monkeys belong?
2. Have squirrel monkeys been shown to be carriers of Cercopithecine herpes virus 1?
3. Name 2 conditions to which squirrel monkeys are particularly prone.
4. (T / F) Sodium pentobarbital is an excellent anesthetic for use in squirrel monkey survival surgeries.
5. (T / F) Dystocias are common in squirrel monkeys.
Answers:
1. Saimiri
2. No
3. Hypothermia and hypoglycemia
4. False, sodium pentobarbital is recommended for use only in terminal procedures.
5. True. This may be due to the large head size of infants as well as their large body weight when compared to that of the dam.

 Steroid resistance in the squirrel money: an old subject revisited. ILAR 41 (1): 019.
This article is a review of the molecular events that led to hypercortisolemia in squirrel monkeys.
It summerizes why homone elvated hormone levels are imortant to laboratory animal science as follows: 1) high circulating levels of some seteroid homones are a normal finding in captive squirrel monkeys, 2) it is generally ageed that this phenomenon has occured as a nomal physiological response to a state of hormone insensitivity or resistance in responsive tissues which mediate the feedback response,3) squirrel monkeys have a relatively normal pitutitary-adrenal phosiology at a higher homonal set-point. Therefore they have an appropriate response to chair restaint and social and environmental manipulation. They are relatively insensitive to the effects of adminstered steroid. They require almost 50x more dexamethasone to achieve a 50% suppression of plasma cortisol levels compared with cynomologus monkeys.
The total level of cortisol is squirrel monkeys is more than 10 times that in humans. Only 4-6% of total cortisol in humans is serum unbound, more than 1/3 of squirrel monky serum is free. This cortisol is maintained at a high level in squirrel monkeys by high levels of adrenocorticotrophin drive increases the synthiesis and secreation of cortisol form the adrenal gland, low rate of metabolic clearance of corosol, perripherial 11beta -hydroxysteriod dyhydronease appears to favor conveerson of inactive cortisone to cortisol. They posses multiple mechanisms to maximixe the levels of free cortisol to compensate for end-organ resistance.
Using reverse transcription-polymerase chain reaction, the author and his colleagues cloned and sequenced the squirrel monkey glucocorticoid receptor (GR). They found that the Squirrel monkey receptor is 97% identical in nucleotide and amino acid sequence to the human receptor's sequence. They found out that the amino acid substitutions within the ligand binding domain of the squirrel monkey GR cannot account for its low binding affinity. It suggests that cytosolic milieu of squirrel monkey cells affects the binding affinity of the squirrel monkey GR.
They then analyzed GR associated proteins. They speculated that low binding activity of the squirrel monkey GR might result form a deficency in or a mutation of one of the heterocomplexes. They first compared the levels of componest of GR heterocomplex in squirrel monky and human lymphoblast. The most differences were seen in the levels of immunophilins FKBP51 and FKBP52. The FKBP51 was more than 10 fold higher in the squirrel monkey cells and FKBP52 was approx one half that in human cells. They also discovered that the inhibitory effect of cytosol from squirrel monky cells on GR binding was reproduced using cytosol form COS-1 cells transiently trasfected with an expression plasmid encoding squirrel monkey FKBP51, supporting the conclusion that inhibitory factor in squirrel monkey cells is FKBP51. How is not known. But it is thought that FKBP51 overepression is the major cause of gluccocorticoid resistance in the squirrel monkey.
Questions:
1.T/F Squirrel Monkeys have lower circulating levels of cortosol than humans?
2. The presense of what immunophilin complex appears to be the maor cause of glucocorticoid resistance in the squirrel monkey?
3.T/F All monkeys in the Callitrichidae family exhibit high levels of cortisol
Answers:
1. False
2. FKBP51
3. False

 Squirrel monkey behavior in research. ILAR 41 (1): 026.
Squirrel monkeys are valuable animal model used for research in atherosclerosis, neuroscience, pharmacology, psychiatry, toxicology, and vision research.
In the past 10 years there have been over 200 articles that refer to the use of behavioral testing of squirrel monkeys.
The article was divided into three major sections, natural behavior, conditioned behavior, and neurobehavioral assessment profiles.
Natural behavior- data collected on squirrel monkeys as they move about their environment either in a natural field setting, a semi natural setting or a captive laboratory environment.
Natural behavior falls into three categories,
1. Behavioral events
2. Behavioral states
3. Behavioral stereotypes
Behavioral events can be brief or can last a relatively long time. Examples would be slap, grab ot hit would be instantaneous, sitting in contact with another animal could last for hours.
There are four major ways to collect natural behavior data. These are:
1. ad libitum scoring where an animal or group of animals is observed for the presence or absence of a response and all occurrences are recorded
2. focal animal observations, where collector observes the onset and ending of behavioral states but only collects data on one animal at a time.
3 .instantaneous scans of a group; behavioral states of the group are assessed at preselected times,example percentage of time found sleeping.
4. one-zero methods: data collection that involves recording whether a response
occurs within a predetermined time. So if an animal scratches itself once or ten times in a set time, they will receive a score of one, if they do not scratch at all they receive a score of 0.
Social behavior of squirrel monkeys
In the wild squirrel monkeys inhabit most types of tropical forest including wet and dry. They are omnivores that eat insects when available but also include fruit, flowers, and lizards when available. They are found in large groups of 50 or more including males and females. Latest reports indicate that they forage as cohesive groups.
In captivity social groups are maintained with one or two males per group due to problems with aggression due to the close confinement. Free ranging squirrel monkeys have four major types of vocalizations: smooth chucks, bent mast chucks, peeps and twitters. Peep calls increase as the group spreads out to forage. Twitters are associated with the beginnings of troop movement. In captive squirrel monkeys smooth chuck calls are associated with positive affiliative associations between monkeys.
Social organization- generally unified by the adult females. Sexual segregation occurs on a seasonal basis, males near the periphery of the group during the non breeding season. Squirrel monkeys in different geographic locations can exhibit more or less sexual segregation. Dominance hierarchies within squirrel monkey groups depend on species. S. boliviensis has a high degree of sexual segregation and have distinct linear dominance hierarchies among males S.
sciureus tend toward sexual integration in a social group, but still demonstrate a linear dominance hierarchy, with all males dominant over all females. S. oerstedi
do not exhibit dominance hierarchy among either sex.
Allomaternal care has been documented in squirrel monkeys. Most commonly it is a female that experienced a reproductive failure and it tends to be juvenile or young adult females. The yearly reproductive cycle includes a distinct 3 month breeding season with a birth season 6 months later.both sexes gain weight prior to breeding season, and weight gain in males is associated with increased spermatogenesis. In field studies birth season takes place based on rainfall and food availability.
Female squirrel monkeys reach maturity at 2.5 to 3 years. Estrous cycles are 7-8 days in duration. The breeding season for squirrel monkeys shifts when they are moved to the Northern hemisphere.
Conditioned Behavior Testing Protocols- this is a protocol that places the squirrel monkey in a situation in which it has to learn to respond to an environmental stimulus or set of stimuli. The two major types of conditioning protocols are classical and instrumental (operant). In classical conditioning, conditioned reflex actions of an animal are entrained to an environmental stimulus that would not normally elicit that reflex. Pavlov's experiment is an example of classical conditioning.
In instrumental (operant) conditioning, the monkey is required to initiate a response that if correct, results in a reward or a punishment. Types of experiments include active avoidance learning, passive avoidance learning, discrimination learning, reversal learning, processing if-then statements, delayed matching to test memory.
Neurobehavioral Assessment Scales
These scales are used to study the effects of different types of stressors on behavior or endocrinology or immunology of the test subjects.
The most commonly used human infant behavioral assessment scale is the Brazelton Neonatal Assessment Scale. This has been modified for use with non-human primate infants, and is referred to as the Infant Behavioral Assessment Scale ( IBAS). The IBAS is best performed when the non-human primate infant is 2 weeks old. The test takes about 115 minutes and consists of 50 different behavioral assessment scales applicable to a primate infant of 2 weeks of age.
These include visual orienting, motor maturity, motor activity, and state control
( which is assessment of infant's overall emotional state).
The IBAS has been used to show in squirrel monkeys that social relationship disruption can be a prenatal stressor of squirrel monkeys.
Questions:
1.Name the three types categories natural behavior falls into.
a. behavioral events, behavioral stressors, behavioral stereotypes
b. behavioral events, behavioral states, behavioral stereotypes
c. behavioral stressors, behavioral sequences, behavioral stereotypes
d. behavioral events, behavioral states, behavioral stressors
2. Squirrel monkeys can be found in what kind of groups in the wild ?
a. groups of 10 or less
b. groups of 20 females with no more than 2 males
c. multimale/multifemale groups of over 50.
d. individuals with offspring
3. Squirrel Monkey estrous cycle?
a. 7-8 days
b. 20-21 days
c. 9-10 days
d. 24 hours
4. Prior to breeding season, both males and females.
a. lose weight
b. gain weight
c. appetite decreases
d. forage less
5. What test is used to assess neurobehavior of an infant non-human primate?
Answers:
1. Brazelton Neonatal Assessment Scale.
2. Bazelton Neonatal Assessment Scale.
3. Infant Behavioral Assessment Scale
4. Primate Infant behavioral Scale.
1.b behavioral events, states and stereotypes
2.c multimale/multifemale groups of over 50
3.a 7-8 days
4.b gain weight
5.c Infant Behavioral Assessment Scale.

 Role of the squirrel monkey in parasitic disease research. ILAR 41 (1): 037.
This article is a literature review covering use of squirrel monkeys in the study of parasitic diseases, primarily of humans.
Order: Primates
Suborder: Anthropoidea
Family: Cebidae
Subfamily: Saimirinae
Genus: Saimiri.
Genus names are controversial with divisions into two or more species listed in different systems. Karyotyping has shown groups with 10, 12, and 14 acrocentric chromosomes. Most research literature refers to Saimiri sciureus, while some refer to country of origin, thus it is difficult to identify exactly which karyotype was used in the literature.
Diseases other than malaria for which the Squirrel monkey is used include: (these occur either in humans or as natural infections in squirrel monkeys or both)
Toxoplasmosis, Encephalitozoon cuniculi, Tritrichomonas mobilensis, Filarial parasites (frequently encountered naturally, experimentally infected with Dipetalonema), trypanosomes (T. rangeli and T. cruzi), Babesia microti, Leishmania donovani (good model for protracted course of infection), shistosomes (many species).
The most prevalent use of squirrel monkeys in parasitic disease research is with malaria parasites. This is divided in the review into malarial parasites of nonhuman primates, and those of humans. Nonhuman primate malarias are better adapted to development in monkeys than human types are.
NHP types:
Plasmodium brasilanum (affects Cebidae, similar o P. Malariae in humans, a chloroquine resistant type exists)
P. simium (Howler monkeys and Sprider monkeys in Brazil, similar to P. vivax of humans, squirrel m. can be infected, spread by Anopheles mosquitoes)
Monoclonal antibodies to P. malariae can abolish infectivity of P. brasilianum in squirrel m.
Old World monkey malarial parasites:
P. inui, P. fragile (similar to P. falciparum and used in vaccine trials.), P. knowlesi, and P. cynomolgi.
P. fragile and P. falciparum both show: deep circulation schizogony and sequestration, high virulence, no marked enlargement of host cell, no Shoffner's stippline, heavy pigmentation, small schizonts, and lack of true relapses. With P. knowlesi human infections have occurred, Exoerythrocytic (EE) bodies are seen in the liver.
Human malarial parasites: Plasmodium ovale, malariae, vivax, and falciparum are the main species of concern; all four have been used to infect squirrel monkeys. P. ovale and P. vivax are similar.
P. ovale shows EE bodies in the liver of squirrel m., but no blood stages. P. malariae causes quartan malaria in humans and has been experimentally been given to squirrel m. Infection of the monkey with P. vivax has met variable success; the Salvador I strain has high potential for vaccine development studies in squirrel m.
Many human strains can be given experimentally to monkey, but mosquitoes feeding on the monkey don't become infected.
Vaccines using recombinant circumsporozoite proteins and irradiated sporozoites have provided partial protection from P. vivax.
P. vivax is found worldwide, P. falciparum is worldwide but mostly in tropical and subtropical areas, the Owl monkey is the primary model for P. falciparum, but several strains have been adapted to squirrel m.
Three basic types of antimalarial vaccines are being developed: blood stage, sporozoite, and transmission-blocking.
Squirrel monkey hepatocytes have been used in karyotyping and genetic stability studies. Also, Plathologic changes of malarial disease have been studied in squirrel monkeys.
Questions:
1. Give the taxonomic chain for the squirrel monkey from Order to Genus.
2. Match the NHP malaria with the human type most similar:
a. Plasmodium brasilianum 1. P. falciparum
b. P. simium 2. P. malariae
c. P. fragile 3. P. vivax (and P. ovale)
3. T or F the species of squirrel monkeys are easily distinguished and consist of S. sciureus and S. osterdii.
4 T or F Toxoplasmosis, Trypanosomes, and Enephalitozoon cuniculi are also studied in Squirrel monkeys.
Answers:
1. Order: Primate, Suborder: Anthropoidea, Family Cebidae, subfamily: Saimirinae, and Genus: Saimiri
2. a - 2, b - 3, c - 1
3. F Speciation is controversial, three different chromosome numbers occur, and different taxonomists divide the species in different ways. Napier and Napaier used the two species listed in this question, others suggest four or more species names.
4. T