Seasonal changes of serum concentrations of estradiol and progesterone in Bolivian squirrel monkeys (Saimiri sciureus)

Serial measurements of estradiol (E2) and progesterone (P) were used to describe the ovarian cycle of the Bolivian squirrel monkey. Group-caged, sexually mature female squirrel monkeys, housed with males, were sampled daily between 0900 and 1100 hr. Sampling was carried out during the breeding and nonbreeding seasons, for periods of 19–20 days from September 1981 to May 1982. Seasonal differences in serum concentrations of E2 and P were found with low levels of E2 and P and an absence of preovulatory surges of E2 during the nonbreeding season. This pattern was also observed in some animals during the breeding season. An abrupt increase in serum P concentrations in December appeared to signal the onset of cycling. Cycling animals had well-defined peaks of E2 (450–9,500 pg/ml) followed by increasing levels of P, which were >200 ng/ml in some animals. After the breeding season, E2 and P levels returned to their initially low levels. Levels of both steroids in cycling animals were higher than those reported for other primates and for previous measurements made in squirrel monkeys. Cycle length based on time interval between consecutive E2 peaks varied from 6–12 days.     

Annual physiological changes in individually housed squirrel monkeys (Saimiri sciureus)

This study investigated whether annual changes in physiology occur in individually housed squirrel monkeys (Saimiri sciureus). Physiological measures were monitored for 20 months. Over the course of the study, all individually housed males and females exhibited clear annual changes in gonadal and adrenal hormone levels, and males exhibited species‐typical changes in body weight. Females exhibited a typical pattern of hormonal changes, with elevations in gonadal steroids occurring during the same months as elevations in cortisol. Males, however, exhibited an atypical pattern, as elevations in hormone levels were not synchronized with each other; rather, elevations in testosterone occurred out of phase with changes in cortisol and body weight. The timing of annual events in individually housed subjects was compared to that in nearby social groups, in which the timing of the breeding season from year to year was determined by social group formations and was outside the naturally occurring breeding season. Elevations of ovarian and adrenocortical hormones in individually housed females were synchronized with indices of breeding in heterosexual social groups. Similarly, weight gain in males was associated with elevations in cortisol and, as with socially housed males, tended to precede seasonal breeding in the social groups. In contrast, annual testosterone elevations for individually housed males were not synchronized with breeding in nearby social groups. We conclude that direct physical interaction is not required for the annual expression of breeding readiness. Synchrony of seasonality among squirrel monkeys may be accomplished by distant social cues in females, but males may require physical interaction for complete synchrony of annual physiological changes. Am. J. Primatol. 47:93–103, 1999. © 1999 Wiley‐Liss, Inc.     

Excretion of estrone,estradiol, and progesterone in the urine and feces of the female cotton-top tamarin (Saguinus oedipus oedipus)

The excretion of three gonadal steroids was studied in the urine and feces of female cotton-top tamarins (Saguinus oedipus oedipus). Each steroid, ¹⁴C-estrone, ¹⁴C-estradiol, and ¹⁴C-progesterone, was injected into a separate female cotton-top tamarin. Urine and feces were collected at 8 hr intervals for 5 days on the three tamarins. Samples were analyzed to determine the proportion of free and conjugated steroids. Steroid excretion patterns were determined by sequential ether extraction, enzyme hydrolysis, and chromatography. Labeled estrone was excreted in a slow and continuous manner into the urine (57%) and feces (43%) with 90% of the steroid conjugated. The nonconjugated form had an elution profile identical to ³H estrone, but the conjugated portion was not completely hydrolyzed by enzyme. Labeled estradiol was excreted primarily in the urine (87%) and was released rapidly. Over 90% of the injected ¹⁴C-estradiol was excreted in urine as a conjugate, of which 41% was converted to an estrone conjugate and the remaining 59% was excreted as a polar estradiol conjugate. Labeled progesterone was excreted primarily in the feces (95%), 61% of which was free steroid. Four to six individual peaks of radioactivity were found when using celite chromatography and high performance liquid chromatography (HPLC), indicating that progesterone is metabolized into several urinary and fecal metabolites. One of these peaks matched ³H-progesterone and others may be pregnanediols, pregnanetriols, and 17-hydroxyprogesterone. These steroidal excretion patterns help explain the atypical hormonal patterns seen during the tamarin ovarian cycle.     

Abnormal behaviors in nursery-reared squirrel monkeys (Saimiri sciureus)

Seventeen squirrel monkeys (Saimiri sciureus), 11 nursery-reared and six mother-reared, were monitored to clarify the type and degree of deviant behaviors that result from rearing this species in the nursery. Two observation periods were used: the first when the subjects averaged 6.7 months of age, the second when they averaged 15.5 months. Thirteen activities involving variations of nonnutritive orality, stereotypic posturing, and agitated behaviors were seen in the nursery-reared subjects, but never in the mother-reared subjects. No consistent gender, subspecies, or age differences were evident. Squirrel monkeys, like chimpanzees and some Old World monkeys, do develop atypical self-directed behaviors when deprived of normal stimulation during early development.     

Spontaneous cryptococcosis of a squirrel monkey (Saimiri sciureus) in French Guyana

An old female squirrel monkey (Saimiri sciureus) with a tumor-like growth of the lower jaw died in shock after 2 months of illness. Histological studies of different tissue samples demonstrated that the pathological agent was Cryptococcus. Multiple foci of fungus existed in the thoracic cavity with essentially pulmonary and glandular localizations.     

Osmotic fragility of erythrocytes in Bolivian and Brazilian squirrel monkeys (Saimiri sciureus).

Median corpuscular fragility of erythrocytes does not differ significantly between fed and fasted Bolivian and Brazilian squirrel monkeys and are similar to values reported in humans and rhesus monkeys. This report further confirms that the fasting hyperbilirubinemia present only in Bolivian squirrel monkeys with a Gilbert-like syndrome is not due to an increased fragility of erythrocytes and should be classified as a nonhemolytic hyperbilirubinemia.     

Postnatal changes of IgG and IgM levels in squirrel monkeys (Saimiri sciureus)

Serum IgG and IgM levels were measured in domestically bred squirrel monkeys (Saimiri sciureus) ranging in age from 0 days to 42 months, as well as in adult squirrel monkeys from the wild estimated to be 60 months or older. The results indicated that the transplacental transfer of IgG occurs in the squirrel monkey but the transferability is lower in the squirrel monkey than in the cynomolgus monkey. Immune response in the squirrel monkey occurs just after birth, as shown by IgM production.     

Mycobacterium kansasii infection in squirrel monkeys (Saimiri sciureus sciureus)

Abstract: This report documents asymptomatic infections of Mycobacterium kansasii in four of five tuberculin positive squirrel monkeys (Saimiri sciureus sciureus). The mycobacterial DNA amplified by polymerase chain reaction (PCR) from a bronchial lymph node had no affinity for the species specific probes of M. tuberculosis, M. avium, and M. intracellular, thus allowing the presumptive diagnosis of an atypical mycobacterial infection. Infection by Mycobacterium kansasii was confirmed by culture of bronchial lymph nodes from three monkeys. The source of the infection was never identified.     

Age-related hormonal differences in cycling squirrel monkeys (Saimiri boliviensis boliviensis)

This study was planned to evaluate the poor reproductive performance of aged squirrel monkeys in a self-sustaining breeding colony. Two groups of monkeys aged 6–8 years (Group 1), and >12 years (Group 2) were evaluated. During the midbreeding season, daily blood samples were obtained for a period of 35 days from 10 animals in each group. Blood samples were assayed for serum estradiol (E), progesterone (P), and bioassayable luteinizing hormone (bio-LH) concentrations and the data were analyzed by ANOVA (analysis of variance). Bio-LH surges were less frequent in the aged breeders (Group 2). Total P output during periovulatory period (day ?;3 to day + 3) and the total P output during the luteal phases of the estrus cycles were significantly lower in aged squirrel monkeys (Group 2, P < 0.003). Although E peaks occurred less frequently in Group 2, they had higher concentrations as compared to Group 1 (P < 0.003). Cumulative periovulatory and luteal phase E levels did not differ between the two groups. The reduction in P output in aged squirrel monkeys may interfere with proper implantation, thus contributing to the lower pregnancy rate observed in this age group. The decreased frequency of bio-LH surges indicated less frequent ovulations in the aged animals which may further impair reproduction with aging. © 1994 Wiley-Liss, Inc.     

Conditions of failure and recovery of maternal behavior in captive squirrel monkeys (Saimiri)

This paper deals with the functioning and malfunctioning of maternal behavior in relation to external and social conditions. During developmental studies in captive squirrel monkey groups, 49 mother-infant pairs were observed. There were several cases of maternal inadequacy subsequent to (1) postnatal transportation, (2) exaggerated social investigation by immatures,and (3) premature allomothering. Brief mother-infant separations by humans did not yield such failures. One female consistently prevented nursing with at least three of her five viable offspring. Complete or partial failure of maternal behavior did not preclude subsequent recovery and/or adequate allomothering. Dedicated to Prof. Dr. Med. Detlev Ploog on the occasion of his 60th birthday.     

Characterization of Gilbert-like syndrome in squirrel monkeys (Saimiri sciureus)

Bolivian squirrel monkeys, unlike those of Brazilian origin, exhibit a marked fasting hyperbilirubinemia (FH) similar to that observed in Gilbert's syndrome in man. Since no delays in the hepatic clearance of sulfobromophthalein or indocyanine green are present, the Bolivian monkey appears to be similar to Gilbert's type I syndrome. FH can be significantly decreased by either phenobarbital or tin-protoporphyrin pretreatment. Nicotinic acid-induced hyperbilirubinemia and delayed tolbutamide clearance were not observed as in the human syndrome.     

Susceptibility of squirrel monkey (Saimiri sciureus) to infection by mammalian schistosomes.

In a study of host-schistosome relationships, the squirrel monkey (Saimiri sciureus) was exposed to 500 cercariae of Schistosoma bovis (Kenya), S. intercalation (Cameroon), S. mattheei (South Africa), 2 strains of S. mansoni (Puerto Rico and South Africa), 2 strains of S. rodhaini (Uganda and Kenya), and Schistosomatium douthitti (North America). It is apparent that the squirrel monkey can be employed as an experimental host for a broad range of mammalian schistosomes. Based upon cercariae-adult worm ratios, it is a good host for S. intercalatum, S. mattheei, the Puerto Rico and South Africa strains of S. mansoni, and Schistosomatium, but only a fair host for S. bovis and the Uganda and Kenya strains of S. rodhaini. Individuality of host-parasite relationships is borne out by the great ranges recorded for egg deposits in different organs as well as by total body egg counts and eggs/worm pair.     

Case report: Esophageal Spirura infection in a squirrel monkey (Saimiri sciureus)

Necropsy of an adult, wild-born squirrel monkey (Saimiri sciureus) revealed 30 to 40 esophageal nematodes. The anterior end of each nematode was firmly attached to the mucosa, with the remaining portion free in the lumen. Histologic changes were limited to the superficial mucosa, where the epithelium adjacent to the nematode was hyperplastic and increased keratin formed a bridge over the body of the parasite. The nematode was identified as belonging to the genus Spirura. The number of parasites in this animal was considered significant and contributed to the death of the animal.     

A preliminary parasitological analysis of fecal samples from a wild population of Costa Rican squirrel monkeys (Saimiri oerstedi).

Fecal samples (n = 18) were obtained from a wild population of squirrel monkeys, Saimiri oerstedi, in Costa Rica. The parasite cysts, eggs, and larvae recovered from these samples are described.     

Dilative cardiomyopathy leading to congestive heart failure in a male squirrel monkey (Saimiri sciureus)

A 17-year-old, 1-kg, colony-housed, male squirrel monkey (Samiri sciureus) developed clinical signs of congestive heart failure. The monkey presented with lethargy, increased heart and respiratory rates, and mild abdominal distention. The clinical history, laboratory analysis, and radiographic findings were consistent with heart failure due to dilative cardiomyopathy. Gross and microscopic examination of the heart confirmed a dilative cardiomyopathy. This is the first report describing congestive heart failure caused by dilative cardiomyopathy in a squirrel monkey. Spontaneous dilative cardiomyopathy may be infrequently observed in the squirrel monkeys because they are not routinely housed in the research environment during their advancing years.     

Seasonality of reproduction in captive squirrel monkeys (Saimiri Sciureus)

Seasonality of reproduction is believed to be influenced by environmental factors such as humidity, temperature, and photoperiod. In primates, there has been much speculation about which environmental factors have the greatest influence on reproductive seasonality. To determine whether environmental factors affect seasonality of reproduction of squirrel monkeys in captivity, I used path analysis to compare number of births and matings per month with monkeys kept in indoor enclosures (maintained at optimal temperatures) and those kept in outdoor enclosures (exposed to the elements). Since a different pattern of seasonality was found to occur, I was able to test whether temperature, rainfall, or photoperiod could explain the temporal variation in reproduction. Squirrel monkeys raised in captivity displayed different patterns of seasonality of reproduction, depending on the conditions in which they are housed ( chi(2)3 25.12, P<0.001; G = 28.10, P<0.001). Temperature seemed to have a large impact on number of births and matings per month (matings: path coefficient = 0.799; births: path coefficient = -1.315). Understanding what factors regulate reproduction for animals and how these factors affect reproduction differently in wild versus captive populations are important to conservation and management of species.     

Capacitation and the acrosome reaction in squirrel monkey (Saimiri sciureus) spermatozoa evaluated by the chlortetracycline fluorescence assay

Capacitation and the acrosome reaction in squirrel monkey seminal spermatozoa diluted in Tyrode's medium (TALP) and TC-199 were monitored by a chlortetracycline (CTC) fluorescence assay. Four CTC patterns, similar to those found in human sperm, were readily characterized by fluorescent staining on the heads of the spermatozoa. The appearance of the capacitated (CP) pattern was dependent on the concentration of the bovine serum albumin. Acrosomal loss was observed in a maximum of 15% of the sperm in the populations studied here. Calcium ionophore A23187 (5 μM to 20μM) induced acrosomal loss in 60–70% of capacitated spermatozoa. However in freshly ejaculated sperm incubated under capacitating conditions or in spermatozoa incubated in Ca^{+ +}-free medium, A23187 failed to induce acrosomal loss. Furthermore, spermatozoa incubated in the presence of seminal plasma or spermatozoa obtained following a 1-hour “swim-up” procedure showed an identical timecourse of appearance of the CP pattern, indicating the lack of effect of seminal plasma on capacitation in the squirrel monkey.     

Sequences and timing of dental eruption in Bolivian captive-born squirrel monkeys (Saimiri sciureus)

Squirrel monkeys, colony-born from Bolivian parents, were studied to establish the sequences and timing of eruption for deciduous and permanent teeth. Infants were born with a naked gingiva, and in only one monkey was di₁ present at birth. The eruption of the lower deciduous teeth preceded their upper counterparts with the exception of di2, dc, and dpm2. No significant differences were found between the right and left quadrants of the mandible and maxilla. No significant sexual differences were found in the age of eruption. By the age of 14 weeks, all deciduous teeth had erupted. The sequence of eruption of the replacement teeth was different from that of milk teeth. The differences lie in the delayed eruption of canine teeth and in the inverted sequence, from the back to the front, of the premolar series. Significant sexual differences were found in total eruption (TE) for PM₃ and I² (P < 0.05) and highly significant differences (P < 0.01) in TE and initial eruption (IE) for C¹, females being more precocious than males. The age at which monkeys completed dental eruption was highly variable, 103–119 weeks for males and 89–112 weeks for females. Differences were found when our results were compared with those of Long and Cooper [1968] for Colombian squirrel monkeys.