Reproduction in the slow loris (Nycticebus coucang)

The reproductive biology of the slow loris (Nycticebus coucang) is poorly documented because of infrequent captive breeding success and the absence of field studies of this species. Reproductive data were collected from a breeding colony of slow lorises held at the Duke University Primate Center for the past 10 years. Nineteen infants were born, with a sex ratio of 1:1 and a neonatal mortality rate of 15.8%. In all cases, litter size was one. Females born in the colony copulated for the first time between 18 and 24 months of age. A male that reached sexual maturity in the colony sired his first offspring at the age of 17 months. Estrous cycles ranged in duration from 29–45 days, with copulations usually occurring for 1 day of estrus. Gestation length averaged 192.2 days. Although a postpartum estrus was observed in three cases of infant death, no conceptions resulted. Lactation lasted approximately 6 months. A clear birth peak was observed, with 12 out of 19 births occurring in March, April, and May. The comparatively low basal metabolic rate of this species may account for the unusually low reproductive rate of the slow loris in comparison with other prosimian primates.     

The subependyma of the primate, slow loris (Nycticebus coucang coucang)

The subependymal plate of the primate slow loris (Nycticebus coucang coucang) has been studied by electron microscopy. It is composed of a mixed population of several cell types in which the subependymal cells preponderate. Free subependymal cells are found in the ‘border area’ near the corpus callosum or the neuropile of the caudate nucleus. In common with the subependymal cells they show a scanty cytoplasm containing mostly free ribosomes. Typical neuroglial cells namely, microglia, astrocytes and oligodendrocytes are also identified in this region. Among the various cell types mentioned there are present also a few occasional cells which have features bearing a resemblance to the subependymal cell on the one hand and to the microglia on the other. The morphological evidence suggests that in parallel with the macroglia the microglia could be derived by stepwise transformation of the subependymal cells.     

The functional anatomy of the ankle and foot of the slow loris (Nycticebus coucang)

The slow loris must use its limb for stabilization and forward progression during arboreal climbing. The orientation of the limb joints, hip, knee, talo-crural, sub-talar and tarso-metatarsal, correlate with movement upon supports lying below and in line with the body axis. The musculature controlling the joints of ankle and foot, and the integument of the sole further indicate the integration of this adaptation.     

Neuroglia in the corpus callosum of the primate, slow loris (Nycticebus coucang coucang)

The corpus callosum of adult slow loris consists of a mixed population of several cell types, i.e. free subependymal cells, oligodendrocytes, astrocytes and microglia. The free subependymal cell is rather small and slender with a somewhat patchy nucleus. It shows scanty cytoplasm with free ribosomes. Oligodendrocytes vary both in nuclear and cytoplasmic densities and can be divided into three classes: light, medium dense and dark types. Their cytoplasm contains microtubules, rough endoplasmic reticulum and Golgi saccules. Astrocytes are pale cells with large amount of filaments in their cytoplasm. Microglia are small cells with granulated nuclei. The cells often show large cytoplasmic protrusions containing the usual cell organelles and lipofuscin bodies in their cytoplasm. Lastly, cells with typical features of neurons are occasionally encountered among the white matter.     

Excretion of radiolabeled estradiol metabolites in the slow loris (Nycticebus coucang)

The excretion pattern of estradiol was studied in the slow loris Nycticebus coucang) and the ring-tailed lemur (Lemur catta) in order to compare steroid excretion in two representative prosimian species. Daily urinary estrone conjugate measurements in the female loris provided little information when applied over prolonged periods. As a result of these negative data, a metabolic study was performed to determine if estrogen excretion patterns in the slow loris differed from those in the lemur, where urinary assays proved a useful tool in characterizing reproductive cycles. Radio-labeled estradiol was injected intravenously, and serial urine and fecal collections were analyzed for radiolabeled metabolites. The results of these studies demonstrate that more than 92% of the radiolabel was excreted in the feces of the loris, in contrast to only 16% excreted in the feces of the lemur.     

The chromosome complement of the slow loris (Nycticebus coucang Boddaert, 1785)

The chromosome complements of two male and two female adult slow lorises (Nycticebus coucang) have been studied in blood cultures cultivatedin vitro for three days. We have observed basic differences in arrangement from previous results, and the existence in the complement of a dimorphic pair not described before in this species. This dimorphic pair does not fit with any known type of chromosome dimorphism or polymorphism, either in rodents or primates. The diploid chromosome number is 50. Nine of the chromosome pairs are metacentric, the remaining 15 pairs, submetacentric. The X chromosome is a long submetacentric, ranking 4 in order of decreasing size. The Y chromosome is a rather long metacentric and ranks 15 in the same order. The autosomes, 2 to 10µ long in metaphase with arm ratios ranging from 1.14 to 2.65, are paired and arranged in order of decreasing size. Chromosome pair No. 5 is dimorphic, one of the chromosomes in the pair being constantly longer than the other. An idiogram of the haploid chromosome complement is presented, incorporating measurements of 30 analyzed nuclei.     

Eastern limit of distribution of the slow loris,Nycticebus coucang

The easternmost known record of the slow loris,Nycticebus coucang, is Tawitawi, Philippines. A report of this species in Mindanao, 500 km northeast of Tawitawi, is based on a mislabeled specimen.     

Reproduction,physical growth and behavioral development in slow loris (Nycticebus coucang,Lorisidae)

Reproduction of slow loris maintained in in- and outdoor enclosures in the natural day-night-cycle of southern Germany seems to be seasonally dependant. Mating occurs during summer, delivery of offspring during winter. Gestation length as determined from mid-estrus was 186–187 days. Copulation takes place over two to five consecutive days during estrus. Litter size for each of the recorded births was one. Lactation lasts for five to seven months. Sexual maturity is reached at about 1 1/2 to 2 years. Physical growth and the first appearance of main locomotor, behavioral and vocal patterns are described until nutritive weaning. With regard to acoustic structures, the vocal repertoire of newborn slow loris is quite similar to that of adults. During ontogeny main changes are discerned in the temporal pattern and pitch frequency of vocalizations and in their use. Results are compared with other primates.     

Learning set formation in slow lorises (Nycticebus coucang)

In primates, learning set formation has been reported in various simian species, but in only few prosimian species. The formation of visual discrimination learning set was tested on a nocturnal prosimian species, slow lorises (Nycticebus coucang). Their performance was higher than that of some New World monkeys. This confirmed the suggestion from the data on black lemurs (Lemur macaco) that there is an overlap between prosimians and simians in learning set ability.     

Mother-infant interactions in captive slow lorises (Nycticebus coucang)

Information is presented about mother-infant interactions and infant development in a rarely studied prosimian primate, the slow loris (Nycticebus coucang). Four dyads were observed, by means of closed circuit TV, in a semi-natural environment for 1 hour per day three times a week. Infants were inactive for the first 6–8 weeks. Although mothers carried infants, they also left them alone for substantial periods of time after the 1st week. Over the 20-week study period, there was a significant decline in ventral contact but not in sitting within 12 inches or engaging in active social interactions. By the end of the study, infants were not yet fully independent. Three of the 4 were primarily responsible for maintaining physical closeness to the mother; they made most of the approaches and mothers made most of the departures. However, only 2 of the 4 infants had assumed responsibility for the initiation and maintenance of social interactions with the mother. By comparison with other nocturnal prosimians of similar size, the rate of development is relatively slow. Unlike many anthropoids, mothers were not strongly protective or rejecting. They did not bring infants back to a fixed location or try to prevent infants from leaving them; and the decline in ventral contact was not accompanied by fights between the pair. The 3 group-living mothers were more protective than the single individually housed mother, and it would seem advisable to isolate mother-infant pairs in laboratory breeding colonies.     

The antecubital organ of the primate slow loris (Nycticebus coucang coucang)

A study of the ‘antecubital organ’ of the slow loris (Nycticebus coucang coucang), was undertaken in light and electron microscopes. As distinct from other prosimian primates there is a complete absence of interstitial cells in the gland suggesting its different functional role. The acinar cells in the ‘antecubital organ’ of slow loris contain large number of smooth ER and electron-dense secretory granules. The granules are seen both in the apical region of the cells as well as in their basal cytoplasmic processes. Some of these processes appear to terminate close to a blood capillary. The structural features of the ‘antecubital organ’ of slow loris suggest that it is a mixed gland of both exocrine and endocrine nature.