Dusky Leaf Monkey Research Articles

Formation and fate of the corpus luteum in the Dusky leaf monkey (Presbytis obscura)

The formation and fate of the corpus luteum have been described for a previously un researched species of South‐east Asian colobine, the Dusky leaf monkey, Presbytis obscura. Histological material from 44 wild female monkeys collected at various stages of the menstrual cycle, pregnancy and lactation over a 12‐month period was available for study. The corpus luteum of the menstrual cycle was a cystic structure and consisted of a thin rim of luteal tissue surrounding a central cavity filled with a meshwork of fibrin. At the end of the luteal phase the corpus luteum either degenerated into a corpus albicans, or became transformed into a corpus aberrans. Corpora aberrantia have previously only been described in the ovaries of the rhesus monkey, where they may persist for many months. Ultimately the corpus aberrans may also degenerate into a corpus albicans. Small corpora lutea atretica were observed during early pregnancy but there was no evidence of corpora lutea accessoria. Anovulatory cycles were common amongst the females included in this study and may play a role in limiting the growth of troops in their natural environment. Comparisons have been drawn between the findings presented here and those published for other species of catarrhine primate.

Testicular histology of the dusky leaf monkey (presbytis obscura) as it relates to birth pattern in Peninsular Malaysia

The testicular histology of the dusky leaf monkey, Presbytis obscura,is described following a study of material from 16 adult males collected over a 13-month period in Peninsular Malaysia. The histological appearances were similar to those of the other cercopithecines studied so far. No seasonal variation in the height of the seminiferous epithelium was observed, and spermatogenesis was seen in all the adult testes. These findings suggest that males of this species are capable of breeding throughout the year. These results are discussed in relation to field observations of births of this species and to the birth patterns exhibited by other species of langur.

The relationship between body and gonadal weights of the dusky leaf monkey (Presbytis obscura)

Data from 25 male and 44 female free-ranging dusky leaf monkeys, Presbytis obscura,are analyzed. In a male the mean total testicular weight, 5.82 g, represents 0.078% of the mean adult body weight, 7.39 kg. The mean total ovarian weight, 0.52 g, represents 0.008% of the mean female adult body weight, 6.47 kg. A moderate degree of sexual dimorphism thus exists in this species, female body weight representing 88% that of the male. No seasonal variation in the adult body weight or total gonadal weight of either sex occurs. Only in males is there a strong positive correlation between left and right gonadal weight, and no correlation exists between the total gonadal weight and the estimated age of either male or female adults. Among adults, only females evince a significant positive correlation between total gonadal weight and body weight. No marked change in total ovarian weight occurs during the menstrual cycle, pregnancy, or lactation.

Early placentation in the dusky leaf monkey ( Presbytis obscura)

Implantation in the dusky leaf monkey, Presbytis obscura, is superficial; the placenta is of the double discoid villous haemochorial type. Immediately prior to implantation the thick endometrium contains highly active uterine glands. There is an early uterine epithelial proliferation at the implantation site but no stromal decidual response. The fetal villi are evenly spread over that part of the chorion in contact with the endometrium and consist of a mesenchymal core covered by an inner layer of cytotrophoblast and an outer layer of syncytiotrophoblast. The endothelial cells of the maternal vessels undergo swelling before disruption of the vessel walls and the establishment of a circulation through the intervillous spaces.

Light microscopy of the endometrium of the dusky leaf-monkey (Presbytis obscura).

Specimens of this langur species were available from juvenile, adult and lactating animals. The endometrial sections of non-pregnant adults were dated from the ovarian appearances. During the cycle the endometrium underwent changes similar to those decribed for women, baboons and macaques, except that stromal oedema was pronounced and diffuse in the langur, occurring before ovulation and throughout the secretory phase.

Isolation and characterization of a new type D retrovirus from the Asian primate, Presbytis obscurus (spectacled langur)

A reverse transcriptase-containing virus (retrovirus) was isolated from a cocultivation of langur lung cells with bat and with human cells. This virus, PO-1-Lu, was first detected 6 months after the cocultivation began. Morphologically it resembles Mason-Pfizer monkey virus (MPMV), a type D retrovirus of primates. Study of its antigenic properties and its RNA genome show it to be related to but distinct from MPMV. An interspecies radioimmunoassay using labeled gp70 of baboon type C virus and antiserum to MPMV type D virus detects the PO-1-Lu envelope protein although both the baboon type C- and the MPMV-specific radioimmunoassays for gp70 do not.

Evolution of primate oncornaviruses: An endogenous virus from langurs ( Presbytis spp.) with related virogene sequences in other Old World monkeys

Gene sequences related to a retrovirus (oncornavirus type D) isolated from a lung cell culture from spectacled langur (Presbytis obscurus) are found in multiple copies (20-40 per haploid genome) in langur cellular DNA; partially homologous virogene sequences are present in the DNA of related Old World monkey species. Primates thus contain gene sequences for at least two distinct classes of genetically transmitted oncornaviruses, the type C class (isolated from baboons) and the type D class described here. The langur virus is partially related to Mason-Pfizer monkey virus, a type D retrovirus isolated from rhesus monkeys. Nucleic acid hybridization studies suggest that Mason-Pfizer monkey virus, now infectious among primates, was derived from an endogenous virus of langurs or from another member of the primate sub-family Colobinae.

Development of behaviors in a male spectacled langur (Presbytis obscurus)

An infant langur,Presbytis obscurus, was observed in a group setting, from birth until 1 year of age. Frequency or duration of 30 behaviors was recorded during 2 hour periods and plotted chronologically. Based on fluctuations and interrelations of these behaviors, age classes were designated. The Maternal Care Period (0–20 days) is characterized by close mother-infant contact, including a great deal of nipple contact and a high frequency of maternal behaviors. The Individuation Period (21–70 days) is typified by maternal restraint and retrieval, and independence and self-oriented behaviors like scratching, mouthing, and locomotory skills. The Socialization Period (71–240 days) is manifested by behavioral fluctuations, involving nipple contact, play, and care by other troop members and coincides with the molt from infant to juvenile pelage. Finally, during the Juvenile Period, the motherinfant distance increases and the mother interacts more with other troop members. Behavioral fluctuations observed in this infant langur are discussed with reference to other primates studied.

Population studies of Malaysian primates

Systematic field studies on the abundance of primates were made in five different types of forest in West Malaysia in 1970. Primate groups of 7 species were seen on 97 occasions during 527 hours of field observations. Secondary forests had the greatest primate density of any of the natural forest habitats surveyed. Estimated primate group densities varied from less than 4 groups per square mile to 40, with an average of 7.2 groups per square mile. The most abundant species was the banded leaf monkey (Presbytis melalophus) with 2.95 groups per square mile, followed by the long-tailed macaque (Macaca fascicularis) with 1.54 groups. Primary forests had a lower density which varied from less than 2 groups per square mile to 15, and averaged 5.9.P. melalophus was again the most abundant species with an average of 2.22 groups per square mile, followed by gibbons (Hylobates lar) and siamangs (H. syndactylus) each with 1.11.M. fascicularis averaged only 0.37 groups per square mile in primary forests. Primates were unexpectedly rare in mangrove forests and rubber plantations. Twenty-four primate groups were found in urban forests and parks. Twenty of these groups wereM. fascicularis, 3 were silver leaf monkeys (P. cristatus) and 1 was the dusky leaf monkey (P. obscurus). In urban areas,M. fascicularis groups varied from 7 to 44 individuals per group, with an average of 24. A great need exists for increased scientific and conservation attention for the primate populations of Malaysia.