Ontogenetic trajectories of chimpanzee social play: similarities with humans

Social play, a widespread phenomenon in mammals, is a multifunctional behavior, which can have many different roles according to species, sex, age, relationship quality between playmates, group membership, context, and habitat. Play joins and cuts across a variety of disciplines leading directly to inquiries relating to individual developmental changes and species adaptation, thus the importance of comparative studies appears evident. Here, we aim at proposing a possible ontogenetic pathway of chimpanzee play (Pan troglodytes) and contrast our data with those of human play. Chimpanzee play shows a number of changes from infancy to juvenility. Particularly, solitary and social play follows different developmental trajectories. While solitary play peaks in infancy, social play does not show any quantitative variation between infancy and juvenility but shows a strong qualitative variation in complexity, asymmetry, and playmate choice. Like laughter in humans, the playful expressions in chimpanzees (at the different age phases) seem to have a role in advertising cooperative dispositions and intentions thus increasing the likelihood of engaging in solid social relationships. In conclusion, in chimpanzees, as in humans, both play behavior and the signals that accompany play serve multiple functions according to the different age phases.     

Hemorrhagic ovarian follicles in llamas

The ovaries of 74 llamas were examined daily by transrectal ultrasonography for at least 30 d. Hemorrhagic follicles were observed in 13 (18%) llamas (incidence per anovulatory dominant follicle, 16%). The proportion of llamas in which a hemorrhagic follicle was detected was different among groups (nonmated, 8 25 ; mated to a vasectomized male, 4 21 ; mated to an intact male, nonpregnant, 1 10 ; mated to an intact male, pregnant, 0 18 ; P<0.05). A hemorrhagic follicle, observed grossly after ovariectomy, was large (13 mm) and fluctuant, with a thin translucent wall and dark red contents. No ovulatory stigma was detected, and after incising the wall, bloody fluid escaped and the follicle collapsed leaving only a small blood clot within the antrum. Ultrasonically, the formation of a hemorrhagic follicle was indicated by scattered free-floating echogenic spots within the follicular antrum which swirled upon ballottement of the ovary. The antral contents appeared to become organized (did not swirl when ballotted) after follicle growth ceased. Ultrasonic indications of antral hemorrhage were not observed in any follicles in which ovulation was later detected (0 45 ovulatory follicles). All of the hemorrhagic follicles (13 13 ) involved the dominant follicle of a wave during which no copulatory stimulus was applied. Hemorrhagic follicles were apparently anovulatory and were repeatable (P<0.05) within individuals. The interval from first detection to the first day of maximum diameter was longer (P<0.05) and maximum diameter was greater (P<0.0001) for hemorrhagic follicles than nonhemorrhagic follicles (16.4 versus 13.1 d and 22.1 versus 12.8 mm, respectively); however, the interwave interval was not affected by the presence of a hemorrhagic follicle. Luteinization of the hemorrhagic follicle was indicated (thickened wall) in two llamas by an elevated plasma progesterone concentration and/or by ultrasound. By their large size, hemorrhagic follicles may be interpreted as hemorrhagic follicular cysts; however, they were not associated with other ovarian irregularities or with infertility.     

Duplication and divergence in humans and chimpanzees

It has become a truism that we humans are genetically about 99% identical to chimpanzees. The origins of this assertion are clear: among early studies of DNA sequences, nucleotide identity between humans and chimpanzees was found to average around 98.9%.(1) However, this figure is correct only with respect to regions of the genome that are shared between humans and chimpanzees. Often ignored are the many parts of their genomes that are not shared. Genomic rearrangements, including insertions, deletions, translocations and duplications, have long been recognized as potentially important sources of novel genomic material(2,3) and are known to account for major genomic differences between humans and chimpanzees.(4) Further, such changes have been implicated in a number of genetic disorders, such as DiGeorge, Angelman/Prader-Willi and Charcot-Marie-Tooth syndromes.(5)     

Comparative rates of violence in chimpanzees and humans

This paper tests the proposal that chimpanzees (Pan troglodytes) and humans have similar rates of death from intraspecific aggression, whereas chimpanzees have higher rates of non-lethal physical attack (Boehm 1999, Hierarchy in the forest: the evolution of egalitarian behavior. Harvard University Press). First, we assembled data on lethal aggression from long-term studies of nine communities of chimpanzees living in five populations. We calculated rates of death from intraspecific aggression both within and between communities. Variation among communities in mortality rates from aggression was high, and rates of death from intercommunity and intracommunity aggression were not correlated. Estimates for average rates of lethal violence for chimpanzees proved to be similar to average rates for subsistence societies of hunter–gatherers and farmers. Second, we compared rates of non-lethal physical aggression for two populations of chimpanzees and one population of recently settled hunter–gatherers. Chimpanzees had rates of aggression between two and three orders of magnitude higher than humans. These preliminary data support Boehms hypothesis.     

Facial width-to-height ratio in chimpanzees: Links to age,sex and personality

Links between the human facial width-to-height ratio (fWHR) and aggressive behaviours have been debated in recent years. The question of whether fWHR is a cue to dominance could benefit from the study of primate species that are closely related to humans. We therefore built on the broad literature in humans, and recent research in capuchins, macaques and bonobos, and examined associations between fWHR in 131 captive chimpanzees from the United States, United Kingdom and Japan, and measures of age, sex, subspecies (Pan troglodytes verus, P. t. schweinfurthii, P. t. troglodytes), and six personality components (Dominance, Extraversion, Conscientiousness, Agreeableness, Neuroticism, and Openness). We found no evidence for sexual dimorphism in fWHR, as has been found in humans. We did find a positive relationship between fWHR and Dominance in P. t. verus, but only in adult females. This finding contrasts with that in humans, where dominant males have wider faces. We discuss these results in light of male-female differences in temporal rank stability, and in contrast to findings for bonobos, providing a useful perspective for fWHR research in humans.     

Yolk synthesis in ovarian follicles ofDrosophila

Summary The autonomous synthesis of yolk proteins in ovarian follicles ofDrosophila melanogaster was analyzed. Vitellogenic follicles were labelled with³⁵S-methionine in vitro and the newly synthesized yolk proteins were separated by SDS-polyacrylamide gel electrophoresis. Possible contamination of the follicle preparations caused by adhering fat body cells could be excluded by culturing follicles in males prior to labelling in vitro. When labelled follicles were cut at the nurse cell/oocyte border the three yolk proteins (YP1, YP2, YP3) were found only in posterior fragments containing ooplasm and follicle cells, whereas two radioactive protein bands (A and B) were detected in nurse cells (anterior fragments). The yolk proteins of these five bands were characterized by peptide mapping. Band A protein, migrating a little more slowly than YP2, is closely related to both YP1 and YP2 while band B contains a yolk protein which is very similar to YP3. Hence, the nurse cells have been identified as a site of vitellogenin synthesis within the ovary ofDrosophila.Supported by the Deutsche Forschungsgemeinschaft, SFB 46     

Mouse ovarian follicles secrete factors affecting the growth and development of like-sized ovarian follicles in vitro

A series of experiments have been carried out to determine whether follicles secrete factors able to affect the growth and development of other, like-sized follicles. Late preantral mouse ovarian follicles were either cocultured or cultured in media conditioned by previously cultured follicles. In particular, the experiments examined whether follicles do secrete such factors, whether the level of FSH in the culture media can affect that process, and what the nature of such secretory factor(s) might be. First, pairs of follicles were cocultured across a polycarbonate membrane containing pores. This showed that communication between the follicles resulted in the stimulation of growth and that the stimulation was due, at least in part, to the production of secretory factor(s). In subsequent experiments, follicles were cultured in media that had been preconditioned by previously cultured follicles. The concentration of FSH in the cultures determined the effect of the conditioned media: conditioned media was stimulatory to follicle growth when levels of FSH remained high throughout the culture, but inhibitory when FSH levels were dropped midway through the cultures. Heat inactivation removed this inhibitory effect, showing that the factor was likely to be a protein; addition of follistatin to the conditioned media did not alter its effect, indicating that the factor was unlikely to be activin. We have shown through a series of culture experiments that mouse follicles secrete factor(s) that can affect the development of other like-sized follicles when cultured from the late preantral to Graafian stages. Furthermore, we have shown that the effect (or production) of such factors is dependent on the FSH environment of the follicles.     

Examining the terminal investment hypothesis in humans and chimpanzees: associations among maternal age, parity, and birth weight

The terminal investment hypothesis (Williams [1966] Adaptation and Natural Selection; Princeton, NJ: Princeton University Press) holds that reproductive effort should increase over time in iteroparous species in which reproductive value declines with age. Attempts to model this hypothesis and test it in various species have produced mixed results. Clutton-Brock ([ 1984] Am. Nat. 123:212-229) argued that simply testing for changes in propagule size with age fails to recognize that the costs of producing offspring of a given size may increase over the lifespan, hence absence of a positive correlation does not defeat the hypothesis. However, this interpretation is weakened by evidence of sequential increases in propagule size independent of age, as such changes reveal a capacity to increase absolute investment over time. Humans and chimpanzees meet the preconditions of the terminal investment hypothesis. Surveying the obstetrics literature, we show that the majority of published studies indicate that parity has a positive effect on birth weight, but age has no effect. Analyzing 436 captive chimpanzee births, we document a positive influence of parity and a negative influence of age. We therefore conclude that, though it is yet to be replaced by a more compelling alternative, the terminal investment hypothesis is not supported in these two species, as absence of a positive effect of age on birth weight cannot be interpreted in a manner congruent with the hypothesis.     

Unconstrained cranial evolution in Neandertals and modern humans compared to common chimpanzees

A variety of lines of evidence support the idea that neutral evolutionary processes (genetic drift, mutation) have been important in generating cranial differences between Neandertals and modern humans. But how do Neandertals and modern humans compare with other species? And how do these comparisons illuminate the evolutionary processes underlying cranial diversification? To address these questions, we used 27 standard cranial measurements collected on 2524 recent modern humans, 20 Neandertals and 237 common chimpanzees to estimate split times between Neandertals and modern humans, and between Pan troglodytes verus and two other subspecies of common chimpanzee. Consistent with a neutral divergence, the Neandertal versus modern human split-time estimates based on cranial measurements are similar to those based on DNA sequences. By contrast, the common chimpanzee cranial estimates are much lower than DNA-sequence estimates. Apparently, cranial evolution has been unconstrained in Neandertals and modern humans compared with common chimpanzees. Based on these and additional analyses, it appears that cranial differentiation in common chimpanzees has been restricted by stabilizing natural selection. Alternatively, this restriction could be due to genetic and/or developmental constraints on the amount of within-group variance (relative to effective population size) available for genetic drift to act on.     

Polymorphic micro-inversions contribute to the genomic variability of humans and chimpanzees

A combination of inter- and intra-species genome comparisons is required to identify and classify the full spectrum of genetic changes, both subtle and gross, that have accompanied the evolutionary divergence of humans and other primates. In this study, gene order comparisons of 11,518 human and chimpanzee orthologous gene pairs were performed to detect regions of inverted gene order that are potentially indicative of small-scale rearrangements such as inversions. By these means, a total of 71 potential micro-rearrangements were detected, nine of which were considered to represent micro-inversions encompassing more than three genes. These putative inversions were then investigated by FISH and/or PCR analyses and the authenticity of five of the nine inversions, ranging in size from approximately 800 kb to approximately 4.4 Mb, was confirmed. These inversions mapped to 1p13.2-13.3, 7p22.1, 7p13-14.1, 18p11.21-11.22 and 19q13.12 and encompass 50, 14, 16, 7 and 16 known genes, respectively. Intriguingly, four of the confirmed inversions turned out to be polymorphic: three were polymorphic in the chimpanzee and one in humans. It is concluded that micro-inversions make a significant contribution to genomic variability in both humans and chimpanzees and inversion polymorphisms may be more frequent than previously realized.     

Mechanism of birth in chimpanzees: humans are not unique among primates

Researchers have argued that the process of human birth is unique among primates and mammals in that the infant emerges with its face oriented in the opposite direction from its mother (occiput anterior) and head rotation occurs in the birth canal. However, this notion of human uniqueness has not been substantiated, because there are few comparative studies of birth in non-human primates. This paper reports the mechanism of birth in chimpanzees (Pan troglodytes) based on the first clear, close-up video recordings of three chimpanzee births in captivity. In all three cases, the foetus emerged with an occiput anterior orientation, and the head and body rotated after the head had emerged. Therefore, these characteristics are not uniquely human. Furthermore, in two of the three cases, the chimpanzee newborns landed on the ground without being guided from the birth canal by the mother. The fact that the human newborn emerges with an occiput anterior orientation has thus far been taken as evidence for the necessity of midwifery in modern humans, but this view also needs revision. Our observations raise the need to reconsider the evolutionary scenario of human birth.     

Treatment of cystic ovarian follicles in dairy cows with chorionic gonadotropin

Thirty dairy cows exhibiting both nymphomania and cystic ovaries - 15 unilateral and 15 bilateral - were injected intravenously with human chorionic gonadotropin (hCG) over a twentyfold dose range, varying from 1.1 to 22.0 IU/kg (0.5 to 10.0 IU/1b) body weight to determine its efficacy of inducing ovulation and subsequent fertilization. Ovulation of cystic and/or noncystic follicles was induced in 28 cows (93.3%), with a higher rate among those with unilateral than bilateral cysts whether based on total (32 vs 22) or mean (2.1 vs 1.5) number of ovulations. While ovulations per cow varied from zero to three, no correlation between dose level of hCG and number of ovulations was evident. Time of ovulation following hCG injection did not differ significantly between unilaterally and bilaterally cystic cows nor between cystic and noncystic follicles, ranging from 23 to 31 +/- 1 hr and averaging 27.3 +/- 1 hr postinjection. A significant difference was found between unilaterally and bilaterally cystic cows in the occurrence of fertilized (11:1), unfertilized (11:6), degenerate (2:2), and unrecovered (8:11) ova.     

Histopathological alterations in the antral ovarian follicles in dairy cows with a tendency to emaciation

The aim of the study was to define interrelationships between histopathological alterations in ovarian antral follicles and body condition in dairy cows with a tendency to emaciation (BCS 1 and 2) compared with dairy cows with normal body condition (BCS 3). The ovaries were recovered from slaughtered cyclic dairy cows (at the luteal phase of the cycle) of Czech Fleckvieh and Holstein breeds at different times of the post-partum period. The animals were estimated as belonging to certain grade of body condition score (BCS) according to a 5-point scale. Only dairy cows with BCS1 (emaciation; n=6), BCS2 (tendency to emaciation; n=5) and BCS3 (optimal body condition status; n=6) were available for the experiment. The ovarian samples were embedded into Technovit 7100 resin; the tissue sections were stained with buffered basic fuchsine with toluidine blue. For acidic mucopolysaccharides (aMPS) a combination of PAS-technique with Alcian blue was used. Histological analysis showed that emaciation was associated with an increased occurrence of late (cystic) and luteinization-related atresia in granulosa and theca cells and increased levels of aMPS in small atretic follicles. Our observations indicate that dairy cows with a tendency to emaciation (BCS 2) or emaciated (BCS 1) have elevated occurrence of late atresia and atresia with luteinization, while initial atresia is less. This expands our basic knowledge of ovarian histopathology providing new insight into the association of antral follicle atresia and body condition status in dairy cows.     

Histochemical and immunohistochemical similarities between hepatic tumors in two chimpanzees and man

A well-differentiated trabecular hepatocellular carcinoma (HCC) and a well-differentiated tumor resembling HCC from each of two chimpanzees were found to have histochemical and immunohistochemical staining characteristics similar to those in human HCCs. Transforming growth factor α was overexpressed in both tumors. Oval cells, thought to be liver stem cell progeny with a possible role in hepatocarcinogenesis, were observed among nontumorous hepatocytes, particularly near the tumors. Hepatic tumors are rare in chimpanzees but their similarities to human HCC provides a useful research model.     

Persistent ovarian follicles in dairy cows: a therapeutic approach

Anestrus is common during the postpartum period in high-producing dairy cows. In a previous investigation, we were able to diagnose persistent follicles of 8 to 12 mm in anestrous cows. This report describes 2 consecutive studies. The objectives of the first were to 1) assess the association of persistent follicles with anestrus; and 2) evaluate 2 therapeutic treatments. In the second study, we compared the effectiveness of the best treatment established in Study 1 with the Ovsynch protocol. For Study 1, anestrous cows were considered to have a persistent follicle if it was possible to observe a single follicular structure > 8 mm in the absence of a corpus luteum or a cyst in 2 ultrasonographic examinations performed at an interval of 7 d. At diagnosis (Day 0), cows were assigned to 1 of 3 treatment groups. Cows in Group GnRH/PGF (n=17) were treated with 100 microg GnRH i.m., and 25 mg PGF2alpha i.m. on Day 14. Cows in Group PRID (n=18) were fitted with a progesterone releasing intravaginal device (PRID, containing 1.55 g of progesterone) for 9 d and were given 100 microg GnRH i.m. at the time of PRID insertion, and 25 mg PGF2alpha i.m. on Day 7. Cows in Group Control (n=18) received no treatment. The animals were inseminated at observed estrus and were monitored weekly by ultrasonography until AI or 5 weeks from diagnosis. Blood samples were also collected on a weekly basis for progesterone determination. The mean size of persistent follicles on Day 0 was 9.4 +/- 0.04 mm. Progesterone levels were < 0.2 ng/mL during the first 35 d in 16 of 18 Control cows. Cows in the PRID group showed a lower persistent follicle rate (16.7% < 70.6% < 88.9%; P < 0.0001; PRID vs GnRH/PGF vs Control, respectively); a higher estrus detection rate (83.3% > 29.4% > 11.1%; P < 0.0001) and a higher pregnancy rate (27.8% > 5.9% > 0%; P = 0.02). For the second study, 145 cows with persistent follicles were randomly assigned to 1 of 2 treatment groups: cows in Group Ovsynch (n=73) were treated with 100 microg GnRH i.m. on Day 0, 25 mg PGF2alpha i.m. on Day 7, and 100 microm GnRH i.m. 32 h later. Cows in this group were inseminated 16 to 20 h after the second GnRH dose (Ovsynch protocol). Cows in Group PRID (n=72) were treated as those in the PRID group of Study 1, and were inseminated 56 h after PRID removal. Cows in the PRID group showed a higher ovulation rate (84.8% > 8.2%: P < 0.0001); a higher pregnancy rate (34.2% > 4.1%; P < 0.0001) and lower follicular persistence rate (22.2% < 63%; P < 0.0001) than those in Ovsynch. Our results indicate that persistent follicles affect cyclic ovarian function in lactating dairy cows. Cows with persistent follicles can be successfully synchronized and time inseminated using progesterone, GnRH and PGF2alpha but show a limited response to treatment with GnRH plus PGF2alpha.