Dingzhen Liu

Potential Chemosignals in the Anogenital Gland Secretion of Giant Pandas, Ailuropoda melanoleuca, Associated with Sex and Individual Identity

With a combination of dichloromethane extraction and analysis by gas chromatography–mass spectrometry (GC-MS), we found 39 compounds (corresponding to 38 GC peaks) in the anogenital gland secretion (AGS) of captive adult giant pandas, Ailuropoda melanoleuca, during the non-mating season. In addition to indole, squalene, and some of the straight-chain fatty acids that had been characterized previously from the AGS of giant pandas, we identified several new compounds such as decenal, two isomers of decadienal, phenylacetic acid, 5-methylhydantoin, hydroquinone, phenylpropanoic acid, and erucic acid. Quantitative comparison of the relative abundances of the 20 main GC peaks revealed that 5-methylhydantoin, indole, and erucic acid are putative female pheromones, whereas squalene and hydroquinone are putative male pheromones. In addition to the presence of a few individual-specific compounds, the relative abundances of most of the 21 constituents varied more among individuals than within individuals. This suggests that individual identity might be coded in both digital and analog form. The chemical composition of different AGS samples from the same pandas consistently displayed a minimum cluster distance, much smaller than that between samples from different individuals in a hierarchical linkage cluster (average linkage) dendrogram. Our results indicate that the AGS might contain an “odor fingerprint.” Although putative sex pheromones such as squalene and erucic acid should be assessed further by bioassay, our study suggests that synthetic chemosignals might be useful in modulating the behavior and physiology of giant pandas.

Cohabitation impaired physiology, fitness and sex-related chemosignals in golden hamsters

This study investigated the impact of long-term paternal presence (cohabitation) on several physiological parameters such as body weight, adrenal weight, cortisol of parents, and the survival of pups compared with brief daily encounters (isolation) of male-female pairs in golden hamsters (Mesocricetus auratus). We showed that females were affected more by cohabitation as evidenced by increased body and adrenal weights, elevated cortisol concentrations, and heavier uteri and spleens as compared with cohabiting male and isolated females. Furthermore, we found that tetradecanoic and hexadecanoic acids of the flank glands were sexually dimorphic, for which they were putative female pheromones. These two compounds were suppressed in females and elevated in males by cohabitation, suggesting that cohabitation impaired sex chemosignals. Overall, we concluded that housing females and males together had deleterious effects on adults and the survival of their pups in the golden hamster.

Reverse chemical ecology: Olfactory proteins from the giant panda and their interactions with putative pheromones and bamboo volatiles

Significance The giant panda, an endangered species and a popular emblem, still conceals puzzling unexplored aspects. It shares with bears, to which it is evolutionary related, a carnivorous digestive system but follows a strictly herbivorous diet. The low energy obtained from such poor food accounts for its slow movements and probably, a reduced reproductive activity. Feeding and mating are regulated by olfaction, still poorly investigated in this species at the molecular level. Here, we describe two odorant-binding proteins with complementary affinities to different chemical classes and present the 3D structure of one of them. In a reverse chemical ecology approach, which could be adopted for other vertebrates, we use ligand-binding data to suggest putative structures of still unknown sex pheromones. The giant panda Ailuropoda melanoleuca belongs to the family of Ursidae; however, it is not carnivorous, feeding almost exclusively on bamboo. Being equipped with a typical carnivorous digestive apparatus, the giant panda cannot get enough energy for an active life and spends most of its time digesting food or sleeping. Feeding and mating are both regulated by odors and pheromones; therefore, a better knowledge of olfaction at the molecular level can help in designing strategies for the conservation of this species. In this context, we have identified the odorant-binding protein (OBP) repertoire of the giant panda and mapped the protein expression in nasal mucus and saliva through proteomics. Four OBPs have been identified in nasal mucus, while the other two were not detected in the samples examined. In particular, AimelOBP3 is similar to a subset of OBPs reported as pheromone carriers in the urine of rodents, saliva of the boar, and seminal fluid of the rabbit. We expressed this protein, mapped its binding specificity, and determined its crystal structure. Structural data guided the design and preparation of three protein mutants bearing single-amino acid replacements in the ligand-binding pocket, for which the corresponding binding affinity spectra were measured. We also expressed AimelOBP5, which is markedly different from AimelOBP3 and complementary in its binding spectrum. By comparing our binding data with the structures of bamboo volatiles and those of typical mammalian pheromones, we formulate hypotheses on which may be the most relevant semiochemicals for the giant panda.

Preliminary study on hand preference in captive northern white-cheeked gibbons ( Nomascus leucogenys )

The postural origin hypothesis and the task complexity hypothesis propose that hand preference in non-human primates evolved in association with body posture and task complexity, respectively. The results of previous studies testing these two hypotheses, however, vary greatly with the different primate species and methods used. To investigate the effect of body posture and task complexity on hand preference, we recorded bouts of hand usage in nine captive northern white-cheeked gibbons (Nomascus leucogenys) housed at Beijing Zoo as they reached for food items in a ground-reaching task, a box task, and a tube task. The results showed that four to seven of the nine gibbons displayed a hand preference at the individual level in different tasks, and that hand preference in individuals was task-specific; there was no group-level hand preference in any task. The box task seemed to elicit a greater strength of hand preference than the ground-reaching task at the individual level. Although the small sample size rules out drawing any strong conclusions concerning hand preference at the group level, our results suggest that the suspensory reaching posture might increase the expression of hand preference at the individual level. This study provides preliminary information on hand preference in captive northern white-cheeked gibbons, and will be helpful for future studies addressing the origin and evolution of hand preference in small apes.

Hormones orchestrated pre- and post-copulatory sexual traits in male Mongolian gerbils

Parkers sperm competition model predicts a negative relationship between pre-copulatory (social status) and post-copulatory (sperm quality and quantity) sexually selected traits, however, empirical studies have revealed considerable inconsistency in this relationship. We hypothesized that there was a trade-off between pre- and post-copulatory sexually selected traits, and hormones (corticosterone, CORT; testosterone, T) orchestrate this relationship. In this study, we measured energetic parameters in the dominant-subordinate Mongolian gerbils (Meriones unguiculatus), whose relationship was established under chronic social encounters in a neutral arena, and then tested the relationship between their social status and sperm quality and quantity. Our results showed that dominant males initiated attack sooner and displayed more aggression, self-grooming and locomotion behaviors in daily social encounters across seven consecutive days. Dominant gerbils also had more and better quality of sperm than that of subordinate males, yet showed no significant differences in energy intake and RMR in comparison with subordinate individuals. In addition, dominant males had higher concentrations of serum T than subordinate males, whereas the concentrations of CORT showed a reverse pattern. The frequency and duration of aggression (indicative of social status) increased with elevated T concentrations. Sperm quality in terms of number and activity were associated with higher concentrations of serum T in dominant gerbils, whereas small sperm counts and poor-quality sperm were associated with relatively higher concentrations of serum CORT in subordinate gerbils. Together, our data indicated that there was no trade-off between pre- and post-copulatory sexually selected traits but hormones orchestrated the relationship between these traits in male Mongolian gerbils.

Enhancing captive breeding in giant pandas (Ailuropoda melanoleuca): maintaining lactation when cubs are rejected, and understanding variation in milk collection and associated factors.

From 1997 to 2002, a female giant panda (Ailuropoda melanoleuca) was artificially stimulated and lactation was maintained, after her neonates were removed due to the females inability to provide maternal care. Milk samples were collected and the amount of milk collected was quantified. The lactation curve of this animal was estimated based on the Gamma function: Y(t)=at(b)e(-ct). The amount of milk collected showed significant, positive relationships with the number of days after parturition both in 1999 and in the whole study period from 1998 to 2002. This females lactation curves fit the type I pattern of a typical mammalian lactation curve. Daily milk collection (g) during the first 30 days after parturition, and from 31 to 60 days after parturition, showed a consistent pattern with one peak at around 8:00 hr. More milk was collected during the latter period than during the former period. The amount of milk (g) collected on mucus excretion days was significantly less than that on days after mucus excretion had ended, yet no significant difference was found between milk collected one day before mucus days and on mucus days, or between milk collected one day before and one day after mucus days. Mucus excretion from the gastrointestinal tract significantly impacted the amount of milk collected. The results from this study may aid the captive propagation and conservation of giant pandas and other endangered and rare captive mammal species.

Do Urinary Chemosignals Code for Sex, Age, and Season in the Giant Panda, Ailuropoda melanoleuca?

The urinary volatile compounds of captive giant pandas, Ailuropoda melanoleuca, were analysed with GC-MS (gas chromatography and mass spectrometry). Samples were collected from adult males and females during the mating season, as well as from adult and sub-adult males during the non-mating season. We detected more than 96 compounds, 50 of which were common to all individuals. The major volatile constituents were ketones, phenols, alcohols, and fatty acids. No single compound was found to be specific for characterising sex, age, and season. MANOVA analysis on the relative abundance of compounds showed that adult males and females differ in four urinary compounds in the mating season and adult males differ in seven compounds between the mating and the non-mating seasons. We also found significant age effects on the relative abundance of urinary compounds in males in the non-mating season. This result suggests that those compounds might be the potential chemosignals signalling information about male pandas’ age, sex, and reproductive state.

Individual Recognition and Odor in Rat-Like Hamsters: Behavioral Responses and Chemical Properties

Individual recognition has been studied across a number of taxa and modalities; however, few attempts have been made to combine chemical and biological approaches and arrive at a more complete understanding of the use of secretions as signals. We combined behavioral habituation experiments with gas chromatography-mass spectrometry of glandular secretions from the left and right flank gland and midventral gland of the rat-like hamster, Tscheskia triton. We found that females became habituated to one scent and then could discriminate individuals via another scent source from the same individual only when familiar with the scent donor. However, this prior social interaction was not required for females to discriminate different individuals in single-stimulus habituation-dishabituation tests. Chemical analyses revealed a similarity in volatile compounds between the left and right flank gland and midventral gland scents. It appears that individually distinctive cues are integratively coded by a combination of both flank gland and midventral gland secretions, instead of a single scent, albeit animals show different preferences to the novel scent. Our results suggest that odors from the flank and midventral glands may provide information related to individuality and aid individual recognition in this species and confirm that prior interaction between individuals is a prerequisite for rat-like hamsters to form multi-odor memory of a particular conspecific.