Total flavonoid contents in bamboo diets and reproductive hormones in captive pandas: exploring the potential effects on the female giant panda (Ailuropoda melanoleuca)

Comparative analysis of different Phyllostachys species on gut microbiome and fecal metabolome in giant pandas (Ailuropoda melanoleuca)

The influences of different bamboo species on the microbiome and metabolome of giant pandas (Ailuropoda melanoleuca) remain understudied. The aim of this study was to investigate the effects of different Phyllostachys species on the gut microbial communities and fecal metabolite profiles in giant pandas. Metagenome and metabolome were performed on the feces of giant pandas fed with different Phyllostachys species (P. edulis, P. iridescens, P. glauca, and P. violascens). The results of metagenome showed that dietary with P. glauca could notably decrease the microbial Shannon index. The relative abundances of both Cellulosilyticum and Pseudomonas were enhanced after dietary with P. iridescens, suggesting P. iridescens could enhance the cellulose-degrading function in giant pandas. However, dietary with P. glauca or P. violascens could increase the relative abundances of certain pathogenic bacteria (Escherichia, Shigella, and Klebsiella). Metabolomics analysis further revealed that all experimental groups exhibited notably elevated levels of fecal flavonoids and fatty acids. In addition, the correlation analysis showed that certain nutrients of bamboo leaves (mainly crude protein and Cu) were significantly correlated with several differential gut bacteria and fecal metabolites. Based on the present results, P. iridescens might be a substitute for the routinely used Phyllostachys species (P. edulis) in the captive management of giant pandas. The results have revealed that bamboo species is an important factor affecting the gut microbiota and fecal metabolites in giant pandas. Our results could provide important information about bamboo species-induced alterations on the microbiome and metabolome in giant pandas.

Grazing-Induced Habitat Degradation: Challenges to Giant Panda Survival Resulting from Declining Bamboo and Soil Quality

Grazing is the primary human-induced disturbance affecting giant panda (Ailuropoda melanoleuca) habitats and has a severe impact on the long-term sustainability of the giant panda population. To address the lack of quantitative studies on grazing's impact on habitat quality, we selected China's most heavily grazed giant panda nature reserve. Utilizing the Maxent model and stoichiometric analysis, we investigated habitat quality degradation caused by grazing and quantified changes in bamboo nutritional quality and soil physicochemical properties. The results indicate that grazing has significantly reduced the suitable habitat area for giant pandas from 101.87 km2 to 80.64 km2. Specifically, high-suitability habitats declined by 14.14%, moderate-suitability habitats declined by 22.70%, and low-suitability habitats declined by 22.88%. Grazing has forced pandas to move to higher altitudes (2650-3057 m) with taller (12-20 m) trees, denser (28-55 plants) shrubs, and sparser (30-69%) bamboo. Additionally, the soil water content has decreased, while soil bulk density, total N, available N, and pH have significantly increased. Reductions in crude protein and ether extract, along with increased crude fiber and ash, have lowered bamboo's nutritional value and palatability. This study elucidates how grazing degrades giant panda habitat quality and provides a scientific basis for its conservation management.

Anogenital scent-marking signals fertility in a captive female Alaotran gentle lemur

The Lake Alaotra gentle lemur (Hapalemur alaotrensis) is one of the 25 most endangered primates in the world and shows low success rate in captive breeding programmes. It is therefore vital to further understand its reproductive biology. We studied a captive troop consisting of five individuals hosted at Jersey Zoo during breeding and non-breeding periods over 1 year. We collected behavioural data (n = 318 h) using all occurrence of some behaviours and ad libitum sampling methods, as well as faecal (n = 54) and anogenital scent (n = 35) samples of the breeding female. We measured sex hormone levels using enzyme immunoassay technique and investigated the volatile component of odour signals using solid-phase microextraction and gas chromatography-mass spectrometry. We observed sexual and aggressive behaviours occasionally during the breeding period. Our regression analysis showed that only period significantly predicted rates of female anogenital scent-marking, whereby the female performed anogenital scent-marking more frequently during the breeding rather than the non-breeding period. In contrast, female hormone levels did not significantly explain variation in rates of neither male nor female olfactory, sexual and affiliative behaviours, suggesting that individuals' behaviour alone is not an effective indicator of the ovulation window. The volatile chemical profile of anogenital odour secretions changed over the study, with four compounds distinguishing the fertile window during the breeding period. In conclusion, our findings suggest that anogenital scent-marking may signal the reproductive status of captive female gentle lemurs.

Chromosome-scale genomes provide new insights into subspecies divergence and evolutionary characteristics of the giant panda

Extant giant pandas are divided into Sichuan and Qinling subspecies. The giant panda has many species-specific characteristics, including comparatively small organs for body size, small genitalia of male individuals, and low reproduction. Here, we report the most contiguous, high-quality chromosome-level genomes of two extant giant panda subspecies to date, with the first genome assembly of the Qinling subspecies. Compared with the previously assembled giant panda genomes based on short reads, our two assembled genomes increased contiguity over 200-fold at the contig level. Additional sequencing of 25 individuals dated the divergence of the Sichuan and Qinling subspecies into two distinct clusters from 10,000 to 12,000 years ago. Comparative genomic analyses identified the loss of regulatory elements in the dachshund family transcription factor 2 (DACH2) gene and specific changes in the synaptotagmin 6 (SYT6) gene, which may be responsible for the reduced fertility of the giant panda. Positive selection analysis between the two subspecies indicated that the reproduction-associated IQ motif containing D (IQCD) gene may at least partly explain the different reproduction rates of the two subspecies. Furthermore, several genes in the Hippo pathway exhibited signs of rapid evolution with giant panda-specific variants and divergent regulatory elements, which may contribute to the reduced inner organ sizes of the giant panda.