Giant salamanders: Farmed yet endangered

A time-course transcriptome analysis revealing the potential molecular mechanism of early gonadal differentiation in the Chinese giant salamander

The Chinese giant salamander (CGS) Andrias davidianus is the largest extant amphibian and has recently become an important species for aquaculture with high economic value. Meanwhile, its wild populations and diversity are in urgent need of protection. Exploring the mechanism of its early gonadal differentiation will contribute to the development of CGS aquaculture and the recovery of its wild population. In this study, transcriptomic and phenotypic research was conducted on the critical time points of early gonadal differentiation of CGS. The results indicate that around 210 days post-hatching (dph) is the critical window for female CGS's gonadal differentiation, while 270 dph is that of male CGS. Besides, the TRPM1 gene may be the crucial gene among many candidates determining the sex of CGS. More importantly, in our study, key genes involved in CGS's gonadal differentiation and development are identified and their potential pathways and regulatory models at early stage are outlined. This is an initial exploration of the molecular mechanisms of CGS's early gonadal differentiation at multiple time points, providing essential theoretical foundations for its captive breeding and offering unique insights into the conservation of genetic diversity in wild populations from the perspective of sex development.

Comparison of the intestinal flora of wild and artificial breeding green turtles (Chelonia mydas)

Gut microbes are pivotal reference indicators for assessing the health status of animals. Before introducing artificially bred species into the wild, examining their gut microbe composition is crucial to help mitigate potential threats posed to wild populations. However, gut microbiological trait similarities between wild and artificially bred green turtles remain unexplored. Therefore, this study compared the gut microbiological characteristics of wild and artificially bred green turtles (Chelonia mydas) through high-throughput Illumina sequencing technology. The α-diversity of intestinal bacteria in wild green turtles, as determined by Shannon and Chao indices, significantly surpasses that of artificial breeding green turtles (p < 0.01). However, no significant differences were detected in the fungal α-diversity between wild and artificially bred green turtles. Meanwhile, the β-diversity analysis revealed significant differences between wild and artificially bred green turtles in bacterial and fungal compositions. The community of gut bacteria in artificially bred green turtles had a significantly higher abundance of Fusobacteriota including those belonging to the Paracoccus, Cetobacterium, and Fusobacterium genera than that of the wild green turtle. In contrast, the abundance of bacteria belonging to the phylum Actinobacteriota and genus Nautella significantly decreased. Regarding the fungal community, artificially bred green turtles had a significantly higher abundance of Fusarium, Sterigmatomyces, and Acremonium and a lower abundance of Candida and Rhodotorula than the wild green turtle. The PICRUSt2 analyses demonstrated significant differences in the functions of the gut bacterial flora between groups, particularly in carbohydrate and energy metabolism. Fungal functional guild analysis further revealed that the functions of the intestinal fungal flora of wild and artificially bred green turtles differed significantly in terms of animal pathogens-endophytes-lichen parasites-plant pathogens-soil saprotrophs-wood saprotrophs. BugBase analysis revealed significant potential pathogenicity and stress tolerance variations between wild and artificially bred green turtles. Collectively, this study elucidates the distinctive characteristics of gut microbiota in wild and artificially bred green turtles while evaluating their health status. These findings offer valuable scientific insights for releasing artificially bred green turtles and other artificially bred wildlife into natural habitats.

The next step for China's national park management: Integrating ecosystem services into space boundary delimitation

The contradiction between ecological conservation and economic development posed significant challenges to the management of National Parks. From the perspective of Ecological Economics, the cause of the contradiction is the difficulty of creating monetary profits from biodiversity conservation, which is the primary target of National Parks. Integrating Ecosystem Services (ESs) into space boundary delimitation is the next step in National Park management since ESs are closely related to human well-being and can provide monetary benefits. Extending the boundary of the National Park to high-ES areas and promoting ES trading can help generate funds for ecological restoration. Using the Sanjiangyuan National Park (SNP) as an example, this study proposed integrating ESs into National Park delimitation for sustainable National Park management. It was found that the current SNP boundary provides insufficient coverage of high-ES areas, while most of the multiple ES supply areas were dispersed to SNP's southeast edge. The Core conservation area showed the most prominent contradiction between ecological conservation and economic development, resulting in many low-level ES sites in the Traditional use area failing to be included in the Restoration area for protection. Future approaches would be well-advised to re-adjust SNP boundary by expanding the ES hotspot areas on the southeastern edge of SNP, as well as expanding funding sources via ecological product trade and other tools to supplement the input for ecological restoration. Overall, this study can act as a reference for optimizing National Parks within and beyond China, and promote the understanding of the Ecological Economy and sustainable development.

Numerous uncertainties in the multifaceted global trade in frogs’ legs with the EU as the major consumer

The commercial trade in frogs and their body parts is global, dynamic and occurs in extremely large volumes (in the thousands of tonnes/yr or billions of frogs/yr). The European Union (EU) remains the single largest importer of frogs’ legs, with most frogs still caught from the wild. Amongst the many drivers of species extinction or population decline (e.g. due to habitat loss, climate change, disease etc.), overexploitation is becoming increasingly more prominent. Due to global declines and extinctions, new attention is being focused on these markets, in part to try to ensure sustainability. While the trade is plagued by daunting realities of data deficiency and uncertainty and the conflicts of commercial interests associated with these data, it is clear is that EU countries are most responsible for the largest portion of the international trade in frogs’ legs of wild species. Over decades of exploitation, the EU imports have contributed to a decline in wild frog populations in an increasing number of supplying countries, such as India and Bangladesh, as well as Indonesia, Turkey and Albania more recently. However, there have been no concerted attempts by the EU and present export countries to ensure sustainability of this trade. Further work is needed to validate species identities, secure data on wild frog populations, establish reasonable monitored harvest/export quotas and disease surveillance and ensure data integrity, quality and security standards for frog farms. Herein, we call upon those countries and their representative governments to assume responsibility for the sustainability of the trade. The EU should take immediate action to channel all imports through a single centralised database and list sensitive species in the Annexes of the EU Wildlife Trade Regulation. Further, listing in CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora) can enforce international trade restrictions. More joint efforts are needed to improve regional monitoring schemes before the commercial trade causes irreversible extinctions of populations and species of frogs.

Husbandry, Captive Breeding, and Field Survey of Chinese Giant Salamander (Andrias davidianus)

The Chinese giant salamander (Andrias davidianus) is the largest extant amphibian species in the world with adults capable of reaching 2 m in length. Wild populations of A. davidianus have declined dramatically during the last century, making it also one of the top threatened species globally. Fortunately, aquaculture for this species developed in China during the 1970s has been extremely successful. Many relevant commercial products of A. davidianus have been produced in recent years on account of its nutritional and medicinal values. Balancing conservation and utilization will be key to the future destiny of A. davidianus. In this chapter, we describe detailed protocols for husbandry in indoor and outdoor facilities, captive breeding under natural-imitative conditions and using artificial insemination, and surveying and monitoring A. davidianus in the field. The protocols presented here aim to make the practices of A. davidianus operative and increase public awareness of this mystical and precious species.

Influence of Frying Methods on Quality Characteristics and Volatile Flavor Compounds of Giant Salamander (Andrias davidianus) Meatballs

Effects of deep fat frying and hot air frying on texture, color difference, sensory score, yield, fat content, and volatile flavor compounds of giant salamander meatballs before and after frying were investigated. The results showed that, compared with the deep fat frying group, hot air-fried giant salamander meatballs had higher hardness, elasticity, and L ${}^{\ast }$ ( $p<0.05$ ), but lower a ${}^{\ast }$ , b ${}^{\ast }$ value, fat content, and yield ( $p<0.05$ ). There was little distinction in sensory score, cohesiveness, and chewiness between the two frying methods ( $p>0.05$ ). Gas chromatography ion migration chromatography (GC-IMS) was used for flavor compound analysis, and 50 flavor compounds were analyzed, containing 22 aldehydes, 11 ketones, 6 olefins, 4 acids, 3 esters, 3 alcohols, and 1 phenol. Compared with the samples before frying, the relative contents of aldehydes and ketones of fried giant salamander meatballs increased significantly, while the relative contents of esters and alkenes decreased significantly. Principal component analysis showed that the GC-IMS spectra of volatile flavor compounds before and after deep fat frying and hot air frying varied greatly, and the cumulative contribution rate of the two principal components reached 86.1%, indicating that the GC-IMS technology might be used to distinguish giant salamander meatballs before and after frying, or with different frying methods. These results may offer a note for development and quality control of the precooked giant salamander meatballs in the future.

Quality Characteristics and Moisture Mobility of Giant Salamander (Andrias davidianus) Jerky during Roasting Process

Quality attributes and water mobility of giant salamander jerkies (GSJs) during roasting process (160°C, for 0, 20, 40, 60, and 80 min) were investigated. The results showed that $a^{\ast },b^{\ast }$ values and shear force increased of GSJs roasting from 20 to 80 min, while $L^{\ast }$ , yield, and moisture content decreased significantly ( $p<0.05$ ). Sensory assessment showed that GSJs at a roasting time of 40–60 min had higher scores. GSJs contained great amount of healthy unsaturated fatty acids (including DHA and EPA), and the total amino acids and essential amino acids were among 59.33–71.77 g·100 g−1 and 25.94–31.40 g·100 g−1, respectively. The mobility of the immobilized moisture and free moisture were shrunk dramatically during roasting. The proton density weighted images also exhibited the moisture shrinkage during roasting. In addition, T22 and T23 were positively correlated with MRI signal, moisture content, and yield of GSJs, but negatively correlated with shear force and overall acceptability, respectively. Thus, in view of various quality attributes and sensory evaluation, a roasting time of 40–60 min was favored for nutritive GSJs production. LF-NMR and MRI might be employed to profile the quality characteristics during roasting as a rapid and nondestructive analytical tool.

Collagens made from giant salamander (Andrias davidianus) skin and their odorants

Two collagens were made from giant salamander (Andrias davidianus) skin by using acid and pepsin extraction methods. The yields of acid-soluble and pepsin-soluble collagens were 26.9 and 58.7%, respectively. The results of spectrum, electrophoresis and amino acid analysis showed that they were type 1 collagen with two α and one β peptides and high imino acid content. They had low solubility at a pH above 6 or salt concentration over 5%. The pepsin-soluble collagen had a better emulsion activity index. The odorants in raw skin and collagens were identified and evaluated using gas-chromatography mass-spectrometer and olfactometry methods and sensory analysis. The fishy and fatty off-odors in skin were not perceivable in the collagens. Sour, ammonia-like, and acrid off-odors were found in the collagens due to acid and enzymatic hydrolysis and protein degradation. The off-odor intensity of pepsin-soluble collagen was low. It could be considered a good and safe collagen material.

Using the 2020 global pandemic as a springboard to highlight the need for amphibian conservation in eastern Asia

Emerging infectious diseases are on the rise in many different taxa, including, among others, the amphibian batrachochytrids, the snake fungal disease and the Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) virus, responsible for Coronavirus disease 2019 (COVID-19) in mammals. Following the onset of the pandemic linked to COVID-19, eastern Asia has shown strong leadership, taking actions to regulate the trade of potential vector species in several regions. These actions were taken in response to an increase in public awareness, and the need for a quick reaction to mitigate against further pandemics. However, trade restrictions rarely affect amphibians, despite the risk of pathogen transmission, directly, or indirectly through habitat destruction and the loss of vector consumption. Thus, species that help alleviate the risk of zoonoses or provide biological control are not protected. Hence, in view of the global amphibian decline and the risk of zoonoses, we support the current wildlife trade regulations and support measures to safeguard wildlife from overexploitation. The current period of regulation overhaul should be used as a springboard for amphibian conservation. To mitigate risks, we suggest the following stipulations specifically for amphibians. I) Restrictions to amphibian farming in eastern Asia, in relation to pathogen transmission and the establishment of invasive species. II) Regulation of the amphibian pet trade, with a focus on potential vector species. III) Expansion of the wildlife trade ban, to limit the wildlife-human-pet interface. The resulting actions will benefit both human and wildlife populations, as they will lead to a decrease in the risk of zoonoses and better protection of the environment.

SIGNIFICANCE STATEMENT

There is an increasing number of emerging infectious diseases impacting all species, including amphibians, reptiles and mammals. The latest threat to humans is the virus responsible for COVID-19, and the resulting pandemic. Countries in eastern Asia have taken steps to regulate wildlife trade and prevent further zoonoses thereby decreasing the risk of pathogens arising from wild species. However, as amphibians are generally excluded from regulations we support specific trade restrictions: I) Restrictions to amphibian farming; II) regulation of the amphibian pet trade; III) expansion of the wildlife trade ban. These restrictions will benefit both human and wildlife populations by decreasing the risks of zoonoses and better protecting the environment.

COVID-19 Highlights the Need for More Effective Wildlife Trade Legislation

Zoonosis-based epidemics are inevitable unless we revisit our relationship with the natural world, protect habitats, and regulate wildlife trade, including live animals and non-sustenance products. To prevent future zoonoses, governments must establish effective legislation addressing wildlife trade, protection of habitats, and reduction of the wildlife-livestock-human interface.