Circulating concentrations of thyroid hormones and cortisol in wild and semi-natural Yangtze finless porpoise (Neophocaena asiaeorientalis)

The association of seasonal dietary shift with fecal metabolome and microbiota in the captive Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis)

The gut microbiota can act as a buffer against changes in energy and food availability and adapt plastically to fluctuations in the host's diet. However, it is unknown how changes in the gut microbiome with the seasons impact microbial metabolism and the accessibility of nutrients to hosts. The study utilized 16S rRNA and UHPLC-MS/MS approaches to examine seasonal fecal metabolome variations in the captive Yangtze finless porpoises (YFPs) to determine if these variations are linked to nutrient intake or gut microbiome composition changes. The YFPs were mostly fed a frozen and live fish diet, with different food intakes yearly. We found that gut microbial diversity remained constant, but community structure varied seasonally. Firmicutes and Cyanobacteria were higher in winter, Actinobacteria in spring and fall, and proteobacteria in summer. The genus Paeniclostridium was significantly higher in the spring season, Romboutsia and Clostridium_sensu_stricto_13 were significantly higher in the summer, while Terrisporobacter and Macrococcus were significantly higher in the fall group. The study reported that seasonal dietary variation significantly impacted the fecal metabolome by affecting the metabolism, including energy, amino acid, carbohydrate, and nucleotide metabolism of the captive YFP. Moreover, significant correlations between metabolome and microbiome were found, and these correlations may indicate that the captive YFP has adapted to cope with dietary variations and enhance energy acquisition. These findings improve our knowledge of the link between microbiota, diet, metabolites, and the physiology of the host and suggest that gut microbial populations may adapt continuously to changes in diet.

Comprehensive assessment of the physical and health features of the threatened Araguaian River dolphin Inia araguaiaensis

The Araguaia River dolphin is endemic to the Tocantins-Araguaia River Basin and is under severe anthropogenic threats. Given the species' vulnerability and historical neglect, preliminary data on its health and physical parameters are presented, along with an evaluation of potential differences between individuals from areas with varying human activity. A comparison of these data with its closely related species, the Amazon River dolphin I. geoffrensis, was also aimed. Twenty-four dolphins were captured and released in Cantão State Park (protected area, n = 10), Tocantins state; and Luiz Alves (exposed to fishing activities, n = 14), Goiás state. Preliminary data indicates no significant differences in the body morphology and physical parameters between individuals from the two areas. Araguaia River dolphins tended to show larger grey areas in their bodies than their counterparts, Amazon river dolphins. Cardiac rate, respiratory frequency, and oral temperature did not vary between individuals from different areas, sex, or age classes. Hematological and serum chemistry variables differences were observed among age classes, mainly related to body and immune system development. Dolphins from Cantão had higher AST and urea/creatinine and lower GGT, total bilirubin, and creatinine than dolphins from Luiz Alves. Such variations may reflect different prey types, intensities of muscle extenuation during capture, or subclinical diseases. Most hematological parameters for the Araguaia River dolphin were outside the reference intervals described for the Amazon river dolphin but inside its minimum and maximum ranges. Conversely, the serum chemistry values from both species overlap with the reference values. The highest serum testosterone was detected in adult males and the highest serum progesterone and estradiol in adult females. Correlations between reproductive hormones and body measurements demonstrated preliminary hormonal variation according to the body's development as the individuals reach sexual maturity. Understanding the current physical and health status of individuals from areas with different human activity intensities is crucial to drive management efforts toward species conservation.

Dolphin Pituitary Gland: Immunohistochemistry and Ultrastructural Cell Characterization Following a Novel Anatomical Dissection Protocol and Non-Invasive Imaging (MRI)

The pituitary gland regulates essential physiological processes in mammals. Despite its importance, research on its anatomy and ultrastructure in dolphins remains scarce. Using non-invasive imaging technology (MRI) and a novel skull-opening and dissection protocol, this study characterizes the dolphin pituitary through immunohistochemistry (IHC) and transmission electron microscopy (TEM). A total of 47 pituitaries were collected from stranded common bottlenose dolphins (Tursiops truncatus). common dolphins (Delphinus delphis), and Atlantic spotted dolphins (Stenella frontalis). as well as from captive common bottlenose dolphins. MRI allowed visualization of the gland's anatomy and its spatial relationship with the hypothalamus and surrounding structures. A modified skull-opening and pituitary extraction protocol ensured the preservation of the adenohypophysis and neurohypophysis for detailed analysis. Histological, immunohistochemical, and ultrastructural studies confirmed the gland's structural organization, identifying eight distinct adenohypophyseal cell types: corticotrophs (ACTH), somatotrophs (GH), gonadotrophs (FSH and LH), lactotrophs (LTH), melanotrophs (MSH), thyrotrophs (TSH), follicular cells, and capsular cells. This study presents the first immunolabelling of thyrotrophs in cetacean adenohypophysis and the first detailed ultrastructural characterization of adenohypophyseal cells in cetaceans, providing baseline data for future research. By integrating multidisciplinary techniques, it advances the understanding of dolphin neuroendocrinology and highlights broader implications for cetacean health, welfare, and conservation.

Comparative Blood Transcriptome Analysis of Semi-Natural and Controlled Environment Populations of Yangtze Finless Porpoise

The Yangtze finless porpoises (Neophocaena asiaeorientalis asiaeorientalis) living in different environments display significant differences in behavior and physiology. To compare and analyze gene expression differences between an ex situ population and a controlled environment population of the Yangtze finless porpoise, we sequenced the transcriptome of blood tissues living in a semi-natural reserve and an artificial facility, respectively. We identified 6860 differentially expressed genes (DEGs), of which 6603 were up-regulated and 257 were down-regulated in the controlled environment vs ex situ comparison. GO and KEGG enrichment analysis showed that the up-regulated genes in the controlled environment population were significantly associated with glucose metabolism, amino acid metabolism, and the nervous system, while those up-regulated in the ex situ population were significantly associated with energy supply and biosynthesis. Further analysis showed that metabolic and hearing-related genes were significantly affected by changes in the environment, and key metabolic genes such as HK, PFK, IDH, and GLS and key hearing-related genes such as OTOA, OTOF, SLC38A1, and GABBR2 were identified. These results suggest that the controlled environment population may have enhanced glucose metabolic ability via activation of glycolysis/gluconeogenesis, the TCA cycle, and inositol phosphate metabolism, while the ex situ population may meet higher energy requirements via enhancement of the amino acid metabolism of the liver and muscle and oxidative phosphorylation. Additionally, the acoustic behavior and auditory-related genes of Yangtze finless porpoise may show responsive changes and differential expression under different environment conditions, and thus the auditory sensitivity may also show corresponding adaptive characteristics. This study provides a new perspective for further exploration of the responsive changes of the two populations to various environments and provides a theoretical reference for further improvements in conservation practices for the Yangtze finless porpoise.