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The razor clam Sinonovacula constricta is the first marine mollusk demonstrated to possess the complete long-chain polyunsaturated fatty acids (LC-PUFA) biosynthetic pathway. This study explored the impact of different microalgae on growth, Fad and Elovl expressions, and fatty acid (FA) profiles in juvenile S. constricta. Results revealed that juveniles fed with Isochrysis galbana (rich in DHA) or Chaetoceros calcitrans (rich in EPA) consistently exhibited higher growth than those fed Chlorella sp. (rich in LA and ALA), underscoring the importance of dietary LC-PUFA in S. constricta's development. Expression of most Fad and Elovl in C. calcitrans and I. galbana-fed juveniles were initially up-regulated, then down-regulated, suggesting LC-PUFA demand for faster growth. Although Chlorella sp.-fed juveniles exhibited decreased mRNA levels for most genes, levels were notably higher lately compared to those fed C. calcitrans or I. galbana, hinting at potential LC-PUFA biosynthesis induction. FA profiles in S. constricta generally mirrored those in ingested microalgae, implying direct FA accumulation from diets. Some microalgal FA were absent in farmed S. constricta, while others emerged, indicating S. constricta's ability to selectively accumulate and synthesize FA. This study enhances the understanding of dietary FA metabolism in S. constricta, valuable for selecting appropriate microalgae in its farming practices. [ABSTRACT FROM AUTHOR]

Sichuan taimen (Hucho bleekeri Salmonidae) populations are declining, and the status of remnant populations in the Qinling Mountains is poorly known. In this study, eDNA and creel netting were used to estimate the distributions of Sichuan taimen in two upper tributaries of the Hanjiang River. A qPCR assay was applied to detect the eDNA of H. bleekeri, and the presence of Sichuan taimen in the Taibai River, but not in the Xushui River, was confirmed. Sampling during summer achieved a relatively higher detection rate. The utility of eDNA techniques for detecting low-density Sichuan taimen was demonstrated in intricate stream ecosystems. The eDNA method can increase the efficiency of the management of endangered freshwater species, such as Sichuan taimen, by providing reliable distribution data. [ABSTRACT FROM AUTHOR]

Environmental DNA (eDNA) techniques have emerged as a cost-effective and non-invasive strategy for monitoring the distribution of endangered aquatic species. Despite their numerous advantages, operational uncertainty at each step of the process represents a significant challenge that can impact the reliability of results. Hence, the optimization of the eDNA analytic protocol is of utmost importance. In this study, the rare and endangered fish species Sichuan taimen was chosen as the target species to evaluate the concordance between different approaches (tissue, pond, and field water samples) for eDNA detection. The results showed that membrane filtration, collection of a 2-L water sample, and utilization of the DNeasy Tissue and Blood DNA extraction kit were suitable for the analysis of DNA in water samples. Furthermore, the mtDNA D-loop region demonstrated potential as a specific molecular marker for the precise identification of Sichuan taimen. Our results indicated that TaqMan fluorescence PCR can serve as the optimal detection method for reliable identification of target DNA even at extremely low concentrations in the field. This study established an optimized eDNA analysis protocol for Sichuan taimen detection, which will provide the basis for future resource investigations aimed at protection of this endangered aquatic species. [ABSTRACT FROM AUTHOR]

The Chinese giant salamander (Andrias davidianus) is the biggest extant and endangered amphibian, which has an incongruous sex ratio during the artificial breeding process and is sex indistinguishable in appearance. The sex development mechanism of this rare species thus needs to be explored. We therefore conducted this study to explore the molecular mechanisms of sex hallmarks or gonad maintenance genes for CGS. In this study, we sequenced and analyzed the sexually mature male and female gonads of Chinese giant salamanders (CGSs) using RNA-seq technology and found a total of 15,063 differentially expressed genes (DEGs) in the testicular and ovarian tissues, of which 7973 (52.93%) were expressed in testicular and 7090 (47.07%) in ovarian tissues. Thirteen gonad DEGs were selected based on gene expression abundance and quantified in the muscle and skin tissues of both male and female CGSs. The results showed that these 13 DEGS, out of the 20 analyzed DEGs, were expressed in both the muscle and skin tissues and only two of them (Bmp15 and ZP3) were consistent in the muscle and skin compared to the gonads of CGSs of the two sexes. Overall, our study should provide an important reference for the sex-characteristics-related genes in this type of species, shedding new light on future research on this topic. [ABSTRACT FROM AUTHOR]

Heat shock proteins (HSPs) play a key role in anti-stress and immune processes and are associated with autoimmune diseases. In order to explore the immunological role of HSPs from Schizothorax prenanti (S. prenanti), SpHSP60 was cloned for the first time in this study, and the gene expressions of SpHSP27, SpHSP60, SpHSP70 and SpHSP90 in the hepatopancreas, head kidney, hindgut and spleen were analyzed by quantitative real-time PCR (qPCR) after treatment with lipopolysaccharide (LPS). The open reading frame of the SpHSP60 gene (GenBank accession number ON245159) is 1728 bp. It encodes a protein of 575 amino acids. Its C-terminus is a highly conserved and repeated glycine sequence, which is an important cofactor in ATP binding. Compared with the control group, most of the SpHSPs were significantly upregulated in the tissues examined at 12 or 24 h after LPS challenge. The most abundant expression of SpHSP70 was found in the head kidney at 24 h after LPS injection, followed by SpHSP27 in the spleen at 24 h; both of these SpHSPs displayed strong expression under the LPS stresses, about 20–70 fold more than that of SpHSP60 and SpHSP90. The temporal expression patterns of the four SpHSP genes were different in the four tissues examined. Taken together, the results suggest that SpHSP27, SpHSP60, SpHSP70 and SpHSP90 participate in innate immunity stimulated by LPS, and the response intensity of the SpHSPs was organ-specific, indicating they could provide early warning information against bacterial infection. The findings in our study will contribute to better understanding the biological processes and important roles of SpHSPs involved in defending against pathogenic bacterial challenge. [ABSTRACT FROM AUTHOR]