Background: The green mud crab (Scylla paramamosain) is the most prevalent crustacean on the southeast coast of China. The molecular regulatory mechanism of sex determination and gonadal differentiation in this species has received considerable attention in recent years because of the huge differences—both biological and economic—between male and female crabs. In this study, next-generation sequencing technology was used to develop deep-coverage transcriptomic sequencing data for the testis and ovary of S. paramamosain. Results: A total of 365,116 reads (testis 171,962, ovary 193,154) with an average sequence length of 285 bp were produced from testis and ovary cDNA libraries. After filtering out contaminating reads, the clean reads were assembled, producing a total of 21,791 isotigs and leaving 22,814 reads as singlets. Using the BLASTX program, 3,471 unique sequences (2,275 isotigs and 1,196 singletons) were annotated with known protein sequences from the NCBI non-redundant (Nr) protein sequence database. The Gene Ontology and KEGG (Kyoto Encyclopedia of Genes and Genomes) analyses allowed the 224 unique sequences that were annotated with enzyme code (EC) numbers to be mapped into 174 KEGG pathways. After comparing the ovary and testis libraries, 4,021 gonad-differentially, 10,522 ovary-specifically, and 19,013 testis-specifically expressed genes were identified. Moreover, 33 ovary-specific, 14 testis-specific, and 34 gonad-differential transcripts were confirmed by semi-quantitative PCR and quantitative real-time PCR. In addition, 8,610 putative simple sequence repeats (SSRs) and 23,879 potential single nucleotide polymorphisms (SNPs) were identified. Conclusion: This is the first large-scale RNA sequencing of S. paramamosain to be reported. We have identified many important functional genes and made a preliminary attempt to construct the regulatory network involved in the gonadal development of crustaceans. The annotated transcriptome data will provide fundamental support for future research into the reproduction biology of S. paramamosain. A large number of candidate SSRs and SNPs were detected, which could be used as genetic markers for population genetics and functional genomics in this species.

Coccidiosis is an important parasitic disease of poultry with great economic importance. Due to drug resistance issues, the study was conducted to investigate how probiotics (Lactobacillus plantarum or L. plantarum) affected oocysts per gram of feces (OPG), fecal scores, feed conversion ratio (FCR), immunomodulatory effect in terms of the cell-mediated and humoral immune response. Serum chemistry (ALT, AST, LDH, and creatinine) was measured in different treated chicken groups. mRNA expression levels of antioxidant enzymes (SOD 1 and CAT), peptide transporter 1 (PepT 1), and tight junction proteins (ZO and CLDN 1) were also examined in chicken groups infected with Eimeria tenella (E. tenella). Chickens supplemented with L. plantarum 1 × 10⁸ CFU (colony-forming unit) showed an improved cell-mediated and humoral immune response, compared with the control group (p < 0.05). Probiotics also enhanced the performance of antioxidant enzymes, PepT 1, and tight junction proteins, and improved serum chemistry (AST, ALT, and LDH), compared with control-infected, non-medicated chickens. However, no significant difference (p > 0.05) was observed in CLDN 1 expression level and creatinine in all treated chicken groups. These findings demonstrated that probiotics supplementation in the feed can protect the birds against E. tenella infection.

In gnathostomes, chemosensory receptors (CR) expressed in olfactory epithelia are encoded by evolutionarily dynamic gene families encoding odorant receptors (OR), trace amine-associated receptors (TAAR), V1Rs and V2Rs. A limited number of OR-like sequences have been found in invertebrate chordate genomes. Whether these gene families arose in basal or advanced vertebrates has not been resolved because these families have not been examined systematically in agnathan genomes. Petromyzon is the only extant jawless vertebrate whose genome has been sequenced. Known to be exquisitely sensitive to several classes of odorants, lampreys detect fewer amino acids and steroids than teleosts. This reduced number of detectable odorants is indicative of reduced numbers of CR gene families or a reduced number of genes within CR families, or both, in the sea lamprey. In the lamprey genome we identified a repertoire of 59 intact single-exon CR genes, including 27 OR, 28 TAAR, and four V1R-like genes. These three CR families were expressed in the olfactory organ of both parasitic and adult life stages. An extensive search in the lamprey genome failed to identify potential orthologs or pseudogenes of the multi-exon V2R family that is greatly expanded in teleost genomes, but did find intact calcium-sensing receptors (CASR) and intact metabotropic glutamate receptors (MGR). We conclude that OR and V1R arose in chordates after the cephalochordate-urochordate split, but before the diversification of jawed and jawless vertebrates. The advent and diversification of V2R genes from glutamate receptor-family G protein-coupled receptors, most likely the CASR, occurred after the agnathan-gnathostome divergence.

Glucose transporters (GLUTs) have been implicated in adaptive and survival responses to hypoxic stress in mammals. In fish, the expression and regulation of GLUT in relation to hypoxia remains unexplored. Here we describe the identification of a hypoxia‐responsive glucose transporter gene (gcGLUT) and the corresponding full‐length cDNA from the grass carp. The gene spans ≈ 11 kb of genomic sequence and consists of 12 exons and 11 introns, and an open reading frame (ORF) of 1599 bp encoding a polypeptide of 533 amino acids, with a predicted molecular mass of ≈ 57 kDa and a pI of 8.34. blastx analysis showed that the ORF shared high sequence identity with the GLUT1 (57–59%), GLUT3 (59–60%) and GLUT4 (55–59%) proteins from different vertebrates. Comparative analysis of GLUT genomic structures showed that the arrangement of exons and position of split codons are highly conserved amongst members of the class I GLUTs suggesting that these genes share a common ancestor. Phylogenetic analysis indicated that gcGLUT is most closely related to the GLUT3 proteins. Northern blot analysis showed that the 3.1‐kb gcGLUT transcript was most abundantly expressed and responsive to hypoxia in kidney. Up‐regulated expression by hypoxia was also evident in eye and gill, but differential patterns of expression were observed. Low expression levels detected in brain, heart, liver and muscle were not responsive to hypoxic stress.