Sigang Fan

Scylla paramamosain is a globally important mariculture crab species. However, its resources for simple sequence repeat (SSR) loci remain severely underdeveloped. In the present study, MISA software was employed to systematically detect and characterize SSR loci across the whole genome of S. paramamosain . A total of 3,184,249 SSR loci were identified in the S. paramamosain genome, with a cumulative length of 241,424,069 bp, accounting for 15.62% of the total genome size. The frequency and density of SSRs were 2,059.64 loci/Mb and 156,158.13 bp/Mb, respectively. A total of 259 distinct repeat motifs were detected, with repeat numbers ranging from 5 to 1,551. Mononucleotide repeats were the most abundant type, followed by dinucleotide repeats. Among all repeat motifs, motif A was the most prevalent, followed by the dinucleotide motifs AG and AC. Regarding chromosomal distribution, chromosome 3 had the most SSR loci, while chromosome 44 had the fewest. Notably, chromosome 44 exhibited the highest SSR frequency and density. In total, 2,382,227 SSR markers were developed; among these, 72.82% were located in intergenic regions, 20.15% in introns, and 7.03% in exons. Sixteen SSR markers were amplified in 32 S. paramamosain individuals, among which eight markers possessed high polymorphism. To the best of our knowledge, this is the first chromosome-level genome-wide SSR analysis in S. paramamosain . These findings provide valuable genetic resources and a theoretical basis for subsequent genetic breeding and germplasm improvement of S. paramamosain .

Cambarellus patzcuarensis is a popular aquarium freshwater crayfish in China. In this study, the mitochondrial genome of C. patzcuarensis was sequenced using Illumina HiSeq. The coding mitogenome of C. patzcuarensis is 15,000 bp in length, consisting 13 protein-coding genes (PCGs), 22 transfer RNAs, and two ribosomal RNAs. The A + T content was 70.17%. Ten PCGs had ATN as the start codon. Three PCGs were stopped with incomplete stop codon. The phylogenetic analysis shown that C. patzcuarensis was grouped with other Procambarus species. These results are useful for understanding the phylogenetic relationships of Cambaridae crayfish.

The yellowfin seabream (Acanthopagrus latus) is an economically important commercial mariculture fish in China and Southeast Asia. Only a few simple sequence repeats (SSRs) of A. latus have been isolated and reported, which has hindered breeding progress. A total of 318,862 SSRs were isolated and characterized from the A. latus genome in this study. All SSRs were 9,069,670 bp in length, accounting for 1.32% of the genome. The density and frequency of SSRs were 468.40 loci/Mb and 13,323.19 bp/Mb, respectively. The major SSRs were dinucleotides (accounting for 76.92%), followed by trinucleotides (15.75%). The most abundant SSR motif was (AC)n (168,390, accounting for 53%), with the highest frequency (245.78 loci/Mb) and density (7304.18 bp/Mb). Most SSRs were located in non-coding regions, such as intergenic regions (34.54%) and introns (56.91%). SSR-containing exons were distributed into 51 gene ontology (GO) terms and significantly enriched in immunity- and growth-related pathways. A total of 217,791 SSR markers were successfully designed. Nine SSR markers were amplified in 29 A. latus individuals, and eight of them possess high polymorphism. The cross-species transferability of 33 out of the 37 tested loci were successfully amplified in Acanthopagrus schlegelii. These results lay the foundation for the molecular marker-assisted breeding and genetic information assessment of A. latus.

Periclimenes brevicarpalis is widely distributed in the Indo West Pacific oceans. The mitochondrial genome of P. brevicarpalis was sequenced and assembled firstly by next generation sequencing technology in our study. The complete mitochondrial genome of P. brevicarpalis was 16,673 bp in size, consisted of 22 transfer RNA genes, 13 protein coding genes and two ribosomal RNA genes. The contents of the four bases were C (25.62%), T (28.73%), A (31.64%), and G (14.01%). The result of phylogenetic analysis showed that P. brevicarpaliswas clustered with Anchistus australis. In conclusion, our research provided valuable data for phylogenetic analysis of the Palaemonidae family as the first report about mitochondrial genomes in Periclimenes.

Atyopsis moluccensis, belonging to the family Atyidae, is one of the popular species in aquarium industry. Here, we sequenced the mitochondrial genome of A. moluccensis. The mitogenome of A. moluccensis is 15,933 bp in length, consisting 22 transfer RNAs, 13 protein-coding genes (PCGs), and two ribosomal RNAs. The composition of A. moluccensis mitogenome is 33.77% for A, 13.81% for G, 28.74% for T, and 23.68% for C. The A + T content of the heavy-strand was 62.51%. Except ND5, most of the PCGs had ATN as the start codon. Only COX2 and ND4 were stopped by incomplete stop codon. The phylogenetic relationship was reconstructed with 16 shrimp from six genera of family Atyidae, which revealed that A. moluccensis and A. gabonensis clustered together and species of the same genus were grouped together in a clade. The data are beneficial in understanding the evolution and phylogenetic relationships of Atyidae shrimp.

The insulin-like growth factor 2 gene (igf2) is thought to be a key factor that could regulate animal growth. In fish, few researchers have reported on the single nucleotide polymorphisms (SNPs) located in igf2 and their association with growth traits. We screened the SNPs of igf2 from the spotted sea bass (Lateolabrax maculatus) by Sanger sequencing and made an association between these SNPs with growth traits. The full-length complementary (c) DNA of igf2 was 1045 bp, including an open reading frame of 648 bp. The amino acid sequence of Igf2 contained a signal peptide, an IGF domain, and an IGF2_C domain. Multiple sequence alignment showed that the IGF domain and IGF2_C domain were conserved in vertebrates. The genome sequence of igf2 had a length of 6227 bp. Fourteen SNPs (13 in the introns and one in one of the exons) were found in the genome sequence of igf2. Four SNPs located in the intron were significantly associated with growth traits (p < 0.05). These results demonstrated that these SNPs could be candidate molecular markers for breeding programs in L. maculatus.

Hypoxia is a major environmental stressor that can damage the oxidation metabolism of crustaceans. Glutaredoxin (Grx) is a key member of the thioredoxin superfamily and plays an important role in the host’s defense against oxidative stress. At present, the role of Grx in response to hypoxia in crustaceans remains unclear. In this study, the full-length cDNA of Grx3 (SpGrx3) was obtained from the mud crab Scylla paramamosain, which contains a 129-bp 5′ untranslated region, a 981-bp open reading frame, and a 1,183-bp 3′ untranslated region. The putative SpGrx3 protein contains an N-terminal thioredoxin domain and two C-terminal Grx domains. SpGrx3 was expressed in all tissues examined, with the highest expression in the anterior gills. After hypoxia, SpGrx3 expression was significantly up-regulated in the anterior gills of mud crabs. The expression of Grx2 and glutathione S-transferases was decreased, while the expression of glutathione peroxidases was increased following hypoxia when SpGrx3 was silenced in vivo. In addition, the total antioxidant capacity of SpGrx3-interfered mud crabs was significantly decreased, and the malondialdehyde content was significantly increased during hypoxia. The subcellular localization data indicated that SpGrx3 was predominantly localized in the nucleus when expressed in Drosophila Schneider 2 (S2) cells. Moreover, overexpression of SpGrx3 reduced the content of reactive oxygen species in S2 cells during hypoxia. To further investigate the transactivation mechanism of SpGrx3 during hypoxia, the promoter region of the SpGrx3 was obtained by Genome Walking and three hypoxia response elements (HREs) were predicted. Dual-luciferase reporter assay results demonstrated that SpGrx3 was likely involved in the hypoxia-inducible factor-1 (HIF-1) pathway during hypoxia, which could be mediated through HREs. The results indicated that SpGrx3 is involved in regulating the antioxidant system of mud crabs and plays a critical role in the response to hypoxia.

Cadmium, one of the most toxic heavy metals, can cause severe oxidative damage to aquatic animals. However, the mechanism whereby the mud crabs respond to cadmium exposure remains unclear. This study investigated the effects of cadmium exposure on oxidative stress and histopathology changes and evaluated the role of the Nrf2 signaling pathway in regulating responses to cadmium-induced hepatotoxicity were investigated in mud crabs. Mud crabs were exposed to 0, 0.01, 0.05, and 0.125 mg/L cadmium for 21 d. The present results indicated that cadmium exposure increased hydrogen peroxide (H₂O₂) production, lipid peroxidation and tissue damage, but decreased the activity of superoxide dismutase (SOD) and catalase (CAT), and caused lipid peroxidation and tissue damage. The results of an integrated biomarker index analysis suggested that the toxicity of cadmium was positively related to cadmium concentration. The expression levels of the Nrf2 signaling pathway (Nrf2, metallothionein, and cytochrome P450 enzymes) were up-regulated after cadmium exposure. Silencing of Nrf2 in vivo decreased antioxidant gene (SOD, CAT, and glutathione S-transferase) expression, suggesting that Nrf2 can regulate antioxidant genes. Knocking down Nrf2 in vivo also significantly decreased the activity of SOD and CAT after cadmium exposure. Moreover, silencing of Nrf2 in vivo enhanced H₂O₂ production and the mortality rates of mud crabs after cadmium exposure. The present study indicated that cadmium exposure induced hepatotoxicity in the mud crab by increasing H₂O₂ content, which decreased the antioxidant capacity, leading to cell injury. In addition, the Nrf2 is activated to bound with antioxidant response element, initiating the expression of antioxidant enzyme genes during cadmium induced hepatotoxicity in the mud crabs.