Development and characterization of 20 microsatellite markers in spotted sea bass (<em>Lateolabrax maculatus</em>) and cross-amplification in related species

The spotted sea bass (Lateolabrax maculatus) is an economically valuable cultured fish species in China. In this study, 20 novel polymorphic microsatellite loci of L. maculatus were isolated from genomic data and characterized using 40 wild individuals. The number of alleles and the effective number of alleles ranged from 2 to 12 (average of 5.1000) and from 1.180 to 8.000 (average of 3.3097). The observed and expected heterozygosities ranged from 0.083 to 0.875 (average of 0.4405) and from 0.153 to 0.875 (average of 0.5633), respectively. Deviation from the Hardy-Weinberg equilibrium was observed in 11 loci (P Lates calcarifer, achieved successful amplification of 16 primers. The microsatellite markers developed in this study could be used for research on genetic breeding of L. maculatus and genetic relationships among tested taxa

Molecular cloning and expression profiles of an insulin-like growth factor binding protein IGFBP5 in the pearl oyster, Pinctada fucata

The insulin-like growth factor binding protein (IGFBP) family participates in transportation, localization, and biological regulation of insulin-like growth factors (IGFs). In the present study, IGFBP5 gene from the Pinctada fucata (PfIGFBP5) was cloned and characterized. The full-length cDNA sequence (1319 bp) contained an open reading frame of 399 bp encoding a predicted protein of 132 amino acids. The amino acid sequence of PfIGFBP5 included an IGF binding domain and multiple cysteine residues. The genomic sequence of PfIGFBP5 consisted of three exons and two introns. PfIGFBP5 was found to be expressed in all tissues and developmental stages investigated, although the expression level was significantly higher in the pearl sac and in trochophore larvae than in other tissues or developmental stages (P < 0.05). Expression of PfIGFBP5 was induced by notching the oyster shell margin; the gene was mainly expressed in the outer epithelium of the mantle, and to a lesser extent in the whole pearl sac, including connective tissues. These findings suggest that PfIGFBP5 is very likely to be involved in modulating biomineralization in the mantle and pearl sac of P. fucata since they are the main organs for shell or pearl formation

The complete mitochondrial genome and phylogenetic analysis of Cancer pagurus (Decapoda, Cancridae)

The complete mitochondrial genome of Cancer pagurus was obtained using next-generation sequencing. The circular genome was 42,736 bp in length, consisting of 13 protein-coding genes, 26 transfer RNA genes, and 2 ribosomal RNA genes. The control region was not found in mitochondrial genome. Of the 41 genes, 21 were encoded by the heavy strand, while the others were encoded by the light strand. The genome composition with A + T bias (74.10%). The phylogenetic analysis suggested that C. pagurus was closest to Austinograea alayseae. The newly described mitochondrial genome may provide valuable data for phylogenetic analysis for Cancridae

Mechanism of Cadmium Exposure Induced Hepatotoxicity in the Mud Crab (Scylla paramamosain): Activation of Oxidative Stress and Nrf2 Signaling Pathway

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

The complete mitochondrial genome and phylogenetic analysis of Cancer magister (Decapoda, Cancridae)

The complete mitochondrial (mt) genome of Cancer magister was obtained using next-generation sequencing. The circular genome was 39,658 bp in length, consisting of 13 protein-coding genes, 26 transfer RNA genes, and 2 ribosomal RNA genes. Unfortunately, the control region was not found in mitochondrial genome. Of the 41 genes, 24 were encoded by the heavy strand, while the others were encoded by the light strand. The genome composition with A + T bias (69.90%). The phylogenetic analysis showed that C. magister and Cancer pagurus was clustered together, then grouped with A. alayseae and Gandalfus puia, which may suggest Cancroidea was close with Bythograeidae. The newly described mitochondrial genome may provide valuable data for phylogenetic analysis for Cancridae

Molecular cloning and functional analysis of type I IFNd of Chinese sea bass (Lateolabrax maculatus) under immune stimulation

Chinese sea bass (Lateolabrax maculatus) is an economically important marine cultured species in China. Interferons (IFNs) play an essential role in innate antiviral immunity. The study on IFN immune system helps prevent and control viral diseases of L. maculatus. We have obtained cloning and characterization of the type I IFNd gene from L. maculatus (LmIFNd) in the present study. The full length of cDNA was 1190 bp, including 5'UTR (untranslated region) of 354 bp, 3'UTR of 278 bp, and an open reading frame (ORF) of 558 bp. It encodes 185 amino acids, and the first 20 amino acids are hypothetical signal peptides. The results of amino acid multiple sequence alignment and phylogenetic tree analysis showed that LmIFNd and mandarin fish (Siniperca chuatsi) IFNd were clustered into one branch, and the gene sequence similarity was as high as 88.9%. The expression of LmIFNd was tissue-specific and highly expressed in the head kidney, spleen, and gill. After infection with Rana grylio virus (RGV), and polyinosinic-polycytidylic acid [Poly(I:C)], the expression of LmIFNd in gill, spleen, and head-kidney was up-regulated significantly. Besides, the expression level of LmIFNd has increased significantly under the stimulation of Vibrio harveyi and Streptococcus iniae. The results show that LmIFNd may play a protective role in both viral and bacterial infections

Physiological, Biochemical Responses and Apoptosis- Related Genes Expressions of Hypoxia and Re- Oxygenation Stress in an Economically Important Mariculture Fish, the Chinese Sea Bass (Lateolabrax maculatus)

The Chinese sea bass (Lateolabrax maculatus) is one of the most important marine aquaculture fish in China. Hypoxia represents a growing threat to L. maculatus in intensive mariculture. Here, effects of hypoxia and re-oxygenation conditions on physiological, biochemical responses and apoptosis-related genes expressions in L. maculatus were investigated. The results showed that the asphyxiation point and critical non-equilibrium point of adult L. maculatus were 0.39 mg/L and 1.17 mg/L dissolved oxygen, respectively. The concentrations of four inorganic ions (Na+, K+, Cl-, Ca2+) in serum and four red blood cell parameters levels (HCT, MCV, MCHC, RDW-CV) were significantly changed in hypoxic and re-oxygenated fish. The concentration of hepatic glycogen was decreased dramatically in re-oxygenated fish compared with control and hypoxic fish, which is contrary to the result of glucose, total cholesterol and triglyceride in serum. Moreover, the activities of certain myocardial enzymes (LDH, CK, CK-MB) were significantly increased in the serum occurred in cardiomyocytes during re-oxygenated condition, speculating that hypoxia/re- oxygenation injury might be occurred in cardiomyocytes. The result of six apoptosis- related genes expressions in heart of L. maculatus showed that pro-apoptotic genes (Cytc, Caspase3, Bax, Stat3) were significantly up-regulated in re-oxygenated condition whereas anti-apoptotic genes were (TET1, SGK1) expressed lower in re-oxygenated condition than that in normal. The experimental results suggested that hypoxia and re-oxygenation had a serious impact on L. maculatus, such as ion balance destroying, innate immune decreasing, oxygen carrying capacity changing, cardiomyocyte apoptosis. Especially, cardiomyocyte injury caused by hypoxia and re-oxygenation after hypoxia is very severely. These findings might be helpful for breeding management and future hypoxia stress study in L. maculatus

Differential Gene Expression during Larval Metamorphic Development in the Pearl Oyster, Pinctada fucata, Based on Transcriptome Analysis

P. fucata experiences a series of transformations in appearance, from swimming larvae to sessile juveniles, during which significant changes in gene expression likely occur. Thus, P. fucata could be an ideal model in which to study the molecular mechanisms of larval metamorphosis during development in invertebrates. To study the molecular driving force behind metamorphic development in larvae of P. fucata, transcriptomes of five larval stages (trochophore, D-shape, umbonal, eyespots, and spats) were sequenced using an Illumina HiSeq™ 2000 system and assembled and characterized with the transcripts of six tissues. As a result, a total of 174,126 unique transcripts were assembled and 60,999 were annotated. The number of unigenes varied among the five larval stages. Expression profiles were distinctly different between trochophore, D-shape, umbonal, eyespots, and spats larvae. As a result, 29 expression trends were sorted, of which eight were significant. Among others, 80 development-related, differentially expressed unigenes (DEGs) were identified, of which the majority were homeobox-containing genes. Most DEGs occurred among trochophore, D-shaped, and UES (umbonal, eyespots, and spats) larvae as verified by qPCR. Principal component analysis (PCA) also revealed significant differences in expression among trochophore, D-shaped, and UES larvae with ten transcripts identified but no matching annotations

Differential Gene Expression during Larval Metamorphic Development in the Pearl Oyster, Pinctada fucata, Based on Transcriptome Analysis

P. fucata experiences a series of transformations in appearance, from swimming larvae to sessile juveniles, during which significant changes in gene expression likely occur. Thus, P. fucata could be an ideal model in which to study the molecular mechanisms of larval metamorphosis during development in invertebrates. To study the molecular driving force behind metamorphic development in larvae of P. fucata, transcriptomes of five larval stages (trochophore, D-shape, umbonal, eyespots, and spats) were sequenced using an Illumina HiSeq™ 2000 system and assembled and characterized with the transcripts of six tissues. As a result, a total of 174,126 unique transcripts were assembled and 60,999 were annotated. The number of unigenes varied among the five larval stages. Expression profiles were distinctly different between trochophore, D-shape, umbonal, eyespots, and spats larvae. As a result, 29 expression trends were sorted, of which eight were significant. Among others, 80 development-related, differentially expressed unigenes (DEGs) were identified, of which the majority were homeobox-containing genes. Most DEGs occurred among trochophore, D-shaped, and UES (umbonal, eyespots, and spats) larvae as verified by qPCR. Principal component analysis (PCA) also revealed significant differences in expression among trochophore, D-shaped, and UES larvae with ten transcripts identified but no matching annotations

The complete mitochondrial genome of Colochirus quadrangularis (Dendrochirotida, Cucumariidae)

The complete mitochondrial genome of Colochirus quadrangularis was obtained and described in this study. This complete mitochondrial genome is 17,157 bp in length and consists of 13 protein-coding genes, 2 ribosomal RNA genes, and 22 transfer RNA genes. Except ND6 and 5 tRNAs, the others were encoded by the heavy strand. The overall base composition of the heavy-strand was 40.23% A, 11.31% G, 21.76% C, and 26.71% T, with a high G + C content of 33.07%. The phylogenetic analysis suggested that C. quadrangularis was closest to Cucumaria miniata. The newly described mitochondrial genome may provide valuable data for the phylogenetic analysis for Holothuroidea