Xia-Min Jiang’s research while affiliated with Ningbo University and other places

The Centropristis striata is an important economically marine fish and facing a serious threat from various pathogens. Edwardsiella piscicida is one of the fish pathogens that seriously infect cultured and wild fish species. To understand the molecular immune mechanisms underlying the response to E. piscicida, a comparative gene transcription analysis was performed through RNA‐Seq technology. The low‐quality sequences were excluded, and the high‐quality sequences were assembled into a total of 60,759 contigs with an average length of 988.95 bp. A gene ontology (GO) analysis was employed to classify 5744 genes according to three major functional categories: molecular function, cellular component and biological process. A total of 19,918 genes were successfully annotated into 26 functional categories according to the clusters of orthologous groups (COG) classification. Furthermore, 15,006 genes were classified into 332 KEGG pathways. The q‐value was introduced to estimate 5109 genes significantly differentially expressed which includes 1781 up‐regulated genes and 3328 down‐regulated genes. The differentially expressed genes were involved in the major immune‐related pathways which refer to the pathogen recognition, inflammation, Toll‐like receptor and chemokine signalling pathways. Moreover, 24,487 potential simple sequence repeats (SSRs) and 193,760 candidate single nucleotide polymorphisms (SNPs) were detected and identified in the C. striata liver transcriptome. This work not only provides a valuable resource for further understanding of the antibacterial molecular mechanism of C. striata but also contributes to facilitate future studies on gene expression and functional genomics.

The effects of light intensity on embryonic development of fertilized eggs of Sepia lycidas were investigated to determine the best light conditions for the embryos’ development. A single-factor experiment was performed to examine the effects of different light intensities (dark or 4.3, 10.2, 29.6, or 50.7 μmol/(m²·s)) on the embryonic development. The hatching rate, incubation period, hatching period and weight, and survival of hatchling cuttlefish were significantly affected by the light intensities (P < 0.05). When light intensity exceeds 10.2 μmol/(m²·s), the weight of hatchling cuttlefish and incubation period gradually decreased with the increase of light intensity, while the hatching rate first increased and later decreased. The sensitivity to light clearly varies among stages of embryonic development; the impact of light intensity on embryonic development appeared from the red-bead stage to hatching. High light intensities can interfere with the development of embryos and lead to abnormal development and premature hatching, reduced hatchability, decreased vitality of cuttlefish hatchlings, and asynchronous hatching, especially at light intensities exceeding 10.2 μmol/(m²·s). Low light intensities are better for embryonic development of S. lycidas than high light, and the light intensity as 10.2 μmol/(m²·s) was thus recommended. During incubation of paralarvae, fertilized eggs should be kept out of direct sunlight, and shading measures should be taken to keep the eggs in low light intensities.

The objective of this study was to investigate the effects of ammonia nitrogen on the embryonic development of the cuttlefish Sepia pharaonis. Embryos were exposed to different concentrations (0, 1, 3, and 5 mg/L) of total ammonia–nitrogen (TAN) during incubation. The developmental rate, malformations, mortality, hatching rate, incubation period, yolk utilization efficiency ratio, and weight of the newly hatched cuttlefish were determined. The results showed that ammonia nitrogen significantly inhibited the development of S. pharaonis embryos and induced malformations and even death. Hatching was delayed, the hatching rate was reduced, mortality and the incubation period increased, and the yolk utilization efficiency ratio and weight of the newly hatched cuttlefish significantly decreased in a dose‐dependent manner after the embryos were exposed to more than 1 mg/L TAN for prolonged period. These variables could be used as an integrative biomarker or indicator of aquatic environmental ammonia contamination. In summary, our results indicated that ammonia caused toxicity in the embryos. When the concentration of TAN is greater than 1 mg/L, ammonia levels should be reduced to prevent toxic effects on embryonic development.

The aim of this study was to provide a reference value for the safe regulation and control of ammonia nitrogen in the aquaculture of Sepia pharaonis. The effects of acute and chronic toxicity of ammonia on the cuttlefish, S. pharaonis, were tested experimentally using juvenile S. pharaonis. The results showed that the half-lethal concentration (LC50 ) values of ammonia nitrogen in juvenile S. pharaonis with a body weight of 6.52 ± 0. 23 g at 24, 48, 72, and 96 h were 31.72, 25.77, 23.33, and 18.33 mg/L, respectively, and the corresponding un-ionized ammonia nitrogen (UIA-N) concentrations were 1.66, 1.35, 1.22, and 0.96 mg/L, respectively. Compared with the control, the survival rate, specific growth rate, and feed intake of juvenile S. pharaonis declined significantly, and the feed conversion ratio and hepatosomatic index increased significantly at 56 d after exposure to >1 mg/L ammonia nitrogen. Juvenile S. pharaonis should be maintained at a concentration of ammonia nitrogen of no more than 1 mg/L (UIA-N is 0.056 mg/L) in culture, and removing harmful nitrogenous wastes from the seawater is critical in maintaining cuttlefish culture.

To investigate the ammonia detoxification pathways of the cuttlefish, Sepia pharaonis, the effects of environmental ammonia nitrogen exposure (control, 1, 3, and 6 mg/L) on nitrogen metabolism were quantified in the hemolymph, liver, and gills. The levels of glutamine synthetase, glutamate dehydrogenase, and arginase activities and ammonia, glutamine, and urea concentrations in the hemolymph, liver, and gills significantly increased upon exposure to 3 and 6 mg/L ammonia nitrogen and exhibited a dose-dependent relationship with the ammonia exposure concentration. These results suggest two main pathways of metabolic ammonia detoxification in S. pharaonis exposed to ammonia in this study: (1) conversion of ammonia to urea, which is stored temporarily or excreted, via the ornithine-urea cycle and (2) conversion of ammonia to glutamine, which can be stored in the body or used for other anabolic processes.

The effect of salinity on the embryonic development of Sepia pharaonis eggs was tested experimentally using S. pharaonis embryos at various developmental stages. The hatching rate, incubation period, hatching period, wet weight of hatchling cuttlefish, and yolk utilization efficiency ratio were quantified at salinities of 18, 21, 24, 27, 30, 33, and 36. These variables were significantly affected by salinity. The weight of the eggs first decreased and then increased during embryonic development. The range of suitable salinities for hatching of S. pharaonis eggs was 27-33, and the optimal salinity was 30.

Arginine kinase is an essential enzyme which is closely related to energy metabolism in marine invertebrates. Arginine kinase provides a significant role in quick response to environmental change and stress. In this study, we simulated a tertiary structure of Sepia pharaonis arginine kinase (SPAK) based on the gene sequence and conducted the molecular dynamics simulations between SPAK and Zn2+. Using these results, the Zn2+ binding sites were predicted and the initial effect of Zn2+ on the SPAK structure was elucidated. Subsequently, the experimental kinetic results were compared with the simulation results. Zn2+ markedly inhibited the activity of SPAK in a manner of non-competitive inhibitions for both arginine and ATP. We also found that Zn2+ binding to SPAK resulted in tertiary conformational change accompanying with the hydrophobic residues exposure. These changes caused SPAK aggregation directly. We screened two protectants, glycine and proline, which effectively prevented SPAK aggregation and recovered the structure and activity. Overall, our study suggested the inhibitory effect of Zn2+ on SPAK and Zn2+ can trigger SPAK aggregation after exposing large extent of hydrophobic surface. The protective effects of glycine and proline against Zn2+ on SPAK folding were also demonstrated.

The aim of this experiment was to determine the optimal initial food for hatchling cuttlefish and to investigate the influence of dietary composition on the growth, survival, and nutritional composition of cultured juvenile cuttlefish, Sepia pharaonis. Six experimental food groups were designated: Artemia nauplii, Calanus sinicus, frozen Hyperacanthomysis brevirostris, Ampithoe valida, H. brevirostris, and subadult Artemia. The results showed that survival, growth body biochemical composition of juvenile cuttlefish were significantly affected by experimental diets (P < 0.05). The optimum initial food was H. brevirostris, yielding a growth rate as high as 6.39%/d and survival rate reaching 81%. Growth rate was significantly positively correlated with dietary protein, Lys, Met, Phe, Iie, Leu, Trp, Arg, Gly, Eicosapentaenoic acid (EPA), Docosahexaenoic acid (DHA), and 16:0 (P < 0.05). Survival was significantly positively correlated with dietary protein, Lys, Met, Phe, Val, Thr, Iie, Leu, Trp, Arg, Gly, EPA, DHA, and 16:0 (P < 0.05). The dietary protein, lipid, Met, Val, Thr, Leu, 18:0, and EPA were prone to accumulation within the body of juvenile cuttlefish (P < 0.05). These results demonstrate that juvenile cuttlefish exhibited the best growth rates and survival when fed a diet that supplied high-protein, low-fat, and larger quantities of Lys, Met, Phe, Val, Thr, Iie, Leu, Trp, Arg, Gly, EPA, DHA, and 16:0.

Arginine kinase is closely associated with adaptation to environmental stresses such as high salinity and heavy metal ion levels in marine invertebrates. In this study, the effects of Cd(2+) on the cuttlefish Sepia pharaonis arginine kinase (SPAK) were investigated. SPAK was isolated from muscles of S. pharaonis and, upon further purification, showed a single band on SDS-PAGE. Cd(2+) effectively inactivated SPAK, and the double-reciprocal kinetics indicated that Cd(2+) induced non-competitive inhibition of arginine and ATP. Spectrofluorometry results showed that Cd(2+) induced tertiary structure changes in SPAK with the exposure of hydrophobic surfaces that directly induced SPAK aggregation. The addition of osmolytes, glycine and proline, successfully blocked SPAK aggregation and restored the conformation and activity of SPAK. Molecular dynamics simulations involving SPAK and Cd(2+) showed that Cd(2+) partly blocks the entrance of ATP to the active site, and this result is consistent with the experimental results showing Cd(2+)-induced inactivation of SPAK. These results demonstrate the effect of Cd(2+) on SPAK enzymatic function and unfolding, including aggregation, and the protective effects of osmolytes on SPAK folding. This study provides concrete evidence of the toxicity of Cd(2+) in the context of the metabolic enzyme SPAK, and it illustrates the toxic effects of heavy metals and detoxification mechanisms in cuttlefish.

Abstract The complete mitochondrial genome of Gnathopogon taeniellus was first determined in this study. It is 16,596 bp in length, contains 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes and one control region in the typical vertebrate gene order and transcriptional direction. There are total of 29 bp short overlaps and 34 bp non-coding intergenic spacers were found in the mitogenome. Overall nucleotide base composition of light strand is 29.3% A, 25.8% C, 17.9% G and 27.0% T. Two start codons (ATG and GTG) and two stop codons (TAG and TAA/T) were used in the protein-coding genes. The origin of light strand replication (OL) was identified between tRNA(Asn) and tRNA(Cys) genes and could fold a hairpin structure. The nucleotide composition of control region is 31.8% A, 20.9% C, 14.0% G and 33.3% T.