Abstract:Three cruises were conducted in May, July, and November 2016 in artificial reef areas constructed in 2010, 2012, and 2014, respectively, and the non-artificial reef area (control area) offshore of Tianjin with three sampling stations for each, totaling 12 sites. The results identified 58 taxa of phytoplankton belonging to 2 phyla and 28 genera. Among these species, Bacillariophyta includes 19 genera and 44 species, and Pyrrophyta includes 9 genera and 14 species. Diatom species are dominant, accounting for 75.9% of all species, followed by dinoflagellates, accounting for 24.1%. Dominant phytoplankton species are Coscinodiscus and Chaetoceros of Bacillariophyta, mainly Coscinodiscus wailesii, C. asteromphalus, C. granii, C. oculus-iridis, C. spp., Chaetoceros castracanei, Ch. lorenzianus, Ch. curvisetus, Pseudo-nitzschiapungens, Guianardia delicatula, Rhizosolenia setigera, Proboscia alata f. indica, and Noctilluca scintillans. Phytoplankton cell abundance showed obvious seasonal changes, with the average cell abundance in November, July, and May at 94.79×104 cell/m³, 39.53×104 cell/m³, and 21.5×104 cell/m³, respectively. Phytoplankton diversity index also had obvious seasonal variation. In November, the Shannon-Wiener diversity index, Margalef index, and Pielou index were higher than in May and July. Comparing the artificial reef areas with the control area, the phytoplankton cell abundance of the control in May was significantly higher than the artificial reef areas. In July and November, phytoplankton cell abundance at the artificial reef constructed in 2014 was significantly higher than other artificial reef areas and the control area. The diversity index in both the control and the artificial reef area constructed in 2012 was lower than the 2010 and 2014 reefs, and lowest in the non-artificial reef area. Clearly, the construction of an artificial reef had a significant effect in improving phytoplankton community diversity, but this diversity is not always increasing consistently but fluctuating.

Abstract:Liusha Bay is one of the main aquaculture areas of marine mollusks in Guangdong Province, characterized by the main producing areas of South Pearl. To assess the environmental effects of aquaculture activities, the phytoplankton composition, abundance, community structure, diversity, and water physicochemical factors were investigated in each season from August 2015 to May 2016. In total, 171 phytoplankton species were detected, with 122 species of diatom belonging to 43 genera, followed by dinoflagellates represented by 44 taxa (10 genera), blue-green algae by two taxa (two genera), chrysophyceae by two taxa (two genera), and euglena by one taxa (one genus). The range of phytoplankton density was 0.05×104~79.04×104 cells/L, which ranked as: summer > spring > autumn > winter. In general, the phytoplankton density in the outer bay was similar to that in the inner bay. The abundance of phytoplankton in summer was distinctly higher than that in the other three seasons. The most common dominant species were Chaetoceros crinitus, Trichodesmium erythraeum, and Coscinodiscus debilis in spring, Skeletonema costatum in summer, Chaetoceros pseudocurvisetus, Bacillaria paradoxa, and Chaetoceros lorenzianus in autumn, and Coscinodisus wailesii, Rhizosolenia delicatula, and Fragilaria islandica in winter. B. paradoxa was the dominant species in spring, autumn, and winter. T. erythraeum was the dominant species in all seasons except for autumn. Redundancy analysis suggested that the main variables affecting the dominant species were water temperature and nitrate (NO3-N) in spring, transparency in summer, and nitrite (NO2-N) in autumn and winter. The phytoplankton diversity and abundance of different cultured zones presented seasonal differences. Compared to 2012, the total coverage of the aquaculture zone in 2015 increased by approximately 50% in the outer bay. Furthermore, coverage of the pearl oyster farming zone decreased by about 90% in the inner bay. Both the distribution of the aquaculture zone and the scale of the mariculture species were significantly changed, and the characteristics of the phytoplankton community responded to these changes. In summer, cage fish farming could efficiently increase nutrient content in seawater and decrease phytoplankton diversity. Furthermore, phytoplankton abundance was decreased by large-scale scallop culture.

Abstract:Based on data from the aquaculture sea-areas of the middle part of Xiangshan Harbor surveyed in autumn of 2014, and spring, summer, and winter of 2015, nutrient levels and seasonal variation in nutrients were evaluated. The results showed that the inorganic nitrogen and phosphorus levels in autumn were higher than those in spring, summer, and winter. Among all regions, the DIN (Dissolved inorganic nitrogen) concentrations in Ninghai seaweed and Xihu Harbor kelp culture areas were higher than the fourth level of seawater standard (0.50 mg/L), except one sampling station in the winter. PO4-P content were higher than the fourth level of seawater standard (0.045 mg/L) in the spring and autumn. This may be due to human activity, which was focused on the development of local economy and urban upgrading. Additionally, the rivers that flowed through the metropolis around Xiangshan Harbor carried domestic wastewater and rainfall, consisting of superfluous inorganic nitrogen and inorganic phosphorus, to the sea water. Conversely, seaweed, as well as algae such as kelp, was originally cultivated to reduce the level of DIN and PO4-P, and has not functioned optimally during recent years, contradicting with the nutrient data from previous investigation. The N/P ratios of the sea water in the middle areas of Xiangshan Harbor were higher than the Redfield ratio in four seasons, lacking in inorganic phosphorus correspondingly. According to the potential eutrophication assessment model, Xiangshan Harbor possessed potential, rich nutrition, with medium levels of restricted phosphorus in four seasons.

Abstract:“Yuemin No.1” is a novel holandric species of tilapia, which was bred with Oreochromis niloticus and O. aureus. In order to reveal the genetic characteristics of tilapia “Yuemin No.1,” the genetic diversity, genetic structure, and genetic relationships among groups of tilapia “Yuemin No.1” and its breeding populations were studied by isozyme electrophoresis and sequence analysis of the D-loop region of mtDNA. The results of isozyme electrophoresis showed that the zymogram of esterase (EST) and lactate dehydrogenase (LDH) were population- and tissue-specific in tilapia. The expression level of EST in the muscle and spleen was extremely low, whereas that in the liver was high. LDH was highly expressed in all the tissues, as revealed by the different zymograms. Ten bands of EST and five of LDH were detected in tilapia “Yuemin No.1” and its breeding populations. The proportion of polymorphic loci (P) ranged from 12.50% to 71.43%, the average observed heterozygosity (Ho) ranged from 0.0417 to 0.6143, and the Hardy-Weinberg genetic deviation index (D) ranged from ‒0.2347 to 0.9072. The result of sequence analysis of the D-loop region of mtDNA revealed that no significant difference occurred in base composition, and that A+T content (63.39%) bias was widespread in all the populations. There were 20 haplotypes in tilapia “Yuemin No.1” and its breeding populations. The nucleotide diversity index (Pi) ranged from 0 to 0.0519. The Pi value of WY1, XX, XY2, and XY populations (0.0440~0.0519) were significantly higher than that of YY1, YY2, and WZ populations (0~0.0009). The genetic differentiation index (FST) among populations ranged from ‒0.0115 to 0.9963. There was no significant genetic differentiation (FST<0.05, P>0.01) between the XY2 and WY1, XX and XY, and WZ and YY2 populations. The average genetic distance between XY2 population and O. niloticus (XX and XY populations) was 0.0639, whereas that between the XY2 population and O. aureus (WZ population) was 0.0695. Cluster analysis revealed two clusters; one cluster included XY, XX, YY1, and XY2 populations, and the other cluster included WY1, WZ, and YY2 populations. This study revealed the biochemical and molecular genetic features of tilapia “Yuemin No.1,” and provide research data for germplasm identification, establishment of breeding populations, and maintainence of stable inheritance of desirable traits.

Abstract:The current development of Xinjiang indigenous fish via large-scale farming has been listed for the positioning and development of aquaculture in Xinjiang. Perca fluviatilis Linnaeus is an indigenous fish and peculiar to the Ergis River in Xinjiang. P. fluviatilis is a cold-water fish, but very few studies have investigated cold-water fish diseases, including bacterial disease. Presently, artificial breeding of perch is being initiated. However, there have been few analyses of disease in perch. In 2016, a large number of perch in the Wujiaqu Fisheries Extension Station died suddenly. Diseased fish exhibited anal swelling, abdominal swelling, surface scale cast-off, rotten tail, and rotten gill symptoms. The dominant bacterial strain was isolated from the fish liver and intestines. After culturing for 24 h at 20℃, ZL1 formed neat edges with a slight uplift in the middle, a smooth surface, a light-yellow color, a special aromatic odor, and bacterial colonies 1.5~2 mm in size. It formed a clear β-hemolysis circle on blood agar. ZL3 and ZL5 formed a round, slightly uplifted, smooth, moist, off-white, translucent, colony of 0.5~1 mm in size, but did not form a hemolysis circle on blood agar. The isolated bacteria were cultured, the bacterial species were identified, and drug susceptibility and pathogenicity tests were performed. Pathogenicity tests and morphological observation showed that the isolates had obvious pathogenicity. Gram staining, physiological and biochemical characteristics, analysis of 16S rRNA gene sequences, and phylogenetic tree development identified ZL1 as Aeromomas sobria, and ZL3 and ZL5 as Edwardisella tarda. Drug sensitivity test showed that ZL1 was highly sensitive to gentamycin, minocycline, and ceftazidime, and resistant to streptomycin, penicillin, and clarithromycin. ZL3 and ZL5 were highly sensitive to levofloxacin, streptomycin, and enrofloxacin, and resistant to gentamicin, ampicillin, penicillin, and sulfamethoxazole.

Abstract:Two retinoic acid receptors, RARalpha and RARgamma, were cloned from Cynoglossus semilaevis using RT-PCR and RACE methods, and their spatial expression patterns were investigated using a quantitative PCR assay. The results showed that full-length cDNA sequence encoding the RARalpha gene is 1823 bp in length, its open reading frame (ORF) length is 1332 bp, encoding 443 amino acids; the RARgamma cDNA sequence is 1959 bp in length, and the length of ORF is 1497 bp, encoding 489 amino acids. Homology analysis showed that C. semilaevis RARalpha and RARgamma have homology identity of 60.8%, and both have 97% homology identity with the Japanese flounder. Phylogenetic analysis showed that C. semilaevis RARalpha and RARgamma clustered into a separate branch with other fish counterparts. Spatial expression analysis showed that the highest expression level of RARalpha mRNA occurred in the kidney, whereas the highest expression level of RARgamma mRNA was in the spleen. RARgamma was also highly expressed in the gill, kidney, and heart. Furthermore, RARalpha and RARgamma mRNA expression were detected in all examined tissues, which indicated that these two retinoic acid receptors were both involved in multiple physiological regulation processes. In addition, the differential expression of these two RAR genes were found in the blind side and ocular skins, wherein they both had highest expression levels in the normal blind side skin, followed by the blacking blind side skin and had the lowest expression levels in the ocular side skin. In ocular skin and blind-side blacking skin, the RARalpha expression levels were higher than RARgamma but without significant difference, wherein in blind-side normal skin, the RARgamma expressed significantly higher than RARalpha. This differential expression pattern indicated that they might play important physiological roles in blind-side hypermelanosis regulation of Cynoglossus semilaevis.

Abstract:The aim of the present study was to assess the effects of heat stress and recovery on biochemical indices and HSP70 mRNA expression in gibel carp (Carassius auratus gibelio). The fishes were selected as experimental animals with an average weight of (72.8±10.1) g under laboratory conditions. Samples used to determine lactic acid (LD) content, glucose (Glu) content, glycogen (Gly) content, hexokinase (HK) activity, pyruvate kinase (PK) activity, and HSP70 mRNA expression were obtained before heat stress (25℃, the control group), 0, 2, 6, and 10 h after stress (32℃), and heat stress recovery (25℃, HSR), respectively. The results revealed no significant difference in LD content compared with that in the control group (P>0.05). Glu content was significantly increased at 0, 2, and 6 h (P<0.01). Gly was significantly increased at 0 h (P<0.01). HK activity was significantly increased at 2 h (P<0.01). PK activity significantly increased at 6 h (P<0.01). Meanwhile, the highest HSP70 mRNA expression was observed at 2 h under heat stress (P<0.01). Following HSR (25℃, 6 h), the HSP70 mRNA expression level recovered to the pre-stress levels (P>0.05). The results provide basic data for research on the mechanism of high temperature adaption in gibel carp, as well as a scientific basis for acute temperature change in aquaculture and breeding.

Abstract:Significant differences exist in the growth rate and body size of male and female spotted halibut (Verasper variegatus), with the females being significantly larger than the males. All-female cultivation can improve breeding efficiency. Studies investigating the mechanism of sex determination and features of sex differentiation may provide valuable information for all-female cultivation. In this study, we successfully identified the sox9 gene of spotted halibut. The total length is 3287 bp, including a 1431 bp ORF, encoding 477 amino acids; the 5¢ UTR is 368 bp and the 3¢ UTR is 1488 bp. Polyadenylic acid tails and AATAAA caudal signals were identified in the 3¢ UTR. The expression of the sox9 gene differed in the brain, eye, gills, heart, liver, gallbladder, intestine, testis, ovary, kidney, and muscle in spotted halibut. Transcript levels were high in the gill, brain, and testis, and were significantly higher in the testis than in the other tissues. A two-phase gender difference was observed in the gonads; sox9 expression was significantly higher in the testis than in the ovary, indicating that sox9 might be associated with male gonad development. The dynamic expression patterns of the sox9 gene in spotted halibut larvae gradually declined from 20 to 50 d after hatching, with a sudden rise observed after 60 d. This increased expression might be associated with differentiation of larval gonad.

Abstract:Based on the dynamic distribution and elimination patterns of Streptococcus agalactiae in Oreochromis niloticus at different water temperatures, we provide a foundation for research on S. agalactiae pathogenesis in O. niloticus, as well as a scientific basis for the prevention and control of S. agalactiae infection in O. niloticus by controlling water temperature and the rational use of drugs. We used O. niloticus infected with S. agalactiae (WC1535 strain) by artificial intraperitoneal injection. First, the mortality rates of infected O. niloticus were assessed at 25℃, 29℃, and 33℃. Then, we performed in vitro isolation, cultured and counted S. agalactiae from the infected fish maintained at three temperatures. Next, we assessed the abundance of S. agalactiae in the brain, liver, spleen, and kidney tissues of the infected fish at the three temperatures. The results showed that fish mortality rate increased with increasing water temperature, and the cumulative mortality rate was 6.67%, 25.56%, and 78.90% at 25℃, 29℃ and 33℃, respectively. Furthermore, the maximum abundance of S. agalactiae in unit mass of the brain, liver, spleen, and kidney tissues of O. niloticus increased with increasing water temperature. Thus, at a high temperature, S. agalactiae propagated rapidly in O. niloticus, whereas the residence time was short. In contrast, at a lower temperature, the propagation time decreased, but the residence time increased. Moreover, our results showed that S. agalactiae abundance was the highest in the spleen and survival time was the longest in the kidney. In conclusion, the propagation and elimination speeds of S. agalactiae in tissues of infected O. niloticus were closely related to water temperature. Our results provide important data for further study of S. agalactiae pathogenesis, ensuring effective prevention and control measures.

Abstract:Grouper is an important global, marine economic resource. As a low-fat, high-protein edible fish, it is in high demand, and thus, its supply is not adequate to meet this demand. In order to improve the muscle quality of the cultured grouper and provide basic data for the development of compound feed, the nutritional components in the muscles of Epinephelus moara, E. lanceolatus, and E. moara (♀) × E. lanceolatus (♂) (hereinafter Yunlong) were analyzed and evaluated by routine biochemical methods. The results showed that the content of crude protein in the muscles of the three grouper species were 20.60%, 19.30%, and 20.00%, respectively, and the content of crude fat were 2.60%, 1.60%, and 4.30%. Sixteen common amino acids were detected in the muscles of the three grouper species. The content of total amino acids (TAA), essential amino acids (EAA), and delicious amino acids (DAA) in wet-weight fish flesh were respectively 16.95%, 7.11%, and 6.31% in E. moara; 17.46%, 7.18%, and 6.83% in E. lanceolatus; and 18.56%, 7.69%, and 7.16% in Yunlong. The proportions of the essential amino acids in the muscles of three grouper species are all in accordance with the FAO/WHO standard. The ratios of branched chain amino acids to aromatic amino acids (F values) in the muscles of the three grouper species were 2.22, 2.57, and 2.60, respectively. According to the amino acid score (AAS) and chemical score (CS), the first limiting amino acid of the three grouper species was methionine, and the second limiting amino acid was valine. In addition, muscles from the three group species were all rich in minerals. Potassium levels were the highest among those of all macroelements, and zinc levels were the highest among those of all trace elements. Studies have shown that these three species of groupers are high-quality marine fish with high nutritional value, which have good prospects for commercial exploitation and utilization.

Abstract:In order to study the quality changes of grass carp during postmortem at room temperature (25℃), the changes in texture, pH, lactic acid, free amino acids, and ATP-related compounds in the dorsal meat of grass carp were measured using texture analyzer, pH meter, lactic acid kit, automatic amino acid analyzer, and high-performance liquid chromatography method in the postmortem process within 30 h. The results showed that hardness and chewiness of the grass carp reached its maximum at 23 h and then rapidly decreased, while springiness, cohesiveness, and resilience of grass carp decreased with the extension of storage time. pH showed a trend of decreasing first and then increasing, and it reached its maximum at 23 h. The content of lactic acid increased initially and then decreased, which reached its minimum value at 23 h. The total amount of fresh sweet amino acids gradually decreased during the postmortem process, while bitter amino acids were just the opposite, which increased during the postmortem process. The content of ATP increased significantly within 10 h, while the content of IMP with umami taste decreased rapidly1. Furthermore, the content of HxR and Hx with bitter taste increased gradually during the storage process. The K value increased during the postmortem process. The change in K value indicated that grass carp could maintain high freshness after storage for 10 h at room temperature, and it reached 68.99% at 27 h, which showed that the fish had spoiled at that time. Therefore, it should be processed as soon as possible, ideally within 10 hours after the death of grass carp at room temperature. This study will enrich the basic theory of postmortem variation of fish and provide support for the quality change of aquatic products.

Abstract:Bantam is a type of miRNA involved in cell proliferation and apoptosis, and can affect immune processes in animals. In the present study, bantam expression in the hepatopancreas and gill of WSSV-infected Chinese shrimp Fenneropenaeus chinensis was determined using the qRT-PCR technique. The results showed that bantam expression in the hepatopancreas of Chinese shrimp 6, 12, 24, and 48 h post infection was (0.16±0.03)(P<0.05), (0.63±0.26), (0.32±0.06) (P<0.05), and (0.41±0.13) fold that of the expression in the controls, respectively. Bantam expression in the gill of Chinese shrimp 6, 12, 24, and 48 h post infection was (0.30±0.17) (P<0.05), (1.88±0.26) (P<0.01), (0.84±0.36), and (0.51±0.25) fold that of the expression in the controls, respectively. The target genes of bantam were predicted using the miRanda software. The ubiquitin-conjugating enzyme E2 was the predicted target gene with the highest score. The Chinese shrimp ubiquitin-conjugating enzyme E2 contains the ubiquitin-conjugating enzyme E2, catalytic (UBCc) domain. Multiple alignment results showed that the UBCc domain was relatively conserved among different species. Phylogenetic analysis showed that the ubiquitin-conjugating enzyme E2 in species with closer taxonomic status was clustered in a branch. Pair-wise and multiple sequence alignment revealed that the ubiquitin-conjugating enzyme E2 was relatively well-conserved. Ubiquitin- conjugating enzyme E2 expression in the hepatopancreas and gill of WSSV-infected Chinese shrimp was further determined using qRT-PCR. The results showed that the expression of ubiquitin-conjugating enzyme E2 in the hepatopancreas of Chinese shrimp 6, 12, 24, and 48 h post-WSSV infection was (0.54±0.10), (1.19±0.62), (3.69±0.51)(P<0.01), and (1.94±0.07)(P<0.05) fold that of the expression in the controls, respectively. The expression of ubiquitin-conjugating enzyme E2 in the gill of Chinese shrimp 6, 12, 24 and 48 h post WSSV infection was (0.22±0.05), (1.34±0.38), (4.29±0.52) (P<0.01), and (1.28±0.79) fold that of the expression in the controls. These results suggest that both bantam and the target gene ubiquitin-conjugating enzyme E2 might be involved in the interaction between Chinese shrimp and WSSV. Whether the altered expression of bantam and ubiquitin-conjugating enzyme E2 represents the immune response of shrimps to WSSV infection, or the hijacking of cells by WSSV during the viral infection process, needs further study.

Abstract:The aim of this study was to elucidate protein autolysis in Antarctic krill (Euphausia superba) after capture on fishing vessels and the maintenance of product quality. Under laboratory conditions, frozen Antarctic krill was used to verify the correlation between non-protein nitrogen (NPN) content and the degree of protein autolysis. The stability of NPN content during 90-days storage at –20℃ was also examined. Fresh Antarctic krill, complete in form or broken because of compression during trawling of the Antarctic krill fishing vessel were selected. The NPN content of Antarctic krill samples at different storage times were measured. The results showed that the NPN content of Antarctic krill had a good correlation with protein autolysis, and there were no significant changes in the NPN content during the 90-day of storage. Therefore, NPN was suitable for evaluating changes in the quality of Antarctic krill after capture. There was no significant change in NPN content during the first hour after the death of the captured Antarctic krill. However, the NPN content increased rapidly afterwards. Antarctic krill should be frozen or processed as soon as possible after capture. Compression during trawling damaged Antarctic krill and accelerated protein autolysis. Thus, the method of trawling used during Antarctic krill fishing requires improvement.

Abstract:To investigate the optimum high-salinity domestication gradient, speed, and mode of Litopenaeus vannamei postlarvae, a salinization experiment was designed. Salinity increased from 30 to 60. Different high-salinity domestication gradients (3/d, 6/d, 9/d, 12/d, and 15/d), speeds (1, 3, 6, 12, and 18 h/time), and modes (early salinization, medium-term salinization, later salinization, and interval salinization) were used. The weight gain, activity, and survival rate of L. vannamei postlarvae were tested during high-salinity domestication. The results showed that the different high-salinity domestication gradients, speeds, and modes had significant effects on the weight gain, activity, and survival rate of postlarvae (P<0.05). The optimal high-salinity domestication gradient was 3~6/d; the survival rate of postlarvae remained at 74.07% to 78.83% in this gradient. When the high-salinity domestication gradient exceeded 9/d, the survival rate of postlarvae decreased sharply (P<0.05), and was only 43.37% in the high-salinity domestication gradient of 15/d. In addition, the rapid high-salinity domestication speed decreased the survival rate and activity. When the domestication speed was faster than 1 h/time, the survival rate of postlarvae was reduced to nearly 50%; as the domestication speed decreased, the growth rate of postlarvae increased. When the high-salinity domestication speed was 6~18 h/time, the daily weight gain of postlarvae was stable at 1.48~1.51 mg. The later salinization and interval salinization were superior to the early salinization and medium-term salinization regarding the postlarvae activity and survival rate, the postlarvae activity was as follows: interval salinization>later salinization>medium-term salinization>early salinization. Overall, the optimal high-salinity domestication gradient was 3~6/d, the best high-salinity domestication speed was 6~12 h/time, which will help postlarvae to reach the scheduled standard and achieve the target weight gain with later salinization and interval salinization.

Abstract:Ruditapes philippinarum is abundant around the seagrass meadow in Chudao, Sanggou Bay. To determine the interactions between R. philippinarum and Zostera marina L., the amount of R. philippinarum was evaluated in the seagrass meadow at Chudao from May to July, 2016. The feeding and metabolic physiology of R. philippinarum were determined based on an individual experiment with flowing water from the field. The interactions between R. philippinarum and Z. marina were investigated in an enclosure experiment in the field. The results showed that the biomass of R. philippinarum was (572.00±20.23) ind./m2, which included 9.01% large (shell length 3.50~4.10 cm), 43.60% medium (shell length 3.00~3.50 cm), and 47.38% small (shell length 2.00~3.00 cm) clams. The ammonia nitrogen excretion, oxygen consumption, clearance rate, and feeding rate were (0.44±0.15) to (1.40± 0.35) μmol/(ind.·h), (0.21±0.02) to (0.33±0.08) mg/(ind.·h), (0.69±0.38) to (0.83±0.66) L/(ind.·h), and (2.57±0.41) to (3.41±0.68) mg/(ind.·h), respectively. These parameters all increased with increasing body weight of the clams. There were four groups (R. philippinarum, Z. marina, Z. marina+R. philippinarum, and control) with three replicates each in the enclosure experiment, which was run for 4 h. The results revealed significant differences in dissolved oxygen concentration among the R. philippinarum, Z. marina+R. philippinarum, and Z. marina groups (P<0.05). The ammonia nitrogen concentration in the R. philippinarum group was significantly higher than that in the other three groups (P<0.05). Total particles in the R. philippinarum and Z. marina+R. philippinarum groups were significantly lower than those in the control (P<0.05), while no significant difference was found between the Z. marina group and the control (P>0.05). The area of R. philippinarum is about 0.5 km2 around Chudao in Sanggou Bay, approximately filter 46 t of suspended particulates and provide 0.4 t of ammonia nitrogen to the Z. marina meadow by the clam each day. The present findings provides basic data for further revealing the ecological roles of R. philippinarum in Z. marina meadow areas.

Abstract:Pyropia yezoensis at different harvest times were obtained from Jing Bay, and its nutritional and umami characteristics were analyzed. Crude protein, crude fat, ash, inorganic elements, and amino acid composition were determined to analyze its nutritional characteristics. Free amino acids and flavor nucleotides were determined to calculate the taste active value (TAV) and equivalent umami concentration (EUC), which indicated the umami of P. yezoensis. The results showed that P. yezoensis from Jing Bay had high protein and low fat content. The protein content exceeded 49% in the first and second harvest, indicating that the P. yezoensis had higher nutritional value in the early stage of the harvest. The K content was the highest among the constant elements, while the P content was the lowest. Fe content was the highest among the trace elements; Zn content was higher, and Co content was the lowest. Pb content was significantly lower than the limited requirements of GB 2762-2017. There were significant differences between P. yezoensis from the first, second harvest and the fourth, sixth harvest in terms of essential and total amino acid content (P<0.05). Glutamic acid and hypoxanthine nucleotide played a major role in the umami contribution; the Equivalent umami concentration (in dry basis) of P. yezoensis in the first, second, fourth, and sixth harvests was 239.71, 190.03, 108.05, and 51.56 g MSG/100 g, respectively. P. yezoensis from Jing Bay has high nutritional values and desirable umami characteristics in the early stage of harvest, and thus, has great market potential.

Abstract:Large-scale green tides have broken out annually in the Yellow Sea since 2007, which, upon twinning with floating Sargassum horneri, became a new hazard and increased the difficulty of preventing and controlling the green tide in Shandong Peninsula. In this study, the similarity of ITS and coxI sequences were analyzed using S. horneri samples collected from ten free-floating populations and three benthic populations in 2016 and 2017 along the offshore of China. The results showed that the coxI sequences of 51 samples were consistent, while there were two variable nucleotide sites within the ITS sequence. Based on genotypic differences, S. horneri samples could be sorted into four categories, among which the genotype of free-floating samples from Dalian Longwangtang, Daqin Island, and Nanhuangcheng Island of Yantai were identical. Free-floating samples from the Golden Beach of Qingdao and benthic samples from Daqin Island of Yantai and Zhangzi Island of Dalian were identical; free-floating samples from Lidao of Weihai and Dongtou of Wenzhou were identical; and free-floating samples from the Sculpture Garden, Wanggezhuang, Dazhushan of Qingdao, Rushan of Weihai, and benthic samples from Gouqi Island were identical. However, there was no difference in genotype among individuals within the same population, even among those occurring in different years. A phylogenetic tree based on ITS sequences of S. horneri showed that samples from China were clustered together; however, there was some genetic distance from the Korean samples. It is possible that the genetic variation of ITS and coxI regions is low in different coastal strains of S. horneri, and that drifting population could be of different origins. These findings will provide a basis for further understanding of the molecular genetic background of S. horneri along the offshore of China.

Abstract:The jumbo squid (Dosidicus gigas) is a pelagic cephalopod endemic to the eastern Pacific Ocean with a valuable commercial role. In this study, fatty acid profiles were identified in jumbo squid muscle tissues from three harvest locations. Comparative analysis was used to evaluate spatial variation in fatty acid profiles of different geographic origins. Results showed significant differences in fatty acid profiles among squid muscle tissues from different sampling locations. The number of fatty acid types from the squid off Peru (28) was high compared with that from squid in the waters of the equatorial central eastern Pacific (27) and those off Chile (24). Nonetheless, among all three geographic origins, the dominant fatty acids were polyunsaturated fatty acids (PUFA), which accounted for 59.68%~69.28% of the total amount of all fatty acids, followed by saturated fatty acids (SFA, 20.71%~27.28%) and monounsaturated fatty acids (MUFA, 10.01%~13.04%). C16:0, C18:0, C20:1n9, C18:2n6, C20:5n3 (eicosapentaenoic acid, EPA), and C22:6n3 (docosahexaenoic acid, DHA) were the primary fatty acids in jumbo squid muscle tissues, which accounted for more than 81% among all areas. The results of analysis of similarity (ANOSIM) and similarities of variance (SIMPER) showed that the spatial heterogeneity of fatty acid profiles was mainly influenced by C16:0, C18:2n6, C20:4n6, and DHA. We propose that the observed variations could be the result of differences in oceanographic conditions, food sources, and energy demands of squid among varied regions. Overall, these results demonstrated the feasibility of using fatty acid analysis to study the feeding ecology of jumbo squid. Novel information on the heterogeneity of fatty acid profiles among harvest locations may have important implications for their nutrition studies and for better utilizing this important resource.

Abstract:Bacillus sp.; Protease; Plackett-Burman design; RSM

Abstract:The accumulation of ammonia nitrogen in water is highly toxic to cultured aquatic animals. The microbiological method has received widespread attention as an efficient way to remove ammonia nitrogen in aquaculture because of its high efficiency and environment-friendliness. The genus Rhodococcus is a very diverse group of bacteria that can remove a variety of compounds, including ammonia nitrogen. Here, the strain XH2, which potently removes ammonia nitrogen, was isolated from aquaculture water during the middle to late (50 d) phase of shrimp cultivation. Its ecological adaptability and feasibility of use as a probiotic to improve aquaculture water quality was evaluated. According to the results of 16S rDNA sequencing and Biolog identification, XH2 was identified as Rhodococcus rhodochrous. Its growth performance and ammonia nitrogen removal efficacy were studied under different salinities (5, 15, 25, 35, and 45), pH (4.5, 6.0, 7.5, 9.0, and 10.5), temperatures (5, 15, 25, 35, and 45℃), and aeration levels (1~2 L/min). The results showed that XH2 had high adaptability to varied ranges of salinity (5~45), pH (6.0~9.0), temperature (15℃~45℃), and ventilation (1~2 L/min), with a maximum observed cell amount of 1.03×109 cells/ml. Specifically, the concentration of ammonia nitrogen in medium was reduced by 90.0%~100.0% during 1~3 d under the following conditions: salinity 25~45, pH 6.0~9.0, temperature 15℃~30℃ and ventilation volume 1~2 L/min (P<0.05). There was no significant difference in nitrite concentrations. Taken together, these data show that the XH2 strain possesses the physico-chemical properties of a suitable alternative in terms of salinity, pH, temperature, and ventilation, which can be applied to most aquaculture ponds for the prevention and control of ammonia nitrogen.

Abstract:Mitochondria are important organelles in cells. Mitochondria can produce ATP and provide energy for almost all biological activities. Mitochondria have a relatively independent genetic system, and nuclear genes also encode certain enzymes responsible for mitochondrial DNA (mtDNA) replication and transcription. Therefore, the number and function of mitochondria is essential for embryonic development. Mitochondrial function depends on the integrity of the mitochondrial genome or the regulation of nuclear genome, as well as the mtDNA copy number. Many studies have investigated mtDNA copy numbers in animals, including studies on oocyte maturation, mammalian embryonic development, and human disease, but none have reported the mtDNA copy number in Exopalaemon carinicauda. To study the profiles of mtDNA copy number at different developmental stages of E. carinicauda, and the energy expenditure of tissues at the different stages of development, total DNA from zygote, zoea Ⅰ, zoea Ⅱ, zoea Ⅲ, zoea Ⅳ, zoea Ⅴ, post larvae, and adult shrimps were used to analyze the mtDNA copy number. One TaqMan probe-based real-time PCR was established to assess the mtDNA copy number. Our results showed that the average copy number of mtDNA per cell was 2366, 2648, 2644, 2873, 3559, 9948, 6452, and 8872 in the zygote, zoea Ⅰ, zoea Ⅱ, zoea Ⅲ, zoea Ⅳ, zoea Ⅴ, post larvae, and adults, respectively. These results show that mtDNA copy number is positively correlated with age, and the correlation coefficient (R) was 0.83, i.e. the copy numbers of mtDNA tend to increase with progressing developmental stages of E. carinicauda.

Abstract:The applicability of three national standard methods including inductively coupled plasma mass spectrometry (ICP-MS), hydride generation atomic fluorescence spectrometry (HG-AFS), and silver salt method used to determine total arsenic content in Antarctic krill (Euphausia superba) and its related products were evaluated in this study. The accuracy of the ICP-MS, HG-AF, and silver salt methods were 100.26%~110.48%, 82.68%~98.50%, and 89.64%~94.89%, respectively, and the RSD was less than 5% in all cases. The results of the three national standard methods were consistent. However, compared with the silver salt method, the ICP-MS and HG-AFS methods were complicated and expensive. Therefore, the silver salt method could be chosen as a quick method for determining the total arsenic content in Antarctic krill and its related products. The content of total arsenic in Antarctic krill, Antarctic krill powder, and Antarctic krill oil were 0.44~0.45 mg/kg, 1.04~1.91 mg/kg, and 0.52~5.50 mg/kg, respectively. To accelerate the establishment of methods to evaluate arsenic morphology and estimate inorganic arsenic quantitatively in Antarctic krill and its related products will be important in the future.