Toxicity of the antifouling biocide Sea-Nine 211 to marine algae, crustacea, and a polychaete

We evaluated the acute toxicity of the antifouling biocide Sea-Nine 211 to the algae Chaetoceros calcitrans, Dunaliella tertiolecta, Tetraselmis tetrathele, and Skeletonema costatum, the crustacea Tigriopus japonicus and Portunus trituberculatus, and the polychaete Perinereis nuntia. The algae, and especially the diatoms C. calcitrans and S. costatum, were sensitive to Sea-Nine 211 toxicity, with the average acute toxicity values being 0.32, 3.9, 1.6, 0.22, 1.6, 12, and 27 μg/l for C. calcitrans, D. tertiolecta, T. tetrathele, S. costatum, T. japonicus, P. trituberculatus, and P. nuntia, respectively. A sediment toxicity test for Sea-Nine 211 using the polychaete P. nuntia revealed demonstrated that the 14-day median lethal concentration was 110 μg/kg dry-wt sediment and that growth was the most sensitive indicator. The chronic toxicity values of Sea-Nine 211 for the diatoms C. calcitrans and S. costatum were within the range of reported Sea-Nine 211 concentrations in seawater in coastal Japan, and the toxicity values for P. nuntia were within the reported concentrations in sediment. Based on these results, Sea-Nine 211 may have toxic effects on some sensitive species residing in the coastal areas of Japan, but the ecological risk posed by Sea-Nine 211 would appear to be confined to a limited area of Japanese coastal waters.     

Isolation of the groESL cluster from Vibrio anguillarum and PCR detection targeting groEL gene

Vibrio anguillarum is a major pathogenic bacterium that causes vibriosis and septicemia in fish and shellfish. In this study, we identified the groESL genes, which encode bacterial chaperonins, from V. anguillarum. The groE gene cluster consisted of a 291-bp groES gene, a 69-bp intergenic spacer region, and a 1,635-bp groEL gene order. Sequence analysis with the groESL gene of Vibrio species exhibited that the groEL gene was more species-specific and suitable than the groES gene for V. anguillarum detection. Owing to the difficulty in distinguishing V. anguillarum from the closely related V. ordalii, we compared the sequences of groEL from V. anguillarum and the groEL homolog hsp60 from V. ordalii, in order to design a primer set based on a region dissimilar between the two. PCR with the groEL primer set produced a clear 195-bp amplicon in six serotypes of V. anguillarum, whereas 23 Vibrio species of 39 samples, including V. ordalii, and 10 species of enteric bacteria gave no bands. PCR using the groEL primers also amplified a unique product from V. anguillarum-infected flounder and oyster tissues. These results demonstrate that the groEL-target PCR assay is a sensitive and species-specific tool for the detection of V. anguillarum infection.     

Homologue gene of bile acid transporters ntcp,asbt, and ost-alpha in rainbow trout Oncorhynchus mykiss: tissue expression,effect of fasting,and response to bile acid administration

Bile acid transporters belonging to the SLC10A protein family, Na+ taurocholate cotransporting polypeptide (NTCP or SLC10A1), apical sodium-dependent bile salt transporter (ASBT or SLC10A2), and organic solute transporter alpha (Ost-alpha) have been known to play critical roles in the enterohepatic circulation of bile acids in mammals. In this study, ntcp, asbt, and ost-alpha-1/-2 cDNA were cloned, their tissue distributions were characterized, and the effects of fasting and bile acid administration on their expression were examined in rainbow trout Oncorhynchus mykiss. The structural characteristics of Ntcp, Asbt, and Ost-alpha were well conserved in trout, and three-dimensional structure analysis showed that Ntcp and Asbt were similar to each other. Tissue distribution analysis revealed that trout asbt was primarily expressed in the hindgut, while ntcp expression occurred in the brain, and ost-alpha-1/-2 was mainly expressed in the liver or ovary. Although asbt and ost-alpha-1 mRNA levels in the gut increased in response to fasting for 4 days, ost-alpha-1 expression in the liver decreased. Similarly, bile acid administration increased asbt and ost-alpha-1 expression levels in the gut, while those of ntcp and ost-alpha-2 in the liver decreased. These results suggested that the genes asbt, ntcp, and ost-alpha are involved in bile acid transport in rainbow trout.     

Susceptibility by amberjack (Seriola dumerili), yellowtail (S. quinqueradiata) and Japanese flounder (Paralichthys olivaceus) to Neobenedenia girellae (Monogenea) infection and their acquired protection

This study investigated: 1) susceptibility differences to infection by Neobenedenia girellae (Capsalidae) between amberjack Seriola dumerili (Carangidae), yellowtail S. quinqueradiata and Japanese flounder Paralichthys olivaceus (Paralichthyidae); 2) growth and egg production of N. girellae on each fish species; 3) acquired protection of each fish species against this parasite. The number of N. girellae on S. dumerili was significantly higher than on S. quinqueradiata and P. olivaceus when these fishes were exposed to oncomiracidia in the same aquarium. Neobenedenia girellae growth on S. dumerili was fastest and, thus the number of eggs laid by parasites on S. dumerili was greater than on the other two species. Seriola dumerili and P. olivaceus, which were previously infected with N. girellae and treated by freshwater bath, acquired partial protection against re-infection by N. girellae. The relative re-infection of three S. dumerili individuals out of eleven individuals was markedly low compared with the initial infection, and the relative initial infection and re-infection on two P. olivaceus out of eleven individuals was markedly low. The results of this study could be useful to control N. girellae infections when cultivating S. dumerili, S. quinqueradiata and P. olivaceus.     

三疣梭子蟹CYP302a1基因克隆及其表达分析

细胞色素P450(CYP)302a1是昆虫蜕皮激素合成通路中的关键酶,为了研究其在三疣梭子蟹蜕皮过程中的调控作用,实验采用反转录PCR(RT-PCR)和cDNA末端快速扩增(RACE)技术,克隆得到了三疣梭子蟹CYP302a1全长cDNA序列(GenBank登录号:KM596851).该序列全长为3 171 bp,包含一个长度为1 626 bp的开放阅读框,编码541个氨基酸;序列分析显示该氨基酸含helix-C、helix-K、helix-I、PERF及heme-binding共5个P450特征保守区域;系统进化树分析发现三疣梭子蟹CYP302a1与日本剑水蚤CYP302a1聚为一小支,再与其他物种CYP302a1聚为一支.采用实时荧光定量PCR(qRT-PCR)技术分析了CYP302a1在不同组织和蜕皮过程中的表达水平变化.结果显示,CYP302a1的表达量在Y器中最高,而在其他组织中均极低(P＜0.05);蜕皮过程中,CYP302a1在蜕皮后期(A、B期)表达量最低,从蜕皮间期(C期)开始上升,至蜕皮前期的D1亚期达到最大值,随后下降.结果表明CYP302a1在三疣梭子蟹蜕皮调控中可能起着重要作用.     

Anguilla huangi Teng, Lin, and Tzeng, 2009, is a junior synonym of Anguilla luzonensis Watanabe, Aoyama, and Tsukamoto, 2009

Anguilla luzonensis and A. huangi were each described in 2009 using eels obtained from northern Luzon Island. We examined the taxonomic status of these two groups of eels using morphological and molecular genetic characters. There were no significant differences in two vertebrae counts between eels of A. luzonensis and A. huangi. Mitochondrial 16S ribosomal RNA and cytochrome b genes sequences were obtained and compared among 28 specimens of A. luzonensis, the holotypes of A. luzonensis and A. huangi, and one specimen of the other 15 anguillid species. The specimens of A. luzonensis exhibited almost identical sequences, including the holotype, with only a few site differences, and the genetic difference between the holotypes of A. luzonensis and A. huangi was within the range of differences of specimens of A. luzonensis. The other anguillid species were genetically very different from A. luzonensis and A. huangi, although A. interioris is a closely related species. It is clear that A. luzonensis and A. huangi are the same species, and according to the principle of priority in zoological nomenclature, A. luzonensis Watanabe, Aoyama, and Tsukamoto, 2009 is the valid species name, and A. huangi Teng, Lin, and Tzeng, 2009 is a junior synonym of A. luzonensis.     

Study of food web structure and trophic level in the sea ponds of an optimized culture model (jellyfish–shellfish–fish–prawn)

The food sources of the main economic animals and trophic levels of biotic communities from an optimized culture model (Rhopilema–Sinonovacula constricta–Paralichthys olivaceus–Penaeus chinensis) in a sea water pond in Donggang, Liaoning province were studied using the stable carbon and nitrogen isotopes technique. The results indicated that the values of δ¹³C range from (?27.28 ± 0.35) ‰ to (?16.65 ± 0.20) ‰ and the values of δ¹⁵N range from (3.68 ± 0.23) ‰ to (13.91 ± 0.26) ‰, both of which exhibited significant fluctuations. The δ¹³C values of P. chinensis, Macrobrachium mipponensis and P. olivaceus were comparatively higher than those of other aquaculture animals, and the δ¹⁵N values of P. olivaceus was also comparatively higher. The contribution to the food sources of aquaculture animals (Rhopilema, S. constricta, P. olivaceus and P. chinensis) was analyzed by using the IsoSource software. The results indicated that fish meat had the greatest contribution to Rhopilema, S. constricta and P. chinensis; P. chinensis had the greatest contribution to P. olivaceus, followed by the M. mipponensis. The trophic level of the biotic communities under that optimized culture model in a sea water pond was 3.54, in which P. olivaceus was in the fourth level (3.54); P. chinensis, Synechogobius hasta, Ablennes anastomella, M. mipponensis, Ditrema temmincki Bleeker, Chelon haematocheilus were in the third trophic levels; Rhopilema, Engraulis japonius, S. constricta and zooplankton (1.00) in the second trophic levels, suspended matters (0.15) including phytoplankton, bacteria, humus, etc., were in the primary trophic levels.     

Dynamic expression pattern of corticotropin-releasing hormone,urotensin I and II genes under acute salinity and temperature challenge during early development of zebrafish

Corticotropin-releasing hormone (CRH), urotensin I (UI) and urotensin II (UII) are found throughout vertebrate species from fish to human. To further understand the role of crh, uI and uII in teleosts during development, we investigated the expression pattern of crh, uI, uIIα and uIIβ genes, and their response to acute salinity and temperature challenge during early development of zebrafish, Danio rerio. The results reveal that crh, uI, uIIα and uIIβ mRNA are detected from 0hpf, and the expression levels increase to a maximum at 6 days post fertilization (dpf), with the exception of uIIα that peak at 5dpf. Exposure of zebrafish embryos and larvae to acute osmotic (30ppt) stress for 15 min failed to modify expression levels of crh, uI, uIIα and uIIβ mRNA from levels in control fish except at 6dpf when uIIα and uIIβ were significantly (P < 0.05) modified. Exposure of embryos and larvae to a cold (18 °C) or hot stress (38 °C) generally down-regulated mRNA levels of crh, uI, uIIα and uIIβ apart from at 3dpf. The results indicate that the contribution of crh, uI, uIIα and uIIβ genes to the stress response in zebrafish may be stressor-specific during early development. Overall, the results from this study provide a basis for further research into the developmental and stressor-specific function of crh, uI, uIIα and uIIβ in zebrafish.     

Effects of stocking density, diet, and water exchange on growth and survival of pearl oyster Pinctada maxima larvae

Three experiments were carried out to separately investigate the effects of stocking density (1.0, 2.0, 4.0 and 8.0 larvae ml^?1), diet (Isochrysis zhanjiangensis, Chlorella spp., Nannochloropsis oculata, 50 % I. zhanjiangensis/50 % Chlorella spp. and 50 % I. zhanjiangensis/50 % N. oculata), and water exchange (25 % once every other day and 25, 50 and 100 % once daily) on growth and survival of pearl oyster Pinctada maxima larvae. Results showed that there existed significant effects of stocking density, diet, and water exchange on the growth of pearl oyster larvae (P < 0.05). Larval survival was significantly affected by stocking density and diet (P < 0.05), but not by water exchange (P > 0.05). Larval growth decreased significantly with increasing stocking density (P < 0.05). A density of 1.0–4.0 larvae ml^?1 was optimal for larval growth of pearl oyster. Chlorella spp. and N. oculata could replace 50 % of I. zhanjiangensis as a food source for the pearl oyster larvae without affecting growth and survival. A water exchange of 25 % once daily provided optimum larval growth and survival.     

尼罗罗非鱼雌雄鱼肌肉组织差异表达基因的筛选

应用引物退火控制技术(ACP)筛选尼罗罗非鱼雌雄鱼肌肉组织差异表达基因,寻找与雌雄鱼肌肉生长发育相关的候选基因。本实验从同等条件下养殖的尼罗罗非鱼群体中随机选取雌、雄鱼各5尾组成RNA池,采用引物退火控制技术,分析了两组个体肌肉组织差异表达基因。利用20对随机引物差异显示扩增,共获得8条ESTs,其中5个已知的ESTs分别为转录变体3(LOC100691543)、60S核糖体蛋白(RL3)、小白蛋白β样蛋白、肌型肌酸激酶M2-CK和转录因子Sox4,其余3个为未知的ESTs。实时定量PCR分析各差异表达基因在尼罗罗非鱼雌雄肌肉组织中的表达发现,8个差异表达基因中转录变体3与ACP6-Y在尼罗罗非鱼雄鱼肌肉组织中的表达均极显著高于雌鱼(P0.01),ACP3-X、60S核糖体蛋白(RL3)、小白蛋白β样蛋白、ACP15-X、肌型肌酸激酶M2-CK与转录因子Sox4在尼罗罗非鱼雌鱼肌肉组织中的表达均极显著高于雄鱼(P0.01)。结果表明,应用引物退火控制技术筛选获得了8个可能参与了雌雄鱼肌肉生长发育调控的ESTs,为进一步筛选雌雄鱼肌肉生长发育相关候选基因奠定了基础。     

Enrichment of aquaculture earthen ponds with Hediste diversicolor: Consequences for benthic dynamics and natural productivity

The present work analysed the potential impacts of the enrichment of semi-intensive production earthen ponds with the ragworm Hediste diversicolor in the benthic dynamics and natural productivity. The macrobenthos and sediment characteristics were analysed in two enriched ponds and two control ponds in May, June and September 2005. The number of species, Margalef species richness and biomass (AFDW) were generally significantly higher in enriched than in control ponds, while for abundance no clear pattern was visible. Multivariate analysis showed differences in macrobenthic community structure of control and enriched ponds. Differences were also visible when the introduced species was removed from the data set, indicating that differences were mainly due to changes in other species abundance. In general, gastropods (Akera bullata, Jujubinus striatus, Hydrobia ulvae, Rissoidae), bivalves (Abra ovata, Cerastoderma spp.), crustaceans (Ampithoe rubricata, Dexamine spinosa, Gammarus insensibilis, Gammarella fucicola, Iphinoe tenella), and also some polychaetes (Desdemona ornata, Terebella spp., Syllis gracilis and Neanthes caudata) greatly increased their abundances in enriched ponds. On the other hand, the abundance of Tubificidae, Capitella spp., Pseudopolydora paucibranchiata, Corophium acherusicum, and Mesopodopsis slabberi decreased. The organic matter content was significantly lower in enriched ponds, probably due to the positive impact of the polychaetes on sediment reworking, resulting in higher organic matter mineralization. Overall the present study indicates that stocking of earthen production ponds with H. diversicolor significantly altered community structure of benthic invertebrates and may improve environmental conditions for fish production by reducing the organic matter accumulation in pond sediments.     

Performance evaluation of venturi aeration system

The venturi aeration is an effective practice to increase the dissolved oxygen accessibility in the water bodies. This study aims to optimize the various geometrical parameters of the venturi aeration system. A non-dimensional technique was applied to find the optimum performance of various geometric parameters i.e. throat lengths (t_l), number of air holes (N), and converging and diverging angles (α and β). These experiments have been carried out using 1124 L capacity of tank having dimensions of 105 cm long, 105 cm wide and 102 cm deep. The experiments were conducted at a constant flow velocity of water (1.096 m/s) with varying throat length (t_l = 20–100 mm keeping 20 mm as interval between two consecutive length), number of air holes (N = 1–17 at an equal hole to hole distance of 5 mm between them), and converging and diverging angles (α and β = 10°, 15°, 20° and 25°). Multiple non-linear regression equations were also developed from the linear relation with the dependent variable (Non-dimensional form of standard aeration efficiency, NDSAE) and independent variables (t_l and N). With the geometrically optimized venturi aerator the optimum performance was found for t_l =100 mm, N = 17, and α and β = 15°. The maximum value of standard oxygen transfer rate (SOTR) and standard aeration efficiency (SAE) obtained was 0.0216 kgO₂/h and 0.611 kgO₂/kWh respectively. From the non-dimensional study, it was found that the NDSAE is the function Reynolds number (Re) and Froude number (Fr). The simulation equations were developed on the basis of Re and Fr for NDSAE, and subjected to 7.378 × 10⁻⁶ < Re < 3.689 × 10^-5 and 0.163 < Fr < 0.817, respectively.     

Isolation and selection of suitable reference genes for real-time PCR analyses in the skeletal muscle of the fine flounder in response to nutritional status: assessment and normalization of gene expression of growth-related genes

In the present study, different reference genes were isolated, and their stability in the skeletal muscle of fine flounder subjected to different nutritional states was assessed using geNorm and NormFinder. The combinations between 18S and ActB; Fau and 18S; and Fau and Tubb were chosen as the most stable gene combinations in feeding, long-term fasting and refeeding, and short-term refeeding conditions, respectively. In all periods, ActB was identified as the single least stable gene. Subsequently, the expression of the myosin heavy chain (MYH) and the insulin-like growth factor-I receptor (IGF-IR) was assessed. A large variation in MYH and IGF-IR expression was found depending on the reference gene that was chosen for normalizing the expression of both genes. Using the most stable reference genes, mRNA levels of MYH decreased and IGF-IR increased during fasting, with both returning to basal levels during refeeding. However, the drop in mRNA levels for IGF-IR occurred during short-term refeeding, in contrast with the observed events in the expression of MYH, which occurred during long-term refeeding. The present study highlights the vast differences incurred when using unsuitable versus suitable reference genes for normalizing gene expression, pointing out that normalization without proper validation could result in a bias of gene expression.     

Side-aspect target strength of Atlantic salmon (Salmo salar), brown trout (Salmo trutta), whitefish (Coregonus lavaretus), and pike (Esox lucius)

The side-aspect acoustic target strengths (TS) of 19 Atlantic salmons (Salmo salar), 16 brown trouts (Salmo trutta), 10 whitefish (Coregonus lavaretus) and 9 pikes (Esox lucius) were measured using a 200 kHz split-beam echosounder, in order to study the relationship between TS and fish size indices (length, weight and side area). The effect of side aspect angle on TS was also studied. Linear models between TS and the logarithm of the fish size indices were fitted with length being best for predicting TS. Typically, the standard error of estimate was 1.2–2.9 dB. The side-aspect TS measurements with specimens of known size showed that the linear relationship between full side-aspect TS and the logarithm of fish length for salmonid (Salmo salar + Salmo trutta) was on average 4.7 dB (SE = 0.7), lower than for whitefish and pike combined. The effect of side aspect angle on TS was modelled with cos³ (2α) function. The differences in the TS between full side aspect and head/tail aspect were 17.4, 19.0 and 19.6 dB for salmonid, whitefish, and pike, respectively.     

Dietary supplementation with Bacillus can improve the growth and survival of the kuruma shrimp Marsupenaeus japonicus in high-temperature environments

This study examined the effects of a commercial Bacillus complex used as probiotics on the performance of Marsupenaeus japonicus under high water temperature after 60 days of rearing. Growth and survival rate of M. japonicus were significantly increased in the probiotics-treated group (P < 0.05). Vibrio count and percentage of Vibrio in the intestinal tracts of M. japonicus reared with Bacillus were significantly lower than in other treatments (P < 0.05). The expressions of immune-related gene including prophenoloxidase, lysozyme, cytosolic manganese superoxide dismutase and hemocyanin subunit L in M. japonicus were significantly increased in the Bacillus-treated group (P < 0.05). The results indicated that Bacillus can be used as a diet supplement to minimize the damages caused by free radicals generated from insufficient oxygen metabolism due to the high-temperature stress, and to enhance immunity and activate the immune response levels. Our findings can improve the growth and survival rates of M. japonicus during the high-temperature farming period.     

Characterization and expression analysis of two distinct neuropeptide Ya paralogues in Jian carp (Cyprinus carpio var. Jian)

Two distinct neuropeptide Ya paralogues (jlNPYa1 and jlNPYa2) were cloned and characterized in Jian carp (Cyprinus carpio var. Jian), with a highly conserved organization encoded by four exons and three introns. The cDNAs for jlNPYa1 and jlNPYa2 were 693 and 730 bp in size, respectively. jlNPYa1 and jlNPYa2 both encoded a 96-amino acid protein, which shared 97.9 % identity. Phylogenetic tree showed that it has two NPYa genes, called jlNPYa1 and jlNPYa2, that presumably resulted from the tetraploidization event in the carp lineage. Analysis of expression profiles of jlNPYa1 and jlNPYa2 showed that the two NPY genes had a broad tissue distribution but expressed primarily in the forebrain, hypothalamus, testis and liver. The expression pattern was different in juvenile and adult (female and male) Jian carp. In juvenile, the highest expression level of jlNPYa1 and jlNPYa2 was detected in the testis. In adult, it was detected in the forebrain. In female hypothalamus, the expression level of jlNPYa1 was significantly higher than that of jlNPYa2. However, the opposite was true in male hypothalamus. The differing distribution patterns of the two NPY genes suggested that jlNPYa1 and jlNPYa2 might play different roles in Jian carp.     

长江流域泥鳅与大鳞副泥鳅种质资源调查与研究

对长江流域泥鳅和大鳞副泥鳅野生群体进行了系统资源调查,结果显示,二倍体泥鳅(2n)与多倍体泥鳅(3n,4n,5n)在长江流域均有分布,其中二倍体泥鳅数目占有绝对优势,少量多倍体泥鳅集中分布于长江流域中游地区及若干湖泊。此外,显著性分析表明,泥鳅和大鳞副泥鳅的雌性个体都显著大于雄性个体,两物种间个体大小无显著性差异。二倍体泥鳅的体长与体质量明显小于三倍体泥鳅及四倍体泥鳅,而三倍体泥鳅与四倍体泥鳅间无显著性差异。野生群体中,泥鳅雌性个体所占比例从上游到下游逐渐减少,大鳞副泥鳅无明显变化。相关性分析显示,泥鳅体质量与地域经度呈负相关,大鳞副泥鳅体质量与地域经度无显著相关性。研究表明,长江流域多倍体泥鳅和大鳞副泥鳅物种资源丰富。     

Complete nucleotide sequences of mitochondrial DNA of long-finned squid Loligo edulis

The complete nucleotide sequence of the mitochondrial genome of long-finned squid Loligo edulis forma kensaki (L. edulis f. kensaki, Teuthida: Myopsida) was determined. It contains 13 protein-coding genes, 12SrRNA, 16SrRNA, and the 22 tRNA genes, and three long noncoding regions. We also determined the mitochondrial genome nucleotide sequence of seasonal brood samples of L. edulis f. budo collected from the western part of the Sea of Japan in the autumn to winter seasons, which showed morphologic discrepancies with L. edulis f. kensaki. Comparison of the two complete sets of mitochondrial DNA data showed that the similarity of the two sequences was as high as 99.9?%, with only eight nucleotide substitutions in coding regions. The complete mitochondrial genome of Loligo edulis f. kensaki from Nagasaki Pref. is 17360?bp and L. edulis f. budo from the Shimane Pref. is 17351?bp. The nucleotide sequences and haplotype patterns in ND1 suggest that L. edulis f. kensaki and L. edulis f. budo share a single genetic background.     

Cohort analysis on a freshwater fish Osteochilus hasselti C. & V. (Cyprinidae) at Bukit Merah Reservoir,Malaysia

An earlier cohort analysis using catch-at-length data (for the period May 1979–April 1980) on the stock of Osteochilus hasselti C. & V. computes statistics on: (1) the total stock at the start of the cohort (N = 22.7 × 10⁵) (these stock numbers decrease progressively at successive lengths, in a steady state and assuming constant natural mortality rate, M = 2.1); (2) catch numbers in a cohort totalling 780 940 individuals; (3) the exploitation rate of the cohort of E = 0.34, suggesting moderate exploitation of the species at Bukit Merah Reservoir, Malaysia.However, the validity of cohort analysis on a species exploited at a very early age depends on the input value of the variables natural mortality rate (M), fishing mortality rate of terminal largest fish (F_ter), and growth parameters (L_∞, K). Because of the methodological difficulties in estimation and verification of M, F_ter and K values of O. hasselti, a range of values of input variables is adopted for comparison. The effect of the variability of M values (0.5, 1.0, 1.5 and 2.5) on the computation results of smaller size-class fishes N_L is significantly different from that based on M = 2.1, showing a much lower population size.The variability of input values of F_ter (range 0.5–2.5) and K (0.28–2.62) is tested on their effects on the population size of recruits. The combined effect of M and K in the relationship of $\text{M}\text{K}$ ranging from 0.8 to 2.5 is varied to decide the possible values of K. In general, the different input values of M, F_ter and K result in lower estimates of the population size of recruits, N_r This is about 28% lower than N_r = 22.7 × 10⁵ when M = F_ter = 2.1 and K = 1.15. With an inherent computational bias, the population size of N_r = 22.7 × 10⁵ is probably an under-estimate, but it is both reasonable and biologically possible for O. hasselti at Bukit Merah Reservoir, Malaysia, since the input variables are generated from representative length composition data of commercial catches and tagging data.     

Culture method and growth characteristics of marine benthic dinoflagellate Ostreopsis spp. isolated from Japanese coastal waters

Blooms of toxic dinoflagellates of the genus Ostreopsis, which is known as a producer of palytoxin (PTX) analogs, may pose a threat to human health in tropical, subtropical, and temperate regions around the world. In the present study, we established a suitable culture method for Ostreopsis spp. isolated from Japanese coastal waters and characterized their growth potential using the method to discuss their bloom dynamics. Each clonal strain of Ostreopsis cf. ovata, Ostreopsis sp.?1, Ostreopsis sp.?5, and Ostreopsis sp.?6 was incubated in 25?×?150?mm test tubes with a flat bottom containing various kinds of medium. Since Ostreopsis spp. strains grew well in IMK and/or f/2 media, we selected these media for cultivation of all the Ostreopsis spp. isolates. Growth rates of O. cf. ovata (0.834?divisions/day), Ostreopsis sp.?1 (0.619?divisions/day), and Ostreopsis sp.?6 (1.04?divisions/day) that produce PTX analogs significantly differed (p?<?0.05) respectively and are clearly higher than those of other reported epiphytic dinoflagellate Gambierdiscus toxicus, Prorocentrum lima, and Coolia monotis cultures, which suggest that these species have ecological advantages to predominate through the algal succession in Japanese coastal waters, resulting in a potential risk to human health in this region.