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1.
For recovery of the declining population of pen shells in the wild, the production of pen shell juveniles for transplantation or aquaculture is underway in Japan. For more stable juvenile production, artificial fertilization methods for pen shells are needed, but methods to induce oocyte maturation (meiosis resumption) used in other bivalves, which make oocytes fertilizable, were ineffective for pen shells. Here, we report evidence showing that retinoic acid (RA) has strong activity in inducing oocyte maturation and activating sperm motility in pen shells. Treatment of fully developed oocytes with 1.0 μM all-trans-RA (at-RA) induced germinal vesicle breakdown, a typical morphological sign of oocyte maturation, but 1.0 μM at-retinol and at-retinal, 2 mM ammonia, and 1.0 μM serotonin were ineffective. Treatment with at-RA for 30 min was sufficient for oocyte maturation and was more potent than its isomers, 9-cis- and 13-cis-RA. Parallel results were obtained for sperm motility activation. Oocyte responsiveness to at-RA increased during the final stage of ovary development. Artificial fertilization was successful only with the oocytes treated with at-RA, and fertilized eggs developed to D-shaped (veliger) larvae without apparent morphological abnormalities. These results indicate the possible application of RA for the artificial fertilization of pen shells.  相似文献   

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3.
Studies considering broodstock conditioning of Ruditapes decussatus mostly used flagellates and diatoms for feeding, mainly Isochrysis galbana and Chaetoceros calcitrans, respectively. The present study evaluated the effect of different microalgal diets on gonadic maturation of R. decussatus including three microalgae species (C. calcitrans, Tetraselmis suecica, and Nannochloropsis oculata) which were used to prepare six diets: three monospecific and three bispecific mixed diets at a proportion of 1:1. Clams were daily fed at a ratio of 1% dry weight of algae/live weight of clam and unfed treatment was used as control. Results showed that clams fed C. calcitrans alone or mixed with T. suecica attained earlier full maturity with the highest response to spawning induction (after 34 conditioning days) and largest proportion in the partial spawning phase for both, followed by T. suecica alone after 48 days. In contrast, N. oculata alone or mixed diets demonstrated poor performance for gonadal maturation. Unfed treatment did not show any sign of maturation. The results indicated that T. suecica has high conditioning potential like C. calcitrans and their mixture gave the highest benefit. Therefore, T. suecica can be recommended for R. decussatus broodstock conditioning.  相似文献   

4.
This study aims to evaluate the efficacy of Streptococcus agalactiae vaccine preparations, administered to tilapia broodstock, in preventing streptococcosis, through specific and non-specific immunity being transferred to the offspring. The study was conducted in two phases. The first was the vaccination of the broodstock using a whole-cell vaccine, an extracellular product (ECP) vaccine, and a combination of the two with a ratio of 1:1. The vaccines were administered to the broodstock 2 and 3 weeks before spawning. The second phase was the challenge test for larvae produced by vaccinated broodstock, and larvae from the unvaccinated control broodstock, through immersion in a suspension of 107 cfu mL?1 pathogenic S. agalactiae for 30 min, at ages 7, 14, 21, and 28 days post-hatching. The parameters evaluated were the broodstock’s blood profile, antibody-lysozyme (in broodstock, eggs, and larvae), and the larvae’s relative percent survival. Treatment with the combined vaccine administered 3 weeks before spawning resulted in the broodstock having significantly better antibody levels, lysozyme activity, and hematology profiles, compared to the other treatments (p?<?0.05). In addition, the larvae produced by broodstock subjected to this treatment, when challenged with the pathogenic S. agalactiae at ages 7, 14, 21, and 28 days, had RPS values of 95.24, 83.33, 72.22, and 56.02%, respectively. It was concluded that the administration of the “whole-cell/ECP” combination vaccine preparation to tilapia broodstock in the 3 weeks before spawning can increase specific and non-specific immunity in the broodstock and protect the larvae from S. agalactiae infection.  相似文献   

5.
The impact of Euspira fortunei as an alien predator on fluctuations in population densities of prey mollusks between 2001 and 2010 on the Tona coast, northern Japan, was investigated. This species increased dramatically from 2002 to 2004. In contrast, prey species such as Ruditapes philippinarum and Macoma incongrua decreased rapidly from 2001 to 2004, whereas Pillucina pisidium and Batillaria cumingii did not show a significant decrease during this period. Using a laboratory experiment, we were able to show that these decreases in the population densities of some species of mollusks but not other species were the result of species-selective predation by E. fortunei, as the experiment revealed that E. fortunei preferred to attack R. philippinarum and M. incongrua rather than P. pisidium, although the predator did expand its diet to include P. pisidium after it had consumed 16 of the 20 preferred prey available (i.e., R. philippinarum and M. incongrua). This case study suggests that invasive naticid predators have the potential to affect the population density and community structure of prey mollusks in recipient coastal ecosystems through predation.  相似文献   

6.
Genetic diversity is vital for the maintenance of genetic pool in cultured shrimps. In order to estimate the current status of genetic diversity in Litopenaeus vannamei shrimp in Iran, as an exotic species, a total of 45 individuals from Amiri and Gorgeaj farms in Jask port of Hormozgan province and one hatchery in Gomishan city of Golestan province, were detected using four microsatellite loci. The number of alleles per locus was 5–10, and the mean effective number of alleles (N e) across populations and loci ranged from 4.834 to 5.148. The overall mean observed heterozygosity (H o) ranged from 0.450 to 0.479, which was lower than the expected one (0.789–0.794). There was nothing remarkable about any of the allele frequencies across populations or loci. The mean inbreeding coefficient (F IS) and pairwise genetic differentiation (F ST) among populations were 41.6 % and 0.133, respectively. The three studied populations departed from Hardy–Weinberg equilibrium (HWE). Analysis of molecular variance revealed 14 % variability among and 86 % within populations. However, considering departing from HWE and the high F IS and F, the moderate pairwise F ST values, importance of introducing genetically diverse broodstock and monitoring to control inbreeding is discussed.  相似文献   

7.
The current study was conducted to investigate the effect of ExcelMOS® in enhancing the immune system of Sparus aurata broodstock and their impact on offspring health through displaying the maternal transfer of immunity. Broodstock were divided into two groups: one was injected intraperitoneally with ExcelMOS® 1 month before spawning, while the other group was used as a control (without injection). Comprehensive increase in survival rate was observed for larvae hatched from ExcelMOS®-injected broodstock than those of the control (P?≤?0.05). Hematological analysis showed increases in leukocyte count and hematocrit percentage (P?≤?0.05) and significant enhancement in immune assays as phagocytic, respiratory burst, lysozyme activities in ExcelMOS®-injected broodstock (P?≤?0.05). Additionally, total immunoglobulin levels in the serum, eggs, and larvae resulted from ExcelMOS®-injected broodstock were highly significant (P?≤?0.05) than those in the control ones. Transmission electron microscopy and semi-thin sections in posterior intestine of ExcelMOS®-injected broodstock revealed reinforcement of the epithelial barrier structure, intestinal integrity, and functionality in combination with the stimulation of innate immune system. In conclusion, immunostimulation of Sparus aurata broodstock using ExcelMOS® has improved survival of larvae and enhanced both innate and adaptive immune defense mechanisms. Further investigations are required to show the effect of ExcelMOS® on fish cultured in intensive culture systems.  相似文献   

8.
Portunus trituberculatus broodstock were stocked in plastic tanks to evaluate the effects of starvation and feeding on gonadal development, blood chemistry, fatty acid composition, and expression of vitellogenin (Vtg) and fatty acid-binding protein genes (FABP) in females. Two treatments (starved and fed) were randomly assigned to triplicate groups of 90 swimming crab broodstock (approximately 230 ± 45 g). In the starved treatment, crabs were starved for 30 days, whereas in the fed treatment crabs were fed once a day with clams. The gonadosomatic index decreased significantly in starved crabs (P < 0.05), as did the serum glucose and cholesterol concentrations; conversely, the total protein concentration in serum significantly increased (P < 0.05). In the ovary, there was a significant relative decline of 18:0, 16:1n-7 and 20:1n-9 fatty acids and relative increases of 20:4n-6, 22:6n-3, 18:1n-9 and 20:5n-3 in starved crabs compared to fed crabs (P < 0.05). Relative expression of Vtg in the ovary decreased significantly in starved crabs (P < 0.05), while there was no significant difference in hepatopancreas Vtg expression between starved and fed crabs (P > 0.05). Starvation suppressed gonadal development in female swimming crab broodstock.  相似文献   

9.
Heterochronic lin-28 is a conserved RNA-binding protein that plays a key role in the timing of developmental events in organisms. As a crucial heterochronic gene, the protein controls developmental events of the second of four larval stages in Caenorhabditi elegans. Heterochronic let-7 miRNAs are often present in various species and highly conserved in sequence and biological function and are required for various biological processes. Previous studies showed that ten let-7 miRNAs were identified in the Japanese flounder (Paralichthys olivaceus) and that they were primarily expressed during metamorphosis. In this study, we clone and characterize the lin-28a gene from P. olivaceus and exhibit its dynamic expression pattern at different developmental stages and various adult tissues. The results show that the P. olivaceus lin-28a gene has high sequence similarity with other species and is highly expressed in the embryonic stage but weakly expressed in the larval stage. In addition, lin-28a overexpression causes cell proliferation and significantly promotes the levels of pre-let-7a and pre-let-7d while markedly depressing let-7a and let-7d expression in FEC (Flounder Embryonic Cell), which indicate that lin-28 possibly blocks the maturation of let-7 miRNAs. Additionally, lin-28a is identified as a target gene of let-7 miRNAs, and let-7 miRNAs directly regulate lin-28a expression by targeting its 3′ UTR. Taken together, lin-28a along with let-7 miRNA participates in a lin-28/let-7 axis pathway that regulates cell division and timing of embryonic and metamorphic events in P. olivaceus.  相似文献   

10.
A field survey and a laboratory experiment were conducted to examine ontogenetic shifts in habitat and diet of the turban snail Turbo cornutus. The main habitat of turban snail juveniles smaller than 10 mm shell height (SH) was turfs of articulated coralline algae, and that of adults larger than 50 mm SH was kelp beds of Ecklonia bicyclis and Ecklonia cava. However, the ontogenetic habitat shift during the juvenile stage of 20–50 mm SH was unclear. From the results of a long-term feeding experiment and stable isotope analysis, the gelidiacean alga Gelidium elegans was assumed to be more important as a food source for juvenile turban snail than E. cava in the field. However, the frequency of individuals inhabiting gelidiacean algal turfs was low in both juvenile and adult stages. Thus, the ontogenetic shifts in habitat and diet did not coincide and other factors, i.e., daytime refuge, are important. As the growth rate was higher in the juveniles fed on the two algal species than those fed on single algal species, co-occurrence of various algal habitats in rocky shore ecosystems as a coastal ecosystem complex may enhance growth of turban snail juveniles feeding on a combination of different algal species.  相似文献   

11.
Extremely low post-settlement survival is one of the largest barriers for artificial rehabilitation of Acropora corals. However, little data have been found for interspecific difference of the post-settlement survival probably because the observation of coral juvenile is difficult in the field. Here, we analyzed the survival of three dominant species of Acropora corals (A. digitifera, A. tenuis, A. yongei), with different colony morphologies and habitat preferences, for 2 years after settlement under the same environmental conditions. The post-settlement survival was significantly higher for A. tenuis than for A. digitifera 3 months after settlement. Two years later, the survival rate of A. tenuis was approximately 15 times higher than A. digitifera. In a separate analysis of three bottle-brush species (A. awi, A. echinata, A. subglabra) and A. tenuis, post-settlement survival was always higher for A. awi than for other two bottle-brush species, suggesting that the initial survival was different among morphologically sister species. Low survival was possibly associated with slow growth rates during the first 7 months. Thus, species selection is important for successful artificial coral rehabilitation, with A. tenuis being the most viable option. Alternatively, new techniques are required to improve post-settlement survival of slow growing coral species.  相似文献   

12.
The Great East Japan Earthquake and accompanying tsunamis occurred on 11 March 2011, causing huge damage to marine organisms. The invasive naticid gastropod Laguncula pulchella (Euspira fortunei), which was introduced with the imported clam Ruditapes philippinarum from China and Korea, survived the earthquake. The “growth break line” observed on the shell surface in over 90% of the individuals collected in Matsushima Bay and Matsukawa-ura Lagoon after the tsunamis was examined by scanning electron microscopy. Each shell presented three layers before and three after the growth break. However, the fracture surface consisted of five layers—two prismatic and three crossed lamellar—around the growth break line. This suggests that shell formation temporarily ceased following the tsunamis and that the five-layered shell may have developed in response to the stress caused by the tsunamis. The newly formed middle layer became thinner after the “tsunami break,” which may be the result of a rapid change in the mineralization process, including rapid shell growth and/or repair. These results suggest that the damage to and forcible removal of habitats by the tsunamis was stressful for L. pulchella. A decrease in or the cessation of shell formation after a tsunami may be a common phenomenon in mollusks that inhabit tidal flats.  相似文献   

13.
A sampling survey to determine the composition and distribution of freshwater eel species was conducted in 12 provinces along the coast of Vietnam from October 2014 to February 2015. The sampled provinces spanned the country from central Vietnam to the south, but freshwater eels were only found in the central part of Vietnam. Species identification of 77 specimens, collected from different habitats (rivers and estuaries), was performed by analysis of both morphological characters and nucleotide sequences of mitochondrial cytochrome oxidase subunit I (COI). The 77 specimens were morphologically and genetically identified as 58 Anguilla marmorata, 17 A. bicolor pacifica, and two A. japonica. This is the first definitive survey about the composition and distribution of freshwater eels in Vietnam where distribution has been hitherto unknown.  相似文献   

14.
To evaluate the impact of mass selection on genetic structure in artificially closed populations of the Pacific oyster Crassostrea gigas, we performed mass selection over six generations on two stocks from Japan and Korea and analyzed their temporal genetic variation and structure using 18 microsatellite makers, which were compared with the base populations of the two selected lines and one wild population from China. The average numbers of alleles (Na), mean observed heterozygosities (Ho), and expected heterozygosities (He) varied over generations in the two selected lines (selected lines of Japan, Na = 10.7–14.9, Ho = 0.757–0.846, He = 0.778–0.871; selected lines of Korea, Na = 9.4–17.3, Ho = 0.736–0.865, He = 0.744–0.854). There was no significant reduction in heterozygosity in the two selected lines. However, the average number of alleles per locus was significantly lower in the fifth and sixth generations of the two selected lines compared with that in the base population and wild population (P < 0.05), suggesting that the successive mass selection in closed populations may increase the sensibility of rare alleles to genetic drift. Equalizing the sex ratio of parents and reducing the selection intensity properly with the increase of selective generations is recommended to minimize the deleterious effect of genetic drift and bottleneck caused by successive mass selection. The information obtained in this study is useful for the design of appropriate management strategies for selective breeding of C. gigas.  相似文献   

15.
In aquaculture, nutrition and supplemented diets have been shown to affect broodstock reproductive performance. In this study, we investigated the effects of dietary supplementation with Cymbopogon flexuosus essential oil (CFEO) microcapsules on reproductive-related parameters in silver catfish (Rhamdia quelen) male broodfish. Adult male broodstocks were separated into three groups according to the concentrations of supplemented CFEO (0.0?=?control; 1.0 or 3.0 mL per kg of diet). After 20 days under experimental conditions, the animals were euthanized and the gonads were harvested for gonadosomatic index, sperm analysis, oxidative stress, and histopathology; testosterone levels were measured in the plasma; gene expression of prl, smtl, pomca, and pomcb was assessed in the pituitary gland by real-time PCR. The results showed no alterations on reproductive parameters in R. quelen males treated with Cymbopogon flexuosus essential oil compared to the control-diet animals. In conclusion, CFEO microcapsules supplied for 20 days in the concentrations of 1.00 or 3.00 mL per kilogram of diet did not affect the reproduction criteria evaluated in this study in male silver catfish.  相似文献   

16.
As an important economic marine species cultured in China, Chinese tongue sole (Cynoglossus semilaevis) has interested us due to its sexual dimorphism and ZW/ZZ sex determination system. In a previous study, dmrt1 was identified as a dosage-dependent male-determining gene. In the present study, a female-specific expressed gene, cse0440, initially annotated as lrp1b-like, was identified from chromosome W of C. semilaevis. In view of the differences between cse0440 and lrp1b in terms of expression pattern, a phylogenetic analysis containing 85 LRP proteins was constructed and provided an evidence to re-annotate cse0440 as cseLRP13. In addition, two orthologues of cseLRP13 were separately identified from W and Z chromosomes: cseLRP13-W and cseLRP13-Z. The subsequent multiple sequence alignment and syntenic arrangements of LRP13 in C. semilaevis, Japanese medaka (Oryzias latipes), large yellow croaker (Larimichthys crocea), striped bass (Morone saxatilis), white perch (Morone americana) and Fugu rubripes (Takifugu rubripes) further supported this re-annotation. RT-PCR and in situ hybridization revealed that cselrp13 was exclusively expressed in the oocytes and follicles of ovaries. These results suggested that lrp13 may play important roles in female reproduction. In future, with the advancement of micromanipulation in flatfish, the detailed function of two lrp13 orthologues in C. semilaevis will be elucidated.  相似文献   

17.
In the whiteleg shrimp Litopenaeus vannamei, the existence of six sinus gland peptides (SGPs) possessing vitellogenesis-inhibiting hormone (VIH) function has been previously demonstrated. Genomic and cDNA sequence information for two of these is already known. Here, we cloned cDNAs for the remaining three, i.e., those encoding Liv-SGP-A, -B, and -F. The deduced amino acid sequences were comprised of a signal peptide, a CHH precursor-related peptide, a mature peptide, and a C-terminal amidation signal. The genomic DNA for Liv-SGP-A, -B, -C, -F, and -G, was found to be organized as three exons and two introns. The insertion of the two introns were conserved in all VIH genes, with intron I being inserted six residues following the signal peptide, and intron II after the 40th residue of the mature peptide. We also quantified the relative simultaneous expression of Liv-SGP-A, -B, -C, -F, and -G in relation to molting and unilateral eyestalk ablation. The expression levels of each gene in the eyestalks of adults did not change significantly during molting or following unilateral eyestalk ablation. However, unilateral eyestalk ablation significantly decreased expression levels at 10 and 20 days for Liv-SGP-A and -C, and at 20 days for Liv-SGP-G in the eyestalks of subadults. This study has therefore clarified the genomic structure of the five major subtype I VIHs in L. vannamei, and elucidated their expression levels in the eyestalks in relation to molting and unilateral eyestalk ablation.  相似文献   

18.
Several outbreaks of Streptococcus agalactiae infection of bighead carp (Aristichthys nobilis) were observed in China. The molecular epidemiology and pathogenicity of S. agalactiae in bighead carp and tilapia (Oreochromis sp.) is poorly understood. In the present study, we identified S. agalactiae strains isolated from diseased bighead carp using the API 20 Strep kit and 16S rDNA sequencing and determined whether these strains came from tilapia. Of the 46 identified S. agalactiae strains, 24 strains were successfully isolated from diseased bighead carps, 20 S. agalactiae strains were isolated from tilapia, and two S. agalactiae strains were isolated from tiger frog (Hoplobatrachus chinensis). The results of molecular typing, including multilocus sequence typing, molecular serotyping, surface protein gene detection, and virulence-related gene detection showed that the 44 strains from bighead carp and tilapia were highly similar, whereas different from tiger frog GBS strains. Remarkably, the bighead carp strain Hn1404 showed high virulence in bighead carp and zebrafish. Moreover, this strain was pathogenic to Nile tilapia (Oreochromis niloticus). In addition, comparative genomic analysis showed that isolate Hn1404 had a close relationship with the bighead carp and tilapia S. agalactiae strains. All the analyses of the genetic characteristics of bighead carp and tilapia strains showed that tilapia S. agalactiae strains could be transmitted to other fish species such as bighead carp.  相似文献   

19.
There is a possibility that deep coastal marine macrophytes will be less critically affected by thermal stress associated with climate change and remain as refugia. Thus, information on them is expected to contribute to conservation of biodiversity in coastal areas affected by climate change. To document the deep-growing Zostera caulescens in relation to the light environment, field surveys were conducted in coastal waters of the central area along the Japan Sea coast of Honshu, Japan, and then the relationship between the light environment and seagrass depth limit was examined. In the coastal waters of Sado Island and Noto Peninsula, the presence of deep coastal communities of Z. caulescens was confirmed in the depth range of 20–25 m. Biomass and shoot density for Z. caulescens, ranging 34.1–51.3 g DW m?2 and 83–112 shoots m?2, were recorded at a depth of 20 m in Ryotsu Bay, Sado Island. For the genus Zostera including the deep-growing Z. caulescens, the relation between the extinction coefficient and seagrass depth limit was described by the fitted regression equation. The minimum light requirement of the deep-growing Z. caulescens was markedly lower than that of the shallow-growing Zostera marina.  相似文献   

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