Distribution of nephrons in the head kidney of three species of Sebastes (Teleostei: Scorpaenidae).

Nephrons are generally not distributed in the head kidney of teleost. Nonetheless, in this study, the nephron structure was identified in the head kidney of three species of Sebastes (Sebastes inermis, Sebastes schlegelii and Sebastes thompsoni). The kidney is Y shaped, with the development in the head kidney. The nephron structure was confirmed in the head kidney and body kidney. In addition, the nephron consisted of renal corpuscles and tubules, and the renal corpuscle consisted of the Bowman's capsule and glomerulus. Histologically, previous studies reported that the nephron structure is similar to that of other marine teleost. The renal tubule is a simple columnar epithelial layer with microvilli and cilia on the free surface, which is observed as a brush border. The Rrk (relative area ratio of kidney to body surface) was 5.14%, 7.58% and 5.17% in S. inermis, S. schlegelii and S. thompsoni, respectively. The Gar (glomerular area ratio of the head kidney) was higher in the central area than in the peripheral area, and species, which showed significant difference (P < 0.05), were in the following order: S. thompsoni (1.60%) > S. schlegelii (0.90%) > S. inermis (0.66%).

Changes in Hematological Parameters and Heat Shock Proteins in Juvenile Sablefish Depending on Water Temperature Stress.

Juvenile Sablefish Anoplopoma fimbria were used to assess the effects of water temperature (8, 10, 12, 14, 16, 18, and 20°C) on hematological parameters and heat shock proteins 70 and 90 for 4 months. Hematological parameters, including red blood cell count, hematocrit, and hemoglobin, were significantly decreased at 18°C. The inorganic plasma components calcium and magnesium were not altered by water temperature. The organic plasma components glucose and cholesterol were notably elevated at 18°C, whereas total protein was reduced. The enzymatic components, including aspartate aminotransferase, alanine aminotransaminase, and alkaline phosphatase, were notably elevated at 16°C or 18°C. The results of this study indicate that a temperature higher than the proper temperature affects the hematological parameters and heat shock proteins of juvenile Sablefish.

Expression profile and reproductive regulation of APGWamide in Pacific abalone (Haliotis discus hannai).

Neuropeptides in the central nervous system regulate reproductive activities in vertebrates. Ala-Pro-Gly-Trp-NH2 (APGWamide), a neuromediator expressed in the neural ganglia of mollusks, controls sexual maturation and reproduction. To clarify the role of APGWamide in sexual behavior regulation and gamete cell maturation in mollusks, we cloned the cDNA of APGWamide precursor (Hdh-APGWamide) and examined the spatiotemporal expression of the transcript in the Pacific abalone Haliotis discus hannai. The 222-amino acid sequence of the precursor deduced from the cDNA sequence showed typical features of gastropod APGWamide precursors. Phylogenetic analysis revealed that Hdh-APGWamide is classified with other gastropod APGWamide precursors, which form a separate branch from those of the bivalves. Hdh-APGWamide mRNA was highly expressed in the neural ganglia in both sexes. In females, the three ganglia (pleuro-pedal ganglion, PPG; branchial ganglion, and cerebral ganglion) showed similar expression in immature and mature animals, whereas in males, the level in the PPG only was higher at maturity (P < 0.05). In vivo injection of APGWamide or 5-hydroxytryptamine (10-3 M) increased the frequency of spawning and the number of released sperm cells by mature males (P < 0.05), while concentrations above 10-7 M enhanced germinal vesicle breakdown in fully developed cultured oocytes (P < 0.05). Thus, the phylogenetic branch of the APGWamide precursor gene in Haliotidae was separate from the other branches under the phylum Mollusca, and this gene exhibited ganglion-specific expression, indicating that it may induce final maturation and spawning in both sexes of Haliotis spp.

Characterization and spatiotemporal expression of gonadotropin-releasing hormone in the Pacific abalone, Haliotis discus hannai.

Gonadotropin-releasing hormone (GnRH) is a key neuropeptide regulating reproduction in humans and other vertebrates. Recently, GnRH-like cDNAs and peptides were reported in marine mollusks, implying that GnRH-mediated reproduction is an ancient neuroendocrine system that arose prior to the divergence of protostomes and deuterostomes. Here, we evaluated the reproductive control system mediated by GnRH in the Pacific abalone Haliotis discus hannai. We cloned a prepro-GnRH cDNA (Hdh-GnRH) from the pleural-pedal ganglion (PPG) in H. discus hannai, and analyzed its spatiotemporal gene expression pattern. The open reading frame of Hdh-GnRH encodes a protein of 101 amino acids, consisting of a signal peptide, a GnRH dodecapeptide, a cleavage site, and a GnRH-associated peptide. This structure and sequence are highly similar to GnRH-like peptides reported for mollusks and other invertebrates. Quantitative polymerase chain reaction demonstrated that Hdh-GnRH mRNA was more strongly expressed in the ganglions (PPG and cerebral ganglion [CG]) than in other tissues (gonads, gills, intestine, hemocytes, muscle, and mantle) in both sexes. In females, the expression levels of Hdh-GnRH mRNA in the PPG and branchial ganglion (BG) were significantly higher at the ripe and partial spent stages than at the early and late active stages. In males, Hdh-GnRH mRNA levels in the BG showed a significant increase in the partial spent stage. Unexpectedly, Hdh-GnRH levels in the CG were not significantly different among the examined stages in both sexes. These results suggest that Hdh-GnRH mRNA expression profiles in the BG and possibly the PPG are tightly correlated with abalone reproductive activities.

Growth performance, oxidative stress, and non-specific immune responses in juvenile sablefish, Anoplopoma fimbria, by changes of water temperature and salinity.

Juvenile sablefish, Anoplopoma fimbria (mean length 15.5 ± 1.9 cm, mean weight 68.5 ± 4.8 g), were used to evaluate the effects on growth, oxidative stress, and non-specific immune responses by changes of water temperature (8, 10, 12, 14, 16, 18, and 20 °C) and salinity (100 (35.0), 90 (31.5), 80 (28.0), 70 (24.5), 60 (21.0), 50 (17.5), and 40% (14.0) (‰)) for 4 months. The growth performance was significantly increased at the temperature of 12 and 14 °C, and the feed efficiency was notably decreased at the temperature of 18 °C. The growth performance and feed efficiency were also significantly decreased at low salinity. The antioxidant responses such as superoxide dismutase and catalase were significantly increased by the high temperature and decreased by the low salinity. The immune responses such as lysozyme and phagocytosis were elevated by the temperature of 18 °C and decreased by the salinity of 50%. The results of this study indicate that the growth performance of juvenile sablefish, A. fimbria, is influenced by the temperature and salinity, and the excessive temperature and salinity levels can affect the antioxidant and immune responses.

Cascading effects from survival to physiological activities, and gene expression of heat shock protein 90 on the abalone Haliotis discus hannai responding to continuous thermal stress.

Increasing temperatures can be a significant stressor for aquatic organisms. Abalones, a type of large marine gastropods, are the most commercially important species in aquaculture for Asia. To evaluate the potential ecological risk posed by temperature stress, we measured biological responses such as survival rate, adhesion ability (falling rate), and foot abnormalities in the abalone Haliotis discus hannai. Additionally, biochemical and molecular responses were evaluated in H. discus hannai exposed to various temperature gradients. The survival rate was reduced in abalones exposed to relative high temperatures (more than 26 °C). Increased temperature stress induced a higher falling rate and abnormal foot structure. Furthermore, increased antioxidant enzyme activities were observed in abalones exposed to relative high temperatures (26 and 28 °C). The activities of superoxide dismutase were induced in a time-dependent manner after high temperature stress. Generally, heat shock protein 90 also increased significantly in H. discus hannai exposed to temperature gradients (more than 24 °C) for 12 h. These results provide valuable information regarding stress responses to increased temperatures, in H. discus hannai: adverse biological and molecular outcomes could be utilized as risk assessments and stress monitoring of marine ecosystems under increased water temperatures.

Serum and ultrastructure responses of common carp (Cyprinus carpio L.) during long-term exposure to zinc oxide nanoparticles.

The uptake of nanoparticles by aquatic organisms such as fish has raised concerns about the possible adverse effects of nanoparticles (NPs). In this study, we aimed to evaluate the toxicological effects in juvenile common carp exposed to zinc oxide nanoparticles (ZnO-NPs) for 12 weeks. The carp were exposed to 0 (control), 0.1, 0.3, 0.8, and 2.4mg/L of ZnO-NPs under a flow-through exposure system. Fish were sampled at 0, 4, 8, and 12 weeks to test for zinc in the test water and blood, and biochemistry analysis; further, they were sampled at 12 weeks to observe ultrastructural changes in the liver, kidney, and gill. In the organic serum, changes in the glutamic pyruvic transaminase/alanine aminotransferase (GPT/ALT) and glutamic oxaloacetic transaminase/aspartate aminotransferase (GOT/AST) levels were significant, but changes in the lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) levels were not significantly different across all exposure periods. In the inorganic serum, the magnesium (Mg), inorganic phosphorus (IP), sodium (Na(+)), and chloride (Cl(-)) levels were significantly different in the exposure group and across exposure periods. However, calcium (Ca) and potassium (K(+)) levels were not significantly different. In the enzyme serum, the glucose (GLU) level significantly increased for the highest exposure group, but the total cholesterol (TCHO), triglyceride (Tg), and total protein (TP) levels were not significantly different during the exposure period. Ultrastructural changes in the liver induced changes in the black granules (of various sizes) in the lysosomes, indistinct nucleus membrane, and non-spherical nucleus. In the kidney, some mild changes were observed in the size and number of the lysosomes in the renal tubule. Desquamation and hypertrophy of pavement epithelial cells and vacuolation in the cytoplasm of the chloride cells were observed in the gill. Nanoparticles were also observed in the red blood cells, cytoplasm of all tissues, and glomerulus of the kidney. The observed changes in the serum and tissues may provide useful information regarding environmental conditions and risk assessments of aquatic organisms.

Expansion of the HSP70 gene family in Tegillarca granosa and expression profiles in response to zinc toxicity.

Zinc (Zn) is an essential micronutrient in organisms and an abundant element in the Earth's crust. Trace amounts of Zn released from natural sources can enter aquatic ecosystems through weathering and erosion. Zn accumulates in organisms, and when its intracellular concentration exceeds a certain level, it can induce oxidative stress and trigger oxidative stress-mediated heat shock protein (HSP) modulation. HSP70 is the most evolutionarily conserved among the HSP families. Despite extensive research on HSP70 genes in bivalves, the HSP70 gene family of Tegillarca granosa is still poorly characterized. We identified 65 HSP70 genes belonging to 6 families in the T. granosa genome, with 50 HSPa12 and 11 HSPa B2 genes highly expanded. On chromosome 11, 39 HSP70 (60%) genes were identified, and the HSPa12A genes were highly duplicated. A total of 527 and 538 differentially expressed genes were identified in the gills and mantle based on Zn exposure, respectively. The Gene Ontology of cellular anatomical entities was significantly enriched with upregulated differentially expressed genes in the gills and mantle. Eight of the 11 HSPa B2 genes were upregulated in both tissues. Most of the genes identified in both tissues were involved in "protein homeostasis" and "inhibition of apoptosis," which are associated with the HSP70 family's resistance to extrinsic and intrinsic stress. Hence, this study identified that the HSP70 gene family plays a vital role in the adaptation of aquatic organisms to heavy metal (e.g., Zn) stress in contaminated environments by compiling the different physiological responses to preserve homeostasis.

Ecotoxicological evaluation of tributyltin toxicity to the equilateral venus clam, Gomphina veneriformis (Bivalvia: Veneridae).

Tributyltin (TBT) is the most common pesticide in marine and freshwater environments. To evaluate the potential ecological risk posed by TBT, we measured biological responses such as growth rate, gonad index, sex ratio, the percentage of intersex gonads, filtration rate, and gill abnormalities in the equilateral venus clam (Gomphina veneriformis). Additionally, the biochemical and molecular responses were evaluated in G. veneriformis exposed to various concentrations of TBT. The growth of G. veneriformis was significantly delayed in a dose-dependent manner after exposure to all tested TBT concentrations. After TBT was administered to G. veneriformis, the gonad index decreased and the sex balance was altered. The percentage of intersex gonads also increased significantly in treated females, whereas no intersex gonads were detected in the solvent control group. Additionally, intersex gonads were detected in male G. veneriformis specimens exposed to relatively high TBT concentrations (20 µg L⁻¹). The filtration rate was also reduced in a dose-dependent manner in TBT-exposed G. veneriformis. We also noted abnormal gill morphology in TBT-exposed G. veneriformis. Furthermore, increases in antioxidant enzyme activities were observed in TBT-exposed G. veneriformis clams, regardless of dosage. Vitellogenin gene expression also increased significantly in a dose-dependent manner in G. veneriformis exposed to TBT. These results provide valuable information regarding our understanding of the toxicology of TBT in G. veneriformis. Moreover, the responses of biological and molecular factors could be utilized as information for risk assessments and marine monitoring of TBT toxicity.

Functional analysis of LFRFamide signaling in Pacific abalone, Haliotis discus hannai.

The invertebrate LFRFamide (LFRFa) and short neuropeptide F (sNPF), consisting of 6 to 10 amino acids, are orthologs for bilaterian NPF/Y, which consist of 36 to 40 amino acids. Recently, a molluscan G protein-coupled receptor (GPCR) for NPF was characterized in Pacific abalone (Haliotis discus hannai). To address the functional evolutionary route of the invertebrate LFRFa and NPF signaling system, in this study, we identified cDNAs encoding LFRFa precursors and the sNPF receptor (Hdh-sNPFR) in Pacific abalone. Four LFRFa mature peptides with 6 or 7 amino acids were predicted: GSLFRFa, GGLFRFa, GTLFRFa, and GSTLFRFa. Hdh-sNPFR was identified as a classical rhodopsin-like GPCR and classified into a molluscan sNPFR group. In HEK293 cells, Hdh-sNPFR was mainly localized in the cell membranes and internalized in the cytoplasm following treatment with LFRFa peptides. Reporter assays demonstrated that LFRFa peptides inhibit forskolin-stimulated cAMP accumulation in Hdh-sNPFR-expressing HEK293 cells. LFRFa precursor and Hdh-sNPFR transcripts were more strongly expressed in the cerebral and pleural-pedal ganglia of Pacific abalone than in the peripheral tissues such as the ovary, gills, intestine, and hepatopancreas. The levels of LFRFa transcripts in the ovary, intestine, and hepatopancreas were significantly higher in mature female abalone than in immature females. Injection of LFRFa induced the egg release and spawning behavior of mature abalone, but suppressed food intake. These results suggest that LFRFa peptides are endogenous ligands for Hdh-sNPFR involved in food intake and reproduction through a Gαi-protein dependent signaling pathway.

Chemo-photothermal therapeutic effect of chitosan-gelatin hydrogels containing methotrexate and melanin on a collagen-induced arthritis mouse model.

Heat stimulation can promote osteoblast differentiation and bone formation. Combining photothermal therapy and chemotherapy is an effective strategy for treating rheumatoid arthritis (RA). Herein, we prepared chitosan/gelatin/ß-glycerophosphate-melanin-methotrexate (CMM) hydrogel that could be used to perform simultaneous chemotherapy and photothermal therapy for patients with RA. The CMM solution was successfully converted to a gel state at body temperature. Due to intrinsic photothermal properties of melanin, CMM hydrogel exhibited effective temperature increase both in vitro and in vivo with increasing time of near-infrared (NIR) laser irradiation. After NIR laser irradiation, 50 % of methotrexate was rapidly released from the hydrogel within 3 h. Its release rate showed an instantaneous increase with additional NIR laser irradiation. After CMM hydrogel was injected directly into the paw joint of each collagen-induced arthritis (CIA) mouse followed by irradiation with a NIR laser (808 nm, 0.5 W/cm2, 3 min), swelling and redness at the inflamed area were significantly alleviated at 14 days after treatment. Micro-CT analysis confirmed that treated joints of mice were similar to normal joints. Hence, CMM hydrogel could be used as an attractive RA therapeutic agent for simultaneous chemo-photothermal therapy.

Light and electron microscopy studies of siphon and siphonal sheath formation in the infaunal bivalve Tresus keenae (Bivalvia: Mactridae).

To understand the habitat ecology of Tresus keenae, an infaunal bivalve, the microanatomical structure of the siphon and the method of siphonal sheath formation were described. The diameter of the incurrent siphon was approximately 1.2 times greater than that of the excurrent siphon. Several irregular tentacles developed inside the distal end of the siphon. The tentacles in the incurrent siphon were approximately twice as long as those in the excurrent siphon. The siphon consisted of six tissue layers, which, from the outside inward, were the siphonal sheath, matrix, outer epithelial layer, connective tissue layer, muscular layer, and inner epithelial layer. The siphonal sheath was composed of an outer cuticle and dense microfilament layer and had vertical ducts. The matrix showed a loose microfilament layer. The outer epithelial layer was simple consisting of ciliated columnar epithelia and secretory cells. There were two types of secretory cells: arenophilic cells and proteinous granular cells. These were all unicellular glands, with cytoplasmic projections developing on the free surface and microstructural features of the cytoplasm showing secretory activity. Histochemical analysis indicated that the secretory granules of the secretory cells, the dense microfilament layer, and the matrix were composed of neutral carboxylated mucopolysaccharides. From these characteristics, it was concluded that the siphonal sheath was formed via the transportation of substances secreted by secretory cells of the outer epithelial layer to the outside through the duct. The hemolymph sinus developed in the connective tissue layer. The muscular layer had alternating longitudinal and circular muscle layers. The inner epithelial layer was simple and consisted of ciliated columnar epithelial cells and secretory cells. Secretory cells are goblet-like cells and contain acidic carboxylated substances. The siphonal sheath was identified starting at approximately 3.5 mm in shell length before the infaunal stage; as it grew, the siphonal sheath thickened, reflecting the infaunal habitat.

Fine structure of Longicollum pagrosomi (Acanthocephala: Pomphorhynchidae) and intestinal histopathology of the red sea bream, Pagrus major, infected with acanthocephalans.

The results described the structure of Longicollum pagrosomi and histopathological characters of the intestine of the red sea bream, Pagrus major, infected with acanthocephalans, using the light and electron microscopes. Among the six samples of P. major, L. pagrosomi was identified in the posterior intestine of five fish samples. Adult L. pagrosomi (total length, 8-27 mm) is divided into the presoma (proboscis, anterior neck, and posterior neck) and metasoma (trunk). The proboscis had vertically arranged hooks (40 µm in length), with ten hooks per row, and the septum was observed between the posterior neck and trunk. The tegument thickness of the proboscis was approximately 15 µm, and it was composed of thin, circular muscle fibers. The outer fibrous membrane was approximately 1 µm, and the connective tissue layer was approximately 35 µm in thickness in the anterior neck. The tegument of the posterior neck enclosed the cephalic ganglion and had longitudinal and vertical muscle fibers, and the tegument thickness was approximately 45 µm. The tegument of the body, which was approximately 1 mm in thickness, was composed primarily of muscle and collagen fibers, and the structure of the tegument was different, depending on the body region. The acanthocephalans had ovaries and oval-shaped eggs with an eggshell (77.5 × 17.1 µm), floating within the body cavity of the trunk. In the infected posterior intestine of P. major, the presoma and the anterior part of the metasoma of L. pagrosomi passed through the intestinal wall and infected the intestinal tissue, perforating the loose connective tissue. In the inflammatory connective tissue, collagen and muscle fibers were fragmented and revealed partial necrosis. Lipid drops and eosinophilic granular cells aggregated in the connective tissue of the tissue capsule. In the vicinity of the acanthocephalan, the mucosal epithelia contained hypertrophied nuclei, and the epithelial layer was collapsed. In an extreme case, the mucosal fold was degenerated because of pressure from the acanthocephalan.

Sex of Mussel Mytilus coruscus (Bivalvia: Mytilidae) : Sequential Hermaphroditism.

Samples were collected from the subtidal region of Jumunjin on the eastern coast of Korea in July 2020. A total of 338 mussels of shell height (SH) 20.8-149.8 mm were used for sex ratio analysis. The sex ratio (F:M) in the same population of mussel Mytilus coruscus was approximately 1:0.7. The sex ratio according to the class of SH was different. The sex reversal pattern of M. coruscus appears to go from male → female → male → female, and as such is determined to be sequential hermaphrodites.

Gonadal Abnormality and Intersexuality of Oplegnathus fasciatus (Teleostei: Oplegnathidae) Collected from the Southern Coast of Korea: A Case Report.

We report on the gonadal structure abnormality and intersexuality found from a survey regarding the reproductive potential of the rock bream, Oplegnathus fasciatus, along the southern coast of Korea. In total, 448 samples were collected for histological analysis (total length 27.5±6.8 cm; total weight 522.9±385.6 g). The sex ratio (F:M) was 1:0.46 (n=307:141), with 68.5% being females. The frequency of oocyte atresia and ovarian neoplasm in the females was 85.3% and 21.5%, respectively, and the frequency of testicular lobule and cyst deformation and testicular neoplasm in the males was 73.1% and 37.6%, respectively. The scale formation in the ovary and testis was approximately 2.0% for both sexes. The intersexuality was 42.2%, with the intersexuality among females being 49.5%, which was significantly higher than that of males (26.2%). Such findings indicate a negative impact on the reproductive output of the rock bream along the southern coast of Korea; however, a more detailed study is required to ascertain accurate causes.

Ovarian transcriptome profiles associated with sexual maturation in Pacific abalone (Haliotis discus hannai).

BACKGROUND: There is now abundant information on genes involved in molluscan oogenesis and their associations with ovarian development. However, few studies have investigated the ovarian transcriptome of Pacific abalone (Haliotis discus hannai). OBJECTIVE: The objective of this study was to identify genes related to ovarian development and maturation in Pacific abalone utilizing RNA-sequencing (RNA-seq) and to verify the genes most relevant to different stages of maturation. METHODS: RNA samples from the ovarian tissues of sexually immature and mature abalone were used to construct cDNA libraries, which were paired-end sequenced on an Illumina HiSeq 2500 platform. Reads from individual samples (unigenes) were aligned to reference transcriptome databases for identification of differentially expressed genes (DEGs) between immature and mature ovarian libraries. Reverse transcription-quantitative polymerase chain reaction was used to verify the RNA-seq data. RESULTS: A total of 8779 unigenes were obtained from the ovaries of immature and mature abalone, with a total length of 3323,279 bp and an average length of 379 bp per gene. Gene ontology analysis assigned 5860 unigenes to biological processes, 855 to cellular components, and 1352 to molecular functions. Overall, 470 DEGs were identified, including 213 and 257 genes down-regulated and up-regulated in mature abalone, respectively. Among these, 13 relevant transcripts, including VTG1 and FZD7, were significantly highly expressed in the ovaries of mature abalone (p < 0.05, fold change > 2). CONCLUSION: This H. discus hannai ovary transcriptome provides molecular targets to better understand ovarian development, oogenesis, and sexual maturation, and to enhance Pacific abalone production.

Prolonged exposure to hypoxia inhibits the growth of Pacific abalone by modulating innate immunity and oxidative status.

In aquatic animals, hypoxia is associated with growth retardation, impaired immunity, susceptibility to pathogens, oxidative stress, and mortality. However, the relative long-term effects of hypoxia on bivalves, including abalone, are not well understood. In this study, we examined the effects of exposure to hypoxic (2.5 and 4 mg O2 L-1) and normoxic (8 mg O2 L-1) conditions on the growth, survival, and immune and antioxidant responses of the economically important Pacific abalone Haliotis discus hannai over a 4 month period. We observed that exposure to 2.5 mg O2 L-1 resulted in marked reductions in assessed shell parameters, average meat weight, and survival compared with exposure to 4 and 8 mg O2 L-1. There were also significant reductions in oxygen consumption and ammonia-N excretion in abalone exposed to 2.5 mg O2 L-1. We also detected initial immunosuppression in the 2.5 mg O2 L-1-treated abalone, as evidenced by a significant reduction in total hemocytes and inhibition of antibacterial and lysozyme activities. Furthermore, intracellular malondialdehyde concentrations were significantly elevated at 1 month in the 2.5 mg O2 L-1 treatment group, whereas there were reductions in the levels of glutathione and enzymatic activities of catalase and superoxide dismutase, thereby indicating potential hypoxia-induced oxidative stress and a depression of antioxidant capacity. After 4 months of treatment, severe hypoxia (2.5 mg O2 L-1) had significantly modulated all measured parameters, whereas exposure to 4 and 8 mg O2 L-1 had induced no significant effects. Collectively, our observations indicate that under long-term exposure to hypoxia, Pacific abalone failed to maintain an effective antioxidant defense system and adequate immunity, with the observed biochemical disruptions leading to a reduction in growth and survival.

Gonadal Maturation and Main Spawning Period of Haliotis gigantea (Gastropoda: Haliotidae).

This study was carried out to obtain information on the developmental biology and the management of biological resources of the abalone Haliotis gigantea in Korea. The sex ratio (female:male) in the present study was 1:1.7 and the proportion of females was 36.6% (n=106/290). Their gonadal structures displayed definitive seasonal changes which were similar in pattern to the changes in the gonad index (GI). The GI showed a pattern of definitive seasonal changes in both males and females it was high in the fall and low in the spring. The reproductive cycle could be categorized into the following six stages: inactive, early active, late active, ripe, spent, and degenerative stage. Based on the monthly changes in GI and stages of gonadal development, October to November was determined to be the main spawning period for H. gigantea on Jeju Island, Korea.

Environmental estrogenic effects and gonadal development in wild goldfish (Carassius auratus).

Serum vitellogenin (VTG) contents of wild goldfish (Carassius auratus) were investigated as a sensitive biomarker for artificial estrogenic compounds in aquatic environments. Goldfish was sampled from a pristine area, a river situated 5 km downstream from a sewage treatment works (STW), and also from the Young-San River in Korea. The female yolk precursor protein VTG was not detected when gonadosomatic index (GSI) was less than 0.85%, while VTG levels of >10 microg/ml were found in males whose GSI was less than 1.53%. In male goldfish sampled from STW and the Young-San River, the higher VTG corresponded to lower GSI. This study suggested a trend that gonad development was connected to VTG levels in both sexes, and the application of GSI and histological analysis provide an attractive possibility that it could be included in the panel of markers used for estrogenic activity investigation of aquatic environments.

Neural Ganglia Transcriptome and Peptidome Associated with Sexual Maturation in Female Pacific Abalone (Haliotis discus hannai).

Genetic information of reproduction and growth is essential for sustainable molluscan fisheries and aquaculture management. However, there is limited knowledge regarding the reproductive activity of the commercially important Pacific abalone Haliotisdiscushannai. We performed de novo transcriptome sequencing of the ganglia in sexually immature and mature female Pacific abalone to better understand the sexual maturation process and the underlying molecular mechanisms. Of the ~305 million high-quality clean reads, 76,684 transcripts were de novo-assembled with an average length of 741 bp, 28.54% of which were annotated and classified according to Gene Ontology terms. There were 256 differentially expressed genes between the immature and mature abalone. Tandem mass spectrometry analysis, as compared to the predicted-peptide database of abalone ganglia transcriptome unigenes, identified 42 neuropeptide precursors, including 29 validated by peptidomic analyses. Label-free quantification revealed differential occurrences of 18 neuropeptide families between immature and mature abalone, including achatin, FMRFamide, crustacean cardioactive peptide, and pedal peptide A and B that were significantly more frequent at the mature stage. These results represent the first significant contribution to both maturation-related transcriptomic and peptidomic resources of the Pacific abalone ganglia and provide insight into the roles of various neuropeptides in reproductive regulation in marine gastropods.