Research of interrenal and chromaffin glands in barfin plaice Liopsetta pinnifasciata from Amursky Bay (Peter the Great Bay,Sea of Japan)

Studies of the barfin plaice Liopsetta pinnifasciata inhabiting Amursky Bay (Peter the Great Bay, Sea of Japan) performed in 1999–2005 showed a twofold reduction in the area of cell nuclei of the interrenal and chromaffin glands after 2001, which indicates a significant weakening of the damaging effect of the environment on fish. It is assumed that one of the main causes of the hypertrophy of both glands in barfin plaices before 2001 was the phenolic pollution of the environment. The study points to the sensitivity of the adrenal system of the barfin plaice to changes in the quality of environment.     

Abnormal oogenesis in barfin plaice <Emphasis Type="Italic">Pleuronectes pinnifasciatus</Emphasis> from the Amursky Bay of the Sea of Japan

Deformed previtellogenic oocytes, oocytes with incomplete cytoplasm vacuolization, and, 2–2.5 month prior to the spawning season, vitellogenic oocytes with sites of homogenized yolk have been revealed during oogenesis of barfin plaice Pleuronectes pinnifasciatus living in the Amursky Bay, one of the most polluted areas in Peter the Great Bay of the Sea of Japan. The early onset of yolk homogenization can point to the forthcoming resorption of oocytes in the plaice during the spawning season. The number of oocytes with such developmental abnormalities varied among females.     

Growth dynamics of the barfin plaice <Emphasis Type="Italic">Liopsetta pinnifasciata</Emphasis> (Pleuronectidae) in Peter the Great Bay (Sea of Japan)

Dynamics of the linear sizes of the barfin plaice Liopsetta pinnifasciata has been considered during the life cycle. Two stages are distinguished: an intensive initial growth (35.9% of the maximum length for 6.0% of the life) and its subsequent gradual variation. The linear growth rate is shown to correspond to the rate of sclerite formation on the scales.     

Asymmetry of the interrenal gland in two flounder species in the spawning period

Significant differences in the area of cell nuclei of the left and right lobes of the interrenal glad have been revealed within the spawning period in two flounder species—the the barfin plaice Liopsetta pinnifasciata and the Korean flounder Glyptocephalus stelleri, which testifies to the different functional activities of these lobes and, accordingly, about the functional asymmetry of the interrenal glad. Individuals with a functionally more active right lobe of the gland prevail for the barfin plaice, whereas with the Korean flounder the number of individuals with a more active left lobe is equal to the number of individuals with a more active right lobe.     

Organochlorine Pesticides in Fishes and Mollusks from Lower Reaches of the Tumen River and of the Contiguous Part of Peter the Great Bay (Sea of Japan)

The content of persistent organochlorine pesticides (DDT and its metabolites, -, - and -isomers of hexachlorocyclohexane, HCH) were studied in the tissues and organs of some fish and molluskan species from the lower reaches of the Tumen River and the contiguous part of Peter the Great Bay (Sivuchya Bay and Zapadnaya Bay of the Furugelm Isl.) and Amursky bay. The highest total content of HCHs (785.60 ng/g of gross mass) was revealed in the digestive gland of the Japanese scallop Mizuhopecten yessoensis from Zapadnaya Bay and in the brain and the liver of the starry flounder Platichthys stellatus from the Tumen River (390.80 and 340.29 ng/g of gross mass). The maximum total content of DDT (270.70 ng/g of gross mass) was recorded in the brain of the dark plaice Pleuronectes obscurus from Zapadnaya Bay and in the liver of the far eastern smooth flounder Pleuronectes pinnifasciatus, caught in Amursky Bay to the west of Skrebtsov Isl. (212.80 ng/g of gross mass). The level of HCHs and DDT in mollusks and flounders from Zapadnaya Bay was higher than that in the same species from Sivuchya Bay. The concentration of organochlorine pesticides (OCP) in P. pinnifasciatus from the inner part of Amursky Bay at Skrebtsov Isl. was higher than in individuals of that species from the open part of the Bay at Peschany Pen. The DDT/DDE and DDT/DDT ratios evidenced the recent entry of DDT into the ecosystem of Peter the Great Bay. The southwest part of Peter the Great Bay, from the mouth of the Tumen River up to Furugelm Isl, was contaminated by HCHs to a greater extent than Amursky Bay. OCPs accumulated in appreciable quantities in the organs of fishes and mollusks of Peter the Great Bay, though their present content does not exceed sanitary–hygienic standards, a subsequent monitoring of their concentrations in biota is necessary.     

Morphofunctional characterization of the reproductive system of the gastropods <Emphasis Type="Italic">Littorina brevicula,L. mandshurica</Emphasis>, and <Emphasis Type="Italic">Nucella heyseana</Emphasis> from uncontaminated and contaminated areas of Peter the Great Bay,Sea of Japan

The structure and state of the reproductive system were studied in the periwinkles Littorina brevicula and L. mandshurica from the coastal area of Vladivostok and in the dogwhelk Nucella heyseana from the protected area of Vostok Bay and from contaminated sites in Amursky Bay. These species were investigated for the presence of imposex and intersex (pathological changes caused by endocrine disruption under the influence of toxic substances). The pathological changes revealed in the gonads of Littorina were oocyte resorption and lipofuscin accumulation; an intersex condition was not found. Imposex specimens (with penis formation) were found among Nucella females from Amursky Bay. The relative penis length in females was 25% of the penis length in males. This kind of pathology was not found in Nucella from clean waters of Vostok Bay.     

Morphology and ecology of the bloom-forming diatom <Emphasis Type="Italic">Chaetoceros contortus</Emphasis> from Peter the Great Bay,Sea of Japan

The morphology of the marine planktonic diatom Chaetoceros contortus Schütt from the Sea of Japan is described using light and electron microscopy. Because of morphological similarity, C. contortus was previously synonymized with the close species C. compressus Lauder by Gran and Yendo [22]. Abundant development of C. contortus was observed in 1997 in Amursky Bay (Sea of Japan). This species reached a maximum density of up to 1.3 × 10⁶ cells/liter near the water surface in mid May 1997 in the period of water-column stratification.     

Pelagic larvae of bivalve mollusks of Amursky Bay,Sea of Japan

Larvae of 63 Bivalvia taxa were found in Amursky Bay. Of these, 47 were identified to the species level. Larvae of 55 taxa were found throughout the bay. The highest species diversity was recorded in the northeastern part and in the center of the southern part of the bay, as well as at the exit from it. Larvae of Mactra chinensis, Mytilus coruscus, Crassostrea gigas, Teredo navalis, Mya japonica, and Mysella ventricosa were widely distributed in the bay. The maximum numbers of species were observed in July and September. A comparison of species lists using the set-theory method showed that the species complexes typical of different parts of Amursky Bay are formed under the influence of the Razdolnaya River runoff flow from the north and marine waters coming from the south. The mean density of larvae during the observation period was 1100 specimens/m³ in the northern and 735 specimens/m³ in the southern part of the bay. The highest density of larvae in Amursky Bay was observed at the end of June, the beginning of July, and in September; the minimal larval density occurred in April, May, and August. While the species diversity was similarly high, the density of larvae was significantly higher in Amursky Bay than in the nearby Ussuriisky Bay.     

Application of the microalga Plagioselmis prolonga for the assessment of water quality in the Amursky and Nakhodka Bays (Sea of Japan)

Based on biotesting, we carried out an estimation of the water quality in the Amursky and Nakhodka Bays (Sea of Japan) using Plagioselmis prolonga (Cryptophyta). The obtained data were compared with the data from water biotesting using Dunaliella salina (Chlorophyta). It was shown that water from the Amursky Bay produced more a negative effect on both microalgae than water from the Nakhodka Bay. It was established that sensitivity of the P. prolonga microalga exceeded that of D. salina. This was confirmed by a sharp decrease of the P. prolonga motile cell number in the studied water.     

Composition of the genus Leptosagitta of the family Sagittidae (Chaetognatha) with descriptions of four new species from coastal waters of the Northwestern Sea of Japan

Keys for the identification of the presently known species of the genus Leptosagitta (fam. Sagittidae) are presented. Four new species of this genus found in shallow waters of Vostok Bay, Amursky Bay (Peter the Great Bay), and Kievka Bay (all of the Sea of Japan) are described in detail: L. kiyashkoi sp. n., L. latyshevi sp. n., L. magna sp. n., and L. pauca sp. n.     

Seasonal and interannual dynamics of larval abundance of <Emphasis Type="Italic">Mytilus coruscus</Emphasis> Gould, 1861 (Bivalvia: Mytilidae) in Amursky Bay (Peter the Great Bay,Sea of Japan)

Based on an analysis of the gonads, as well as the size composition and abundance of larvae in plankton, we determined the seasonal and long-term dynamics of the reproduction of the mussel Mytilus coruscus in Amursky Bay (Peter the Great Bay, Sea of Japan). Mussel gonads were in a mature condition in late July-early August; the spawning season continued from mid-August to mid-September. The larvae of this species occurred in plankton from June to September, under surface water temperatures of 14.5–23.5°C. The density of larvae in different years varied from 350 to 4500 ind/m³. Two peaks of larval abundance were observed annually, in June and September. The first peak was apparently provided by allochthonous larvae, the second, by larvae of the local population. The high density of larvae of M. coruscus in the plankton of Peter the Great Bay enabled us to consider this species as a potential object for mariculture.     

Year-class strength regulation in plaice (Pleuronectes platessa L.) on the Swedish west coast

Year-class strength of plaice (Pleuronectes platessa) has been studied over periods of 10 and 35 years, respectively, in two shallow sandy areas on the Swedish west coast. In one area, Gullmar Bay (N 58 ° 19 – W 11 ° 33), 0-group plaice were sampled quantitatively with a drop trap at 0–0.7 m depth and densities between 0.2 and 3.8 ind./m² were recorded in early summer. In the other area, Laholm Bay (N 56 ° 30 – W 12 ° 55), 0-group plaice were sampled semi-quantitatively in August with young-fish trawl at 1.5 m depths. Densities between 0.001 and 0.28 ind./m² were assessed.The effects of temperature and wind (in the winter and early spring) and predation (in early summer), on the recruitment of 0-group plaice were investigated. In Gullmar Bay high recruitment occurred after severe winters and in years when on-shore winds dominated during spring. No such correlations were found in Laholm Bay. In Gullmar Bay a significant inverse relationship was found between the density of O-group plaice in early summer and the biomass of brown shrimp (Crangon crangon) and the shore crab (Carcinus maenas), the main predators in the nursery area.The importance of physical and biological factors regulating recruitment in plaice are discussed.     

The primary production of Amursky Bay (Sea of Japan) in the summer of 2008

In July 2015, the assimilation number (An) of phytoplankton in Amursky Bay was measured using optical dissolved oxygen sensors (Rinko). The primary production (PP) in the photic layer of Amursky Bay was calculated based on the measured An and chlorophyll vertical profiles obtained during a hydrochemical survey on August 23?28, 2008. The total production in the bay at that period was 840 tC/day. During a phytoplankton bloom, the excess production of biomass leading to the hypoxia of the bottom water was estimated to be approximately (1.0?2.0) × 10³ tC/day.     

Effect of the Meristem on Sporification of Laminaria cichorioides

Isolated disks from vegetative thalli of Laminaria cichorioides Miyabe collected in April in Amursky Bay, Sea of Japan, cultivated separately from meristematic sites, developed sporangial sori after 4–6 weeks of cultivation, i.e., 4 months earlier than in natural conditions. The development of reproductive organs in intact plants, on meristematic sites, and also on vegetative disks, cultivated together with meristematic sites, was not observed. The effect of the meristem on L. cichorioides reproduction is supposed to be conditioned by inhibitors of sporification produced by this tissue. We offer a mechanism of sporification regulation for laminarian algae in natural conditions.     

The distribution of cirripede larvae (Cirripedia: Thoracica) in the Amursky and Ussuriisky bays of the Sea of Japan

Based on data from plankton surveys that were carried out in the waters of the Amursky and Ussuriisky bays of the Sea of Japan from May to October 2007 and 2008, the species composition, time of occurrence, density, and distribution of cirripede larvae (Cirripedia: Thoracica) were studied. The larvae of five species of this group were revealed. Their average density does not exceed 400 ind./m3 and their proportion in the total meroplankton does not exceed 22%. In the summer season, the larvae of Amphibalanus improvisus prevailed and in the autumn season the nauplii of Balanus rostratus prevailed. The number of larvae of barnacles was higher in Amursky Bay, with deep-sea species nauplii being concentrated in its central part and shallow water ones in the northern and central parts, in the zones of costal gyres. In Ussuriisky Bay, the density of larvae of most species decreased seaward from the coast. The abundance of larvae of invasive species A. improvisus show that it has successfully become naturalized in Amursky Bay and is gradually replacing the native species Chthamalus dalli and Balanus crenatus in the lower littoral and upper sublittoral zones.     

Seasonal density dynamics and distribution of brachyuran crab larvae (Decapoda: Brachyura) in Amursky and Ussuriysky bays, Sea of Japan

The species composition, period of occurrence, density, and distribution of brachyuran crab larvae (Decapoda: Brachyura) in the Amursky and Ussuriysky bays (Sea of Japan) were studied in May–October 2007 and 2008. The larvae of this group were not numerous, with peak densities occurring in July at maximum water temperatures. The average brachyuran larvae density was up to 126.9 ind./m³ in Ussuriysky Bay and 68 ind./m³ in Amursky Bay; the contribution of Brachyura to all decapod larvae reached 80–90%. In Amursky Bay, the highest density of brachyuran larvae (up to 584 ind./m³) was observed along the western coast over depths to 20 m; in Ussuriysky Bay, the larval density was highest (up to 1817 ind./m³) in the shallowwater northern part and progressively decreased with depth. Larvae of 18 brachyuran species were found in plankton samples. In Amursky Bay, intertidal crab larvae of the genus Hemigrapsus dominated, Eriocheir japonica larvae were fairly numerous. Larvae of the pea crabs Pinnixa rathbuni and Tritodynamia rathbunae and zoeae of the bigtooth rock crab Glebocarcinus amphioetus were predominant in Ussuriysky Bay.     

0-group flatfish growth conditions on a nursery ground (Bay of Canche, Eastern English Channel)

The settlement and growth conditions of three 0-group flatfish species, sole (Solea solea L.), plaice (Pleuronectes platessa L.) and dab (Limanda limanda L.) in the Bay of Canche, French coast of the Eastern English Channel, were investigated during summer 1997. 0-group dab were the more abundant of the three species (75.4%) followed by plaice (21%) and sole (3.6%). Analyses of fish size distribution indicated that settlement of plaice occurred before sole and dab. Growth of sole was faster than that of plaice, which in turn was faster than that of dab (0.68, 0.43 and 0.33 mm d^?1 respectively). Sole differed from plaice and dab by their larger mean length attained at the end of their first summer stay in the nursery ground. Growth performances of 0-group sole and plaice were analysed by comparing estimated growth in the field with predicted maximum growth according to temperature-growth rate models from experimental studies of growth with unlimited food supply. The data of this study suggest that plaice growth may have been limited during late summer, whereas sole growth does appear to have been determined only by water temperature.     

Development of non-radioisotopic immunoassay systems for measuring flounder IGF-I

A time-resolved fluoroimmunoassay system (TR-FIA) for measuring flounder insulin-like growth factor-I (IGF-I) was developed using biotinylated flounder IGF-I, anti-fish IGF-I antiserum and europium-avidin conjugate. The detection limit per well was <5 pg/well corresponding to <0.5 ng/ml in a basic procedure for sample of 10 microl/well and to <0.08 ng/ml in a procedure modified for high volume samples (up to 70 microl/well). Specificity of the assay was validated using various IGF-Is and insulins. All IGFs except seabream IGF-I showed very low or no crossreactivity. Binding inhibition curves for flounder and seabream IGF-Is were completely identical to each other. Intra- and interassay variations ranged from coefficients of variations of 3.9% to 7.2%. Recovery tests using barfin flounder plasma varied from 82.7 to 101.6% in the added range from 20 to 160 ng/ml. This assay system was applied for measuring total plasma IGF-I in barfin flounder injected porcine growth hormone (GH). A group injected with GH at the dose of 0.05 IU/gBW showed a significant increase of total plasma IGF-I compared with those of albumin-injected (control) and initial groups. In addition, I was able to substitute time-resolved fluorometric detection in this assay system with enzymatic fluorometric detection (FIA). Binding inhibition curve for flounder IGF-I in this substituted assay system showed equal performance with that of the TR-FIA system. Correlation of IGF-I levels between TR-FIA and FIA was high (r(2)=0.957) in plasma samples from barfin flounders in various physiological conditions. Thus, the present study shows precision and efficiency of two non-radioisotopic immunoassay systems for measuring flounder IGF-I.     

Seasonal variations of biotransformation and antioxidant parameters in liver of the smooth flounder <Emphasis Type="Italic">Liopsetta pinnifasciata</Emphasis> from Amursky Bay (Sea of Japan)

This study examines the seasonal dynamics of the activity of some antioxidant enzymes, the biotransformation enzyme glutathione-S-transferase, and levels of reduced glutathione and malondialdehyde in the liver of the flounder Liopsetta pinnifasciata from Amurskii Bay, Sea of Japan. The individual variability of biomarkers was fairly low. Significant sex differences were only found for superoxide dismutase.