A histological investigation of the occurrence of non-reproductive female bluefin tuna Thunnus thynnus in the Mediterranean Sea

The presence of non-reproductive Atlantic bluefin tuna Thunnus thynnus females in the Mediterranean Sea was investigated through histological analysis of the gonads. Three hundred and twenty-six ovary samples were collected from adults captured at different locations in the Mediterranean Sea during the reproductive seasons between 1998 and 2008. Only three specimens were considered to be in a non-reproductive state: two of them were in a reabsorbing state showing ovaries with early vitellogenic oocytes and extensive α and β atresia of vitellogenic follicles; the third showed gonads with perinucleolar oocytes and was considered to be in a resting state. The low occurrence of non-reproductive individuals found in this study makes it unlikely that non-reproductive individuals aggregate with reproductive ones during their migration towards spawning grounds. Further research is suggested in order to investigate the potential presence of non-reproductive individuals on non-spawning grounds during the reproductive season.     

Histological assessment of White Sea cod <Emphasis Type="Italic">Gadus morhua marisalbi</Emphasis> gonads in the summer of 2011–2013

In this paper the reproductive status of Gadus morhua marisalbi (White Sea cod) was investigated using histological methods. There was a high prevalence in gonad abnormalities. In 90.0% of females nucleoli hypertrophy and oocyte resorption observed, and in 95.0% of males germ cell were characterized by destruction processes. For the first time a case of hermaphroditism was documented in White Sea cod. The prevalence of individuals with bisexual gonads was 3.8% in the histologically examined specimens. Reproductive disorders are not species-specific, and similar gonads anomalies have been observed in other species of fish, especially near sites with high anthropogenic impact.     

On occurrence and biology of Berg wrymouth <Emphasis Type="Italic">Cryptacanthodes bergi</Emphasis> (Cryptacanthodidae) in the north-western part of the Sea of Japan

With consideration of the data obtained in the period from 1981 to 2009, the occurrence of Berg wrymouth Cryptacanthodes bergi is estimated in the north-western part of the Sea of Japan. Almost all captures of wrymouth were made in Peter the Great Bay (only once was it caught in the Northern Primor’e) in a bathymetric range 18–60 m. Captures of Berg wrymouth are confined to aleurite bottom sediments. The size of captured specimens varied from 11 to 29 cm. The ratio of males and females in collections was close to 8: 1. In July–September, the gonads of females were at maturity stages III and IV and gonadosomatic index varied from 3 to 14%; in males, gonads were at stages II–III and III and gonadosomatic index varied from 0.5–2.7%, respectively.     

Biology of the amphioxus,Branchiostoma belcheri in the Ariake Sea,Japan II. Reproduction

We investigated the reproduction of the amphioxus Branchiostoma belcheri in the southern Ariake Sea, Japan, from 1999 to 2002. Gonads were very small or almost absent from September to December and began to develop in January. Changes in the gonad length index indicated that spawning began in mid June, after the gonads had attained maximum size. Although most gametes were extruded during the first spawning, some remained in the gonads. Shrunken gonads were much smaller but contained gametes, and the second spawning occurred around 10 July. It was unclear whether all adults spawned twice, but a large proportion of individuals did. After the first spawning, both males and females lost 30% of their body weight. Most one-year-old individuals did not spawn, and the minimum size at maturity was ca. 20 mm. We found no termination of reproduction among very large individuals. The average number of gonads was significantly larger on the right side of the body (26.2 in males and 26.1 in females) than on the left side (24.0 in males and 23.5 in females). We found two hermaphrodites in a total of 11,184 specimens examined. Each had four or three ovaries among a total of 45 or 54 gonads.     

Filamentous Fungi Associated with Bivalve Mollusks from Polluted Biotopes of Ussuriiskii Bay,Sea of Japan

We have studied for the first time the taxonomic composition of filamentous fungi associated with the bivalve mollusks Crenomytilus grayanus (Bunker, 1853) and Modiolus modiolus (Linnaeus, 1758), collected in polluted biotopes of Ussuriiskii Bay (Peter the Great Bay, Sea of Japan). One hundred fifty-five strains of higher fungi were isolated, and 35 species of filamentous fungi were identified. Out of these, 28 species were anamorphous fungi of the genera Aspergillus (12), Penicillium (10), Acremonium (1), Alternaria (1), Aureobasidium (1), and Cladosporium (3) (Deuteromycota), and 7 were species of the genera Chaetomium (6) and Myxotrichum (1) (Ascomycota). Twenty-four species of filamentous fungi were isolated from the internal organs of C. grayanus: 8 from the muscles, 8 from the hepatopancreas, 6 from the female gonads, 4 from the mantle, 3 from the kidneys and male gonads, and 1 from the gills. Twenty-one species of filamentous fungi were isolated from the internal organs of Modiolus modiolus: 10 from the muscles, 6 from the hepatopancreas, 5 from the female gonads, 3 from the kidneys, 3 from the mantle, and 1 from the gills. The bulk of the isolated species of the genera Aspergillus, Penicillium, Cladosporium, and Chaetomium were pathogenic and toxigenic fungi.     

Social control of sex change in the Red Sea razorfish Xyrichtys pentadactylus (Teleostei,Labridae)

Synopsis The Red Sea razorfish, Xyrichtys pentadactylus, a territorial haremic labrid with dominance hierarchies within the harems. Theory predicts that primary males (fish developing initially as males) should be rare or nonexistent in haremic territorial species because the larger secondary males (males which have undergone sex and/or color change) limit access to females. Histological examination of gonads of 95 specimens showed that all males are derived from females by sex change (i.e. they are secondary males). During five months of field studies 100% of more than 200 observed matings were pair spawnings — the usual mating practice for monandric (having one type of male) species. Sex change in females was induced by male removal in nature. Isolation of four groups of females in aquaria showed that the largest female in the social group changes sex in the absence of a male, demonstrating that sex change is socially-controlled in this species.     

Fungal life in the extremely hypersaline water of the Dead Sea: first records.

The first report, to our knowledge, on the occurrence of filamentous fungi in the hypersaline (340 g salt l-1) Dead Sea is presented. Three species of filamentous fungi from surface water samples of the Dead Sea were isolated: Gymnascella marismortui (Ascomycota), which is described as a new species, Ulocladium chlamydosporum and Penicillium westlingii (Deuteromycota). G. marismortui and U. chlamydosporum grew on media containing up to 50% Dead Sea water. G. marismortui was found to be an obligate halophile growing optimally in the presence of 0.5-2 M NaCl or 10 30% (by volume) of Dead Sea water. Isolated cultures did not grow on agar media without salt, but grew on agar prepared with up to 50% Dead Sea water. This suggests that they may be adapted to life in the extremely stressful hypersaline Dead Sea.     

Hormonal status in different phenotypic forms of Black Sea trout <Emphasis Type="Italic">Salmo trutta labrax</Emphasis>

In three phenotypic forms (parrs, trout form, and kumzha form) of fish-farm Black Sea trout (age 1+) and wild Black Sea trout (age 1+ and 2+), Salmo trutta labrax, inhabiting the basin of the Mzymta River, the content of monoamines (dopamine, noradrenalin, and serotonin) and of their metabolites (3,4-dihydroxyindolacetic acid, 3-methoxy-4-hydroxyphenyl glycol, and 5-hydroxyindolacetic acid) was investigated in brain regions (forebrain, optic tectum, brainstem, hypothalamus, and hypophysis) and the level of cortisol, thyroxin, triiodothyronine, growth hormone, and adrenocorticotropic hormone was investigated in blood. Data on length and weight of fish body and maturation stage of gonads are indicated. The hormonal level differs in the fish of different phenotypic forms. It is the highest in specimens of the kumzha form which completed parr-smolt transformation. Among wild fish, numerous mature females at age 1+ were found which indicated the presence of a dwarf form of the Black Sea trout in the Caucasus in the Mzymta River.     

Fishes of the Bellingshausen Sea and Peter I Island

The unknown benthic ichthyofauna of the Bellingshausen Sea was analysed. Some data concerning the ichthyofauna of Peter I Island were also included. A total of 583 specimens belonging to 32 species were collected mainly by an Agassiz trawl and baited traps set between 86 and 1,947 m depth. A total of 72.2% of the specimens (89.0% of them Nototheniidae) were caught with the Agassiz trawl, whereas 27.8% of the individuals (90.1% of them Zoarcidae) were captured with traps. The Bellingshausen Sea ichthyofauna was dominated by Zoarcidae (43.9% of individuals, 35.8% by weight) and Nototheniidae (43.0 and 15.2%, respectively). Twenty-two of the 23 species captured in the Bellingshausen Sea are reported for the first time from this area. Trematomus scotti was the dominant nototheniid in the Bellingshausen Sea whereas Lepidonotothen larseni was dominant off Peter I Island.     

Survival of Filamentous Fungi in Hypersaline Dead Sea Water

A variety of filamentous fungi have recently been isolated from the Dead Sea (340 g/L total dissolved salts). To assess the extent to which such fungi can survive for prolonged periods in Dead Sea water, we examined the survival of both spores and mycelia in undiluted Dead Sea water and in Dead Sea water diluted to different degrees with distilled water. Mycelia of Aspergillus versicolor and Chaetomium globosum strains isolated from the Dead Sea remained viable for up to 8 weeks in undiluted Dead Sea water. Four Dead Sea isolates (A. versicolor, Eurotium herbariorum, Gymnascella marismortui, and C. globosum) retained their viability in Dead Sea water diluted to 80% during the 12 weeks of the experiment. Mycelia of all species survived for the full term of the experiment in Dead Sea water diluted to 50% and 10% of its original salinity. Comparison of the survival of Dead Sea species and closely related isolates obtained from other locations showed prolonged viability of the strains obtained from the Dead Sea. Spores of isolates obtained from the terrestrial shore of the Dead Sea generally proved less tolerant to suspension in undiluted Dead Sea water than spores of species isolated from the water column. Spores of the species isolated from the control sites had lost their viability in undiluted Dead Sea water within 12 weeks. However, with the exception of Emericella spores, which showed poor survival, a substantial fraction of the spores of Dead Sea fungal isolates remained viable for that period. The difference in survival rate between spores and mycelia of isolates of the same species points to the existence of adapted halotolerant and/or halophilic fungi in the Dead Sea.     

Distribution and some biological features of bottom skate <Emphasis Type="Italic">Bathyraja bergi</Emphasis> in the Russian waters of the Sea of Japan

The spatial and depth-related distribution, the size spectra, and the feeding peculiarities have been studied for the bottom skate Bathyraja bergi in the Russian waters of the Sea of Japan for the trawl catches performed in 1986?2015. The species is found at the depths of 38?577 m at the water temperature of 0.3?3.8°C; during the warm season, the fish keep mainly at the shelf, while they keep at the continental slope in the cold period of the year. This species is found nearly everywhere at the preferred depth range, except a part of the Strait of Tartary. The highest population density has been registered in the southwestern Peter the Great Gulf, along the border with the Korean waters. The schools of the bottom skate of the continental slope and the island shallows do not interact with each other. The specimens reach a body length of 129 cm and a body weight of 13.84 kg. The feeding habits indicate that this species is a predator; decapods (59.9%), cephalopods (23.0%), and fish (15.3%) dominate in the food. In spring, average daily ration constitutes 0.9% of the body weight. In the Russian waters of the Sea of Japan, the bottom skate is a common species, however, it is not abundant; the biomass of the population in this area is approximately 1500 tons.     

Somatic cells serve as a potential propagule bank of <Emphasis Type="Italic">Enteromorpha prolifera</Emphasis> forming a green tide in the Yellow Sea,China

For the last 2 years, vast accumulations of the unattached filamentous green alga, Enteromorpha prolifera, have occurred during summer along the coastal region of the Yellow Sea, China. However, algae do not seem to occur after the end of the fertile season. It has been suggested that banks of microscopic forms of the algae, primarily spores, function as a survival mechanism for this opportunistic alga. Therefore, in this study, field surveys and laboratory cultures were conducted to determine if somatic cells were serving as a propagule bank to enable the algae to survive through periods of unfavorable conditions. Laboratory experiments demonstrated that somatic regeneration was one of the most important approaches by which E. prolifera colonized and flourished in the study area. Indeed, at least 19.32% of somatic cells from the filamentous segments could survive for 2 months under various temperatures (0, 5, 10, 15, 20, and 30°C at an irradiance of 60 μmol photons m⁻² s⁻¹) and irradiances (darkness, 5 10, 15, 20 and 30 μmol photons m⁻² s⁻¹ at a temperature of 20°C). Additionally, greater than 35.85% of the somatic cells could survive at 0°C or in darkness for 2 months, and no less than 15.99% of these cells resumed growth when the temperature and irradiance were adjusted to the normal levels (20°C and 60 μmol photons m⁻² s⁻¹). Furthermore, the results of field surveys revealed that viable E. prolifera was widespread in high quantities in the sediment of the Yellow Sea when the macroalga was absent. Taken together, the results of this study suggest that somatic cells may act as an overwintering stage for the annual spring bloom of E. prolifera. These findings should be useful in future studies conducted to behavior of somatic cells in green tide as well as in the management of future spring blooms of E. prolifera.     

Extant silicoflagellates from the Northeast Aegean (eastern Mediterranean Sea): Morphologies and double skeletons

Silicoflagellate abundance, vertical distribution and morphology were studied during spring (March 2014) at three sampling stations located in the Northeast Aegean Sea adjacent to the Dardanelles Strait and characterized by a variable influx of cold, low-salinity Black Sea water. The silicoflagellate assemblage was dominated by Dictyocha stapedia and Stephanocha speculum with minor contribution of D. aculeata and Octactis pulchra. While specimens of D. stapedia were represented by the typical morphologies described in other areas of the Mediterranean Sea, populations of S. speculum displayed peculiar characters: they were large, predominantly 7-sided, with a small apical ring as well as apical ring spines, concave basal ring sides and non-rotated apical structure. Some of these features have been described for S. speculum at high latitudes, but the combined characters make these specimens slightly different from the high latitude populations. Similar morphologies have been observed in the western Black Sea, thus we can infer that the peculiar specimens detected in the Northeast Aegean are associated with the influx of Black Sea water masses.     

Biochemical composition of the Atlantic bonito Sarda sarda from the Aegean Sea (eastern Mediterranean Sea) in different stages of sexual maturity

The content (% wet mass) in water, ash, lipid, crude protein, DNA and RNA of different tissues was determined during sexual maturation of bonitos Sarda sarda from the Aegean Sea. A total of 220 specimens were collected in the following stages of sexual maturity: immature, resting, developing, mature, spawning and spent. Highest lipid levels in the white muscle, red muscle and liver were measured in immature specimens, while lowest levels were found in spawning bonitos. The gradual percentage of lipid reduction from immature to spawning bonitos was relatively higher in the liver (females 71·2% and males 64·4%) than in the white (females 59·2% and males 53·5%) and red (females 62·1% and males 51·7%) muscle. Lipid levels in the gonads increased gradually from the immature to spawning stage. The decrease of lipid in the somatic tissues was more intense in females than in males, and gonadal lipid content was higher in females than in males. There was a strong reverse correlation between water and lipid percentage in all tissues. Protein content decreased significantly only in spawning bonitos. The percentage of protein reduction from immature to spawning stage was relatively higher in males than in females in both white (females 3·4% and males 4·6%) and red (females 4·6% and males 5·1%) muscles. Protein content in the liver was significantly lower than in the other tissues, being highest in mature females. Gonadal protein content in females increased with maturation and decreased after spawning. The content in ash exhibited considerable stability. The RNA:DNA ratio exhibited a similar pattern of variation in both muscles. The RNA:DNA ratio increased during gonadal development gradually from the developing to spent stage. It was concluded that in S. sarda during gonadal development, there was an increase in gonadal lipid accompanied by a decrease in somatic tissue lipid reserves. Thus, reproductive inactive bonitos have more lipid in their edible part and a higher nutritional value than active ones.     

Utilities of Luminous Bacteria from the Black Sea

Luminous bacteria, isolated from summer specimens of water of the Black Sea, have been identified as strains of Photobacterium phosphoreum and Vibrio fischeri (two of each). Morphological, physiological, and biochemical properties of the four strains have been characterized, and the kinetic behavior of luciferases isolated therefrom has been studied. The sensitivity of the luminescence of the strains to certain toxic agents has been compared to that of the test strain Ph. phosphoreum (Cohn) Ford. The results obtained indicate that the new strains show promise as bioindicators.     

Long-term changes in the phytobenthos of the southern Åland Islands,northern Baltic Sea

Marine macrophytes and -algae have undergone major changes in abundance and species composition over the last decades, primarily due to eutrophication. However, comparable studies conducted in the mid 20th century are rare, but potentially valuable for enabling insight into changes in the benthic communities from the early onset of the eutrophication of the Baltic Sea. In the present study, the submerged phytobenthic community in the exposed southern archipelago of the Åland Islands was examined in 2018 and compared with surveys conducted in 1956 and 1993, respectively. The aim was to analyze long-term changes in the phytobenthic community in relation to the general large-scale anthropogenic drivers since the 1950s. Between 1956 and 1993, a decrease in the total number of species/taxa, an increase of filamentous algae coverage and a decrease in the depth range of Fucus vesiculosus was observed. These changes in the phytobenthic community continued between 1993 and 2018, suggesting no changes in the previously described negative trends. Between 1956 and 2018, a general shift in the distribution of phytobenthic functional groups, (grouped according to morphology and type of algae; green, brown and red) occurred, with increased coverage of filamentous brown and green algae, and decline in red algae coverage. The depth range of F. vesiculosus also decreased by >50% between 1956 and 2018. The results support findings that the eutrophication of the northern Baltic Sea is still at a high level, which slows down or prevents the recovery of offshore phytobenthic communities, despite the progress seen in other areas. Thus, the likely main drivers behind the changes are the direct and indirect effects of eutrophication in combination with warmer water, i.e. an effect of climate change.     

Mycobiota of the giant oyster <Emphasis Type="Italic">Crassostrea gigas</Emphasis> (Thunberg, 1787) (Bivalvia) from the Peter the Great Bay of the Sea of Japan

Mycological investigation of the Pacific (giant) oyster Crassostrea gigas (Thunberg, 1793) (Bivalvia) from the Peter the Great Bay of the Sea of Japan was carried out. The taxonomic composition of filamentous fungi associated with C. gigas was studied. The taxonomic composition of the fungi associated with the giant oyster included 22 species of filamentous fungi of which 17 species were identified. The latter belonged to six genera: Alternaria, Aspergillus, Botrytis, Fusarium, Penicillium, and Trichoderma. The distribution of filamentous fungi in the internal organs of the bivalve mollusk was studied.     

Trace element levels in fish from clean and polluted coastal marine sites in the Mediterranean Sea, Red Sea and North Sea

The bioaccumulation of Hg, Cd, Zn, Cu, Mn and Fe was evaluated in the muscle and liver tissue of four fish species (Siganus rivulatus, Diplodus sargus, Lithognatus mormyrus and Plathychtis flesus) from clean and polluted marine coastal sites in the Red Sea, Mediterranean Sea and North Sea within the framework of the MARS 1 program. Representative liver samples were screened for organic contaminants (DDE, PCBs and PAHs) which exhibited very low concentrations. The levels of Cd, Cu, Zn, Fe and Mn found in the muscle tissue in this study were similar among the four species and within the naturally occurring metal ranges. However, differences were found among the sites. In the Red Sea, Cu was higher in the muscle of S. rivulatus at Ardag and Zn at the Observatory (OBS). Cu, Zn and Mn were higher in the Red Sea than in the specimens from the Mediterranean. The differences were attributed to different diets derived from distinctively different natural environments. D. sargus from Haifa Bay (HB) had higher Cd, Cu and Mn values than specimens from Jaffa (JFA), and L. mormyrus higher Cd, Fe and Mn in HB, corresponding to the polluted environmental status of the Bay. No differences in metal levels were found among the North Sea sites, except for Fe that was lower at the Eider station. Hg was low in all the specimens, but the values varied with species and sites. The lowest Hg values were found in S. rivulatus, the herbivorous species, as expected from its trophic level. Hg in P. flesus was higher than in S. rivulatus but still low. Higher Hg values were found in the muscle tissue of L. mormyrus,with the highest values in D. sargus, both carnivorous species from the same family. Hg in D. sargus was higher in HB than in JFA, as expected, but in the larger specimens of L. mormyrus from JFA values were higher, while in the small specimens there were no differences in Hg values. The levels of all metals were higher in the liver than in the muscle, with enrichment factors ranging from 3 to 104, depending on species and sites. The lowest enrichment values were found for Hg. Based on liver values, the specimens of S. rivulatus from the OBS had the highest levels, as well as D. sargus and L. mormyrus from JFA, contrary to the known relative environmental status of the sites. Received: 25 February 1999 / Received in revised form: 5 June 1999 / Accepted: 7 June 1999     

Reproductive function state of the scallop Mizuhopecten yessoensis Jay from polluted areas of Peter the Great Bay, Sea of Japan

The morphology of gonads and development of offspring of the scallop Mizuhopecten yessoensis sampled from six stations in Peter the Great Bay (Sea of Japan) were studied. The retardation of gametogenesis, oocytes resorption, autolysis of spermatozoa and their phagocytosis were observed in the gonads of the scallops from polluted sites. The number of hermaphrodites was about 6% against 0.3–0.4% in the scallop populations from clean areas. In the offspring development, a decrease in fertilisation success,diminution in percent of normal trochophores, D-veligers, veligers, and retardation of larval growth were recorded. The scallop populations inhabiting polluted areas of Peter the Great Bay seem to be incapable of normal reproduction. Development of offspring was a more sensitive index of disturbance of the reproductive function than morphology of scallop gonads. Analysis of the offspring development of common species of marine invertebrates is suggested to be used as a sensitive indicator of adverse environmental conditions. This revised version was published online in August 2006 with corrections to the Cover Date.