Developmental defects of coronary vasculature in rat embryos administered bis-diamine

BACKGROUND: Conotruncal anomalies are often associated with abnormal coronary arteries. Although bis‐diamine is known to induce conotruncal defects, its pathological effects on coronary vascular development have not been demonstrated. This study sought to assess the teratogenic effects of bis‐diamine on coronary vascular development and the pathogenesis of this anomalous association. METHODS AND RESULTS: A single 200 mg dose of bis‐diamine was administered to pregnant Wistar rats at 10.5 days of gestation. Fifty‐two embryos from 10 mother rats underwent morphological analysis of the coronary arteries. Three embryos each were removed from four mothers on embryonic days (ED) 14.5, 15.5, 16.5, and 17.5 and used for immunohistochemical studies using the anti‐vascular cell adhesion molecule (VCAM)‐1 antibody. Conotruncal anomalies were detected in 48 of 52 embryos, and an aplastic or hypoplastic left coronary artery was found in all of them. In control embryos at ED 16.5, VCAM‐1‐positive epicardial cells were transformed into mesenchymal cells in vascular plexus, which appeared to differentiate into the endothelial cells of coronary vasculature. In the heart at ED 17.5, coronary vasculature was well developed and connected with coronary ostia near the aorta. However, poor epicardial–mesenchymal transformation and subsequent differentiation was revealed in bis‐diamine‐treated embryos at EDs 16.5 and 17.5, causing abnormal development of the coronary vasculature and incomplete connections with coronary ostia of the aorta. CONCLUSIONS: Anomalous coronary arteries in the bis‐diamine‐treated embryos are induced by the disruption of epicardial–mesenchymal transformation and subsequent poor development of coronary vasculature. Incomplete hatching of the coronary ostium is associated with abnormal truncal division. Birth Defects Res (Part B) 92:10–16, 2011. © 2010 Wiley‐Liss, Inc.     

Biomass of pelagic fungi in Baltic rivers

Concentrations of pelagic fungal biomass, determined as the content of ergosterol in particulate matter, were measured in 49 Baltic rivers during summer 1999. The ergosterol concentration varied 12-fold, from 12.6 to 152.5 ng l⁻¹ (average of 56.4 ng l⁻¹) and correlated positively with concentrations of dissolved organic matter and inorganic nutrients as well as with spectral DOM properties indicative of terrestrial sources. The fungal biomass was 12- to 100-fold lower than the biomass of pelagic bacteria, suggesting that fungi in the water column of the rivers probably were of minor importance in the riverine ecosystems at the sampling time. Handling editor: J. Padisak     

Species assemblages of pelagic fish embryos in the southern North Sea between 1984 and 2000

The occurrence and abundance of the pelagic eggs of southern North Sea spring-spawning fish were analysed between 1984 and 2000. Species number varied between six (1986) and 14 (1999) and was positively correlated with sea surface temperature. With one exception, dab eggs were always the most abundant and usually highly dominant. Ranking of species depended on temperature, but no significant differences in ranking between years was discernible. Although with the increase in temperature in the 1990s a change in species assemblage was evident [species belonging to the boreal-Mediterranean (Lusitanian) group became more apparent in the species assemblage] this did not lead to an increased species diversity (Shannon Index) or a change in other community parameters. It appears that the recent developments regarding spawning stock biomass of commercial North Sea fish is reflected in the declining egg abundance of the respective commercial and larger species (i.e. cod, flounder, plaice) and an increase in abundance of the eggs of small species (i.e. long rough dab, rockling) over the years. Received in revised form: 5 November 2001 Electronic Publication     

Does the western Irish Sea gyre influence the distribution of pelagic juvenile fish?

The western Irish Sea is an important spawning and nursery ground for many commercially exploited fish. Spawning begins in the Irish coastal regions in early spring, and moves offshore as the season develops. As a result of the onset of seasonal heating in spring, stratification isolates a dome of cold bottom winter water in the deep (>100 m) basin of the western Irish Sea. The resultant density fields drive a cyclonic gyre which dominates the circulation of the region during late spring and summer and is characterized by anticlockwise current speeds which exceed 0.2 ms^–1, after removal of tides. Surveys of pelagic juvenile (0-group) fish in 1994, 1995 and 1996, showed that they were coincident with the centre of the gyre. Physical data from 1994 and 1995, were used to describe the horizontal and vertical structure of the water column and the associated circulation regime. The behaviour and swimming speeds of pelagic juvenile fish were insufficient to explain their apparent shift in abundance away from the coast to the central western Irish Sea. Drifter and current data suggested that their entrainment into the gyre could provide both the transport and retention mechanisms.     

Sea warming and fish distribution: the case of the small pelagic fish, Sardinella aurita, in the western Mediterranean

This study analyses the temporal and spatial changes in abundance and distribution of the warm water species round sardinella (Sardinella aurita) in the western Mediterranean over the last decades in relation to sea water temperature. In the western Mediterranean basin (1950–2003), a significant positive relationship was found between round sardinella landings and temperature anomalies. Along a latitudinal gradient off the Mediterranean Iberian coast (1989–2004), a gradual increase in species abundance was observed from south to north, with a certain time lag going northwards, associated with the increase in sea water temperature. The abundance of round sardinella in the two warmest and southernmost areas was positively and significantly correlated with sea surface temperature registered during the start of gonad maturation the previous year. In addition, the positive relationship established between water temperature and abundance of round sardinella in the coldest and northernmost study area demonstrates that there is a temperature limit for the distribution of this species in the western Mediterranean. In addition, this study analyses round sardinella larvae distribution and abundance in the summers of 2003 and 2004, and conducts a comparison with the situation 20 years ago (summer 1983). Results show a marked increase in larval abundance during the last decades and the present appearance of larvae in the northernmost study areas, where they did not occur 20 years ago. This indicates the successful reproduction of round sardinella in the northern part of the Mediterranean, where the species has expanded, confirming its establishment in the area.     

Feeding activities of two euryhaline small-sized fish in a western Baltic brackish fjord

The daily food intake and feeding activities of the common gobyPomatoschistus microps (Krøyer) and the nine-spined sticklebackPungitius pungitius (L.) were investigated in the brackish Schlei fjord. At the investigation site of Olpenitz, salinities varied between 11 and 15‰, and water temperatures between 5 and 18°C during the period of in-situ experiments in 1981 and 1982. Common gobies sometimes attained a density of more than 100 individuals per square metre, nine-spined sticklebacks as much as 18 individuals per square meter. Their food changed depending on the supply of plankton or benthos. Regarding numbers, their food consisted mainly of harpacticoids, in springtimes of calanoids; with regard to weight, amphipods, polychaetes or chironomid larvae often prevailed. The total food ingestion, measured by means of its relation to fish weights (fullness index), was highest in spring and summer: 2.3% inP. microps and 2.6% inP. pungitius. Low fullness indices of 0.8% inP. microps and 0.3% inP. pungitius were found during times of low water temperatures. 24-h field investigations revealed that the adultP. microps presented clear diurnal rhythms with highest fullness indices after dawn and a further maximum at dusk. Only young gobies ingested some benthos at night.P. pungitius displayed similar rhythms in which maximum fullness indices varied during the day. This species seems to forage every four hours. At dusk, both species preferred benthos to plankton. The results are discussed with respect to the implications of diurnal and seasonal fluctuations in prey choice by small-sized fish populations.     

Influence of solar ultraviolet-B on pelagic fish embryos: osmolality, mortality and viable hatch

Eggs of dab (Limanda limanda) and plaice (Pleuronectes platessa) were experimentally exposed to ultraviolet-B (UV-B) radiation in a solar radiation simulator. The experimental design tried to simulate present and future conditions with reference to increased UV-B exposure due to northern hemisphere ozone loss, employing mainly two scenarios, a reduction to 270 (S1) and to 180 (S2) Dobson units (DU) in single or repetitive exposures of 2, 4 or 6 h. Depending on the total dose of UV-B irradiation and the developmental stage, exposed eggs displayed loss of buoyancy as a sublethal effect, as well as increased embryo mortality and reduced viable hatch. In the single exposure experiments only under conditions of 180 DU for 6 h were effects apparent. Double exposure under conditions of 270 DU did not lead to lasting effects. At the sublethal effect level, i.e. loss of buoyancy, considerable photorepair was observed. It was concluded, that under the present general weather conditions in spring and at the present levels of environmental ozone, allowing for a reduction to 180 DU, the embryonic development of North Sea spring spawning fish is not endangered by UV-B radiation. Received in revised form: 19 June 2000 Electronic Publication     

Partial diel vertical migrations in pelagic fish

1. Field studies on diel vertical migration (DVM) usually report uniform behaviour with population-wide ascents and descents during crepuscular periods. This contrasts partial seasonal migrations of many animal populations, where individuals choose either the resident or the migrant strategy depending on population density, feeding opportunity and predation risk in the resident and migrant habitats. 2. We tested whether DVM of freshwater zooplanktivorous fish (Coregonus spp.) resembles partial migrations. Twenty-eight hydroacoustic surveys were performed in the deep Lake Stechlin (Germany) between 2000 and 2010, with samplings encompassing all months between March and December. Zooplankton samples were simultaneously taken in epilimnetic and hypolimnetic layers. Fish obtained from depth-stratified samplings by a midwater trawl were used to test for individual differences between residents and migrants. 3. We show for the first time that DVMs of freshwater fish resemble patterns of partial migrations often found in seasonal environments. Across all samplings, 7-33% of fish did not ascend at dusk, but exhibited the resident strategy. The proportion or residents increased at low zooplankton feeding rates in the daytime habitat and during months when the temperature difference between daytime and night-time habitats was minor. 4. Slightly larger size and higher caloric density of migrants over residents in one of the coexisting Coregonus species suggested that individual differences contributed to the migration strategy performed. However, these results were based on one sample only, and extrapolation to the entire data set is not possible. 5. Our results are indirect evidence that the balance between migrants and residents may primarily depend on the trade-off between feeding gains and metabolic and predation costs of migration. However, the results also suggest that the global fitness consequences for the resident and migrant strategies may not be identical, rendering the importance of individual traits in the 'decision to migrate' likely.     

Small fish use the hypoxic pelagic zone as a refuge from predators

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First observation of microcystin-LR in pelagic cyanobacterial blooms in the northern Baltic Sea

Cyanobacterial bloom samples from the Gulf of Finland (northern Baltic Sea) were collected in July 2003 and analyzed for microcystins and nodularins, cyanobacterial peptide hepatotoxins, by ELISA, HPLC-UV and LC-MS. The blooms consisted mainly of the genera Nodularia, Anabaena and Aphanizomenon. The main hepatotoxin in the samples was nodularin-R (Nod-R), all the samples also contained demethylnodularin-R. The presence of microcystin-LR was confirmed in three locations out of nine by multiple reactant monitoring on the triple quadrupole mass spectrometer. This is the first reported finding of microcystins in the Baltic Sea from the open sea area. Anabaena was the likely producer of microcystin-LR in the samples.     

Feeding ecology of pelagic fish species in the Gulf of Riga (Baltic Sea): the importance of changes in the zooplankton community

The feeding ecology of four pelagic fish species was studied in relation to their prey availability in the Gulf of Riga (Baltic Sea) during the summer 1999-2006. The zooplankton community was dominated by the cladoceran Bosmina longispina, rotifers Keratella cochlearis and K. quadrata and the copepod Eurytemora affinis, with the highest interannual variability in abundance recorded for B. longispina. The last influenced the diet of adult sprat Sprattus sprattus, juvenile smelt Osmerus eperlanus and three-spined stickleback Gasterosteus aculeatus as these were strongly selecting for B. longispina. The fish feeding activity did not match the abundance dynamics of their preferred prey, suggesting that fishes may switch to consume other prey in case the preferred diet was limited. A considerable dietary overlap indicated high potential competition between pelagic fish species. While herring Clupea harengus membras and G. aculeatus were relying on very different food, the diets of young O. eperlanus and G. aculeatus were very similar. Interannual variability in zooplankton composition and abundance significantly affected the diet composition of fishes, but those changes were insufficient to exert a consistent influence upon fish feeding activity and total amounts of zooplankton consumed.     

Uranium and thorium in muscle tissue of fish taken from the southern Baltic

The determination of U and Th was carried out on pooled samples of muscle tissue of cod (Gadus morhua), herring (Clupea harengus), sprat (Sprattus sprattus) and some other species of fish caught in 1981 in the southern Baltic. The levels of U obtained in the present study are generally within the ranges presented by other authors for fish from different aquatic regions of the world. The concentrations of U are similar to those found for Th in Baltic fish analysed. The concentration factors CF_U(Th), discrimination factors DF_U/Th and Th/U ratios (by weight) were calculated and discussed. These coefficients were also compared with values determined in other Baltic organisms. Transfer of U and Th along a food chain from potential prey (diet) to fish as predator (consumer) was quantified with a transfer factor.     

Eggs of pelagic fish from the Sargasso Sea with special reference to Anguilliformes

Pelagic fish eggs from IKMT hauls, taken during the 1979 Sargasso Sea Expedition, were sorted and classified according to structural aspects. 13 types were distinguished, one of them classified as exocoetid, two of them as anguilliform. One of the anguilliform egg types could be determined as belonging toDerichthys serpentinus.     

Developmental defects resulting from arginine auxotrophy in Aspergillus nidulans

A mutant of Aspergillus nidulans, isolated for inability to form asexual spores (conidia) on complete medium, was found to regain the ability to conidiate if the medium was supplemented with arginine. On minimal medium the mutant required arginine for growth but at a much lower concentration than that required for conidiation. This mutant, designated argB12, thus defines a phase-critical gene, i.e. a gene whose function is in greater demand for development than for growth. In addition to its aconidial phenotype, the mutant also exhibited (depending on the medium) aberrant sexual development and a low efficiency of conidial germination. In crosses, each of these developmental phenotypes segregated with arginine auxotrophy. Genetic and biochemical analyses showed the argB12 mutation to be an allele of the previously described argB locus, mutants of which lack ornithine transcarbamylase. Arginine-requiring mutants at at least two other loci were also found to be defective in asexual sporulation, but the germination defect appears to be specific to argB mutants.     

Evolution of cannibalism in the larval stage of pelagic fish

Larvae of several ocean pelagic fish species, such as tunas and marlins, have been known to have large jaws, but the ecological significance of this unique morphological character has been hardly analyzed in evolutionary ecology. Pelagic spawners produce small and nutrition-poor ova, and spawning and nursery grounds of the open ocean migratory fishes are oligotrophic. We hypothesize that cannibalism would be a possible life style in the larval period and the large mouth gape would be an adaptive morphological characteristic for a cannibal in the oligotrophic pelagic environment. We showed that mouth gape size of the open ocean pelagic fish is significantly larger than that of offshore/coastal pelagic fish in larval period. A mathematical model demonstrated that cannibalism would tend to evolve in high sea environment. Our findings suggest an evolutionary pattern of cannibalism trait in the larval stage of pelagic fishes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Developmental potential of isolated blastomeres from early murine embryos

Experiments were designed to evaluate the effect of blastomere separation on blastocoele formation and development of viable fetuses. Two-cell and four-cell murine embryos were dissociated into individual blastomeres and cultured to the blastocyst stage. For embryos of both stages, zona removal and blastomere separation reduced (P<0.05) the number of viable embryos at the onset of culture and reduced (P<0.01) the frequency of continuation of development of blastomeres to the blastocyst stage. Attempts to repeatedly split two-cell stage embryos decreased in vitro development to blastocysts. The number of cells in two-cell embryos that were cultured to blastocyst was not different for control (64.8 +/- 11.5) or for two-cell embryos cultured without the zona pellucida (60.9 +/- 10.1) but was reduced (P<0.01) for one-half embryos that were cultured to blastocysts (35.6 +/- 10.6). The cell number of blastocysts obtained from dissociated four-cell (1/4) embryos (17.4 +/- 1.4) was similarly reduced (P<0.01). In vivo development was assessed after cultured embryos were transferred to the uteri of day 3 pseudopregnant females. Zona free intact embryos (2/36, 6%) and zona free half embryos (7/36; 19%) developed less frequently (P<0.05) than intact controls (45/100). Noncultured morula briefly exposed to pronase to thin the zona had similar impaired development. Embryos with thinned zona or no zona developed less frequently (21/82, 2/72 respectively, P<0.05) than nonpronase-treated controls (50/83).     

Regeneration of plantlets from mature embryos of western larch

Summary Larix occidentalis Nutt. can be micropropagated using whole excised mature embryos. The basal medium for induction (over 70% response) was half-strength Quoirin and LePoivre salts with Schenk and Hildebrandt organics and N⁶-benzyladenine singly or with kinetin at a final concentration of 10μM. Bud elongation was best on half-strength Schenk and Hildebrandt or Bornman’s mineral salts, and elongated shoots could be maintained on either half-strength Quoirin and LePoivre or Schenk and Hildebrandt formulations containing 0.05% activated charcoal, 2% sucrose, and 0.7% agar. Axillary buds developed naturally on elongating juvenile shoots, but a high sucrose treatment (6%) for 2 wk enhanced the number produced. Very good rooting (80 to 100%) was obtained by pulsing shoots for 2 to 3 h in a solution of indole butyric acid (1 mM, pH 4.5–5.0), or by planting shoots in peat-vermiculite moistened with basal medium containing 5μM α-naphthalene acetic acid, pH 5.0. Rooted shoots were hardened before transfer to the greenhouse, and initially were kept at low light and high humidity after transfer to ex vitro conditions. This research was supported initially by a National Research Council of Canada, Division of Energy Contract, and subsequently by a Natural Sciences and Engineering Research Council of Canada strategic grant to T. A. Thorpe.     

Feeding habits and gill raker morphology of three planktivorous pelagic fish species off the coast of northern and western Kyushu in summer

Feeding habits and gill raker morphology were examined for the three major planktivorous pelagic fishes, Japanese anchovy Engraulis japonicus , Pacific round herring Etrumeus teres and Japanese jack mackerel Trachurus japonicus , off the northern and western coasts of Kyushu, in the north‐eastern part of the East China Sea in the summer months of 2001. Using fishes in the same size range (80–140 mm, standard length), the stomach contents of the three fish species were compared. The diet of the Japanese anchovy mainly consisted of Oncaeidae copepods, while the diets of the Pacific round herring and Japanese jack mackerel were dominated by calanoid copepods at all stations. Comparisons between prey size in the stomach, zooplankton size in the water and gill raker morphology suggested that the stomach contents of the three species were characterized mainly by the difference in the feeding behaviour between Japanese anchovy (filter‐feeding) and the other two species (particulate‐feeding), rather than by the difference in the morphology of feeding apparatus only. It was concluded that behavioural adaptations in the feeding of these pelagic fishes brought about trophic partitioning to some degree in this pelagic ecosystem in summer. Although the diets of these three species overlapped to some extent, there was still little likelihood of competition between the Japanese anchovy and the other two species. The potential for competition between the Pacific round herring and the Japanese jack mackerel is discussed.     

Structuring of the cyanobacterial community by pelagic fish in subtropical reservoirs: experimental evidence from Australia

1. Subtropical reservoirs of Australia are commonly subject to summer blooms of cyanobacteria. The potential for food web manipulation to control cyanobacterial blooms was investigated in Lake Maroon, south east Queensland using enclosures in which the density of the Australian gudgeon Hypseleotris spp. was manipulated. 2. Zooplankton biomass and community structure were strongly affected by fish density. A size dependent predation effect of Hypseleotris on zooplankton was observed at ambient fish densities, and the community shifted towards a dominance of copepod juveniles and nauplii. Substantial increases in the populations of Ceriodaphnia and calanoid copepods were observed at low fish densities and in the absence of fish. 3. At ambient fish densities total phytoplankton and the proportion of cyanobacteria were maintained at levels similar to those prevailing at day 0. Total phytoplankton and the proportion of cyanobacteria decreased substantially at low fish densities and in the absence of fish. Chlorophytes became dominant in the ‘no fish’ treatment and the grazing‐resistant species Oocystis and Dictyosphaerium were significantly higher than at ambient fish densities. 4. The experiment demonstrated a strong positive relationship between Hypseleotris density and cyanobacteria, and the results suggest that subtropical reservoirs may be suited to food web manipulation as a means of controlling summer cyanobacterial blooms.