Genetic Inactivation of European Sea Bass (Dicentrarchus labrax L.) Eggs Using UV-Irradiation: Observations and Perspectives

Androgenesis is a form of uniparental reproduction leading to progenies inheriting only the paternal set of chromosomes. It has been achieved with variable success in a number of freshwater species and can be attained by artificial fertilization of genetically inactivated eggs following exposure to gamma (γ), X-ray or UV irradiation (haploid androgenesis) and by restoration of diploidy by suppression of mitosis using a pressure or thermal shock. The conditions for the genetic inactivation of the maternal genome in the European sea bass (Dicentrarchus labrax L.) were explored using different combinations of UV irradiation levels and durations. UV treatments significantly affected embryo survival and generated a wide range of developmental abnormalities. Despite the wide range of UV doses tested (from 7.2 to 720 mJ.cm⁻²), only one dose (60 mJ.cm⁻².min⁻¹ with 1 min irradiation) resulted in a small percentage (14%) of haploid larvae at hatching in the initial trials as verified by flow cytometry. Microsatellite marker analyses of three further batches of larvae produced by using this UV treatment showed a majority of larvae with variable levels of paternal and maternal contributions and only one larva displaying pure paternal inheritance. The results are discussed also in the context of an assessment of the UV-absorbance characteristics of egg extracts in this species that revealed the presence of gadusol, a compound structurally related to mycosporine-like amino acids (MAAs) with known UV-screening properties.     

Construction and characterization of a bovine BAC library with four genome-equivalent coverage

A bovine artificial chromosome (BAC) library of 105 984 clones has been constructed in the vector pBeloBAC11 and organized in 3-dimension pools and high density membranes for screening by PCR and hybridization. The average insert size, determined after analysis of 388 clones, was estimated at 120 kb corresponding to a four genome coverage. Given the fact that a male was used to construct the library, the probability of finding any given autosomal and X or Y locus is respectively 0.98 and 0.86. The library was screened for 164 microsatellite markers and an average of 3.9 superpools was positive for each PCR system. None of the 50 or so BAC clones analysed by FISH was chimeric. This BAC library increases the international genome coverage for cattle to around 28 genome equivalents and extends the coverage of the ruminant genomes available at the Inra resource center to 15 genome equivalents.     

The use of a Visual Implant tag to monitor the reproductive performance of individual milkfish Chanos chanos Forsskal

Nine-year old milkfish (3.8 kg, average body weight) were individually marked with Visible Implant (VI), tas to monitor their reproductive performance following hormonal induction. All tags were retainei after one year; only 5 out of 64 tags were not readable due to improper implantation. The advantages of using VI tags include: less taging time (less than one minute), high retention rate, longer retention, infection-free, and easily readabfe.

Zusammenfassung

Nutzung visueller Implantate zur individuellen Verfolgung der Fortpflanzungsleistung bei Milchfischen Chanos chanos Forsskal
Neun Jahre alte Milchfische (durchschnittliches Körpergewicht 3,8 kg) wurden individuell mit visuellen Implantaten (VI) markiert, um die Reproduktionsleistung nach Hormoninduktion zu verfolgen. Alle Marken waren noch nach einem Jahr in den Fischen vorhanden. Lediglich 5 von 64 Markierungen konnten aufgrund unkorrekter Implantation nicht gelesen werden. Die Vorteile der Nutzung von VI-Markierungen liegen in der kurzen Handhabungszeit (unter 1 min.), hohen Retentionszeit der Marken, infektionsfreien Methodik und der leichten Lesbarkeit.     

New 4-aryl-1,3,2-oxathiazolylium-5-olates: Chemical synthesis and photochemical stability of a novel series of S-nitrosothiols

S-nitrosothiols (RSNOs) remain one of the most popular classes of NO-donating compounds due to their ability to release nitric oxide (NO) under non-enzymatic means whilst producing an inert disulphide by-product. However, alligning these compounds to the different biological fields of NO research has proved to be problematic due to the inherent instability of such compounds under a variety of conditions including heat, light and the presence of copper ions. 1,3,2-Oxathiazolylium-5-olates (OZOs) represent an interesting subclass of S-nitrosothiols that lock the –SNO moiety into a five membered heterocyclic ring in an attempt to improve the compound’s overall stability. The synthesis of a novel series of halogen-containing OZOs was comprehensively studied resulting in a seven-step route and overall yields ranging between 21 and 37%. The photochemical stability of these compounds was assessed to determine if S-nitrosothiols locked within these mesoionic ring systems can offer greater stability and thereby release NO in a more controllable fashion than their non-cyclic counterparts.     

Dynamics of understory vegetation in an old-growth boreal coniferous forest, 1988–1993

Abstract. Understorey vegetation changes in a South Norwegian old-growth coniferous forest were studied between 1988 and 1993 in 200 1-m² vegetation plots. Our aims were to quantify the amount of between-year compositional change, and to elaborate the environmental basis for long-term vegetation change, including the previously identified gradient structure with a major gradient related to topography (and soil nutrient status and soil depth) and a minor gradient reflecting paludification and canopy coverage. Species richness (yearly mean and cumulative species number) and change in species richness differed between vascular plants and cryptogams, and between forest types. The number of vascular plant species decreased in pine forest in dry years; bryophyte species number increased in spruce forest. Statistically significant vegetation change, as tested by constrained ordination (CCA) with time as the constraining variable, is demonstrated for most one-year periods and for the five-year period in most forest types. Vegetation change along identified gradients, measured as plot displacement along DCA ordination axes, also occurred. The magnitude of year-to-year vegetation change was related neither to forest type nor to one-year period; different responses to climatic and environmental change were observed in each forest type. The largest average displacement observed, from medium-rich spruce forest towards poor spruce forest, was interpreted as a long-term trend. Humus-layer pH decreased by ca. 0.25 units from 1988 to 1993, most strongly in medium-rich spruce forest where exchangeable Ca decreased and Al and Mn increased strongly. Our study supports the hypothesis that vascular plants show a long-term and broad-scale response to soil acidification. Change in bryophyte composition is linked to some very long growing-seasons. Detailed analysis of short-term vegetation dynamics enhances the interpretation of long-term changes and stresses the complementarity of univariate and multivariate methods in the analysis of vegetation change.     

Vertical distributions of primary production and grazing by Calanus glacialis jaschnov and C. hyperboreus krøyer in Arctic waters (Barents Sea)

Summary Simultaneous measurements of phytoplankton primary production, and zooplankton grazing by Calanus glacialis and C. hyperboreus were carried out over a 24h period at two stations northeast of Spitzbergen in July and August 1985. Phytoplankton biomass was concentrated in a sub-surface maximum, and our results suggested that 65% to 90% of the carbon produced was grazed by these copepods. At both stations maximum grazing rates by these zooplankton were observed within and below the depth of maximum primary production. At least one third of regenerated primary production could be sustained by ammonia excreted by the large zooplankton species Calanus glacialis and C. hyperboreus.     

Data manipulation and gradient length estimation in DCA ordination

Abstract. The effects of different kinds of data manipulation on gradient length estimation by non-linear rescal-ing (as in DCA ordination) are evaluated by considering the first axis inDCA ordinations of 11 field data sets from four investigations. Gradient length estimates are dependent on the range of the abundance scale; the more the scale favours the quantitative aspect (abundance) of the data over the qualitative aspect (presence), the longer the DCA axes. The gradient length estimate decreases when infrequent species are deleted. A new formula is proposed to replace the option for downweighting of rare species in DCA, as the option presently available has some undesirable properties. Some implications for interpretation of gradient length estimates by non-linear rescaling in general (and in DCA in particular) and for comparison of gradient length estimates between studies, are discussed. The potential of non-linear rescaling of gradients for estimation of β diversity is emphasized.