The aim of this study was to evaluate the potential use of the harpacticoid copepod
Tisbe spp as prey in
Hippocampus reidi culture together with the effect of natural (14 L/10D) or prolonged ...(24 L/0D) photoperiod. After release, the juveniles were divided into four experimental groups as follows: group A (control group) fed rotifers (
Brachionus plicatilis) followed by
Artemia nauplii subjected to 14 L/10D photoperiod; group B fed a mixed diet of rotifers and
Tisbe spp nauplii followed by a combination of
Artemia nauplii and
Tisbe spp copepodites/copepods subjected to 14 L/10D photoperiod; group C fed rotifers (
B. plicatilis) followed by
Artemia nauplii subjected to 24 L/0D photoperiod and group D fed a mixed diet of rotifers and
Tisbe spp nauplii followed by a combination of
Artemia nauplii and
Tisbe spp copepodites/copepods subjected to constant light. We observed higher survival and better growth performance in juveniles fed a combined diet and subjected to an extended photoperiod respect to those fed a standard diet or exposed to natural photoperiod. In conclusion, we found that the harpacticoid copepod
Tisbe spp may be considered a valuable live prey for
H. reidi culture when used as a supplement to the traditional diet based on rotifers and
Artemia nauplii and that photoperiod may play an important role in the successful culture of this species.
In the present study we demonstrated the efficiency of the Mediterranean calanoid copepod
Centropages typicus as live prey in
Amphiprion clarkii larviculture. After hatching, larvae were divided into ...two experimental groups as follows: group A (control) fed rotifers followed by
Artemia nauplii and group B fed
C. typicus nauplii and copepodites. On day 11 post-hatch, larvae fed
C. typicus showed better survival and growth compared to those fed a standard rotifer/
Artemia diet (90
±
2 vs 43
±
2%; 6.6
±
0.2 vs 6.0
±
0.2 mm; 5.8
±
0.3 vs 4.5
±
0.3 mg, respectively). At a molecular level, a significant increase of insulin-like growth factors I and II (IGF I and IGF II) gene expression and a significant decrease of myostatin (MSTN) gene expression were evidenced in group B larvae fed copepods. Considering these results,
C. typicus may be recommended as a valuable life prey for
A. clarkii larviculture.
•N-N2O emissions were attenuated in soybean rotations with cereals.•Rotations with low C:N ratio of residues returned to soil increased N-N2O emissions.•At sequence scale, N-N2O emissions represented ...0.62% of total N inputs.•IPPC overestimated N-N2O emissions and penalized sequences that included cereals.
Nitrous oxide (N-N2O) emissions in the agricultural sector represent ca. 25% of total N-N2O emissions on a global scale. In Argentina, information on agricultural emissions is scarce, and thus, N-N2O emissions are estimated by IPCC equations. Most reports in Argentina have estimated N-N2O emissions at crop scale, while few studies estimated emissions at the cropping system scale. Soybean in Argentina is mainly planted as monoculture, though, the inclusion of cereals in crop rotations may modify soil properties associated with N-N2O emissions such as water-filled pore space (%WFPS), soil temperature, or nitrate content. The objectives of this work were to: i) compare N-N2O emissions in crop sequences that include soybean in different proportions; ii) evaluate the impact of these emissions in relation with N inputs (fertilizer + BNF) at the cropping sequence level, and iii) compare these observations with emissions as estimated by the IPCC equation (tier 1). During two years, N-N2O emissions, soil N-NO3-, soil WFPS, and soil temperature were measured biweekly in a long-term experiment under no-tillage in four sequences: i) full-season soybean monoculture (S-S); ii) winter cover crop/soybean (CC/S); iii) double-cropped wheat/soybean -- maize (W/S-M), and vi) double-cropped wheat/soybean -- winter cover crop/maize (W/S-CC/M). Aboveground biomass, yield (expressed in glucose equivalents), and nitrogen (N) uptake were determined for each crop at harvest. For soybean, additionally to these variables, N derived from biological N fixation (BNF) was determined, as well. N-N2O emissions were scaled to yield and to vegetative biomass. During the two years of this study, cumulated biomass (expressed in glucose equivalents) was significantly lower in S-S and CC/S (29.5 and 36.8 Mg GluEq ha−1, respectively) than in W/S-M and W/S-CC/M (48.6 and 54.6 Mg GluEq ha−1, respectively). In the same period, exported cumulated N with grains was similar among sequences averaging 277 kg N ha−1, while the largest cumulated N input (N fertilizer + BNF) was 392 kg N ha−1 in W/S-CC/M, surpassing the other sequences by 100%. N-N2O flux rates were the lowest in W/S-M (7.8 μg N-N2O m-2h−1) and the highest in CC/S (19.0 μg N-N2O m-2h−1). Therefore, at the cropping sequence level, N-N2O emissions represented on average 0.62% of cumulated N inputs. A multiple regression model indicated that N-N2O emissions were more related to soil %WFPS (0–20 cm) and soil temperature (at 10 cm). IPCC direct emission equation (tier 1) overestimated N-N2O emissions for W/S-M and W/S-CC-M. In absolute terms, sequences including cereals showed similar cumulated emissions to S-S, however, when emission were scaled to unit yield or vegetative biomass, sequences that included cereals in the rotation attenuated N-N2O losses.
Aims This study aims to (i) asses the contribution of biological N fixation (%Ndfa) in the soybean production area of Argentina, (ii) build a model for predicting %Ndfa using crop, soil, and ...meteorological variables, and (iii) estimate %Ndfa at the country level using values obtained in this study. Methods %Ndfa was assessed in paddocks and experimental plots located in an area 22–39° S and 56–66° W. %Ndfa was determined using the natural 15N abundance method. A complete data set of soil and meteorological variables (n–47) was used to develop a model for predicting %Ndfa. Results A median value of %Ndfa in aboveground biomass of 60 % (interquartile range 46–71 %) was estimated. Larger %Ndfa values were observed in areas with high crops yields. When seed yield was above 3.7 Mg ha−1, effective rainfall during fallow and mean temperature in the seed-filling period explained %Ndfa. Below 3.7 Mg ha−1, soil phosphorus content, pH, and effective rainfall in the vegetative period explicated %Ndfa. Conclusions Soybean production systems in Argentina showed larger %Ndfa than reported values in literature that may affect global N balances. Identified soil and meteorological variables may be useful for predicting %Ndfa in future studies, taking into account their spatial variation in the soil-plant system.
Research highlights ► EDs impair body weight. ► In the hypothalamus several peptidergic hormones and neurotransmitters controlling feeding behaviour are impaired by EDs. ► EDs derange lipid ...metabolism by targeting key metabolic sensors. ► The phthalate DEHP at low doses triggers lipid synthesis and decreases food intake stimulus.
Considering the well‐known problems arising from the use of rotifers and Artemia as live prey in larval rearing in terms of fatty acid deficiencies, the aim of this study was to evaluate a partial or ...complete replacement of traditional live prey with preserved copepods during the larviculture of gilthead sea bream (Sparus aurata). Sea bream larvae were randomly divided into 4 experimental groups in triplicates: group A larvae (control) fed rotifers followed by Artemia nauplii; group B fed a combined diet (50%) of rotifers–Artemia and preserved copepods; group C fed rotifers followed by preserved copepods; and group D fed preserved copepods solely. Survival and biometric data were analysed together with major molecular biomarkers involved in growth, lipid metabolism and appetite. Moreover, fatty acid content of prey and larvae was also analysed. At the end of 40 days treatment, a stress test, on the remaining larvae, was performed to evaluate the effects of different diets on stress response. Data obtained evidenced a positive effect of cofeeding preserved copepods during sea bream larviculture. Higher survival and growth were achieved in group B (fed combined diet) larvae respect to control. In addition, preserved copepods cofeeding was able to positively modulate genes involved in fish growth, lipid metabolism, stress response and appetite regulation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Understanding the drivers of greenhouse gas (GHG) emissions is one of the most critical global environmental challenges to mitigate the increasing global temperature. Nitrous oxide (N
2
O) emissions ...are highly variable in space and time and are controlled by multiple proximal drivers, that is, those that affect N
2
O emissions directly and in short timescales, and distal or indirect drivers that influence emissions over long timescales. Here we present a quantification of N
2
O emissions in grasslands and forests throughout the Pampas and the Semiarid Chaco in Argentina and reveal distal and proximal drivers, analyzing them in both spatial and temporal models. We measured N
2
O emissions, soil and climate variables monthly in nine sites over two years. Mean annual temperature and the following soil properties: phosphorous availability, carbon:nitrogen ratio, clay and sand percentages were the main distal drivers controlling N
2
O emissions in the spatial model, while among proximal drivers, only soil nitrate contents were positively related to N
2
O emissions. When considering the seasonal variability of N
2
O emissions (temporal model), we found that emissions were positively related to proximal drivers, such as soil nitrate and soil temperature. Our results show that soil N
2
O emission drivers differ between spatial and temporal models in natural grasslands and forests, explaining up to 85 and 56% of variations in N
2
O emissions, respectively. Temperature increased N
2
O emissions in both spatial and temporal models; therefore, future global warming may increase background emissions from natural ecosystems with important positive feedbacks on the earth system warming.
Our work provides strong support for the hypothesis that Sinularia flexibilis ingests diatoms such as Thalassiosira pseudonana. We assessed algal ingestion by S. flexibilis through estimates of algal ...removal, histological analyses, scanning electron microscopy observations, and gene expression determination (18S and silicon transporter 1) by real time PCR. Cell counts are strongly suggestive of algal removal by the coral; light and scanning microscopy provide qualitative evidence for the ingestion of T. pseudonana by S. flexibilis, while molecular markers did not prove to be sufficiently selective/specific to give clear results. We thus propose that previous instances of inability of corals to ingest algae are reconsidered using different technical approach, before concluding that coral herbivory is not a general feature.
Copepods are the natural food items for marine fish larvae but are still difficult to be cultured on a continuous basis. Therefore, suitable storage techniques for copepod subitaneous eggs are of ...great interest. Cold‐stored copepod embryos still develop and retain a physiological activity during the cold storage period. As a consequence, their nutritional quality may change over the time of storage with these changes possibly affecting both eggs viability and larval fish survival and development. In this study, the clownfish, Amphiprion polymnus, was used as an experimental model to compare, for the first time, the effects of diets based on enriched rotifers and Artemia (control), Acartia tonsa copepods of a continuous culture and A. tonsa originated from 6 months cold‐stored eggs. The effects of the different diets were tested through morphometric, molecular and biochemical approach. This study demonstrated that after a 6 months cold storage period, the quality of copepods obtained from those eggs was suboptimal for A. polymnus larval rearing. In fact, larvae fed those copepods showed lower growth and survival performances respect to the other experimental groups.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Mediterranean demersal trawl fisheries traditionally operate using small diamond-shape meshes in the codend, which tend to retain almost all animals. We investigated the effect of mesh configuration ...on the size selectivity of nine species (the scaldfish
Arnoglossus laterna, the broad-tail shortfin squid
Illex coindettii, the European hake
Merluccius merluccius, the red mullet
Mullus barbatus, the Norway lobster
Nephrops norvegicus, the common pandora
Pagellus erythrinus, the deepwater rose shrimp
Parapenaeus longirostris, the Mediterranean horse mackerel
Trachurus mediterraneus and the poor-cod
Trisopterus minutus capelanus) commonly captured in the Mediterranean demersal trawls. Two codends having meshes with the same opening (ca. 38
mm) but different mesh configuration (DM38: diamond-mesh and SM38: square-mesh configuration) were fished daily and alternately on the same trawl. They demonstrated a substantial improvement in selectivity with square-mesh. Selectivity was measured using the covered codend technique, the cover being supported by circular hoops.
The results were analysed taking into account the between-haul variation in selectivity. Two other important external variables were identified: the trawling depth and the codend catch, which for some species influenced between-haul variation, but there was no evidence of a coherent effect on selectivity parameters.
The selectivity of 40
mm diamond-mesh codend has been reported to be rather poor because a large proportion of the codend catch is immature and smaller than the minimum landing size (MLS) or first maturity size. With the exception of the flatfish (
A. laterna), the effect of a change of mesh configuration from diamond- to square-mesh on size selectivity positively affected the retention length at 50% (
L
50). However, square-meshes were found to be unsuitable for flat and/or deep-bodied fish as these escape more readily from diamond-meshes.
The Council Regulation (EC) No. 1967/2006, concerning management measures for the sustainable exploitation of fishery resources in the Mediterranean, establishes the MLS of marine organisms. However, the increase in
L
50 with square-mesh would not avoid some of the existing contradictions in allowing the use of codend mesh which leads to lower
L
50 than the MLS.
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