Sperm quality in male <Emphasis Type="Italic">Barbus barbus</Emphasis> L. fed different diets during the spawning season

Sperm quality of Barbus barbus L. was compared among the three following dietary regimes: Group A, fed 100% commercial diet (Karpico™ containing 33% crude protein and 6% fat), Group B, fed 78% commercial diet and 22% frozen chironomid (Chironomus plumosus) larvae, and Group C, fed 56% commercial diet and 44% frozen chironomid larvae. Concentrations of polyunsaturated fatty acids (PUFAs) in Group A, B, and C were 39.1, 42.0, and 44.6, respectively, as a percentage of total fatty acids. Sperm morphology, volume, concentration and motility, total number of spermatozoa, and osmolality of the seminal plasma were compared during the spawning season. Dietary regime did not influence sperm volume, concentration, or total number of spermatozoa, osmolality of seminal plasma, or the percentage of motile sperm, but significantly affected sperm morphology (except for anterior and posterior parts of the midpiece) and sperm velocity (P < 0.05). Groups B and C showed similar sperm characteristics during the spawning season compared to Group A. Almost all parameters changed either among or within groups during the spawning season, suggesting differences in terms of the optimal time for sperm collection. The best time for sperm collection was March for Group A, but April for Groups B and C, when the osmolality of the seminal plasma measured 289 mOsmol kg⁻¹ and sperm motility was maximal. Spermatogenesis, hydration, and cell decomposition were confirmed as the three major parameters controlling sperm characteristics during the spawning season. The possible correlation between sperm morphology and motility requires further study.     

Residual plant nutrients in crop residues – an important resource

With increasing demand for sustainable production, the need to effectively utilise site-based resources increases. One such resource is the remaining crop residues, both above and below ground, after harvest. In order to assess the magnitude of this resource, this study determined the plant nutrient contribution of residues from 17 different crops in seven different regions of Slovakia over a nine-year period. The soil profile 0.0–0.3?m was taken into account at belowground residues sampling. The results showed that winter rape, mustard, corn maize, triticale, winter rye with straw and sunflower left the most residues, exceeding 8 tons of dry biomass per hectare. Root crops (sugar beet, potatoes) and peas left less than 3 tons of residual dry biomass per hectare. Using these data, the nutrient potential coefficient, i.e. the amount of nutrients left by production of one ton of the main product was calculated by polynomial regression. With these coefficients and the known yield of a given crop, it was possible to calculate how much nitrogen, phosphorus and potassium each crop leaves in the soil after harvest. It was found that the amount of nitrogen left ranged from 20 to 132?kg, phosphorus from 2 to 24?kg and potassium from 13 to 218?kg per hectare. This has to be taken into account when calculating the fertiliser requirement of the subsequent crop in order to achieve better resource utilisation, thereby reducing the risk of eutrophication and improving farm profits by reducing expenditure on fertiliser.     

Identification of genetic sources with attenuated <Emphasis Type="Italic">Tomato chlorosis virus</Emphasis>-induced symptoms in <Emphasis Type="Italic">Solanum</Emphasis> (section <Emphasis Type="Italic">Lycopersicon</Emphasis>) germplasm

The whitefly-transmitted Tomato chlorosis virus (ToCV) (genus Crinivirus) is associated with yield and quality losses in field and greenhouse-grown tomatoes (Solanum lycopersicum) in South America. Therefore, the search for sources of ToCV resistance/tolerance is a major breeding priority for this region. A germplasm of 33 Solanum (Lycopersicon) accessions (comprising cultivated and wild species) was evaluated for ToCV reaction in multi-year assays conducted under natural and experimental whitefly vector exposure in Uruguay and Brazil. Reaction to ToCV was assessed employing a symptom severity scale and systemic virus infection was evaluated via RT-PCR and/or molecular hybridization assays. A subgroup of accessions was also evaluated for whitefly reaction in two free-choice bioassays carried out in Uruguay (with Trialeurodes vaporariorum) and Brazil (with Bemisia tabaci Middle-East-Asia-Minor1—MEAM1?=?biotype B). The most stable sources of ToCV tolerance were identified in Solanum habrochaites PI 127827 (mild symptoms and low viral titers) and S. lycopersicum ‘LT05’ (mild symptoms but with high viral titers). These two accessions were efficiently colonized by both whitefly species, thus excluding the potential involvement of vector-resistance mechanisms. Other promising breeding sources were Solanum peruvianum (sensu lato) ‘CGO 6711’ (mild symptoms and low virus titers), Solanum chilense LA1967 (mild symptoms, but with high levels of B. tabaci MEAM1 oviposition) and Solanum pennellii LA0716 (intermediate symptoms and low level of B. tabaci MEAM1 oviposition). Additional studies are necessary to elucidate the genetic basis of the tolerance/resistance identified in this set of Solanum (Lycopersicon) accessions.     

Changes in forest soil organic matter quality affected by windstorm and wildfire

Purpose

Windthrows and fires are major natural disturbances in forest ecosystems, which can affect organic matter in the surface and the mineral layer of forest soil. The main aim of this study was to evaluate the changes occurring in the structure and properties of humic acid (HA) in the lands where windthrows and wildfires occurred.

Materials and methods

In November 2004, the forest in the area of 12,000 ha in the Tatra National Park, Slovakia, was seriously damaged by northern wind gusts exceeding 200 km/h. In July 2005, a wildfire broke out in a 220 ha of wind-damaged area. The HAs have been isolated from four research plots: (a) the area where the fallen trees were removed (EXT); (b) an area after windstorm covered by wood from struck trees (NEX), left for spontaneous succession; (c) an area after extracted timber, damaged by the surface wildfire (FIR); and (d) a reference intact spruce forest area (REF). Changes in the chemical structure of the HAs isolated from the research plots were determined on the basis of elemental analysis and UV-Vis, EPR, IR, and ¹³C NMR spectroscopy.

Results and discussion

All used analytical methods showed a decrease in the humification degree of the humic acids extracted from the soils where the spruce forest has been affected by a wildfire and a windthrow. In the case of the control sample HA (REF), the calculated atomic H/C and O/C ratios and the degree of aromaticity (α) calculated from the ¹³C NMR spectra were higher, indicating higher aromaticity of HA from the REF area. The more complex and developed structure of REF HA was confirmed by the higher value of E^1%₆ and the lower E4/E6 ratio obtained using UV-Vis spectroscopy. Also, the higher g-parameters determined from the EPR spectra of the stable radicals present in HA confirmed the lower aromaticity on the plots that have been subjected to the calamities. The ¹³C NMR spectra and the elemental analysis show that the structure of the HA extracted from the NEX plot is the closest to the REF.

Conclusions

The results of the systematic research showed significant changes in the structure of HA taken from spruce forest soils that were subjected to windstorms and fires. An enrichment of the HAs in aliphatic carbon and so a lower humification degree of the organic matter in the areas calamity-affected were observed. The results clearly indicate that the HAs extracted from the disturbed plots of the spruce forest are not as stable as those extracted taken from the control plot.

     

Potentially toxic elements in the riparian soils of the Sava River

Purpose

Riparian zone contamination is a growing problem for several European catchments due to high anthropogenic pressures. This study investigates As, Cd, Cr, Cu, Ni, Pb, and Zn concentrations in the Sava River riparian zone, characterized by wide agricultural areas, various geological substrates, and different types of industrial pollution. The accumulation and mobility of these elements were studied because they are listed as priority substances in the Water Framework Directive and environmental objectives for surface waters.

Materials and methods

Sampling was performed during the sampling campaign of the EU 7th FW-funded GLOBAQUA project in September 2015 during a low-water event. Soil samples were collected along the Sava River at 12 selected sampling sites, from a depth of 0–30 cm, at a distance of 10–15 m from the river bank. The extent of pollution was estimated by determining total and readily soluble element concentrations in the soils. Potential ecological risk and the source of the selected elements in the soils was determined using the enrichment factor (EF), potential ecological risk index (RI), and statistical methods such as the principal component analysis (PCA) and multiple linear regression analysis (MLRA).

Results and discussion

This study showed that concentrations of the selected elements increase along the Sava. In terms of origin, PCA and MLRA indicated that Cr and Ni in soils are predominantly lithogenic, while As, Cd, Pb, and Zn are both lithogenic and anthropogenic (ore deposits, industry, and agriculture). PCA singled out Cu since its origin in soil is most probably from specific point-source pollution. EF was generally minor to moderate for most of the examined elements, apart from Cu, for which the EF was significant at one sampling site. Overall ecological risk (RI) fell within the low-risk category for most sites, apart from Belgrade sampling site (BEO), where high total Cd content affected individual and overall ecological risk indicators, indicating Cd could represent a considerable ecological risk for the downstream riparian zone.

Conclusions

At downstream sites, there was a noticeable increase in PTE content, with Cd, Cr, Ni, and Zn exceeding the proposed threshold values for European soils, indicating rising contamination in riparian soils. In terms of the ecological risk, only Cd could pose a potential ecological threat for the downstream riparian zone.

     

Thermal tolerance of paralarvae of Patagonian red octopus Enteroctopus megalocyathus

Patagonian red octopus, Enteroctopus megalocyathus, is a merobenthic octopus whose paralarvae have been successfully cultured up to juvenile octopuses. At present, high mortality during the paralarval period prevents the scaling from experimental rearing to commercial aquaculture. The aim of the study was to determine upper (CTMax) and lower (CTMin) thermal tolerance, acclimation response ratio (ARR) and thermal tolerance polygon of paralarvae from different culture conditions and subjected to seven acclimation temperatures (6, 8, 10, 12, 14, 16, 18°C) during the first 5 days of paralarval life. Culture conditions were two types of egg incubation (maternal care and artificial incubators) and two feeding regimes (fed or starved). Fed paralarvae showed thermal preferendum, while unfed paralarvae preferred much higher temperatures than those of acclimation. CTMin and CTMax increased along with the acclimation temperature. Lower values of ARR were obtained in paralarvae from artificial incubation, with this type of paralarva showing the least adaptability to thermal changes. Starved paralarvae showed the lowest values for thermal tolerance range (TTR) and smaller areas of thermal polygon than fed paralarvae. Rearing temperatures above 16°C may be considered suboptimal to paralarvae and affected by the conditions during the embryonic incubation. Rearing temperatures below 8°C may be considered suboptimal for all hatched paralarvae. Therefore, the other temperatures within this range could be used in the context of improving the culture management of paralarvae.     

Rapid de-adhesion of northern pike <Emphasis Type="Italic">Esox lucius</Emphasis> eggs using sodium hypochlorite

The elimination of egg stickiness is required for effective artificial reproduction of northern pike, but until now, available methods have required at least 40 min. Sodium hypochlorite was tested under laboratory conditions, and exposure to aqueous concentrations of 0.025–0.05% for 40 s effectively eliminated stickiness without adverse effects. Fertilization and hatching rates in laboratory trials were similar to those observed in eggs treated with traditional methods using clay or milk for 40 or 60 min, respectively, as well as those without treatment. Testing using conventional hatchery incubation techniques did not reveal differences in fertilization rates, while the number of hatched larva was significantly higher in eggs treated with sodium hypochlorite vs. clay. Eggs treated with sodium hypochlorite retained transparency, which facilitated monitoring of embryo development.     

Occurrence and genetic diversity of Blackcurrant reversion virus found on various cultivated and wild Ribes in Latvia

A large‐scale survey was carried out to assess the occurrence, natural host range and genetic diversity of Blackcurrant reversion virus (BRV) in cultivated and wild Ribes in Latvia using RT‐PCR and sequence analyses of 3′ NTR of BRV RNA2. The virus was detected in all surveyed habitats in most of the studied Ribes, except gooseberries, Ribes sanguineum, Ribes laxiflorum and crossbreeds between blackcurrants and gooseberries. The overall occurrence of BRV was 27%, although it varied significantly among the surveyed Ribes habitats, exceeding 40% in home gardens and germplasm collections. Among cultivated Ribes, blackcurrants were the most infected and BRV was detected in all commonly grown cultivars. The virus was detected for the first time in Ribes aureum, Ribes fragrans, Ribes nigrum var. pauciflorum and Ribes fasciculatum var. chinense. The sequence identities of the studied fragments of RNA2 3′ NTR varied from 92.8% to 99.7% among 26 BRV isolates from various cultivated, ornamental and wild hosts from Latvia and from 91.1% to 97.1% when they were compared with 27 corresponding sequences from GenBank. Phylogenetic analyses revealed that the major clustering of isolates was not related to host, origin or symptoms. Grouping of BRV isolates based on host or location was identified within the phylogenetic subclusters. Several well‐supported clades were formed within the subclusters, including a group of BRV isolates from redcurrants that had unique nucleotide substitutions. Five putative recombinants were identified for the first time among BRV isolates from Latvia, Finland, Scotland and the Czech Republic.