Effects of biofloc technology on reproduction and ovarian recrudescence in Nile tilapia

The objectives of this study were to evaluate the reproductive cycle, morphological changes of ovary and mobilization of energy reserves in Nile tilapia reared with biofloc technology (BFT). In general, the growth and reproductive performance were highly similar between BFT and Control system (clear water). Difference between the systems was found in the hepatosomatic index (using mixed‐effects models), which suggested that BFT can alter the energy mobilization in the post‐spawning period. The absolute and relative fecundity, fertilization rate, number of larvae produced per female, gonadosomatic index, proportion of oogenesis cells, number of post‐ovulatory and atretic follicles were similar between the two systems. We also did not detect a reduction in the reproductive cycle length in Nile tilapia reared in BFT. Because there was no evidence of the negative effects of BFT on Nile tilapia reproduction, we concluded that BFT might be used for breeder stocking of this species.     

Associations between morphometric variables and weight and yields carcass in Pirapitinga Piaractus brachypomus

The objective of this work was to evaluate the association between morphometric variables and carcass characteristics in Pirapitinga. We used a thousand specimens of Pirapitinga with an average weight of 1,200 g, which were stunned, slaughtered, weighed, measured, and processed for morphometric and processing yield analysis, to obtain weights, carcass and fillet yields. Initially, the linearity of the variables was verified. Pearson's simple and partial correlation tests were performed between all metrics. Track analysis was performed considering the weights and yields of carcass and filet as dependent variables and the others as independent variables. Ridge regression models were used to eliminate the effects of multicollinearity among the independent variables. Observations showed that the simple correlations between body weights and yields were superior to the partial ones in terms of magnitude. The length and circumference of the specimens were the measures most linearly associated with weight, carcass weight and fillet with rib weight. As for carcass yield and fillet yield, linear correlation coefficients were low and not significant when associated with body weights. With the path analysis, we could observe significant positive correlations between the morphometric measurements for weight, carcass weight and fillet with rib weight. The standard length, body circumference and body circumference/body height ratio are the most correlated. The latter are the most important variables in the evaluation of body weights in Pirapitinga fish. They can serve as criteria for indirect selection in searching for fish with better carcass characteristics. As for fillet and carcass yields, the morphometric variables have not shown to be efficient for indirect selection.     

Application of morphometric measures in estimation of body weight and discrimination of Astyanax lacustris and Astyanax fasciatus

The objective of this study was to verify the direct and indirect correlation between morphometric measures, ratios, body weight and yield in two lambari species Astyanax lacustris and Astyanax fasciatus and whether the discriminant analysis is capable of separating and allocating the species. We used 102 lambari yellow tail and 60 lambari red tail. The fish were weighed and submitted to the evaluation of the morphometric measurements. The direct and indirect effects were evaluated by the method of track analysis, considering weight at slaughter, weight of body parts and body yields as dependent variables and measures and morphometric ratios as explanatory variables. Astyanax lacustris presented higher height and body width, carcass yield and trunk, while A. fasciatus presented higher head yield and viscera weight. The discriminant analysis was able to classify 79.5% of the two species. Track analysis demonstrated that the morphometric measurements can be used for estimation of body and body components’ weight in A. lacustris and A. fasciatus. However, regarding the corporal yield; the morphometric measures were insufficient to explain the yield variations of the species.     

Living on the edge: morphological and behavioral adaptations to a marginal high-elevation habitat in an arboreal mammal

Habitats are characterized by different local environmental conditions that influence both behavior and morphology of species, which can result in habitat-dependent phenotypic differences among animals living in heterogeneous environments. We studied 3 alpine populations of Eurasian red squirrels (Sciurus vulgaris), 1 living in a marginal high-elevation habitat at the edge of the species’ altitudinal distribution, and 2 occurring in higher-quality habitats. Here, we investigated whether squirrels living in the marginal area differed in 2 morphological parameters (body size and body mass) and/or in the expression of 4 personality traits estimated with an open field test and a mirror image stimulation test (activity, exploration, activity-exploration, and social tendency). Furthermore, we tested whether within-individual variance of the traits (behavioral plasticity) was higher in the edge habitat. Male squirrels in the edge habitat were smaller and weighed less than in the other study areas, while among females, size–habitat relationships were less marked. These sex-specific patterns were explained by a strong association between body mass and reproductive success in female squirrels. Squirrels in the marginal habitat were more active, explorative, and had a more social personality than in the other habitats. However, in contrast to our predictions, behavioral plasticity was smaller in the marginal habitat, but only for the trait exploration. Our results suggest that animals choose the habitat that best fits their personality, and that habitat-related differences in selective pressures may shape animals’ morphology.     

Target and non-target site mechanisms of fungicide resistance and their implications for the management of crop pathogens

Fungicides are indispensable for high-quality crops, but the rapid emergence and evolution of fungicide resistance have become the most important issues in modern agriculture. Hence, the sustainability and profitability of agricultural production have been challenged due to the limited number of fungicide chemical classes. Resistance to site-specific fungicides has principally been linked to target and non-target site mechanisms. These mechanisms change the structure or expression level, affecting fungicide efficacy and resulting in different and varying resistance levels. This review provides background information about fungicide resistance mechanisms and their implications for developing anti-resistance strategies in plant pathogens. Here, our purpose was to review changes at the target and non-target sites of quinone outside inhibitor (QoI) fungicides, methyl-benzimidazole carbamate (MBC) fungicides, demethylation inhibitor (DMI) fungicides, and succinate dehydrogenase inhibitor (SDHI) fungicides and to evaluate if they may also be associated with a fitness cost on crop pathogen populations. The current knowledge suggests that understanding fungicide resistance mechanisms can facilitate resistance monitoring and assist in developing anti-resistance strategies and new fungicide molecules to help solve this issue. © 2023 Society of Chemical Industry.     

Neotropical Bats from Costa Rica harbour Diverse Coronaviruses

Bats are hosts of diverse coronaviruses (CoVs) known to potentially cross the host–species barrier. For analysing coronavirus diversity in a bat species‐rich country, a total of 421 anal swabs/faecal samples from Costa Rican bats were screened for CoV RNA‐dependent RNA polymerase (RdRp) gene sequences by a pancoronavirus PCR. Six families, 24 genera and 41 species of bats were analysed. The detection rate for CoV was 1%. Individuals (n = 4) from four different species of frugivorous (Artibeus jamaicensis, Carollia perspicillata and Carollia castanea) and nectivorous (Glossophaga soricina) bats were positive for coronavirus‐derived nucleic acids. Analysis of 440 nt. RdRp sequences allocated all Costa Rican bat CoVs to the α‐CoV group. Several CoVs sequences clustered near previously described CoVs from the same species of bat, but were phylogenetically distant from the human CoV sequences identified to date, suggesting no recent spillover events. The Glossophaga soricina CoV sequence is sufficiently dissimilar (26% homology to the closest known bat CoVs) to represent a unique coronavirus not clustering near other CoVs found in the same bat species so far, implying an even higher CoV diversity than previously suspected.     

Responses of apple fruit size to tree water status and crop load

The combined effects of irrigation rate and crop load on apple yield and fruit size were examined in two commercial apple orchards (cv. Golden Delicious) in a semi-arid zone. The irrigation rates applied were 1, 3 and 7 mm day(-1), and the two fruit thinning treatments involved adjusting crop load to 100 and 300 fruits per tree at Ortal and 50 and 150 fruits per tree at Matityahu. Unthinned trees served as the control. The fruit from each tree was picked separately, and fruit size distribution was determined with a commercial grading machine. Midday stem water potentials varied from -0.9 to -2.8 MPa, crop load varied from 80,000 to 1,900,000 fruit ha(-1) and crop yield varied from 10 to 144 Mg ha(-1). Midday stem water potential decreased with increasing crop load in all irrigation treatments at Matityahu, but only in the 1 mm day(-1) treatment at Ortal. The extent of the lowering of midday stem water potential by crop load decreased with increasing soil water availability. At both orchards, a similar response of total crop yield to crop load on a per hectare basis was observed. Mean fruit mass and relative yield of fruit > 70 mm in diameter increased with midday stem water potential, with the low crop loads having similar but steeper slopes than the high crop load. The responses of mean fruit mass and relative yield of fruit > 70 mm in diameter to midday stem water potential were similar at both orchards, perhaps indicating that thresholds for irrigation scheduling are transferable to other orchards within a region. Factors that may limit the transferability of these thresholds are discussed.     

Osmotic regulation in leaves and roots of olive trees during a water deficit and rewatering

We evaluated the osmotic adjustment capacity of leaves and roots of young olive (Olea europaea L.) trees during a period of water deficit and subsequent rewatering. The trials were carried out in Basilicata (40 degrees 24' N, 16 degrees 48' E) on 2-year-old self-rooted olive plants (cv. 'Coratina'). Plants were subjected to one of four drought treatments. After 13 days of drought, plants reached mean predawn leaf water potentials of -0.45 +/- 0.015 MPa (control), -1.65 +/- 0.021 (low stress), -3.25 +/- 0.035 (medium stress) and -5.35 +/- 0.027 MPa (high stress). Total osmotic adjustment increased with increasing severity of drought stress. Trees in the high stress treatment showed total osmotic adjustments ranging between 2.4 MPa at 0500 h and 3.8 MPa at 1800 h on the last day of the drought period. Osmotic adjustment allowed the leaves to reach leaf water potentials of about -7.0 MPa. Active osmotic adjustment at predawn decreased during the rewatering period in both leaves and roots. Stomatal conductance and net photosynthetic rate declined with increasing drought stress. Osmotic adjustment in olive trees was associated with active and passive osmotic regulation of drought tolerance, providing an important mechanism for avoiding water loss.