Age structure and multi-model growth estimation of longnose stingray Hypanus guttatus (Dasyatidae: Myliobatoidei) from north-east Brazil

We collected 729 Hypanus guttatus from the northern coast of the state of Rio Grande do Norte (RN), of which 196 were used to estimate age and growth. Ninety-five were male (12.7 to 57.0 cm disc width; W_D) and 101 were female (13.0 to 88.5 cm W_D); females were significantly larger than males. Cross sections of vertebrae showed band-pairs ranging from 0 to > 14 in females and from 0 to 9 in males. New-borns presented an opaque edge at birth in vertebrae without a birthmark. The average percentage of error (APE; %E) for the entire sample provided evidence that ages were repeatable. The mean monthly marginal increment (I_M) indicates annual band-pair formation from August to November. The annual cycle model for one band-pair deposition provided the best fit to data based on the AIC, with peaks between August and October, similar to that found in the I_M analysis, suggesting an annual formation pattern. A multi-model approach that included four models based on the observed mean W_D at age indicated a modified von Bertalanffy growth model as the best for describing the species growth: W₀ (W_D at birth) = 14.6 cm for both sexes; females W_∞ = 98.61 cm (95% CI = 87.34–114.61 cm); k = 0.112 year⁻¹ (CI = 0.086–0.148 year⁻¹); males W_∞ = 60.22 cm (CI = 55.66–65.35 cm); k = 0.219 year⁻¹ (CI = 0.185–0.276 year⁻¹). The age-at-maturity in males and females is 5 years and 7 years, respectively. The age composition shows that most (84%) specimens were aged 0 to 2 years. The information provided here is essential for analytical assessments of H. guttatus, which is subject to significant fishing pressure mainly on new-borns and juveniles.     

In silico and in vivo analysis of ABI3 and VAL2 genes during somatic embryogenesis of Coffea arabica: competence acquisition and developmental marker genes

Plant Cell, Tissue and Organ Culture (PCTOC) - The employment of biotechnology-based approaches such as somatic embryogenesis has been applied to several plants including Coffea sp. Despite the...     

Length–weight relationship of thirteen demersal fishes from the tropical Brazilian continental shelf

This study provides the length‐weight relationship (LWR) for 13 demersal fish species belonging to 11 families and 8 orders. Data were collected in the northeast Brazilian continental shelf during two scientific surveys (2015 and 2017) using a bottom trawl net (side length of body mesh: 40 mm, side length of cod‐end mesh: 25 mm) at 35 stations between 15 and 60 m of depth. We provide novel LWRs for four species and expand the size range of 9 relationships previously established.     

Evaluation of neuroprotective activity of digoxin and semisynthetic derivatives against partial chemical ischemia

Recently, cardiotonic steroids (CTS) have been shown to lead to the activation of Na,K-ATPase at low concentrations in brain, promoting neuroprotection against ischemia. We report here the results of the use of digoxin and its semisynthetic derivatives BD-14, BD-15, and BD-16 against partial chemical ischemic induction followed by reperfusion in murine neuroblastoma cells neuro-2a (N2a). For chemical ischemic induction, sodium azide (5 mM) was used for 5 hours, and then reperfusion was induced for 24 hours. Na,K-ATPase activity and protein levels were analyzed in membrane preparation of N2a cells pretreated with the compounds (150 nM), in the controls and in induced chemical ischemia. In the Na,K-ATPase activity and protein levels assays, the steroids digoxin and BD-15 demonstrated a capacity to modulate the activity of the enzyme directly, increasing its levels of expression and activity. Oxidative parameters, such as superoxide dismutase (SOD) activity, lipid peroxidation (thiobarbituric acid reactive substance), glutathione peroxidase (GPx), glutathione (GSH) levels, hydrogen peroxide content, and the amount of free radicals (reactive oxygen species) during induced chemical ischemia were also evaluated. Regarding the redox state, lipid peroxidation, hydrogen peroxide content, and GPx activity, we have observed an increase in the chemical ischemic group, and a reduction in the groups treated with CTS. SOD activity increased in all treated groups when compared to control and GSH levels decreased when treated with sodium azide and did not change with CTS treatments. Regarding the lipid profile, we saw a decrease in the content of phospholipids and cholesterol in the chemical ischemic group, and an increase in the groups treated with CTS. In conclusion, the compounds used in this study demonstrate promising results, since they appear to promote neuroprotection in cells exposed to chemical ischemia.     

Seasonal variation in natural mortality factors of Tuta absoluta (Lepidoptera: Gelechiidae) in open‐field tomato cultivation

The seasonal variation in natural mortality of phytophagous insects is determined by the relative importance of biotic and abiotic factors in agroecosystems. Knowledge regarding these factors throughout the year represents a key concern for IPM programmes. Seasonal population fluctuations of tomato pinworm, Tuta absoluta, led to an investigation of its natural mortality factors during the rainy season when the population level is low and during the dry season when population peaks occur. The aim of this study was to verify the seasonal variation in T. absoluta mortality factors in tomato crops. Immature stages of T. absoluta were obtained from laboratory‐rearing in the laboratory. These were taken to the field and monitored over two years. The mortality causes for each stage of insect development from egg to adult were assessed daily. Multiple biotic and abiotic mortality factors affected the immature T. absoluta stages such as rainfall, physiological disturbances, diseases, parasitoids and predators. The key T. absoluta mortality factor during summer–spring was predation. In addition, larvae predation correlated positively with temperature, wind velocity, photoperiod and rainfall. Nevertheless, during winter–fall, the key mortality factor was parasitism. Therefore, the critical stage for mortality was 3rd‐ and 4th‐instar larvae, being more vulnerable to natural control factors. Finally, the results showed the importance of vertical and horizontal action on natural mortality factors.     

Formicidal activity of indole derivatives on Atta opaciceps (Borgmeier): Lethal,behavioural and locomotive effects

The leaf‐cutting ants of the genus Atta are of extreme importance for agriculture and forestry. Few active products can be employed to control these pests and, therefore, the discovery of new insecticidal products represents a fundamental strategy for its management. In this study, we evaluated the mortality, behaviour and locomotion of workers of Atta opaciceps (Borgmeier) exposed to synthesized indole derivatives. The most active compound was 4d [1‐(1H‐indol‐3‐yl)pentan‐1‐one] (LD₅₀ = 0.018 μg/mg), while the 4e [1‐(1H‐indol‐3‐yl)hexan‐1‐one] (LD₅₀ = 3.82 μg/mg) was the least active compound. These two derivatives reduced the survival of A. opaciceps over time and altered the behaviour and locomotion of these ants. This study demonstrates the potential of indole derivatives to produce new formicidal products, since, in addition to being effective, it also affects the ant's behaviour and locomotion.     

Characterisation of regenerants obtained under selective conditions after Agrobacterium-mediated transformation of citrus explants reveals production of silenced and chimeric plants at unexpected high frequencies

Genetic transformation has been achieved for several citrus genotypes. However, regeneration of escapes at high frequency is a major problem, making the available procedures rather inefficient. Attempts to improve selection by increasing the concentration of kanamycin, used as the selective agent, or substituting it by geneticin have been unsuccessful. Here, we have critically assessed the actual frequency and origin of escapes in citrus by using visual screening with -glucuronidase (gusA) and green fluorescent protein (gfp) markers, by studying the persistence of engineered Agrobacterium in the explants, and by characterising through Southern blot analysis all the regenerants obtained under kanamycin selection. Our results show that inefficient selection could be attributed to the protection of the non-transformed cells from the selective agent by the surrounding transformed cells, and to the persistence of kanamycin-resistance Agrobacterium in explant tissues over long periods of time after co-cultivation. This also explained the high frequency (12%) of chimeric shoots that were commonly recovered. High frequency regeneration of chimeras that resulted from the fusion of different transformation events is reported for the first time. On the other hand, molecular analysis of all the regenerants reveals that transformation frequency is underestimated when based on the expression of a screenable marker gene, and that low expressors and silenced lines could account for at least 25% of those plants considered escapes based on selectable and screenable marker analysis. Consequences of these results at the practical level are also discussed.     

Floral Biology and Pollination Mechanisms in Two Viola Species—From Nectar to Pollen Flowers?

The genus Viola is represented by four related species in Brazil belonging to section Leptidium, one of the most primitive sections in the genus. Floral biology and pollination by bees were studied in Viola cerasifolia and V. subdimidiata in high-altitude areas in south-eastern Brazil. Flowers are zygomorphic and spurred. The five stamens are arranged in a cuff around the ovary, and pollen is released by means of apical connective projections, which form a cone surrounding the base of the style. The connective projections of the inferior stamens are elongated and curved to form a hook-shaped structure. Nectar-secreting tissue can occur in the basal connective appendages of the inferior stamens, which project into the spur. Flowers of V. subdimidiata secreted a mean volume of 0.14 micro l nectar over a 24-h period; approx. 40 % of flowers did not secrete any nectar. The main pollinators of these Viola species are female bees belonging to the genus Anthrenoides (Andrenidae), which search mainly for pollen. These bees seem to be oligolectic and obtain large amounts of pollen from Viola by vibrating the flowers or by moving the hook repeatedly back and forth. Males of Anthrenoides patrol Viola clusters and also feed on nectar, acting as secondary pollinators. The basic floral structure in the genus Viola fits that of 'nectar flowers'. The uncommon hook-shaped projections, scanty nectar production, and behaviour of pollinators suggest that V. cerasifolia and V. subdimidiata are shifting their reward for pollinators from nectar to pollen. Based on floral morphology, this shift may be widespread in Viola sect. Leptidium.     

Probing the volume changes during voltage gating of Porin 31BM channel with nonelectrolyte polymers

To probe the volume changes of the voltage-dependent anion-selective channel (VDAC), the nonelectrolyte exclusion technique was taken because it is one of the few existing methods that may define quite accurately the rough geometry of lumen of ion channels (in membranes) for which there is no structural data.Here, we corroborate the data from our previous study [FEBS Lett. 416 (1997) 187] that the gross structural features of VDAC in its highest conductance state are asymmetric with respect to the plane of the membrane, and state that this asymmetry is not dependent on sign of voltage applied. Hence, the plasticity of VDAC does not play a role in the determination of lumen geometry at this state and the asymmetry is an internal property of the channel.We also show that the apparent diameter of the cis segment of the pore decreases slightly from 2 to 1.8 nm when the channel's conductance decreases from its high to low state. However, the trans funnel segment undergoes a more marked change in polymer accessible volume. Specifically, its larger diameter decreases from approximately 4 to 2.4 nm. Supposing the channel's total length is 4.6 nm, the apparent change in channel volume during this transition is estimated to be about 10 nm(3), i.e. about 40% of the channel's volume in the high conductance state.     

Extracellular metalloproteinases in Phytomonas serpens

The detection of extracellular proteinases in Phytomonas serpens, a trypanosomatid isolated from tomato fruits, is demonstrated in this paper. Maximal production occurred at the end of the logarithmic phase of growth. These enzymes exhibited selective substrate utilization in SDS-PAGE, being more active with gelatin; hemoglobin and bovine serum albumin were not degraded. Three proteinases were detected in SDS-PAGE-gelatin, with apparent molecular masses between 94 and 70 kDa. The proteolytic activity was completely blocked by 1,10-phenanthroline and strongly inhibited by EDTA, whereas a partial inhibition was observed with trans-epoxysuccinyl-L-leucylamido-(4-guanidino) butane (E-64) and soybean trypsin inhibitor; phenylmethylsulfonyl fluoride weakly inhibited the enzymes. This inhibition profile indicated that these extracellular proteinases belong to the metalloproteinase class.