Influence of temperature on muscle fibre hyperplasia and hypertrophy in larvae of blackspot seabream,Pagellus bogaraveo

The effects of temperature on Pagellus bogaraveo muscle cellularity were investigated, by morphometry, throughout the endogenous feeding stage, testing two rearing temperatures: 14 and 18 °C. The following parameters were estimated in transversal body sections at post‐opercular and post‐anal body levels: the total cross‐sectional muscle area, the total number of fibres and the mean cross‐sectional fibre area. At hatching, no significant influence of the temperature was observed on the morphometric parameters measured in the white muscle. At mouth opening, an increase in the number of post‐opercular white fibres was promoted by the highest temperature. During embryonic development, the red muscle fibre number in the post‐anal part of the larvae increased with higher temperature, but it appears that the difference was no longer present at mouth opening. An increase in the fibre area and in the total cross‐sectional area of red muscle at the post‐anal level was promoted by a 4 °C increase in the temperature during the vitelline phase. In conclusion, the axial musculature of blackspot seabream embryos/larvae reacted differently to temperature influence according to the body location, strongly supporting the need to look at and account for different body locations when evaluating muscle cellularity in fish, namely in growth/aquaculture‐related studies.     

Soil dissolved organic carbon responses to sugarcane straw removal

Global demand for bioenergy increases interest in biomass‐derived fuels, as ethanol from sugarcane straw. However, straw is the main carbon source to soil and its removal reduces C input, affecting active fractions (dissolved organic carbon, DOC) and C storage. To quantify the effects of straw removal on DOC and C stocks, we built lysimeter system using soil (Rhodic Kandiudox) from sugarcane field. We evaluated four soil depths (1, 20, 50 and 100 cm) and four straw removal rates: no removal NR, medium MR, high HR and total TR, leaving 12, 6, 3 and 0 Mg/ha on the soil surface, respectively. After rainfall, drainage water was collected and analysed for DOC content. Soil C stocks were determined after the 17‐month. Total DOC released at 1‐cm depth amounted to 606, 500, 441 and 157 kg/ha in NR, MR, HR and TR, respectively. Net‐DOC suggests straw as the main source of DOC. Most of DOC in NR (50%) was retained within the 1–20 cm layer, resulting in higher C stock (10 Mg/ha) in the topsoil. In HR and MR, DOC retention was higher within 20–50 cm, suggesting differences in DOC composition. DOC in TR was 40% higher at 20 cm than at 1 cm, indicating C losses from topsoil. Low concentrations of DOC were found at 100‐cm depth, but representing 30% in TR. Straw removal for bioenergy production is sustainable, but we should leave at least 3 Mg/ha of straw to ensure DOC production and soil C storage, taking account the DOC contribution to key soil functions.     

Inheritance of type IV glandular trichome density and its association with whitefly resistance from <Emphasis Type="Italic">Solanum galapagense</Emphasis> accession LA1401

Tomato is affected by a large number of arthropod pests, among which the whitefly (Bemisia tabaci) is considered to be one of the most destructive. Several accessions of the wild species of Solanum galapagense, including accession LA1401, are considered resistant to whitefly (B. tabaci). This resistance has been associated with the presence of type IV glandular trichomes on the leaf surface. Our research aimed to study the inheritance of type IV glandular trichome density and its association with resistance to whitefly (B. tabaci biotype B) in populations derived from the interspecific cross Solanum lycopersicum × S. galapagense ‘LA1401.’ High estimates for both broad-sense and narrow-sense heritabilities of type IV glandular trichome densities suggest that inheritance of this trait is not complex. Whitefly resistance was associated with high density of type IV glandular trichomes. F₂ (S. galapagense × S. lycopersicum) population plants selected for the highest densities of type IV glandular trichomes showed similar levels of resistance to those found in the donor of resistance LA1401.     

Nitrate Mobility in Variable-Charge Tropical Soils

ABSTRACT

Nitrate (NO₃ ^–-N) leaching in tropical soils, which are more weathered, is influenced by their mineralogical, physical, and chemical characteristics. Thus, the present study aimed to evaluate the effect of the variation of net electrical charge on the mobility of nitrate, applied as potassium nitrate (KNO₃) or calcium nitrate (Ca(NO₃)₂), in samples from A and B horizons of three Red-Yellow Latosols (Oxisols), with different mineralogical and textural characteristics. Hydrochloric acid (HCl) or sodium hydroxide (NaOH) volumes were added to previously sterilized soil samples in order to condition five hydrogen potential (pH) values, obtaining different net electrical charges. The experiment was carried out with leaching columns under laboratory conditions. The soil columns were percolated with solutions of KNO₃ or Ca(NO₃)₂ or water (control). An increase in positive net charges was significant and varied according to the soil and percolating solution; in general, it resulted in an increase of up to 50% in nitrate adsorption in some soils. Larger amounts of adsorbed nitrate were observed in the columns filled with the B horizon of the clayey gibbsitic Red-Yellow Latosol, showing adsorption of 85% for a positive net charge of 2 cmol_c kg^?1. Regarding kaolinitic soils, lower adsorption was observed in the medium-textured kaolinitic Red-Yellow Latosol, which had lower clay content and positive net charge. Application of Ca(NO₃)₂, as a percolating solution, increased nitrate adsorption compared to the application of KNO₃. This effect may be attributed to the increase in positive net charge promoted by calcium (Ca²⁺), being more evident for the highest negative net charges.     

Shrimp rearing in biofloc integrated with different mullet stocking densities

This work compared the effects of different densities of Mugil curema integrated in the rearing of Litopenaeus vannamei in a biofloc system on the yield and ecological performance of the system. For that, an experiment lasting 55 days was conducted. Four groups were evaluated as follows: (a) T0: shrimp reared without mullet, (b) T10: shrimp reared with 22 fish per tank, (c) T20: shrimp reared with 43 fish per tank, and (d) T30: shrimp reared with 65 fish per tank, each treatment with four replicates. The sludge:biomass ratio was higher in the T0 treatment, while the T10–T20 treatments were more efficient, producing more biomass and less sludge. The use of water was 17% more efficient in all treatments with mullet. Mullet survival was higher in the T10 and T20 treatments (mean: 84 ± 8%) than in the T30 (61 ± 5%) treatment. The fish final biomass and yield limits of the system were 0.37 kg and 3.7 kg/m³ respectively. Finally, there was no increase in the total nitrogen output of the system up to the T10 density. In conclusion, it is possible to integrate mullet up to 3.7 kg/m³, increasing the yield in 20% and decreasing water use.     

Bedellia somnulentella (Lepidoptera: Bedelliidae): new hosts of the genus Ipomoea (Convolvulaceae) in Brazil

Journal of Plant Diseases and Protection - Bedellia somnulentella (Zeller 1847) (Lepidoptera: Bedelliidae) is an invasive pest in Ipomoea batatas (Convolvulaceae)-producing regions in the tropics....     

Dynamics of degradation of high-quality tropical forage according to levels of nitrogen supplementation

Tropical Animal Health and Production - The present study aimed to evaluate the degradation dynamics of high-quality tropical forage according to the levels of nitrogen supplementation. In this...