Callosobruchus maculatus is an important predator of cowpeas. Due to infestation during storage, this insect affects the quality of seed and crop yield. This study aimed to investigate the effects of CrataBL, a multifunction protein isolated from Crataeva tapia bark, on C. maculatus larvae development. The protein, which is stable even in extreme pH conditions, showed toxic activity reducing the larval mass 45% and 70% at concentrations of 0.25% and 1.0% (w/w), respectively. Acting as inhibitor, CrataBL decreased by 39% the activity of cysteine proteinases from larval gut. Conversely, the activity of serine proteinases was increased about 8-fold. The toxic properties of CrataBL may also be attributed to its capacity of binding to glycoproteins or glycosaminoglycans. Such binding interferes with larval metabolism, since CrataBL-FITC was found in the fat body, Malpighian tubules, and in the feces of larvae. These results demonstrate the potential of this protein for controlling larvae development.
This study focused on the characterization of a novel cysteine proteinase inhibitor from
Enterolobium contortisiliquum
seeds targeting the inhibition of the growth of
Callosobruchus maculatus
larvae, an important cosmopolitan pest of the cowpea
Vigna unguiculata
during storage. The inhibitor was isolated by ion-exchange besides of size exclusion chromatography. EcCI molecular mass is 19,757 Da, composed of two polypeptide chains. It strongly inhibits papain (Ki
app
0.036 nM) and proteinases from the midguts of
C. maculatus
(80 μg mL
−1
, 60% inhibition). The inhibitory activity is reduced by 40% after a heat treatment at 100 °C for 2 h. The protein displayed noxious activity at 0.5% and 1% (w/w) when incorporated in artificial seeds, reducing larval mass in 87% and 92%, respectively. Treatment of
C. maculatus
larvae with conjugated EcCI-FIT and subsequent biodistribution resulted in high fluorescence intensity in midguts and markedly low intensity in malpighian tubules and fat body. Small amounts of labeled proteins were detected in larvae feces. The detection of high fluorescence in larvae midguts and low fluorescence in their feces indicate the retention of the FITC conjugated EcCI inhibitor in larvae midguts. These results demonstrate the potential of the natural protein from
E. contortisiliquum
to inhibit the development of
C. maculatus
.
The present work provides the estimates of morphometric relationships for 13 freshwater fish species collected in tarumã River, Jaru Biological Reserve, in May and September 2015 using gill nets. New length–weight relationships for 2 species, new maximum weight for 4 species and maximum sizes recorded for 3 species of the Amazonian basin.
We analyzed the seasonal variation in the diet, trophic niche breadth (Levins index), the partitioning of food resources (Pianka’s symmetric index) and trophic level (weighed average of trophic level of each prey determined in FishBase and SeaLifeBase platform) of Plagioscion squamosissimus (Heckel, 1840) and Hydrolycus scomberoides (Cuvier, 1819) in the Machado River, Rondônia, Brazil. Fish samplings were conducted bimonthly from June 2013 to May 2015 in five sites, using eight sets of gillnets. The occurrence frequency and volumetric frequency were used to quantify the food items. We analyzed the stomach contents of 283 individuals, 134 of H. scomberoides and 149 of P. squamosissimus. Fish were the most consumed food item by both piscivorous species. However, H. scomberoides mostly ingested pelagic fish (e.g. Characiformes fishes and Prochilodus nigricas Spix & Agassiz, 1829), while P. squamosissimus mostly consumed benthic fish [e.g. Pimelodus blochii Valenciennes, 1840 and Tenellus trimaculatus (Boulenger, 1898)]. Hydrolycus scomberoides presented the trophic level 3.55 for both periods analyzed, while P. squamosissimus 4.01 in the flood period and 3.82 in the drought period. Seasonal variations in the diet of H. scomberoides and P. squamosissimus were observed (PERMANOVA). Specifically, P. squamosissimus consumed mainly “Siluriformes” fishes and P. blochii in the drought period. The trophic niche breadth of P. squamosissimus was greater than that of H. scomberoides in the flood period. The species P. squamosissimus and H. scomberoides had low (0.35) food niche overlap in both seasons analysed. The data indicated that P. squamosissimus has a generalist feeding habit, while H. scomberoides is specialized in prey selection. The overlap of food niche between the species in both periods of the hydrological cycle was low, indicating that niche partitioning was probably the main mechanism of coexistence of these species, with little relationship with variations of the hydrological cycle.
O objetivo deste estudo foi caracterizar a dieta de indivíduos machos de Melanosuchus niger e Caiman crocodilus em um lago da Reserva Extrativista do Lago do Cuniã, Rondônia. Foram coletados intestinos dos animais em novembro/2016, estação chuvosa, fornecidos pela Cooperativa local (COOPCuniã). As cavidades abdominais dos jacarés foram abertas e seu estômago foi retirado e armazenado em álcool a 70%, e os alimentos foram analisados. Foram analisados 82 estômagos, 42 de M. niger e 40 de C. crocodilus. Alimentos como fragmentos de aves, anfíbios, crustáceos, insetos e material vegetal foram ingeridos pelas espécies estudadas. No entanto, os itens mais representativos na dieta de M. niger e C. crocodilus foram peixes da ordem Characifomes e Siluriformes sem importância comercial.
Few studies on fish assemblages and relations with environmental factors in aquatic systems in southeastern Amazonia have been carried out when compared to other areas in the Amazon. Therefore, which are the main environmental variables and processes responsible for structuring them remains unknown. We hypothesized that fish assemblages respond the variation in the physical-chemistry variables between seasons of the hydrological cycle in a pristine river in the Amazon. The study was performed on fish assemblages of the Tarumã River, Jaru Biological Reserve, Rondônia. Samplings were carried out in five sites along the river in March and September, 2015, which included fish collection and environmental data measurements. Principal component analysis was performed to ordinate the sites in high water and low water seasons, according to environmental variables. We used a similarity analysis in order to identify the individual contribution of species in hydrological period and a partial redundancy analysis for quantify the relative importance of environmental variables in the species composition. As predicted by our hypothesis, the species composition was influenced by dissolved oxygen and temperature. Myloplus rubripinnis, Serrasalmus compressus, and S. rhombeus were the most abundant during high water, while S. rhombeus, Myloplus lobatus, Prochilodus nigricans, and Hydrolycus armatus were the dominant species during the low water.
Context Plastic pollution can be even more problematic to the environment when this material is fragmented into small pieces forming microplastics (MPs). Aims The objectives of the present study were to investigate the abundance, morphotypes, predominant polymers, and colour of MPs on surface waters, and compare the effect of the hydrologic cycle on the abundance and richness of MP categories along a stretch of the Paraíba do Sul River basin, the water system of which flows through the most populous area in Brazil. Methods Samples were taken from the superficial layer of the water column in high-water and low-water periods 2021, using bottles and plankton net. Key results In total, 15 categories of MP were determined and 290 plastic particles were collected in both periods. A greater abundance of MPs was found during the high-water period than in the low-water period, considering both sampling methods. Conclusions The MPs in the surface waters of the Paraíba do Sul River are significantly influenced by the rainfall regime. Implications In view of climate change, which encompasses an increase in the frequency and intensity of river floods, our results present significant implications for the management of MPs in riverine and marine systems, within the context of global climatic alterations.
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