Using underwater currents as an occupational enrichment method to improve the stress status in rainbow trout.

This study investigated the effects of occupational enrichment, specifically underwater currents, on the stress status of rainbow trout (Oncorhynchus mykiss). A total of 540 fish were divided into three groups: control tanks without artificial currents (CO), tanks with randomly fired underwater currents (RFC), and tanks with continuous current throughout the day (CT). After 30 days, half of the fish in each group underwent a 5-day pre-slaughter fasting (5D), while the others were fed until the day before slaughter (0D). Fish in the RFC group exhibited lower levels of plasma cortisol and acetylcholinesterase enzyme activity in hypothalamus and optic tract than other groups, suggesting an improved stress status. RFC group also showed higher levels of non-esterified fatty acids (NEFA) in 5D fish and higher liver glycogen stores, suggesting improved energy reserves. In comparison, the CT group had higher LDH levels, possibly due to their increased swimming activity. The CO group had significantly lower NEFA levels at 5D compared to the RFC group, suggesting lower energy reserves. The RFC fish had darker and yellow-reddish skin and liver color, suggesting an improved stress status and lower lipid reserves, respectively. Overall, although a significant stress response was not observed in fasted individuals, possibly due to the relatively short fasting period, the study suggests that providing occupational enrichment using randomly fired underwater currents for 1 month helped to improve stress status in rainbow trout, indicating that occupational enrichment during the grow-out phase can positively impact the welfare of rainbow trout during routine handling procedures.

Environmental enrichment improves growth and fillet quality in rainbow trout.

BACKGROUND: Some environmental enrichment methods, such as occupational enrichment (OE), can improve fish growth, but little is known about its effects on fillet quality. In this study, we evaluated the effects of OE using underwater currents on different aspects of fillet quality and muscle metabolism in rainbow trout (Oncorhynchus mykiss), before and after a handling procedure (fasting). The trout were placed in groups of 30 in separate tanks in three treatments for 30 days: no artificial currents (CON), randomly fired underwater currents (RFC), and continuous underwater currents (CUC). Additionally, half of the individuals in each treatment were fasted (5 days, 45.2 °C days). RESULTS: Slaughter weight, condition factor, and relative growth were lower in CON fish, indicating a positive effect of OE on growth. Rigor mortis, muscle pH, and muscle glycogen levels were similar among treatments, indicating no effect of OE on classical measures of fillet quality. However, significant differences were found regarding fillet colour and muscle enzymes. The fillets of RFC fish were more salmon-pink in colour, which is favoured by consumers. Also, activity levels of pyruvate kinase and glycogen phosphorylase in muscle were significantly higher in CUC fish, probably due to increased energy demands, as pumps were on continually in that treatment. CONCLUSION: Overall, RFC fish seemed to have received enough stimulation to improve growth while not being excessive in terms of exhausting the animals (avoiding negative effects on muscle metabolism), whereas OE may have provided a hormetic effect, allowing fish to better adjust to fasting. © 2023 Society of Chemical Industry.

Antibiotic resistance of Staphylococcus aureus isolated from the oral cavity of paraguayan participants from Coronel Oviedo, year 2021

A cross-sectional study was carried out to identify the resistance profile of Staphylococcus aureus colonizing the oral cavity of patients. Sampling was carried out with sterile swabs. Mannitol-positive colonies were cultured on blood agar, identifying S. aureus by conventional biochemical tests that included positive results for catalase, coagulase, DNAse and latex agglutination test for S. aureus. The resistance to 11 antibiotics was tested. Forty-three subjects were included; 83.7% presented oral pathologies, and 6.9% had a history of hospitalization, 18.6% mentioned having used antibiotics in the last three months. S. aureus was isolated in 3 patients; the 3 isolates presented resistance to penicillin, while 2 of the three isolates were resistant to oxacillin and cefoxitin. Resistance to erythromycin and clindamycin was also present in one patient. Two of the cases presented resistance to various drugs and didn´t report any risk factors.

Se realizó un estudio transversal para identificar el perfil de resistenia de S. aureus que se encuentra colonizando la cavidad bucal de los pacientes. La toma de muestras se realizó con hisopos estériles. Se cultivaron colonias positivas a manitol en agar sangre, identificándose S. aureus mediante pruebas bioquímicas convencionales que incluyeron resultados positivos para catalasa, coagulasa, ADNasa y aglutinación en látex para S. aureus. Se probó la resistencia a 11 antibióticos. Se incluyeron cuarenta y tres sujetos; el 83,7% presentó patología bucal y el 6,9% tenía antecedentes de hospitalización, el 18,6% mencionó haber utilizado antibióticos en los últimos tres meses. Se aisló S. aureus en 3 pacientes; los 3 aislados presentaron resistencia a penicilina, mientras que 2 de los tres aislados fueron resistentes a oxacilina y cefoxitina. Un paciente también presentó resistencia a eritromicina y clindamicina. Dos de los casos presentaron resistencia a diversos fármacos, sin haber reportado factores de riesgo.

Biogeomorphic succession in a fluvial-lacustrine delta of the Middle Paraná River (Argentina): Feedbacks between vegetation and morphodynamics.

The Leyes' Delta lies at the Middle Paraná River, the second-largest fluvial system in South America, and it is being quickly formed into the Setúbal fluvial lake, Argentina. In the context of the Fluvial Biogeomorphic Succession theory, our aim was to better understand interactions between physical and biotic processes contributing to the formation of the Leyes' Delta. We studied the genesis, morphologic development, and vegetation in three groups of its deltaic islands with contrasting formation ages. Different methodologies were applied. Genesis and morphologic development were interpreted from time-series of satellite images and aerial photography obtained from 1974 to 2014. Then landforms and vegetation communities were mapped on the most current images, and they were corroborated and characterized during fieldwork. Our results evidence that the three island groups (Channel crevasse splay islands, Delta bar-plain islands, and Delta front islands) were formed via two different geomorphic processes, determining differences in the initial vegetation colonization. Eight fluvial-lacustrine landforms and eight vegetation communities, both differently represented among the island groups, currently characterize these islands. The species richness accumulation curves and beta diversity showed that the morphodynamic activity can be as important in the floristic composition of the deltaic islands as formation ages. The floristic composition differed statistically among island groups. After identifying three of the four phases of the FBS, we concluded that even though the morphodynamic activity under which islands were formed determined differences in the initial vegetation colonization, under similar subsequent levels of morphodynamics the resulting vegetation heterogeneity tends to be similar even under contrasting genesis. Among the vegetation types, Lotic prairies would play a key role in the morphologic evolution of the deltaic islands, therefore, their distribution and interactions with flow and sediments should be considered during the studies of social ecological systems as the Leyes' Delta, in Santa Fe, Argentina.

Macrophytes as potential biomonitors in peri-urban wetlands of the Middle Parana River (Argentina).

The aims of this study were to measure the concentrations of nutrients and pollutants in peri-urban wetlands, to analyze the plant morphology of the most representative macrophyte species, and to determine their potential use as biomonitors. Four wetlands in the Middle Paraná River floodplain evidencing contamination or anthropogenic impact were studied. The studied species were Typha domingensis Pers., Eichhornia crassipes (Mart.) Solms., Alternanthera philoxeroides (Mart.) Griseb., and Pistia stratiotes L. Besides, the same plant species from an uncontaminated wetland considered as control were studied. A. philoxeroides showed the highest total phosphorus (TP) concentration in leaves throughout the study, while the other species showed a higher TP concentration in roots than in leaves. Since metal concentration in A. philoxeroides tissues was always higher than in sediment, further studies focused on its phytoremediation capacity should be carried out. T. domingensis exhibited the highest Zn concentrations in roots followed by Pb, and E. crassipes presented the highest values of Pb concentrations in roots. The aerial part height of the plants from peri-urban wetlands was significantly higher than that of the plants from the control, while the root length was significantly lower. The root length of P. stratiotes showed a negative correlation with soluble reactive phosphorus (SRP) concentration in water. All the root anatomical parameters of T. domingensis and E. crassipes showed a positive correlation with nitrate and ammonium concentrations in water. The studied macrophytes evidenced a high tolerance, enabling them to grow and survive in peri-urban wetlands that receive pollution from different sources. The use of aquatic and wetland plants as contaminant bioindicators and bioaccumulators in the Middle Paraná River floodplain is completely feasible.