Cypermethrin-based formulation Barrage® induces histological changes in gills of the Pantanal endemic shrimp Macrobrachium pantanalense

Pantanal shrimp Macrobrachium pantanalense was exposed for 96 h to the cypermethrin-based formulation Barrage®. Population-relevant endpoints (survival, swimming behavior) as well as histopathology of gills were analyzed. A 96 h-LC50 of 0.93 μg/L of cypermethrin was calculated while equilibrium disturbances were observed at 1.25 μg/L. Histological examination showed predominantly regressive changes in the gills of shrimp exposed to concentrations of 0.25 and 1.25 μg/L. Three levels of lesions were observed in the gills: I- Intercellular edema, epithelial lifting of the lamellae and lamellar fusion, fat vacuoles and hypertrophy of gill epithelial cells or mucous cells; II- nuclear changes, atrophy (reduction of volume and number) and hyperplasia of gill epithelia and III- necrosis. This study shows the high sensitivity of the shrimp M. pantanalense to the pesticide Barrage® highlighting the importance of monitoring agrochemicals residues in the Pantanal region (Brazil) and conduct risk evaluation studies to prevent deleterious effects on the aquatic communities of Pantanal.publishe

Morphological and morphometric features of nematode-cysts in Gymnotus inaequilabiatus liver in the Brazilian Pantanal

Abstract The aim of this study was to determine the morphometric measures and morphological aspects of nematode-cysts in Gymnotus inaequilabiatus, and the presence of melanomacrophage centers (MMCs) associated with the periphery of cysts and in the liver parenchyma. Adult specimens, 34 female (123.1 ± 43.9g) and 45 male (135.5 ± 43.4g), from Paraguay River, Corumbá, Brazil, were used. The number of nematode-cysts was determined in 79 livers and 25 of them randomly selected for histopathological analysis and morphometric measures of nematode-cysts (mean diameter, thickness of collagen layer, and cyst-wall layer). The percentage of cysts with MMCs on the periphery and density in the liver parenchyma was estimated. The average number of macroscopic cysts was of 48.7 ± 2.78. Granulomatous reaction was observed surrounding the cysts. Diameter, collagen layer and cyst-wall measurements were 293.0 ± 75.18 (µm), 17.72 ± 6.01 (µm) and 12.21 ± 9.51 (µm), respectively. The number of nematode-cysts was correlated with hepatosomatic index, (r=0.26, P<0.05). Collagen layer was correlated with cyst diameter (r=0.62, P<0.01). Pericystic and parenchymatous MMCs were moderately (r=0.48) and highly (r=0.90) correlated with nematode-cysts number. Morphological characteristics of hepatic tissue and cysts-nematodes measures suggest that G. inaequilabiatus acts as a paratenic host to nematodes in the larval stage