A histology-based study in apparently healthy wild freshwater stingrays Potamotrygon motoro

Abstract

Histopathological studies are important as a reference in pathological process. There are a few of these studies in elasmobranchs. The aim of this study was to describe the histology of kidney, spleen, liver, and gills of wild apparently healthy Potamotrygon motoro. However, we observed some pathological findings in these animals. Nineteen P. motoro were collected from the Parana River, Brazil. Histology of kidney, spleen, liver, and gills were performed according to usual procedures. Briefly, the organs were immersed in 10 % formaldehyde solution for 48 h and routinely processed, embedded in paraffin (5-6 mm thick), and subsequent staining with hematoxylin-eosin (HE), Perls', and Schmorl's stains. Histological surface areas were measured using Image Pro Plus software 6.3. We observed that melanomacrophages around the portal vein were larger and more abundant than in the area without the bile duct. Moderate steatosis was observed in most fish, large amount of melanomacrophages and lymphocytes in the gills, liver, and spleen comparing with other studies in this species that could suggest that the immune system in these animals is constantly active. No clinical signs were observed in the fish. Studies are necessary to characterize the immune response against pathogens in elasmobranchs, especially in the Potamotrygon species.

Exploring the elusive deep‐sea sharpnose sevengill shark (Heptranchias perlo) in the Adriatic Sea: Novel records, health assessments and conservation implications

“…Melanomacrophages (MMs) were identified as individual pigmented macrophage cells dispersed throughout the liver parenchyma, aligning with observations in other elasmobranchs (Borucinska et al, 2009; de Moraes et al, 2016; Gajić et al, 2020). The species exhibited a lower mean number of MMs in the liver compared to another demersal species ( Scyliorhinus canicula ) from the Adriatic Sea.…”

Eugenol and Lippia alba essential oils as effective anesthetics for the Amazonian freshwater stingray Potamotrygon wallacei (Chondrichthyes, Potamotrygonidae)

“…In Potamotrygon motoro, the presence of these cells was recognized and associated with the immune response, acting as the site of antigen processing(Moraes et al 2016), and with environmental pollution triggered by gold and oil exploitation in the occurrence area of this species in Peruvian territory (Ramos-Espinoza et al 2017). However, in the present study, the arrival of melanomacrophages in the gills of P. wallacei exposed to concentrations of 100 µL L − 1 eugenol and 175 µL L − 1 EOLA cannot be attributed entirely to the toxic effect of these anesthetics.…”