Hematology and blood biochemistry profile of the freshwater stingray Potamotrygon magdalenae as a tool for population assessment in artificial environments

Hematological and blood biochemical reference information is important to establish physiological status of freshwater stingray populations and improve care and management protocols in artificial environments. Here, we used a commercial freshwater stingray with high mortality rates in the market (Potamotrygon magdalenae), as an example to understand how artificial environments and handling protocols influence physiological status of captive freshwater stingrays. To this purpose, blood from five adult males and six adult females was collected to perform complete blood counts and blood chemistry analyses. All sampled animals showed good body condition with no differences between sexes. Differences between sexes were only found for the differential count of lymphocytes. Red blood results were consistent with previously studied potamotrygonids while white blood results showed higher values of leukocytes, thrombocytes, heterophils and lymphocytes in P. magdalenae compared to other Potamotrygonids. All types of leukocytes described for elasmobranchs were found except neutrophils and basophils. Blood metabolites showed an influence of ex situ diet in total protein, triglycerides and cholesterol. Glucose results were consistent while urea showed lower levels than those recorded for other freshwater stingrays. These results highlight the importance of physical, physiological and health analysis in freshwater stingrays as a part of welfare assessment to improve monitoring protocols and survival rates in public or private aquaria.

Eugenol and Lippia Alba Essential Oils as Effective Anesthetics for the Amazonian Freshwater Stingray Potamotrygon Wallacei (Chondrichthyes, Potamotrygonidae)

This study assessed the potential of eugenol and the essential oil of Lippia alba (EOLA) in providing suitable anesthetic induction and recovery times, and their consequent effects on the blood and respiratory physiology, as well as the gill architecture of an Amazonian freshwater stingray, Potamotrygon wallacei, at the onset of the anesthetic event and after 48 h of recovery. Juveniles of P. wallacei (n = 12) were exposed to increasing concentrations of eugenol (75, 100, 125 and 150 µL L− 1) and EOLA (150, 175, 200 and 225 µL L− 1) in an immersion bath. Anesthetic induction was found to be faster with the use of eugenol compared to EOLA. On the other hand, the stingrays anesthetized with eugenol displayed a longer recovery time than those exposed to EOLA. The highest concentrations of eugenol caused moderate to severe histological changes in the gills. No significant changes were found for hematocrit and plasma metabolites in the stingrays anesthetized with all concentrations of both eugenol and EOLA just after the onset of anesthetic action, when compared to those recovered after 48 hours. Investigations regarding the potential use of these natural anesthetics are unprecedented for freshwater stingray species and 200 µL L− 1 EOLA is recommended as the most suitable anesthetic for use in juveniles of P. wallacei.

Conservation Status of Shark Landed in Local Fish Market in Pangandaran Regency, Indonesia

Pangandaran has a great fishery potential. Therefore, fishing communities make fisheries a source of economy, especially in the fishing sector, namely by buying and selling the catch. Fish buying and selling activities are increasing in line with the fish consumption needs of the community. This has an effect on increasing fishing activity, causing a decrease in fish production. The study was conducted to find out information on the IUCN group of fish that are still sold in the fish market. The research was conducted by direct observation in the field at the Pangandaran fish market and its surroundings. Observations show that the Pangandaran fish market still sells fish that are listed in the IUCN. There are sharks and ray fish sold at the Pangandaran fish market. The species found were 3 species spread over five observation locations with details of one species listed IUCN-Least concern, and one species registered IUCN-Vulnerable for hammerhead shark and IUCN- Near Threatened for blacktip shark. The sharks identified as Appendix II species while the freshwater stingray belongs to Appendix III of CITES. Because endangered fish are still sold routinely, conservation is needed to preserve the biota. Fisheries management in the catching process also needs to be done so that endangered fish caught can be minimized.

Morphological, cytochemical and ultrastructural aspects of blood cells in freshwater stingray species in the middle Rio Negro basin of Amazonian Brazil

In the present work, we examined the morphology, dimensions, cytochemical staining reactions and ultrastructure of blood cells from three freshwater stingray species, Potamotrygon wallacei, Potamotrygon motoro and Paratrygon aiereba, living in the waters of the middle Rio Negro basin (Barcelos, Amazonas, Brazil). We identified erythrocytes, erythroblasts, thrombocytes and four types of leukocytes (basophils, heterophils, lymphocytes and monocytes) in the blood of these stingray species. In all the freshwater stingray species studied, the shapes and dimensions of these cells were similar to those of marine elasmobranchs. Positive PAS staining occurred in heterophils and thrombocytes, and weak staining occurred in lymphocytes and monocytes, while metachromasia only occurred in basophils. Positive Sudan Black B staining was observed in thrombocytes and lymphocytes, and weak staining occurred in heterophils. Basophils and heterophils were the only cells with positive bromophenol blue staining, while no peroxidase staining was observed in any of the four leukocyte types. This is the first study to establish the dimensions and cytochemical staining profiles of blood cells in Amazonian stingray species. Because these elasmobranch species are exported as ornamental fish to countries worldwide, this study can contribute to establishing standards for blood constituents that may be helpful in assessing the health and welfare of these fish in artificial systems.

Morphological, Cytochemical and Ultrastructural Aspects of Blood Cells in Freshwater Stingray Species in the Middle Rio Negro Basin, Amazonian, Brazil

Examined the morphology, dimensions, cytochemical staining reactions and ultrastructure of blood cells from three freshwater stingray species, Potamotrygon wallacei, Potamotrygon motoro and Paratrygon aiereba, living in the waters of the middle Rio Negro basin (Barcelos, Amazonas, Brazil). We identified erythrocytes, erythroblasts, thrombocytes and four types of leukocyte (basophils, heterophils, lymphocytes and monocytes) in the blood of these stingray species. In all the freshwater stingrays studied, the shape and dimensions of these cells were similar to those of marine elasmobranchs. A positive PAS reaction occurred in heterophils and thrombocytes, and a weak reaction in lymphocytes and monocytes, while a metachromasia reaction only occurred in basophils. Sudan black staining was positive for thrombocytes and lymphocytes, and only a weak reaction occurred in heterophils. Basophils and heterophils were the only cells stained with bromophenol blue, while no peroxidase reaction was observed in any leukocyte type. This is the first study to establish the dimensions and cytochemical staining reactions of blood cells in Amazonian stingray species. Since these elasmobranch species are exported as ornamental fish to countries worldwide, this study can contribute towards establishing standards for blood constituents that may be helpful in assessing the health and welfare of these fish in artificial systems.

Did titanic stingrays wander the Pliocene Mediterranean Sea? Some notes on a giant-sized myliobatoid stinger from the Piacenzian of Italy

A fossil caudal spine of a stingray (Elasmobranchii: Batomorphii: Myliobatoidei) is here reported from upper Pliocene (Piacenzian) shallow-marine deposits exposed at the La Serra locality of Tuscany (central Italy). In spite of being incomplete, this specimen displays an amazing maximum preserved anteroposterior length of 420 mm, which to our knowledge makes it the longest stingray stinger ever reported from both the fossil and the Recent records. Tentatively referred to the family Dasyatidae, the herein described fossil appears to be more than twice as long as the longest caudal spines reported from any living myliobatoid species of the Mediterranean Sea. Therefore, it represents a stingray taxon that is no longer featured in the present-day Mediterranean ray assemblage, and as such, it expands our knowledge on the Pliocene biodiversity of the Mediterranean Sea. Given that the living species Bathytoshia brevicaudata (the smooth stingray) and Urogymnus polylepis (the giant freshwater stingray), while displaying the greatest values of total stinger length (up to c. 375 mm in the latter) among extant myliobatoids, are also known as the largest living species of stingrays besides Mobulidae, it seems much reasonable to hypothesise that the caudal spine from La Serra belonged to a very large- sized stingray individual which would have been larger than (or at least comparable in dimensions to) the largest members of the titan-sized B. brevicaudata and U. polylepis .