Influence of anticoagulants and processing time in haematological analysis in butter ray (Dasyatis hypostigma - Santos & Carvalho, 2004), maintained under human care.

Dasyatis hypostigma is a species of ray found primarily in coastal and estuarine waters of the Atlantic Ocean. It plays an important role in marine ecosystems by regulating populations of small fish and invertebrates. The aim of this study was to evaluate the influence of different anticoagulants and processing times on the haematological parameters of D. hypostigma, as well as to describe the morphology of its blood cells. Blood samples from 11 D. hypostigma individuals housed at the Marine Aquarium of Rio de Janeiro were collected following tonic immobilization techniques and distributed into tubes containing different anticoagulants (K2 EDTA, sodium citrate, lithium heparin and sodium heparin). The samples were analysed immediately after collection and again 6 h later. The results showed significant effects of the anticoagulants on haematological parameters such as packed cell volume, mean corpuscular haemoglobin concentration and mean corpuscular volume. Time also influenced some parameters, particularly in samples treated with sodium heparin, where minor variations in cell counts were observed. Morphological analysis of the blood cells revealed typical characteristics of various leukocytes, erythrocytes and thrombocytes. Lithium heparin is the anticoagulant of choice for processing blood samples from D. hypostigma, although sodium heparin may also be used. EDTA and citrate should not be used for this species. Samples should be processed as promptly as possible. To the best of our knowledge, this is the first study to describe the blood cell morphology of D. hypostigma.