Microscopic studies on characterization of blood cells of endangered sea turtles

Because all species of sea turtles are included on the Red List of the World Conservation Union, the efforts to conserve sea turtles, the advances in their medical management, and the studies on physiological parameters have increased in recent years. The classification of blood cells in reptiles is inconsistent because variable criteria have been used to categorize cells or because cellular lineages are uncertain. However, the classification of blood cells from sea turtles is very important because these species are intensively scrutinized in captivity in clinical settings and in the wild during research projects. Characterization of blood cells in reptiles is mainly based on microscopic studies including cytochemical stains, morphometric studies, and ultrastructural characterization. Using as model a morphologic study of blood cells of loggerhead sea turtles (Caretta caretta) we review the three aspects included in the study of characterization. Cytochemical stains including benzidine peroxidase, chloroacetate esterase, alpha-naphthyl butyrate esterase (with and without sodium fluoride), acid phosphatase (with and without tartaric acid), Sudan black B, periodic acid-Schiff, and toluidine blue were used to identify six types of white blood cells: heterophils, eosinophils, basophils, lymphocytes, monocytes and thrombocytes. Morphometric characterization using an image analysis program was also performed to obtain the maximum length, minimum length, area, and perimeter for the cells and the nuclei. Ultrastructural characteristics of blood cells were obtained using transmission electron microscopy. This triple approach permits an adequate characterization of blood cells in reptiles and emphasises the usefulness of the microscopic studies in sea turtle conservation.