Blood cell morphology and leukocyte differential of Morelet’s crocodile (Crocodylus moreletii) (Crocodylidae)

The objective of the study was to determine the morphological characteristics of peripheral blood cells (erythrocytes, leukocytes, thrombocytes) and the leukocyte differential count (heterophils, eosinophils, basophils, lymphocytes, monocytes, azurophils) of captive Morelet’s crocodiles (Crocodylus moreletii) from Veracruz, Mexico. Peripheral blood from 80 apparently healthy farmed crocodiles (39 subadults [19 females, 20 males] and 41 adults [18 females, 23 males]) was examined for morphology through stained blood smears and manual count was used for the leukocyte differential. Blood was collected during the non-breeding (n = 42) and breeding (n = 38) seasons. Blood examination indicated similar morphological characteristics of blood cells in subadult and adult individuals and in females and males in both seasons. Erythrocytes were the largest blood cells and lymphocytes the smallest. The leukocyte differential count showed that lymphocytes were the most abundant leukocytes and basophils the least numerous. The percentages of some leukocytes showed difference by season (non-breeding and breeding) in subadult and adult males (p < 0.05) and by size (subadults and adults) in males and females but only in the non-breeding season (p < 0.05). The leukocytes that showed the greatest variation were lymphocytes, heterophils and eosinophils. The knowledge of blood cell morphology and the leukocyte differential count in healthy farmed Morelet’s crocodiles will allow the accurate diagnosis of some diseases of captive and wild individuals.