Hematology of dugongs (Dugong dugon) in southern Queensland

Background: Little is known of the hematology of the dugong (Dugong dugon), a secretive and endangered coastal marine mammal.

Objectives: This paper reports hematologic reference intervals (RI) for dugongs and characterizes morphologic, cytochemical, and ultrastructural features of dugong leukocytes.

Methods: Blood was collected from live, apparently healthy dugongs and analyzed using Cell-Dyn 3700 or Sysmex XT-2000iV hematology analyzers. Blood films were subjected to a series of cytochemical stains, and leukocyte structure was examined using transmission electron microscopy.

Results: Reference intervals were established for 14 hematologic variables, total solids, and fibrinogen for 92 dugongs. Significant differences in some variables were found for animal size class, sex, and pregnancy status, and between analyzers. Subadults had higher leukocyte and lymphocyte counts than adults. Males had higher total solids and fibrinogen than females. Pregnant females had higher HCT, MCV, and circulating nucleated RBC, and lower platelet counts than nonpregnant females. Lymphocytes were usually the predominant circulating leukocyte. Heterophil cytoplasmic granules were abundant, fine, round to ovoid, and intensely eosinophilic, and round to ovoid or rod-shaped, and variably electron dense in electron microscopy. Eosinophils contained larger round eosinophilic to orange cytoplasmic granules, which ultrastructurally were bicompartmental with a round eccentric electron-dense core. Cytochemical staining of dugong heterophils suggests biochemical similarity to those of manatees and elephants, and for eosinophils, similarity to those of elephants, ruminants, and equids.

Conclusions: Generation of hematologic RI and characterization of leukocyte morphology improves evaluation of dugong health across this population and serves as a reference for other populations outside southern Queensland.