Hemolymph cytology, hemocyte count, glucose, and electrolyte reference intervals in 93 Cameroon red tarantulas (Hysterocrates gigas)

Abstract Background Theraphosidae is a large family of tarantula spiders commonly kept as pets or display animals by zoological institutions. Interest and demand for arachnid medicine have grown over the last decade. While hemolymph analysis could be a fundamental tool for arachnid health assessment, RIs are generally lacking for arachnid species. Objectives The objectives of this study were to describe the appearance of hemocytes and establish RIs for total and differential hemocyte counts as well as hemolymph glucose and electrolyte concentrations in the Cameroon red tarantula (CRT) ( Hysterocrates gigas ). Methods Ninety‐three CRTs were anesthetized using isoflurane or sevoflurane, and hemolymph was collected from the heart. Hemocyte counts were performed using a hemocytometer and trypan blue stain, and differential cell counts were estimated using light microscopy and a Wright stain. Hemocytes were also characterized with transmission electron microscopy (TEM). Hemolymph glucose and electrolyte concentrations were obtained using a blood gas analyzer. The American Society for Veterinary Clinical Pathology (ASVCP) guidelines were used to calculate RIs. Results The most abundant hemocytes were plasmatocytes, followed by granulocytes, cyanocytes, and prohemocytes. Hemocytes were characterized by TEM except for cyanocytes. All RIs had a broad range, likely due to a combination of population heterogeneity, high biologic variability of the species, and the propensity of samples to clot. Conclusions The current study is the first to establish RIs for hemolymph cytologic parameters with a sample size of over 20 individuals in any theraphosid species. RIs for CRT hemolymph biochemical analytes are also reported.