Original Article Comparative Study of Some Haematological Parameters of Two Wild Chaetophractus villosus (Mammalia, Dasypodidae) Populations E. B. Casanave 1 and N. N. Polini 2 1 Ca ´tedra de Fisiologı ´a Animal y CONICET; 2 Ca ´tedra de Ana ´lisis Clı ´nicos II, Departamento de Biologı ´a, Bioquı ´mica y Farmacia, Universidad Nacional del Sur, Bahı ´a Blanca, Argentina Abstract. The study of haematological parameters of a species is of great interest both for the comprehension of its biological characteristics in general and its physio- logical adaptations in particular. In this work, we studied haematological parameters of two wild populations of armadillo Chaetophractus villosus (population I, n = 25 and population II, n = 30). The animals came from a range of 150 km to the north west of Bahı ´a Blanca, Argentina. Blood samples were obtained from anaes- thetised animals by cardiac puncture, between 8:00 a.m. and 10:00 a.m. Blood was collected in EDTA and processed for haematological screen by routine techni- ques. Erythrocyte parameters (total erythrocytes, haematocrit, haemoglobin, erythrocyte indices and erythrocyte sedimentation rate) and leucocyte para- meters (total leucocytes and percentage composition) were studied. Population I had higher values for erythrocytes, haematocrit and haemoglobin than popula- tion II. With the exception of eosinophils (p>0.05), no differences were found between populations of erythro- cyte indices, erythrocyte sedimentation rate, total leucocytes and leucocyte percentage composition. The sample of population II featured a greater number of young animals than population I, age may therefore partially account for the differences. These results may also be influenced by a higher loading of parasites observed in population II. Keywords: Armadillo; Chaetophractus villosus; Hae- matological parameters; Mammals Introduction The order Xenarthra includes sloths, anteaters and armadillos, a group of mammals that inhabit South America (Redford and Eisenberg 1992). The Dasypodi- dae family comprises the armadillos, with nine genera and approximately twently species, all of which are neotropical and share burrowing habits. Only Dasypus novemcinctus has reached the southern region of the United States (Taulman and Robbins 1996). Armadillos, particularly Chaetophractus villosus, present certain unique features, some of which make them suitable for biomedical research: remarkable adaptability to labora- tory conditions, relatively low body temperature (Casanave and Affanni 1994, 1995); ability to endure hypoxic stress, when ventilation is hampered by soil (Affanni et al. 1986, 1987; Casanave et al. 1995); low metabolic rate (McNab 1984); and a great development of olfactory neuroanatomical structures (Garcı ´a Samar- tino et al. 1987). Nevertheless, despite the amount of research on the haematological parameters of the nine- banded armadillo, Dasypus novemcinctus (Ebaugh and Benson 1964; Lewis and Doyle 1964; Szabuniewicz and McCrady 1969; Dhindsa et al. 1971; Strozier et al. 1971; Giacometti et al. 1972; Purtilo et al. 1975; D’Addamio et al. 1978), there is no information about the blood parameters of the wild Chaetophractus villosus. Such a study would be of broad interest since it is widely agreed that the understanding of an animal’s physiological state as well as the identification of certain pathological conditions can be aided by our knowledge of its normal pattern of blood parameters and the changes experienced by the latter. The objective of this work was to establish some normal haematological parameters for two wild C. villosus populations. Comparative Haematology International (1999) 9:13–16 ß 1999 Springer-Verlag London Limited C OMPARATIVE HAEMATOLOGY I NTERNATIONAL Correspondence and offprint requests to: Dra. Emma Beatriz Casanave, Departamento de Biologı ´a, Bioquı ´mica y Farmacia, Universidad Nacional del Sur, San Juan 670, 8000, Bahı ´a Blanca, Argentina.