Haemostatic mechanisms of the armadillo Chaetophractus villosus (Xenarthra, Dasypodidae)

Haemostatic mechanisms in humans are formed by two activation pathways, named tissular factor pathway and contact system pathway, and a common pathway, that promotes the formation of the fibrin clot. These mechanisms have also been identified in other mammals. In this work we evaluate their presence in the armadillo Chaetophractus villosus, a mammal of the neotropical Xenarthra Order. Twenty animals (ten males and ten females), previously adapted to captivity, were used. Fibrinogen (Fbg) was measured at the beginning and at the end of the experimental period; prothrombin time (PT), activated partial thromboplastin time (APTT) and thrombin time (TT) were measured at the same time during the experience. Neither Fbg nor the other parameters evaluated showed sex-related differences, but Fbg diminished during the experimental period. TT related to PT and APTT showed longer times and larger dispersion of the individual values. Compared to the human beings, PT and TT were longer and APTT was shorter. Considering those results, we conclude that C. villosus has the same basic coagulation system as human beings. However, in this species the contact system pathway seems to play a greater role in the activation of the coagulation system than it does in man, and the common pathway appears to limit the velocity of the system.