Hepatozoon species are the most abundant hemoparasites of snakes.

• Abstract
• Materials and Methods
• Results
• Discussion
• References
• Tables
• Figures

Morphologic analysis of the parasites

Boa constrictor amarali - H. terzii presented an elongated and slender shape, with a cellular area of 35.3 ± 4.1 µm²; the length was 14.6 ± 0.4 µm and the width 2.6 ± 0.4 µm. The cytoplasm was slightly stained with no granulations. The nucleus was homogeneous, dense and parallel to the larger axis of the parasite. In 57.3% of the parasites the nucleus was slightly displaced towards one of the extremities and in 42.7% it was in a central position. The area of the nucleus was of 9.2 ± 1.6 µm², the length was 4.6 ± 0.9 µm and the width 2 ± 0.3 µm (Fig. 1A). Some erythrocytes were infected with more than one parasite.

Crotalus durissus terrificus - The Hepatozoon sp. studied presented an elongated and slender shape. Its cellular area was of 33.2 ± 4.1 µm²,the length was 14.7 ± 0.6 µm and the width 2.4 ± 0.4 µm. The cytoplasm was lightly stained and homogeneous. The nucleus was homogeneous, dense, and parallel to the longer axis of the parasite. In 51.5% of the parasites the nucleus was lightly displaced towards one of the extremities and in 48.5% it was in a central position. Its area was 8.5 ± 1.7 µm², its length 5.1 ± 0.8 µm length and its width 1.7 ± 0.4 µm (Fig. 1B).

Philodryas patagoniensis - H. philodryasi presented an elongated and slender shape, with a cellular area of 37.5 ± 7.2 µm², a length of^. 14.3 ± 1.1 µm length and a width of 2.8 ± 0.5 µm. Its cytoplasm was homogeneous and lightly stained. The nucleus was homogeneous, dense and parallel to the larger axis of the parasite. In 93.7% of the parasites the nucleus was lightly displaced toward one of the extremities and in 6.3% it was in a central position. Its area was of 9.6 ± 1.8 µm², its length 5.2 ± 0.8 µm and its width 2.0 ± 0.4 µm (Fig.1C). More than one gamont infecting the same erythrocyte was usually found in this host.

Hydrodynastes gigas - This snake presented two different parasites: (1) H. cyclagrasi, a large parasite almost occupying the entire cytoplasm of the erythrocyte, presented an elongated and wider shape. Its cellular area was 115.2 ± 11.8 µm², its length 21.7 ± 1.4 µm and its width 6.4 ± 0.8 µm. The parasite cytoplasm presented granulations and deep staining. The nucleus was homogeneous and arranged perpendicularly to the longer axis of the parasite. In 76.1% of the parasites the nucleus was slightly displaced towards one of the extremities and in 23.9% it was in a central position. Its area was 13.9 ± 2.6 µm², its length 5.1 ± 0.5 µm and its width 3.3 ± 0.6 µm (Fig. 1D). A "hook" was usually observed at one of the extremities of the parasite; (2) H. migonei, the smaller form was less elongated and more oval in shape. Its cellular area was 48.6 ± 5.9 µm², its length 11.8 ± 1.1 µm and its width 5 ± 0.6 mm. Its cytoplasm was homogeneous and lightly stained and contained a round and large nucleus in relation to the size of the parasite. In 52.5% of the parasites the nucleus was slightly displaced towards one of the extremities and in 47.5% it was in a central position. The area of the nucleus was 13.3 ± 2.7 µm², the length was 4.5 ± 0.6 µm and the width 3.5 ± 0.6 µm (Fig. 1E).

Comparative analysis of the various parasites - Analysis of parasite area, length and width showed that the parasites of the various species had different dimensions (p < 0.05), except for the length of Hepatozoon sp. of C. durissus terrificus and H. terzii (p > 0.05) (Table I). The various parasites also differed in terms of nucleus area and width (p < 0.05), except for H. philodryasi and H. terzii (p > 0.05) (Table I). The parasites showed two different patterns in terms of nuclear length: one shared by H. philodryasi, Hepatozoon sp. of C. durissus terrificus and H. cyclagrasi, and the other shared by the species H. terzii and H. migonei (Table I). Multivariate analysis showed that the studied parasites can be divided into three different groups: one of them includes the species H. terzii, H. philodryasi and Hepatozoon sp. of C. durissus terrificus; and the other two consist of H. migonei and H. cyclagrasi (Fig. 2).

Comparative analysis of infected and non-infected erythrocytes - Comparative analysis of infected and non-infected erythrocytes (t test) showed that the values obtained for 73.3% of the analyzed variables were significant-ly different (p < 0.05) (Table II). We observed that linear dimensions (nuclear or erythrocyte length and width) were different in 85% of the cases, whereas area dimensions were different in only 50.0% of the cases (Table II).

Multivariate analysis, which was applied only to the linear variables, showed that H. cyclagrasi induced strong changes in erythrocyte morphology (Fig. 3). The changes in erythrocyte morphology induced by the species H. terzii, Hepatozoon sp. of C. durissus terrificus and by H. migonei were less obvious than the changes induced by H. cyclagrasi (Figs 4, 5, 6). The changes induced by H. philodryasi were not evident (Fig. 7).

H. terzii, Hepatozoon sp. of C. durissus terrificus and H. philodryasi induced light flattening of the erythrocyte nucleus, which, however, was not dislocated to the cell periphery of. In contrast, H. cyclagrasi dislocated the erythrocyte nucleus to one of the poles in 55.5% of cases and laterally in 44.5%, and also induced a marked deformation of the erythrocyte. H. migonei caused displacement of the erythrocyte nucleus to the poles in 63.1% of cases and laterally in 36.9%. In spite of this displacement, the changes in the erythrocyte were less evident.