International Journal of Marine Science, 2016, Vol.6, No.18, 1-14
4
and microgamonts (Figs.3-8). The macrogamonts (6 X 5.6 µm) were provided with large nuclei and prominent
nucleoli. Finally macrogamont transformed into macrogametes without further division and provided with small
dense granules and large amylopectin granules in the cytoplasm (Fig.8). The parasitophorous vacuole became
narrow as the parasite increased in size or in other cases tear off due to parasite`s huge-size (Fig.7).
Microgamonts underwent multiple fission and spread along the intestinal epithelia (Figs.3-8). More than one
microgamont can be seen inside blood cells in one epithelial cell (Fig.7). Microgamonts grew after penetration of
merozoites to the blood cells and became a uninucleated zoite (Fig.8). The later grew in size to reach 4.6 X 4.5
µm and the parasitophorous vacuole enlarges too. The nucleus of the uninucleated zoite underwent many divisions
(Fig.3). Later the microgamont had a large lobulated nucleus. This suggests that the nucleus underwent
endopolygony. The lobules of the nucleus began to separate and migrated to the external of the microgamont.
Microgametes appeared as evaginations of the external boundary of the microgamont inside the parasitophorous
vacuole (Fig.8). As development proceeded, the flagellated microgametes were released and left the rest of the
cytoplasm inside the microgamont (Figs.9-11).
Syngamy took place and the spherical zygote with centrally located nucleus was formed (11.1 X 8.3 µm). As an
external wall gradually formed, the zygote transformed into an oocyst (Fig.12) with two types of granules in the
cytoplasm, amylopectins and small sized lipid granules.
As sporogony proceeded, the oocyst shrank (4.8 X 5 µm) and its wall thickened. The micropyle with its cap were
out of focus. The nucleus of the completely formed oocyst (Figs.13–14) (13.8 X 10.1 µm) began to divide into
two nuclei followed by cytokinesis forming two sporoblasts, later on the nucleus of each sporoblast divided into
four small nuclei, the later surrounded with a part of cytoplasm and formed four sporozoites (Fig.14). In this way
eight sporozoites would form from the two sporoblasts leaving residual cytoplasm (Figs.13-15). This study
concluded that the macrogamonts, the zygote and the oocyst are formed extraintestinal inside blood cells. This
study observed the later stages inside leucocytes.
Ultrastructurally, uninucleated zoites were observed in leucocytes but it was very difficult to determine whether
this stage was also extracellular (Fig.16). This stage had a large prominent nucleus with only mitochondria in its
cytoplasm, dense granules and microtubules (Fig.17). This stage became gradually irregular in shape. Remains of
micronemes were observed adhering to the pellicle interiorly as if it secretes its contents inside the parasitiphorous
vacuole. Fully formed gamonts appeared without apical complexes, each surrounded by a vacuole with thin wall
and filled with electron dense compact material. Gamonts enlarged in diameter and the contents of their vacuoles
disappeared except some microtubules. The wall of each vacuole differentiated into an outer dense electron layer
and an inner light electron one. The fully formed gamont appeared irregular with an irregularly-shaped nucleus,
ER and a number of vacuoles containing filamentous structures (Figs.18-19). Microgamonts were spherical in
shape with prominent nuclei and peripherally situated chromatin. It contained a number of microtubules
underneath its pellicle, a number of mitochondria in the cytoplasm and the parasitophorous vacuole appeared later
(Fig.19). Bodies with dense electron material appeared in the zygote similar to that of wall forming bodies.
Smaller bodies with dense electron material were observed perhaps they represent the wall forming bodies
(Figs.20 -21).
Invaginations or cytostomes were also observed (Fig.21). Cytostomes are sometimes connected with food
vacuoles. The amount of amylopectins increased in the zygote stage. The oocyst was surrouned by two
homogenous layers, similar to each other in shape and electron dense characteristics. A third layer appeared
interiorly irregularly shaped with highly dense electron material (Fig.21). As the oocyst developed, the nucleus
became homogenous and provided with a nucleolus and the third layer thickened and cracked. Gradually the
parasitophorous vacuole disintegrated followed by complete lysis of the lecocyte host cell. Flattening of the
neighbouring cells occurred due to gradual enlargement of the oocyst (Figs.20–21).
