A Coccidian Parasite Inhabiting the GI Tract and Leucocytes of <i> Styela plicata </i> (Lesuaer, 1823) and <i> Ciona intestinalis </i> (Linnaeus, 1767) Sampled from the Arabian Gulf (Saudi Arabia)

Abstract

Styela plicata and Ciona intestinalis were collected from the shallow water of the Arabian Gulf, Saudi Arabia during 2011 – 2014. Breeding and non breeding seasons were considered. Specimens were dissected alive in seawater and isolated parts from the intestine were sampled. In a previous study, a sporocyst of a coccidian was observed completely embedded in the intestinal epithelial cells of Styela plicata . Since that time, the author tried to find all stages of the life cycle of this coccidian parasite and describe them. Ascidians may obtain parasites from their food through water filtration, or directly swallow an unsporulated oocyst with incurrent water. Sporozoites initiate infection probably homoxenously or heteroxenously. Sporozoites then enter host intestinal epithelial cells and there transform into meronts. Merozoites of the final merogony enter blood cells to initiate the gametic cycle, and become either macrogamonts or microgamonts. Microgamontes became trophozoites (uninucleated zoite). These divide by multiple fission to produce large numbers of flagellated microgametes. Macrogamonts develop into macrogametes without further division. Syngamy produces zygotes, then merogony proceeds to form merozoites which enter new host cells extraintestinal like blood cells to produce more merogonous cycles. The present study concluded that the investigated parasite may belong to Genus Isospora (schneider, 1881). Since in isosporans sporogony leads to the formation of four sporozoites inside each sporoblast and this agametic phase develop extraintestinal.