Sarcocystis acanthocolubri sp. n. infecting three lizard species of the genus Acanthodactylus and the problem of host specificity. Light and electron microscopic study

In the present investigation, macroscopic sarcocysts of Sarcocystis acanthocolubri were observed in muscles of 42 (4.3%) out of 975 Acanthodactylus sp. lizards collected from different geographical areas in Egypt. The infection rate was 6.4% in Acanthodactylus boskianus , 2.1% in Acanthodactylus sculentus , and 5% in Acanthodactylus paradalis . The highest infection rate was recorded in the lizards captured from Baltem (10% in A. boskianus and 8% in A. paradalis ). The infection rate was usually higher in females (7.4%) than in males (3.8%). Moreover, the highest infection rate was recorded in summer (7.53%), autumn (3.57%), and spring (3.11%), and the lowest was recorded in winter (0.91%). Also, old animals had higher infection rates (10.8%) than young ones (0–2.7%). Macrocysts measured 0.95 × 10.12 mm. Both macroscopic and microscopic sarcocysts were enclosed only by a primary cyst wall, which had many finger-like, stalkless, and non-branched protrusions giving it a striated appearance. The primary cyst wall measured 3.9 μm. A dark granulated ground substance was found directly underneath the protrusions and is extended interiorly dividing the cyst cavity into many compartments containing the parasites (metrocytes and merozoites). Metrocytes were found directly under the ground substance and usually multiply asexually by endodyogeny producing two merozoites from each metrocyte. Both metrocytes and merozoites had the apical complex structures characteristic to the genus Sarcocystis . Transmission experiments with three snake species indicated that the snake Spalerosophis diadema is the proper final host belonging to the family Colubridae. The prepatent period was 16 days, while the patent period was 35 days. The results obtained from the present investigation revealed that this is a new species which was named Sarcocystis acanthocolubri .