The present study focuses on the body surface of some flatworms that the phylogenetic relationship of their taxa has been questionable. The study is also extended to investigate the polymerase chain reaction (PCR) technique as a method to evaluate molecular variations between members of these taxa. Representatives of the major flatworm taxa were chosen to define the degree of homology and diversity in the fine structure of the body wall. Aspidogaster conchicola was chosen as a representative of aspidogastrid trematodes, Cynodiplostomum azimi and Eumasenia aegypticus to represent digenetic trematodes, Macrogyrodactylus clarii as an example of monogenea and a caryophyllid species to represent monozoic eucestodes. Collective comparative results showed that certain types of inclusion bodies and vesicles were shared between some species, while others were very specific. Mitochondria appeared in different forms, sizes and regions reflecting the level of metabolic activity. In regards to the degree of development of the musculature of the body and attachment organs, Macrogyrodactylus clarii was the most developed as demonstrated with the thickness and arrangement of the muscle fibers. Two types of tegumental cells were observed in Aspidogaster conchicola, Eumasenia aegypticus and Macrogyrodactylus clarii, while both Cynodiplostomum azimi and the caryophyllid species had only one type. The size and electron density of the tegumental cells and their richness with inclusion bodies, vesicles, and glycogen granules were species specific. Phylogenetic analysis of the five species based on ultrastructural tegumental features confirmed the monophyletic status of all studied species; the caryophyllid species together with the two studied digenetic trematodes form one clade with 54% similarity value, while Macrogyrodactylus clarii and Aspidogaster conchicola are derived from one clade with a similarity value of 75%. The studied species were genetically differentiated and the similarity coefficient was detected by means of RAPD technique using five random primers. A high similarity value was detected between the caryophyllid species and Cynodiplostomun azimi (76%) and between Macrogyrodactylus clarii and Aspidogaster conchicola (71%), while a low similarity value was scored between Aspidogaster conchicola and Cynodiplostomum azimi (42%).
Platyhelminthes, Tegument, Ultrastructure, PAPD-PCR, Phylognetic analysis