Ultrastructural studies of three species of Oesophagostomum (nematoda) by scanning electron microscopy.

The surface structure of three predominant intestinal helminth species of Oesophagostomum i.e., Oesophagostomum columbianum, Oesophagostomum venulosum and Oesophagostomum asperum were studied with the help of scanning electron microscopy. Oesophagostomum columbianum has hook like bent structure anteriorly with well developed lateral cervical alae that are interrupted at several intervals. It has external corona radiata (ECR) and internal corona radiata (ICR), ECR comprises of 21 elements and ICR comprises two small elements to each element of ECR. Posterior end of male O. columbianum has bursa with well developed genital cone. On the other hand O. venulosum showed presence of 18 elements in ECR with each element containing two small elements internally constituting ICR. Oesophagostomum asperum had three tier arrangement of the cephalic vesicle with 12 elements in ECR with each element containing two small elements in constituting ICR. Vagina of matured females is covered with copulatory cement.