Ultrastructural observations on the tegumental surface of Polyonchobothrium clarias Woodland, 1925 (Cestoda: Bothriocephalidae), infecting the catfish Clarias gariepinus in Egypt.

Abstract

The fine structure of the tegument of mature proglottids in Polyonchobothrium clarias, Woodland, 1925, family: Bothriocephalidae, a cestode parasite of the cat fish Clarias gariepinus was studied using transmission electron microscopy.The ultrastructural observations of the tegument revealed that it consists of distal cytoplasm connected with underlying perikarya by cytoplasmic bridges. The distal cytoplasm differs in thickness between the different regions of P. clarias and lies on the basal lamina below which there are two layers of muscles, circular and longitudinal bundles. The main characteristic inclusion in the distal cytoplasm is the presence of electron-dense bodies and vesicles of variable size, shape and density. The tegument perikarya lies beneath the surface musculature.Three different types of microtriches varying in shape and size have been observed on the tegumental surface of the mature proglottids of P. clarias, filiform, blade-like spiniform and digitiform microtriches. Multiple functions of such structures; the amplification of the surface area for digestion, absorption, excretion, movement, attachment to the intestinal mucosa of their hosts and external protection. The types and distribution of microtriches are considered to be of systematic and phylogenetic importance.