Mode of attachment of a polyopisthocotylean parasite, Metamicrocotyla cephalusto the gills of Mugil cephalus through the study of haptoral compartments

The monogenean parasite, Metamicrocotyla cephalus uses the ventrally located haptor provided with two symmetrical rows of clamps in its attachment to the middle regions of the gill filaments of Mugil cephalus. Several factors are reported that protect the parasite from dislodgement by the breathing water current of the host. Firstly, the body of adult parasite produces 45 degrees with the longitudinal axis of the gill filament and its length is nearly equal to the free distal region of the filament located anterior to the site of attachment. So, the parasite did not bend to loop around the gill filaments as exhibited in mature ones with bodies longer than the gill filaments. Secondly, clamps can tightly grip two successive secondary gill lamellae in alternate positions which are directed inwardly towards the longitudinal axis of the haptor. Thirdly, the number of clamps depends on the age of the parasite where it increases as the age increases. Fourthly, the middle clamps are the largest while the anterior ones are the smallest. Fifthly, there is an exocytotic movement of electron-dense secretory bodies through the thin syncytium in the interior surface of the clamp. Sixthly, the clamp sclerites are embedded into the radial muscle fibers and directly inserted into the sclerite walls especially the median ones. Seventhly, the lateroposterior sclerite II is able to penetrate the gill tissue with its tip under the controlled action of three groups of muscle fibers. Thus, the protrusion and retraction of clamp are controlled by longitudinal haptoral muscle strands and extrinsic muscle fibers forming a highly organized array inside the haptor

Comparative topography and ultrastructure of tegument in a polyopisthocotylean parasite [Metamicrocotyla cephalus] and a monopistho-cotylean parasite [Dactylogyrus Extensus]

Comparative topography and ultrastructure was done for the tegument architecture between a polyopisthocotylean parasite [Metamicrocotyla cephalus] and a monopisthocotylean parasite [Dactylogyrus extensus] for the first time. The result showed that the tegument of M. cephalus is characterized by many foldings producing closely packed annular corrugations superimposed with a complex configuration of many robust papillae bearing microvillus-like projections, thin terminal web just underneath the apical plasma membrane, membranous projections from the basal plasma membrane inside the syncytium, one type of tegumental cell producing two tegumental secretory bodies inside the syncytium [electron-lucent bodies "ts1" and electron-dense bodies "ts2"] and the syncytium is thick [1.3-3 micro m]. The tegument of D. extensus was characterized by the weak annulations and many minute folds like microvilli, some invaginations in the apical plasma membrane form small vacuoles, eruption of some secretory bodies through the apical plasma membrane, three kinds of secretory bodies inside the syncytium from two different tegumental cells [small electron-dense granules "td1" and large fusiform moderately electron-dense bodies containing fibrous threads "td2" from one cell type and thin dumbbell-shaped electron-dense bodies "td3" from other cell type] and the syncytium is thin [1.4-1.5 micro m]. The possible functions of the distinctive features of the tegument whether presence or absence have been discussed, especially the proposed role played during the life of the parasite and the possibility of making them as characteristic features of the polyopisthocotyleans than the monopisthocotyleans