COMPARATIVE FINE STRUCTURE OF OUTER TEGUMENT OF LIGULA INTESTINALIS AND SCHISTOCEPHALUS SOLIDUS

The outer tegument (epidermis) of the plerocercoid stage of Ligula intestinalis, removed from the body cavity of the minnow (Phoxinus phoxinus) was examined by electron microscopy to determine whether the outer level was similar to that of the plerocercoid of Schistocephalus solidus from the stickleback Gasterosteus aculeatus. Significant differences were observed in Ligula in the arrangement of microtriches, presence of extrusions, and vesicular composition below the outer plasma membrane. The outer tegument of Ligula, though basically similar to Schistocephalus, shows certain differences, even though the plerocercoids of each species occupy a similar environment, the fish body cavity. The situation in each case, however, is not the same, as the plerocercoids of Ligula promote a significant host reaction and live for a considerable length of time, whereas in Schistocephalus there is less host reaction and the plerocercoid does not reach a comparable size or age due to the length of life of its host G. aculeatus. © 1968.