Scolex morphology of the cestode Silurotaenia siluri (Batsch, 1786) (Proteocephalidae : Gangesiinae), a parasite of European wels (Silurus glanis)

The morphology of the scolex of the tapeworm Silurotaenia siluri (Batsch, 1 786) (Proteocephalidae: Gangesiinae), a specific parasite of European wels (Silurus glanis L.), was studied using light, scanning (SEM), and transmiss ion electron (TEM) microscopy. The scolex of S. siluri is rather uniform in shape and size; it is globular, and has four prominent, anteriorly directe d suckers and a spherical, muscular apical organ corresponding to the roste llum of cyclophyllidean cestodes. The rostellum-like apical organ is armed with five to six irregular rows of small hooklets with a wide, oval basal p late and a short, posteriorly curved blade. The excretory system of the sco lex is formed by sinuous secondary canals ending blindly beneath the distal layer of the tegument, not opening outside. The surface of the scoter is c overed with filiform microtriches; giant spine-like and blade-like microtri ches, incorrectly interpreted as spines or hooklets in previous description s of S. siluri, are present on the neck region and posterior margins and in ternal cavities of the suckers. It is assumed that tegumental spines report ed in the scolices of other proteocephalideans (subfamilies Acanthotaeniina e and Gangesiinae, genera Spasskyellina and Nomimoscolex) could indeed be s piniform microtriches.