Abstract. The egg shell of Huffmanela huffmani Moravec, 1987 forms three main layers: an outer vitelline layer, a middle chitinous layer, and an inner lipid layer. The vitelline layer, forming the superficial projections of the egg shell, comprises two parts: an outer electron-dense, and an inner electron-lucid part. The chitinous layer is differentiated into three parts: an outer homogenous electron-dense part, a lamellated part, and an inner electron-dense net-like part. The lipid layer comprises an outer net-like electron-lucid part, and an inner homogenous electron-lucid part. The polar plugs are formed by electron-lucid material with fine electron-dense fibrils.

The morphology of the scolex of the tapeworm Silurotaenica siluri (Batsch, 1786) (Proteocephalidae: Gangesiinae), a specific parasite of European wels (Silurus glanis L.), was studied using light, scanning (SEM), and transmission electron (TEM) microscopy. The scolex of S. siluri is rather uniform in shape and size; it is globular, and has four prominent, anteriorly directed suckers and a spherical, muscular apical organ corresponding to the rostellum of cyclophyllidean cestodes. The rostellum-like apical organ is armed with five to six irregular rows of small hooklets with a wide, oval basal plate and a short, posteriorly curved blade. The excretory system of the scolex is formed by sinuous secondary canals ending blindly beneath the distal layer of the tegument, not opening outside. The surface of the scolex is covered with filiform microtriches; giant spine-like and blade-like microtriches, incorrectly interpreted as spines or hooklets in previous descriptions of S. siluri, are present on the neck region and posterior margins and internal cavities of the suckers. It is assumed that tegumental spines reported in the scolices of other proteocephalideans (subfamilies Acanthotaeniinae and Gangesiinae, genera Spasskyellina and Nomimoscolex) could indeed be spiniform microtriches.

Summary :In the scolex-neck region of the adult Proteocephalus macrocephalus two types of eccrine gland cells are present. The first type of gland cells, localized in the frontal part of the scolex only, contains large, more or less round electron lucid granules. The second type of unicellular glands produces large electron dense granules. These electron dense granular gland cells are localized primarily in the neck region, only few are present in the scolex apex. The secretion of both types of gland cells is concentrated in the ducts opening to the exterior. The ducts are fixed to the plasmalemma of the tegument by septate junctions. The function of both types of gland cells is discussed.

Abstract. In the apical glandular region of the adult Proteocephalus torulosus (Batsch, 1786), two types of eccrine gland cells are present. The first type of unicellular gland produces large electron-dense granules of various sizes. The second type contains small electron-dense granules. Most cells form glands with large granules; glands with small granules are infrequent. The secretion of both types of gland cells is concentrated in the apical parts of the cyton and in the ducts opening to the exterior. On the scolex of P. torulosus, there are regional structural differences of the microthrix border. The apical glandular region bears filamentous microtriches only. On the remaining frontal part, surrounding the glandular region, there are blade-like and filamentous microtriches. The lateral parts of the scolex and suckers bear blade-like microtriches. Possible functions of both types of gland cells and different parts of the scolex microthrix border are discussed. The unique structure of the frontal part of the scolex of P. torulosus and its differences from Proteocephalus macrocephalus, P. longicollis and P. percae correlate well with the putative basal phylogenetic position of P. torulosus among European species of Proteocephalus.The information about the ultrastructure of the tegument, including gland cells, may be useful in the systematics of proteocephalidean and other fish cestodes

Abstract. In the adult fish trematode Crepidostomum metoecus (Braun, 1900), four types of sensory receptors were observed inside the forebody tegument and one type beneath the tegument basal lamina. Two types of sensory receptors extend through the thickness of tegument and have a free cilium inside a pit (types I and II). Two types (III and IV) are nonciliate and entirely intrategumental in location. Type IV receptor with large horizontal and thin vertical rootlets was described earlier in aspidogastreans only. Below the basal lamina, nerve endings in close association with muscle fibres, comparable with those in the Aspidogastrea, were detected.

Nonciliate, uniciliate, and multiciliate receptors were shown by transmission electron microscopy to occur in the body tegument of Echinostoma revolutum (Froelich 1802) cercariae. Detailed studies revealed three types of nonciliate, four types of uniciliate, and one type of multiciliate sensory endings. Most receptors were singly distributed. Only a few of them formed paired receptor complexes in three regions of the cercarial body. These receptor complexes were found to possess nonciliate, uniciliate, and multiciliate sensory endings.

The neodermis of the whole early rostellum of Silurotaenia siluri (Batsch, 1786) bears filamentous microtriches. At the base, there are five to six irregular rows of hooks and spine-like microtriches. The rostellar hooks of S. siluri originate through the enlargement of microtriches. Electron-dense hook substance is deposited along the edges of the microthrix to form the hook blade and basal plate. The blade does not become hollow as in the cyclophyllidean cestodes. The basal plate of the hook, corresponding to the handle and the guard of Cyclophyllidea, is formed by the deposition of hook substance around the base of the microthrix. Within the centre of the base, only a narrow cleft-like core is occupied by distal cytoplasm. The hook bases are more deeply inserted into the distal cytoplasm, as the bases of the spine-like microtriches are localized on the rostellum below the rows of hooks. No hemidesmosomes, fixing the hook base to the basal lamina, are present. Eccrine gland cells and uniciliate and nonciliate sensory receptors of the primitive rostellum are described.

Abstract. Five types of presumed ciliate sensory receptors were detected in the forebody papillae of the adult fish trematode, Crepidostomum metoecus (Braun, 1900). The cilia are short and submerged in a tegumental pit. The apical bulb part of all types of receptors observed is supported by a dense collar and connected to the tegument basal plasma membrane by a circular septate junction. In sensory receptors types I and III no rootlet is present; the bulbs of sensory receptors types III and IV contain an electron-dense formation.