The surface structures and gland cells of the posterior rosette organ of Gyrocotyle urna Grube et Wagener, 1852, a member of the group presumed to be the most basal of the tapeworms (Cestoda: Gyrocotylidea), was studied by scanning electron and transmission electron microscopy. Surface structures on the outer (oriented away from the intestinal wall) and inner (in contact with the intestinal wall) rosette surfaces differ from each other and represent a transitional form between microvilli and microtriches typical of tapeworms (Eucestoda). The inner surface of the rosette possesses numerous glands. On the basis of the size and electron-density of their secretory granules, three types of unicellular gland cells can be distinguished. The least common type (Type I) is characterized by the production of small, round, electron-dense granules of about 0.3 µm in diameter, whereas another type of secretion (Type II) is formed from homogenous, moderately electron-dense, spheroidal granules of about 0.7 µm in diameter. The most common type of glands (Type III) is recognized by a secretion comprising large, elongate, electron-dense granules of about 1 µm long and 0.5 µm broad. The secretory granules of the three types of the glands are liberated by an eccrine mechanism and the gland ducts open via small pores on the inner rosette surface. The complex of secretory glands of the posterior rosette of G. urna is similar to those in the anterior attachment glands of monogeneans (as opposed to the types of glands present in other helminth groups). However, the tegumental surface structures of Gyrocotyle are supporting evidence for the relationship between the Gyrocotylidea and Eucestoda.
The ultrastructure of three types of unicellular scolex gland cells in adult cestode Bothriocephalus claviceps (Goeze, 1782) is described. The first type - apocrine gland cells transport their secretion (small rounded electron dense granules) via thin ducts into the tegument where it accumulates as projections on the body surface. The second type - eccrine gland cells press out their secretion (large oval electron dense granules) through ducts which open to the exterior surface of the tegument. The third type - microapocrine gland cells transport their secretion (large rounded electron dense granules) through thin cytoplasmic processes into the distal cytoplasm of the tegument. The secretory discharge occurs by means of évaginations of the outer tegumental plasmalemma and their subsequent detachment. The possible functions of the scolex gland cells are discussed.
This review critically examines the ecological costs and benefits of ultraviolet vision in European owlflies. On the one hand it permits the accurate pursuit of flying prey, but on the other, it limits hunting to sunny periods. First the physics of detecting short wave radiation are presented. Then the advantages and disadvantages of the optical specializations necessary for UV vision are discussed. Finally the question of why several visual pigments are involved in UV vision is addressed.
The article considers the writings of the sculptor Andreas Schweigl (1735-1812) and the painters Ignaz Chambrez (1758-1842) and Josef Heřman Agapit Gallaš (1756-1840). Around the year 1800, these three Moravian artists recorded their thoughts and insights in a number of texts that variously combined the traditional literary genre of artist’s biography with artistic topography, art criticism and a historical interpretation of early Moravian art and culture. Since all three were in some way connected with the new system of art education, the aim of this study is to examine whether and in what way standardized education affected not only their professional careers, but also their thinking. For all three, that thinking was rooted in a historical interpretation of the early art and culture of Moravia. All three discuss the function of art, artistic ideals, and to some extent the concept of the creative genius, as well as reflecting, directly or indirectly, on the theme of decadence as one stage in the cyclical view of history, in line with the paradigm of the age. The author sets out to compare their texts and in general terms show 1) how artists themselves viewed the importance of art education at the end of the 18 century; 2) how they responded to the changing role of the artist in society; and 3) how they defined artistic ideals and the artist’s social purpose. It is the wider implications of these changes in the artist’s social status, and in the function of art in Moravia and Central Europe generally, that form the primary focus of this study., Pavel Suchánek., and Obsahuje bibliografické odkazy