No abstract

No abstract

The ultrastructure of the mature spermatozoon and the spermiogenesis of a cestode belonging to the family Metadilepididae is described for the first time. The mature spermatozoon of Skrjabinoporus merops is characterized by twisted peripheral microtubules, the presence of a single crested body, periaxonemal sheath and electron-dense rods, and the absence of intracytoplasmic walls and inclusions (glycogen or proteinaceous granules); no peripheral microtubules where nucleus contacts the external plasma membrane. Four morphologically distinct regions of the mature spermatozoon are differentiated. The proximal part (Region I) contains a single crested body, periaxonemal sheath is absent in some (proximal) sections and is present in others situated closer to the nucleus. The central Region II is nucleated, and is followed by Region III that contains a periaxonemal sheath. The distal pole, Region IV, is characterized by disintegration of the axoneme. Spermiogenesis follows the type III pattern (Bâ and Marchand 1995) although in S. merops a slight flagellar rotation is observed. The differentiation zone is characterized by the absence of striated roots and intercentriolar body; two centrioles are present, one of which gives rise to a free flagellum. The latter rotates and undergoes proximodistal fusion with the cytoplasmic protrusion of the differentiation zone. Spermiological characters of S. merops are similar to those of the families Taeniidae and Catenotaeniidae. The mature spermatozoon differs from those of the Dilepididae (where the metadilepidid species have previously been classified) by the lack of glycogen.

No abstract

_________________________________________________________________ AbstractGeneral atmospheric circulation is the system of atmospheric motions over the Earth on the scale of the whole globe. Two main types of circulation have been identified: zonal -characterized by low amplitude waves in the troposphere moving quickly from west to east, and meridional with stationary high amplitude waves when the meridional transfer is intensified. The prevailing type of circulation is related to global climate. Based on many years of observations, certain "circulation epochs" have been defined when the same type of circulation prevails for years or decades. Here we study the relation between long-term changes in solar activity and prevailing type of atmospheric circulation, using NAO index reconstructed for the last four centuries as a proxy for large-scale atmospheric circulation. We find that when the southern solar hemisphere is more active, increasing solar activity in the secular solar cycle results in increasing zonality of the circulation, while when the northern solar hemisphere is more active, increasing solar activity increases meridional circulation. In an attempt to explain the observations, we compare the shortterm reaction of NAO and NAM indices to different solar drivers: powerful solar flares, high speed solar wind streams, and magnetic clouds. ___________________________________________________________________________