Ultrastructure of the nerve cells and sensilla of Geocentrophora baltica (Platyhelminthes,Lecithoepitheliata) and the surface sensilla in the Geocentrophora group |
| |
Authors: | Inger Böckerman Olga I Raikova Maria Reuter Oleg Timoshkin |
| |
Institution: | (1) Department of Biology, Åbo Akademi University, Artillerigatan 6, FIN-20520 BioCity, Åbo, Finland;(2) Zoological Institute of the Academy of Sciences of Russia, Universitetskaya nab. 1, 199034 St. Petersburg, Russia;(3) Limnological Institute, Siberian Division of the Russian Academy of Sciences, Box 4199, 664033 Irkutsk, Russia |
| |
Abstract: | Two types of nerve cell could be distinguished ultrastructurally in the central nervous system of Geocentrophora baltica (Prorhynchida, Lecithoepitheliata). Both show invaginations in the plasma membrane, but they differ in the character of the cytoplasm (light or densely stained) and the distribution of the neuronal vesicles (evenly or in groups). Different kinds of vesicles and neuronal release sites are observed. Special features of the synapses are pronounced local thickenings of the presynaptic membrane connected to paramembranous densities. In G. baltica and five endemic Geocentrophora spp. from Lake Baikal six types of surface sensillum were observed at the epidermal surface: 1. those with a long thin rootlet; 2. a short, balloon-shaped cilium with an aberrant axoneme and a reduced rootlet; 3. a rootlet branching into many striated bundles; 4. a thick rootlet; 5. a reduced rootlet and numerous neurotubules;and 6. collared sensilla each with one cilium in a deep pit surrounded by a collar of 11 to 12 microvilli. The variable number of microvilli in the collared sensillum is considered plesiomorphic relative to the stable number of eight microvilli known in sensilla of the Prolecithophora, Proseriata, and Rhabdocoela. The ultrastructure of the collar sensillum indicates that the Lecithoepitheliata is only distantly related to the Prolecithophora and higher turbellarians. |
| |
Keywords: | ultrastructure nervous system sensilla cilia Lecithoepitheliata Lake Baikal |
本文献已被 SpringerLink 等数据库收录! |
|