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Ultrastructural study of the Central Nervous System of Endemic Geocentrophora (Prorhynchida, Platyhelminthes) from Lake Baikal
Author(s) -
Böckerman Inger,
Reuter Maria,
Timoshkin Oleg
Publication year - 1994
Publication title -
acta zoologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.414
H-Index - 37
eISSN - 1463-6395
pISSN - 0001-7272
DOI - 10.1111/j.1463-6395.1994.tb00961.x
Subject(s) - biology , ultrastructure , flatworm , cytoplasm , neuron , nervous system , synaptic vesicle , turbellaria , vesicle , central nervous system , extracellular , anatomy , neuroscience , microbiology and biotechnology , zoology , membrane , biochemistry
The ultrastructure of the central nervous system of four species of the Geocentrophora group (Prorhynchida, Lecithoepitheliata) has been studied with Geocentrophora wagini as a model organism. This is the first ultrastructural study of the nervous system in flatworms of the endemic Geocentrophora group from Lake Baikal. The neurons are characterized by invaginations of the plasma membrane with extracellular material (ECM) extending deep into the neuronal cytoplasm. Two types of neuron are distinguished on the basis of the character of the cytoplasm and the content of neuronal vesicles. Several more vesicle types are observed in the nerve processes in the neuropile. The following kinds of neuronal release sites are distinguished: single synapses, shared synapses, nonsynaptic release sites characterized by omega profiles and neuromuscular contacts. Special features of the synapses in the species of Geocentrophora are pronounced local thickenings of the presynaptic membrane connected to paramembraneous densities. The ECM‐filled invaginations and the local presynaptic thickenings are features that distinguish the neurons of Geocentrophora spp. from previously described turbellarian neurons.