Embryogenesis of the central nervous system of the pond snail Lymnaea stagnalis L. An ultrastructural study

T. Nagy, K. Elekes

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

The ultrastructural characteristics of the developing CNS of the pond snail, Lymnaea stagnalis, were investigated, with special attention paid to three specific stages of embryonic development, representing distinctly different phases of both the body morphogenesis and gangliogenesis. These were the 35% (veliger), the 50-55% (metamorphic), and the 75% (post-metamorphic, adult-like) stages of embryonic development. Also, a brief comparison was done with the CNS of hatchlings (100% of embryonic development). During embryogenesis specialized axo-axonic synapses and elements of the glial system, including the ganglionic (neural) sheath, were rarely observed, whereas the frequent occurrence of unspecialized axo-somatic contacts could be demonstrated. Synapse-like axo-axonic connections could be found first in 75% embryos, showing asymmetric vesicle clustering on the 'presynaptic' side and increased electron density of the apposed membranes. These phenomena may reflect the dominance of modulatory processes in the CNS during embryogenesis, and the absence of the neural sheath may facilitate trophic and/or hormonal influences within the developing ganglia. The gradual increase in the size of ganglia and the diameter of their neuropils was not accompanied by any widening of the cell body layer or increasing diameter of the nerve cell bodies until the very end of embryogenesis. With respect to the ultrastructural organization of the neuropil, and possibly the entire CNS, a determining stage seems to be that of metamorphosis. Two types of neuropil could be observed at this time; the metamorphosing neuropil with an irregular organization of wavy axon profiles, and well-structured neuropil with a regular organization of axon profiles. Ganglia with irregular or regular neuropil occurred simultaneously in the developing CNS.

Original languageEnglish
Pages (from-to)43-60
Number of pages18
JournalJournal of Neurocytology
Volume29
Issue number1
DOIs
Publication statusPublished - 2000

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Lymnaea
Neuropil
Snails
Embryonic Development
Central Nervous System
Ganglia
Synapses
Axons
Morphogenesis
Neuroglia
Cluster Analysis
Embryonic Structures
Electrons
Neurons
Membranes

ASJC Scopus subject areas

  • Neuroscience(all)
  • Anatomy
  • Cell Biology
  • Histology

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Embryogenesis of the central nervous system of the pond snail Lymnaea stagnalis L. An ultrastructural study. / Nagy, T.; Elekes, K.

In: Journal of Neurocytology, Vol. 29, No. 1, 2000, p. 43-60.

Research output: Contribution to journalArticle

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