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Nerve elements in the planula of the hydrozoan Pennaria tiarella
Author(s) -
Martin Vicki Joan,
Thomas Mary Beth
Publication year - 1980
Publication title -
journal of morphology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 74
eISSN - 1097-4687
pISSN - 0362-2525
DOI - 10.1002/jmor.1051660103
Subject(s) - biology , microtubule , anatomy , cilium , golgi apparatus , cell type , ultrastructure , microbiology and biotechnology , cell , endoplasmic reticulum , genetics
The nerve elements described by light microscopy for the hydrozoan planula have not previously been identified ultrastructurally. This electron microscopic study confirms the presence of two distinct nerve cell types in the planula of the hydroid Pennaria tiarella . Type I nerve cells occur at the base of the ectodermal epithelium just apical to the forming foot processes of the epitheliomuscle cells. The perikaryon contains mitochondria, microtubules, neurosecretory granules, and a prominent Golgi body. Neurites rich in microtubules project from these cells and form a nerve plexus of transversely and longitudinally oriented processes throughout the length of the planula. The Type II nerve cell extends from the free surface of the planula to the mesoglea and bears a single cilium surrounded by long microvilli. The Type I and II nerve cells closely resemble the sensory‐motor‐interneurons and neurosensory cells of Hydra .