. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. GANGLIONIC CELLS OF PLANULAE 321. Figure 3. Dividing "neural" interstitial cell at the base of the ectodermal epithelium. Once such divi- sions are completed the progeny begin to differentiate into ganglionic cells. Such ganglionic cells grow neurites in between the cell bodies causing the cell bodies of the progeny to move apart. NS. nucleus; NU. nucleolus, xl 1,670. characterized by a single apical cilium and numerous cy- toplasmic microtubules and neurosecretory droplets. Martin and Thomas (1980) and Thomas el a
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. GANGLIONIC CELLS OF PLANULAE 321. Figure 3. Dividing "neural" interstitial cell at the base of the ectodermal epithelium. Once such divi- sions are completed the progeny begin to differentiate into ganglionic cells. Such ganglionic cells grow neurites in between the cell bodies causing the cell bodies of the progeny to move apart. NS. nucleus; NU. nucleolus, xl 1,670. characterized by a single apical cilium and numerous cy- toplasmic microtubules and neurosecretory droplets. Martin and Thomas (1980) and Thomas el al. (1987) demonstrated that planular sensory cells are derivatives of the ectodermal epithelium. Ganglionic cells are found at the base of the ectoderm and possess neurites rich in microtubules and mitochondria. Ganglionic cells arise from undifferentiated interstitial cells (Martin and Thomas, 1981a, b). Surprisingly, the cytomorphosis of sensory cells (Martin, submitted) and ganglionic cells in planulae has never been described. This study employs transmission electron microscopy to examine the differentiation of ganglionic cells in hy- drozoan planulae of Halocordyle disticha. Beginning with the young interstitial cell and ending with the fully formed ganglionic cell and its neurites, this work pres- ents the first comprehensive morphological description of ganglionic cell differentiation and genesis of the neural plexus in the planula, identifies two morphological types of ganglionic cells in the planula, and provides morpho- logical evidence suggesting that larval ganglionic cells are multifunctional neurons. Materials and Methods Colonies of the marine hydrozoan Halocordyle disti- cha were collected from pier pilings in Morehead ( 'ity, North Carolina. Fronds from male and ' Figure 1. Interstitial cells in the endoderm of an 8 hour embryo. These cells are undiffereMi that contain a centrally located nucleus with one to several nucleoli (arrows). A few segments if rough en
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
