Classification of Nerve Cells Dissociated From Tentacles of the Sea Anemone Calliactis parasitica

Nerve cells from tentacles of the sea anemone Calliactis parasitica were dissociated in 1000 units/ml of collagenase for scanning electron microscopic studies and in 0.125% elastase followed by 12 units/ml of ficin for cell counts using light microscopy. The studies revealed 33 distinguishable neuronal shapes, which were categorized as either sensory cells having an apical cilium or ganglion cells with or without a perikaryal cilium and further subdivided into unipolar, bipolar and multipolar neurons based on the number of processes that extended from the perikaryon. Unipolar sensory cells were characterized by an apical cilium adjacent to the perikaryon and a long, simple or terminally branched axon. Unipolar ganglion cells lacked an apical cilium. Bipolar sensory cells had a neck between the cilium and perikaryon and an oppositely directed axon. Bipolar ganglion cells had isopolar processes or asymmetrical processes, which were simple or complexly branched. One type of bipolar ganglion cell with isopolar processes had a perikaryal cilium. Multipolar sensory cells had a distinct neck between the perikaryon and the cilium and two or more simple or complexly branched processes extending from the triangularly shaped cell body. Multipolar ganglion cells had variously shaped perikarya from which extended three or more short or long processes that were simple or complexly branched. One type of tripolar ganglion cell had a perikaryal cilium. The different types of nerve cells were quantified, and statistical comparisons were made.