The Ultrastructure of Neurons and Neuroglia in the Cerebral and Pleuro-Pedal Ganglia of Haliotis asinina Linnaeus

The ultrastructure of neurons and neuroglia in the cerebral and pleuro-pedal ganglia of Haliotis asinina are described. There are four types of neurons (NR1-4) and three types of neuroglia. (NG1-3). The NR1, which is the largest nerve cell, has a round nucleus with a thin rim of heterochromatin attached to the nuclear envelope. The cytoplasm contains numerous rough endoplasmic reticulum, mitochondria, but only a few small elementary granules. The nuclei of NR2 , NR3 and NR4 have increasingly condensed heterochromatin. The cytoplasm of these cells contain relatively few organelles such as rough endoplasmic reticulum, mitochondria and elementary granules. The NG1 is spindle-shaped with little perinuclear cytoplasm. The NG2 and NG3 are highly ellipsoid in shape. The cytoplasm of NG1 and NG3 is very thin and contains ribosomes, a few rough endoplasmic reticulum and mitochondria. The cytoplasm of NG2 is extremely thin and contains only ribosomes. There are no elementary granules in the neuroglia.