ON THE NEUROSECRETORY SYSTEM OF RIVULOGAMMARUS SYRIACUS CHEVREUX

¹ Department of Biology, Faculty of Science, University of Mosul, Mosul, Iraq

1. The different types of neurosecretory cells occurring in the central nervous system of the freshwater amphipod, Rivulogammarus syriacus, their distribution, neurosecretory activity, and the mode of discharge of the neurosecretory substances were studied.

2. There are six types of neurosecretory cells designated as A, B, B, C, D and E which show definite localization in the central nervous system. The B cells are found only in the medio-dorsal region.

3. These cells can be divided into two groups on the basis of their secretory activities.

(a) The first group of cells (A, C and E types) have dense granulated cytoplasm marked by small granular bodies. These bodies aggregate into larger and darker stained ones and are finally discharged either through the cell membrane into the tissue fluid or into the axons.

(b) The second group of cells (B, B and D types) have neurosecretory granules in the form of a ring outside the Nissl zone. The granules aggregate to form large masses which disappear through the cell and leave vacuoles behind.

4. The contents of the sinus gland show CHP-positive, PAS-positive, toluidine blue positive and sometimes acidophilic substances.

5. It appears that the frontal organs are associated with neurosecretory release.

6. The physiological activities of these neurosecretory substances in the central nervous system of Rivulogammarus are as yet unknown.