ON THE NEUROSECRETORY SYSTEM IN THE CEPHALIC REGION OF THE ISOPOD, TECTIGEPS JAPONIGUS

Abstract

Topographical and histological studies on the neurosecretory system were carried out in Tecticeps japonicus, an isopod.
The sinus gland attached closely to the distal part of the optic lobe. Some of the axones comprising the sinus gland originate in the neurosecretory cells in the brain. Independently of the sinus gland, the pseudofrontal organ is present in the antero-ventral portion of the optic lobe. It is lined with a layer of cells and has a central cavity. Two kinds of substances are contained in this organ. A bundle of nerve tracts which rises in the brain is supplied to the pseudofrontal organ, in which are found granules positive to PAS reaction or acidic dye. Four kinds of neurosecretory cell groups are found in the brain (B1-B4) and 3 kinds of such groups are present in the optic lobe (E1-E3). Axones arising from B1, B3 and B4 are a part of the components of the sinus gland. In these cell groups, 4 types of neurosecretory cells are distinguishable according to their morphological characters. Besides these, several neurosecretory cells exist solitarily in the brain and the optic lobe.