Cytology and Histology of the Cerebral Neurosecretory Systems in some Tropical Earthworm Species

Abstract

The cerebral ganglia of tropical earthworms, Metaphire houlleti, Metaphire posthuma (Megascolecidae), Eutyphoeus gammiei (Octochaetidae) and Eudrilus eugeniae (Eudrilidae) revealed mainly two categories of neurosecretory cells (NSCs) -A cells and B cells. Thick cortical tier of A cells stained intensely with AF and were differentiated into A1, A2 and A3 types on the basis of their shape, size and location. The sub-cortical B cells, lying close to the neuropile stained lightly with AF. While the axons of A1 cells discharged neurosecretory material (NSM) beneath the perineurium, those of A2, A3 and B cells generally transported NSM at the margin of the neuropile forming "accumulation zone". Our present study revealed that in earthworms, in absence of any well-defined neurohaemal organ, there was a phenomenal deposition of NSM in the "accumulation zone" or tissue spaces beneath the highly vascular perineurium from where the secretion readily entered the capillaries by diffusion to meet the physiological demand of the animal.

Effects of dehydration and subsequent hydration stress on the cerebral neurosecretory cells of Eudrilus eugeniae (Kinberg, 1867)

“…These characteristics indicate functional attributes of cerebral A and B neurosecretory cells in E. eugeniae especially when possible 'super-elevation' in the osmotic concentration of the body fluid is accounted for. According to Chaudhuri and Banik [9] neurosecretory A cells and B cells correspond to peptidergic and aminergic neurones in the central nervous system of earthworm. According to Zimmermann [10], both aminergic and peptidergic neurons of the supraoesophagal ganglia are considered to be indispensable for regulation of the osmotic balance in dehydrated worms, Lumbricus terrestris.…”

Basic Histological Techniques (MicroTechniques) for Staining of Animal Tissue

“…Because most of the tissues are colourless, histological sections must be stained or dyed before study under the microscope. Dyes stain the tissues selectively to enhance the cellular contrast and to highlight features of tissues [4,5,6,7,8]. Common histological stains and reactions are given in Table 1 [1].…”