Histomorphological changes in neurosecretory cells of eyestalk, brain and thoracic ganglia of Parapenaeopsis stylifera (Crustacea: Penaeidae) in relation to ovarian maturation

Abstract

Histomorphological changes in neurosecretory cells of eyestalk (optic ganglia), brain and thoracic ganglia of Parapenaeopsis stylifera during different stages of ovarian maturation were recorded. There were five types of neurosecretory cells (NSCs) in eyestalk with size in range of 5-35 µm. They were distributed along medulla externa, medulla interna and medulla terminalis. Axonal terminals of these neurosecretory cells were found to terminate in sinus gland. Brain and thoracic ganglia possessed five types of neurosecretory cells such as giant neuron (80 µm), A (61-80 µm), B (41-60 µm), C (21-40 µm) and D (20 µm). They were arranged in several groups in different parts of brain - in anterior region B, C and D cells were observed, in posterior region giant neurons and Acells more in numberwhile A, B, C and D cells were found in lateral regions. Of the three regions in thoracic ganglia (anterior, middle and posterior), NSCs were distributed in anterior and posterior portions but were lacking in middle region. Aand B cells were noticed in anterior region followed by C and D cells. In posterior region, giant neurons and Acells were seen. Ovarian maturation in Parapenaeopsis stylifera seems to be under dual control of inhibitory action by the secretion of B and C cells of eyestalk and stimulatory influence by giant neuron (GN), Aand B cells of brain and thoracic ganglia as these NSCs of eyestalk were active in immature stage whereas cells of brain and thoracic ganglia were active in mature females. The active stage of secretion was characterized by hypertrophy, increase in number of nucleolus, staining intensity, granulation and migration of secretory material towards axon. Histochemical tests demonstrated that the neurosecretory cells of the shrimp were strongly positive to acid fuchsin, paraldehyde fuchsin but exhibited feeble reaction to Sudan black B and periodic acid-Schiff's reagent (PAS).