VPP 322: Aquatic Animal Diseases, Health Care and Management (1+1)

ROLE OF EYE STALK IN THE REPRODUCTION OF MARINE SHRIMP

• In marine shrimp, the egg production (vitellogenesis) is mainly influenced by the neurosecretory centres located in the ganglia of eyestalk (X organ sinus gland complex), brain and and thoracic ganglia while X organ sinus gland complex of the eyestalk inhibits vitellogenesis under the influence of its hormone viz., gonad inhibiting hormone (GIH) , the brain and thoracic ganglia promote vitellogenesis by their hormone, viz, gonad stimulating hormone (GSH) .
• In nature, the sectretion of GIH is suppressed and thereby, the GSH promotes vitellogenesis. On the basis of this principle, the ovarian development and maturation of gonads are obtained in marine shrimps through the unilateral eye stalk ablation (removal of one of the eye stalks). It is also worth mentioning here, that removal of both the eye stalks though lead to rapid ovarian growth, mentioning does not result under this condition, because the ova are reabsorbed in the ovary, which may be due to the following.
• The eye stalks apart from GIH, produce other neurosecretory hormones which regulate lipid metabolism and protein synthesis in hepatopancreas; induce hyperglycaemia in blood to combat stress; regulate calcium metabolism during cuticle formation; effect water balance during moulting inhibit production of moulting hormone by ‘Y’ organ and influence movement of pigments in chromatophores. As these physiological functions are affected by the removal of both eye stalks is enough in favouring spawning as it helps in the normal functioning of all metabolic processes. Further it is also interesting to note that the behavioural pattern of the eye-stalk ablated females especially their feeding and mating are also not affected.