Serotonin modulation of hemolymph glucose and crustacean hyperglycemic hormone titers in Fenneropenaeus indicus

Crustacean hyperglycemic hormone (CHH), a neurohormone synthesized and released from the X-organ sinus gland complex, is primarily involved in carbohydrate metabolism. Biogenic amines and peptidergic neuroregulators are known to modulate the release of CHH. Although mechanisms involved in hormone release in the shrimp, Fenneropenaeus indicus is poorly understood. Daily variations in the levels of crustacean hyperglycemic hormone and serotonin in the shrimp F. indicus were studied. Both CHH and glucose levels increase during the first hours after the beginning of darkness. The animals were injected with serotonin and glycemic and CHH levels were determined after 2 h of injection. Serotonin caused significant hyperglycemia (P < 0.0.5) in both intact and eyestalk ablated shrimp. These results support the hypothesis that serotonin produces hyperglycemia in crustaceans by triggering release of hyperglycemic hormone both from the eyestalk and from the other sites of its release.