Variation in the Biochemical Constituents during Different Moulting Stages in Green Tiger Shrimp, Peneaus semisulcatus

A hallmark of crustacean physiology is the periodic shedding of their old exoskeleton achieved by moulting as an external manifestation of a discontinuous growth process. Crustacean metabolism, reproduction and behavior are all affected by the periodic shedding of the exoskeleton and the characteristics of moulting cycles. There are major gaps in our understanding of moulting patterns of commercially raised shrimp; hence, further investigations on the duration of each moult stage, in-moult cycle and the relationship between biochemical constituents and moult cycling are essentially needed. The present research work was aimed at describing characteristic features and biochemical changes that occur at various stages (A-D) during moulting cycle of the Indian green tiger shrimp Penaeus semisulcatus. Experimental animals (wet weight, 20 ± 2 g) were reared individually in aerated plastic aquaria under normal laboratory conditions (12L: 12D; 28.2ºC) and 50% of the water was replaced daily for one month. Animals were provided twice daily with commercial Magnum Scampi feed ad libitum and were observed regularly for moulting by setal development and biochemical analysis in conjunction with established parameters for morphological changes during the moulting cycle. Results showed that muscle protein content peaked during the post-moult stage A (51.23 ± 2.51 mg/g) and gradually declined through the inter-moult and pre-moult stages. Similarly in the hepatopancreas, distinct increase in the total protein content was observed during the post-moult stage B (15.78 ± 0.26 mg/g) and a steady decline was noticed thereafter (p < 0.05). Significantly higher levels of total sugars from muscle tissues were observed in late post-moult stage B (51.23 ± 2.65 mg/g) and minimum level of total sugars were observed in late pre-moult stage D2-3 both in muscle tissue (28.43 ± 2.98 mg/g) and in hepatopancreas (18.79 ± 1.62 mg/g). A sharp fall in lipid content of muscle tissues was observed in inter-moult stage C (19.54 ± 1.45 mg/g) and a corresponding decline (48.21 ± 3.25 mg/g) was observed in the hepatopancreas. The present study documents and further expands our understanding of the physiological and biochemical changes occurring in P. semisulcatusduring four different moulting stages and will provide useful criteria for identifying different stages in the life cycle of this commercially farmed shrimp.