The effects of gradual or abrupt changes in salinity on digestive enzymes activity of Caspian kutum,Rutilus kutum (Kamensky, 1901) larvae |
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Authors: | N Gheisvandi A Hajimoradloo R Ghorbani S H Hoseinifar |
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Institution: | Department of Fisheries, Faculty of Fisheries and Environmental Sciences, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran |
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Abstract: | This study investigates the effects of gradual or abrupt changes in rearing salinity on food transit time and digestive enzymes activity of Caspian kutum (Rutilus kutum) larvae. The larvae (532 ± 0.05 mg) were supplied and randomly allocated into 12 tanks at a density of 45 fish per tank. Experimental treatments were fresh water (salinity 0) FW] as control, exposure to salinity 5 T1], and gradual transfer to salinity 10 in two steps of first to 5 h, then and after 12 h to a salinity of 10 T2], and abrupt change (direct transfer to a salinity of 10 T3]). Results showed at 8 h after start of feeding that the larvae intestine was filled with food pellets except in treatment T1. Enzyme activity responded to salinity change as follows: the highest trypsin, amylase, and chymotrypsin activities were observed in T1; however, these were not significantly different to treatment T3 (P > 0.05). Trypsin activity peaks in the FW and T2 groups occurred 8 h after feeding, and in T3 and T1 groups 5 h after feeding. Peak chymotrypsin and alkaline phosphatase activity was observed 5 and 8 h after feeding in all experiments, respectively. The highest α amylase activity in FW and T2 groups occurred 5 h after feeding, while in T3 and T1 these peaks were observed 8 h after feeding. These results indicate that salinity had some noticeable effects on the activities of digestive enzymes after feeding. |
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