The effect of water temperature on gut mass and digestive enzyme activity in sea cucumber Apostichopus japonicus,including relative gut mass (RGM),amylase,lipase,pepsin and trypsin activities were studied at temperatures of 7,14,21,and 28°C over a period of 40 days.Results show that RGM significantly decreased after 40 days at 21°C and markedly decreased over the whole experiment period at 28°C;however,no significant effect of duration was observed at 7 or 14°C.At 14°C,trypsin activity significantly decreased over 10 and 20 days,then increased;amylase and trypsin activity significantly decreased after 40 days at 28°C.However,no significant effect of duration was found on amylase,pepsin or trypsin activities in the other temperature treatment groups.At 28°C,lipase activity peaked in 20 days and then markedly decreased to a minimum at the end of the experiment.On the other hand,pepsin activity at 28°C continuously increased over the whole experimental period.Principle component analysis showed that sea cucumbers on day 40 in the 21°C group and in the previous 20 days in the 28°C group were in the prophase of aestivation.At 28°C,sea cucumbers aestivated at 30-40 days after the start of the experiment.It is concluded that the effect of temperature on the digestion of A.japonicus is comparatively weak within a specific range of water temperatures and aestivation behavior is accompanied by significant changes in RGM and digestive enzyme activities.
