Heat shock response of the blue crab Portunus pelagicus:thermal stress and acclimation

Objective:To determine the effect of prior heat shock on the CTMax of differently acclimated Portunus pelagicus(P.pelagicus)as well as the time course of the changes in CTMax post heat shock.Methods:Crabs P.pelagicus were held in laboratory aquaria in tanks,which were supplied with filtered and aerated seawater.Crabs were acclimated at 20℃,25℃,30℃and 35℃for 3 weeks before their CTMax was determined.The CTMax was recorded for each crab as the median temperature during the 5 min period when a crab was not able to right itself,the average CTMax was calculated.The effect of heat shock on subsequent CTMax was measured.Crabs were heat shocked at temperature 1℃lower than the CTMax for 20 min,followed by either 0.5 h,1 h or 1.5 h recovery at 20℃.The same procedure was repeated at other acclimation temperatures(25℃,30℃and 35℃).Results:Temperature acclimation of P.pelargicus from 20-35℃progressively increased the CTMax.Acclimation at 35℃the CTMax was 42.66℃,whereas acclimation at 20℃the CTMax was 39.8℃.In P.pelagicus acclimated,at 20℃the CTMax values after heat shock were significantly higher than crabs in control for 30 min,1 h and 1.5 h after heat shock.In the 25℃and 30℃acclimated crabs,the CTMax values after heat shock were significantly higher than control only in 30 min and 1 h after heat shock.No significant differences in 35℃acclimated crabs between control and heat shocked crabs were found after recovery for 30 min,1 h,or 1.5 h.Conclusions:Heat shock caused significant rises in the CTMax,however,this increase was progressively reduced with longer recovery times at the acclimation temperature.For 20℃acclimated crabs,the increased CTMax was still evident after 90 min,but for 25℃and 30℃crabs,the response was over after 90 min.Heat shock of 35℃crabs was problematical,the CTMax gave no increased thermotolerance.It must be concluded that the combination of a high heat shock temperature and CTMax determinations were too damaging.

Chitinase activity potential and identification of chitinolytic bacteria isolated of swimmer crab’s cell

This study aimed at investigating the chitinase enzyme activity produced by chitinolytic bacteria from the skin of blue swimmer crab(Portunus pelagicus)and identification of the genus isolate.This study consists of two stages:firstly,the qualitative and quantitative activity of the chitinase enzyme;and secondly,biochemical identification of the bacteria.The quantitative chitinase enzyme activity is measured using the UV-Vis spectrophotometer UV-Vis at the wavelength at 660 nm.The chitinase enzyme is obtained from the isolation of chitinolytic bacteria cultured within a media to grow solid chitin,which contains colloidal chitin substrate as chitinase inductor at the temperature of 30℃.The highest chitinolytic activity is obtained from the 24 h supernatant culture,with a value of enzyme activity at 0.149 U/mL.Macroscopic and microscopic identification showed that the chitinolytic bacteria isolate R1,whereas the biochemical cell shows the characteristics of the genus Pseudomonas.