Ambient temperature-associated stress can affect normal physiological functions in ectotherms. To assess the effects of cold or heat stress on amphibians, giant spiny frogs () were acclimated at 22°C followed by exposure to 5°C or 30°C for 0, 3, 6, 12, 24 and 48 h, respectively. Histological alterations, apoptotic index, generation of mitochondrial reactive oxygen species (ROS), antioxidant activity indices and stress-response gene expression in frog livers were subsequently determined. Results showed that many fat droplets appeared after 12 h of heat stress and the percentage of melanomacrophage centres significantly changed after 48 h at both stress conditions. Furthermore, the mitochondrial ROS levels were elevated in a time-dependent manner up to 6 h and 12 h in the cold and heat stress groups, respectively. The activities of superoxide dismutase, glutathione peroxidase and catalase were successively increased with increasing periods of cold or heat exposure, and their gene expression levels showed similar changes in both stress conditions. Most tested heat shock protein (HSP) genes were sensitive to temperature exposure, and the expression profiles of most apoptosis-related genes was significantly upregulated at 3 and 48 h under cold and heat stress, respectively. Apoptotic index at 48 h under cold stress was significantly higher than that under heat stress. Notably, lipid droplets, , and might be suitable bioindicators of heat stress. The results of these alterations at physiological, biochemical and molecular levels might contribute to a better understanding of the stress response of, and perhaps amphibians more generally, under thermal stress.
In crustaceans, chitinases (Chts) play crucial roles in physiological functions such as chitinous food digestion, moulting and stress responses. Chitinases have been identified in both prokaryotes and eukaryotes, but the composition and number of Cht family members vary across species, especially in crustaceans. Seven Cht transcripts, all of which contained the conserved enzyme activity motif, were cloned from Scylla paramamosain for the first time, and SpCht1-SpCht6 were clearly classified into groups 1-6, respectively, through phylogenetic analysis. Notably, SpCht7, which had two catalytic domains, was identified for the first time in crabs and crustaceans.Although SpCht7 could not be grouped into any known Cht subclasses, it clustered together with insect Cht7 and could be classified into a novel subclass that we named group 7. The tissue distributions of SpChts, as well as their expression profiles during embryonic and larval development, growth-related moulting, salinity and cadmium stresses, were also investigated. The results suggested that SpChts might have different and varied biological functions. These results would be helpful for understanding and clarifying the roles of chitinases in crab development, moulting and responses to environmental stress. These results also provide new insight into the origin and evolution of the chitinase gene family in crabs and other crustaceans.
K E Y W O R D Schitinase, development, moulting, Scylla paramamosain, stress
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