Abstract:
Owing to increasing concern of global climate-change, temperature rise is of great interest which can be primarily
evaluated from the seasonal variations in some organisms. Aquatic environment can be extremely
stressful to its inhabitants because most of them are poikilothermous. In the present study, attempt was made to
evaluate the biological effects of oxidative-stress and adaptive/antioxidant capacities during temperature variations
(36–40 °C for 24hrs to 72hrs) in Bellamya bengalensis both in environmental and laboratory conditions by
testing some biomarkers like HSP70, catalase (CAT), superoxide dismutase (SOD), reduced glutathione (GSH)
and glutathione reductase (GR). The biomarker potency of the molecules and the anti-oxidative metabolicnetwork
was postulated and extrapolated to find its resemblance to the climate-change associated organismal
variations. In a natural and eco-restored environment in the Eastern part of India, 10–20 fold increases in CAT,
SOD and HSP70 protein expressions (Western blot results) were noticed in Bellamya paralleling to their increased
enzymatic activities (gel zymogram studies) due to the seasonal (summer versus winter) temperature variation.
It is evident from the consecutive three years’ study that this variation resulted in the unfavorable physicochemical
changes of water quality parameters like dissolved oxygen, biochemical oxygen demand, alkalinity and
consequently decreased the animal density in summer. And that was revived due to their higher reproductionrate
in post rainy/winter season when temperature normalizes resulting in a restoration of favorable environment.
In laboratory condition, the reduced GR and increased GPx indicated the oxidative damage as evident by
higher tissue MDA level following to higher mortality. Changes in SOD and CAT activities suggest activation of
physiological mechanism to scavenge the ROS produced during heat stress. However, when mortality increased
at different time points (36 °C−72 h and 38 °C−72 h), these enzyme activities also decreased as they failed to
save the tissues from ROS. The results suggest that temperature variation does alter the active oxygen metabolism
by modulating antioxidant enzyme activities, which can be used as biomarker to detect sub-lethal effects
of climate change-associated pollution. The parity in environmental and laboratory experimental results may
justify this laboratory experiment as model heat-stress experiment and indicate temperature as a universal
stressor which alone or in combination with other water parameters initiates a consistent adapting behavior. The
Bellamya bengalensis being the highest faunal representative in its habitat may serve as a good bioindicator species.
