Response of heart rates to cadmium-exposed stress and early warning capacity in Anodonta woodiana juveniles

Abstract:

This study investigates the response of heart rates to cadmium-related stress and its early warning capacity among juveniles of “standardized” Anodonta woodiana, a unique bioindicator used in the “Freshwater Mussel Watch” project. Heart rates of early juvenile mussels at several typical growth stages, from heartbeat-clearly-observed to shells-no-longer-transparent, i.e., EJ1 [25 days old; shell length (1.5±0.1) mm], EJ2 [55 days old; shell length (10.5±0.6) mm], EJ3 [70 days old; shell length (20.4± 0.9) mm], and EJ4 [85 days old; shell length (30.0±2.0) mm], were studied under non-lethal/non-injury conditions. The response of heart rates to different concentrations of Cd2+ (0.0025, 0.005, 0.025, 0.1, and 0.5 mg/L) in EJ4 were examined. The results show that heart rates of early juveniles generally differed little between ante meridiem and post meridiem (P>0.05) states. Heart rates were linearly and negatively correlated with age and shell length (P<0.05). Heart rates were linearly and negatively correlated with exposure time in the exposure groups of 0.0025 and 0.5 mg/L Cd2+ (P<0.05). However, heart rates were linearly and negatively correlated with Cd2+ concentrations in all exposure groups (P<0.05). These results indicate that a new early warning/monitoring system for Cd2+ contamination may be developed using responses characteristic of “standardized” A. woodiana to Cd2+ concentrations.