Physiological and Transcriptional Responses of the Blood Clam Anadara kagoshimensis (Tokunaga, 1906) During Cadmium Exposure

Cadmium (Cd) exposure can affect metal handling, metabolism and tissue condition in bivalves on different timescales. We examined these responses in the blood clam Anadara kagoshimensis (Tokunaga, 1906) exposed to a nominal Cd concentration of 100 μg/L. Respiration, tissue Cd, redox biomarkers and histology were assessed over 480 h, alongside hepatopancreas RNA profiles at 0 h, 24 h and 21 d. Oxygen consumption reached its lowest exposed mean at 96 h. At 480 h, Cd concentrations were 44.23 ± 8.99 μg/g dry weight in the hepatopancreas and 31.75 ± 1.81 μg/g in the gill. SOD and CAT activities followed tissue-specific trajectories, GSH content declined, and MDA showed non-monotonic changes. Histological observations included epithelial detachment and disruption of digestive tubule structure. Descriptive expression comparisons identified metal handling, redox, cell-death and immune-related candidates, with more twofold expression differences at 21 d than at 24 h. qRT-PCR examined ten selected targets using three tank-derived RNA samples per time. Together, the physiological measurements, tissue observations and exploratory expression profiles describe a tissue- and time-dependent response to Cd exposure and identify candidates for further functional study.