Exposure to As(III) and As(V) changes the Ca2+-activation properties of the two major fibre types from the chelae of the freshwater crustacean Cherax destructor

• Exposure to inorganic arsenic species affects the functional properties of crustacean muscle.
• Fibres activated at lower [Ca2+] after exposure to As(III) and As(V) in both fibres.
• Maximum Ca2+-activated force significantly higher after exposure to As(V) in both fibre types.

Arsenic is a known carcinogen found in the soil in gold mining regions at concentrations thousands of times greater than gold. Mining releases arsenic into the environment and surrounding water bodies. The main chemical forms of arsenic found in the environment are inorganic arsenite (As(III)) and arsenate (As(V)). Yabbies (Cherax destructor) accumulate arsenic at levels comparable to those in the sediment of their environment but the effect on their physiological function is not known. The effects of arsenic exposure (10 ppm sodium arsenite, AsNaO2 – 5.7 ppm As(III)) and 10 ppm arsenic acid, Na2HAsO4·7H2O – 2.6 ppm As(V)) for 40 days on the contractile function of the two major fibre types from the chelae were determined. After exposure, individual fibres were isolated from the chela, “skinned” (membrane removed) and attached to the force recording apparatus. Contraction was induced in solutions containing increasing [Ca2+] until a maximum Ca2+-activation was obtained. Submaximal force responses were plotted as a percentage of the maximum Ca2+-activated force.As(V) exposure resulted in lower levels of calcium required for activation than As(III) indicating an increased sensitivity to Ca2+ after long term exposure to arsenate compared to arsenite. Myosin heavy chain and tropomyosin content in individual fibres was also decreased as a result of arsenic exposure. Single fibres exposed to As(V) produced significantly more force than muscle fibres from control animals. Long-term exposure of yabbies to arsenic alters the contractile function of the two major fibre types in the chelae.