Final answer:
The crayfish manages nitrogenous wastes and ion balance by excreting them through its Malpighian tubules.
Step-by-step explanation:
The most accurate explanation of the management of nitrogenous wastes and ion balance in the crayfish is excretion through Malpighian tubules. In crayfish, the Malpighian tubules perform the excretory function and maintain osmotic balance. These tubules actively transport ions into the lumen, which draws water, electrolytes, and nitrogenous waste into the tubules. Water and electrolytes can be reabsorbed when faced with low-water environments, while uric acid is excreted as a thick paste or powder to conserve water.