[Campbell Biology P.1040] A vampire bat faces unique excretory challenges depending on its ac... | Practice Question

A vampire bat faces unique excretory challenges depending on its activity. Immediately after feeding, it excretes large volumes of dilute urine, but when in the roost, its diet primarily consists of protein. Based on this information and general knowledge of kidney function, what is the most significant excretory challenge for a vampire bat during its roosting period, and how does the kidney typically adapt?

  • A: Challenge: Eliminating excess water to reduce body mass for flight after feeding, and then managing high nitrogenous waste from protein digestion in the roost. Adaptation: Rapid excretion of dilute urine followed by production of concentrated urine.
  • B: Challenge: Preventing blood clotting due to anticoagulants in saliva. Adaptation: Kidneys secrete specific enzymes to neutralize anticoagulants.
  • C: Challenge: Maintaining constant blood glucose levels after consuming protein-rich blood. Adaptation: Kidneys regulate glucose reabsorption to prevent hypoglycemia.
  • D: Challenge: Recovering from potential dehydration due to long flights and lack of water sources. Adaptation: Kidneys highly efficient in water reabsorption, producing extremely hyperosmotic urine at all times.

Explanation

The vampire bat first consumes large volumes of blood, becoming too heavy to fly, so its kidneys rapidly excrete large volumes of dilute urine to shed excess water and reduce body mass. Once in the roost, its diet is primarily protein, which, upon digestion, generates large amounts of nitrogenous waste like urea . The kidney must then shift to concentrating urine to efficiently excrete these wastes with minimal water loss, facing a different regulatory problem.