Marine crabs have internal gills covered by an exoskeleton, and, because their whole body is covered by exoskeleton, they cannot expand their body enough to generate much negative pressure within the gill chambers to draw water in over their gills. Which of the following would serve to increase the efficiency of gas exchange by marine crabs?
A) a countercurrent exchange system
B) oxygen- carrying molecules in the blood
C) movement of limbs or other structures to create a current over the gills
D) all of the above
E) only B and C

Question

Quizplus · Accepted Answer

All the options listed would serve to increase the efficiency of gas exchange in marine crabs. A countercurrent exchange system maximizes the gradient for diffusion of gases, oxygen-carrying molecules in the blood increase the capacity for oxygen transport, and movement of limbs or other structures can help draw water over the gills, facilitating gas exchange.

Marine Crabs Have Internal Gills Covered by an Exoskeleton, And