Question

In the crayfish, blood is pumped into spaces called sinuses around the organs. After delivering oxygen and picking up wastes, the blood drains back into the heart through the ostia. What type of circulatory system is this?

a. open
b. close

Answer 1

Crayfish have an open circulatory system, where the blood, or hemolymph, is not enclosed in blood vessels and directly bathes the organs, in contrast to a closed circulatory system found in vertebrates.

Step-by-step explanation:

The circulatory system described, where blood is pumped into spaces around the organs and then drains back into the heart through ostia, is characteristic of an open circulatory system. In this type of system, the fluid that circulates around the body mixed with blood, known as hemolymph, is not confined entirely within blood vessels but rather flows within the body cavity or hemocoel.

This contrasts with a closed circulatory system, where blood is confined to blood vessels and separates from the interstitial fluid. In an open system, as is found in most arthropods like crayfish and many mollusks, the hemolymph directly bathes organs and tissues, facilitating gas and nutrient exchange without the need for a network of capillaries as seen in closed systems.

Therefore, the final answer is that crayfish have an open circulatory system, which is typical of arthropods and functions with a different efficiency trade-off compared to closed systems found in vertebrates like fish and birds.