The crown-of-thorns sea star, Acanthaster planci, preys on the flesh of live coral. If coral animals are attacked by these sea stars, then what actually provides nutrition to the sea star, and which chemical (besides the toxin within their nematocysts) do the corals rely on for protection?

A) medusae; silica

B) polyps; silica

C) exoskeleton; calcium carbonate

D) polyps; calcium carbonate

Answer: The correct answer is : D) polyps; calcium carbonate

Explanation: This starfish feeds exclusively on hard corals. It can be brown, dark gray, purple, orange or red, the difference in color lies in the food they eat. It has its body covered with thorns that uses them as a means of defense.

d) polyps; calcium carbonate

Explanation:

The Acanthaster planci It is a kind of invasive starfish, which destroys corals: it has poisonous spines and feeds on coral polyps at the expense of the reef.

On the other hand, CO2 reacts with water, forming carbonic acid and reducing the available calcium carbonate, an essential element so that marine organisms, from clams to hedgehogs, can form their skeletons and shells.