Respiration is a process of exchanging gas.
Answer:
These structures that protect the sponges from most predators, but not turtles, are spicules.
Explanation:
Sponges <em>skeleton</em> is composed of <em>calcium carbonate and siliceous</em> micro-structures called <u>spicules</u>. Their morphology is so varied that it is used in taxonomy for identification and classification.
There are different kinds of spicules:
- <em>Monoaxonic spicule</em>: needle-shaped, straights or curves
- <em>Tetraxonic spicules:</em> they have four prolongations
- <em>Triaxonic or Hexaxonic spicules</em>
- <em>Poliaxonic spicules </em>
Two terms can be applied to any of these spicules kinds:
- <em>Megaspicules</em>: They are elongated and compose the main architecture of the sponge skeleton
- <em>Microspicules</em>: Variable in shape and size, with ancillary functions
Sponges have few predators thank to the spicule structures and their high toxicity. Many of them are capable of perforating soft tissues and producing urticant substances.
