Which term refers to the motile male gametes of animals?

The term that refers to the motile male gametes of animals is "sperm," which is also commonly referred to as spermatozoa. Sperm cells are specialized for reproduction and possess a flagellum that allows them to swim towards the egg for fertilization. They are typically produced in the male reproductive system through a process called spermatogenesis, which involves several stages, including the transformation of spermatids into fully functional spermatozoa.

In contrast, the other options do not accurately describe male gametes. A solute refers to a substance that is dissolved in a solvent, often used in the context of solutions in biology and chemistry, not related to reproductive cells. Species is a term for a group of organisms that can interbreed and produce fertile offspring, which does not pertain specifically to male gametes. Spermatids are the intermediate cells in the process of sperm development but are not motile and do not have the characteristic structure needed for swimming. Thus, the correct term for motile male gametes in animals is indeed sperm (or spermatozoa).