108 學年度學測英文 第 43 題

Angelfish, often found in the warm seas and coral reefs, are among the most brightly colored fish of the ocean. Brilliant colors and stripes form amazing patterns on their body. These patterns actually help the fish to hide from danger among roots and plants. At night, when these fish become inactive, their colors may become pale. Often, the young ones are differently colored than the adults. Some scientists believe that the color difference between the young and the old indicates their different social positions.

Another interesting fact about angelfish is that they have an occupation in the fish world. Most of them act as cleaners for other fish and pick dead tissue from their bodies. This is not their food, though. Their diet consists mainly of sponge and algae.

One particular kind of angelfish, the blackspot angelfish, has a special capability that allows it to change gender from female to male. However, the change is not made at random; it happens for a specific reason. Angelfish live in groups, and each group has one male fish, which is blue in color, and four female fish, which are yellow. The male angelfish is the strongest and largest member of the group. He is the one who protects and looks after the females. When the male dies, the group needs a new “security guard.” This is when the largest female in the group begins to change in appearance. She begins to grow larger in size, and after a week, she starts changing color, from yellow to blue. Slowly, her behavior toward the other fish also changes. She begins behaving like a male. Two weeks later, black stripes appear on her body, indicating the gender change is complete. She is now completely male!