Fins, Shoals and Stress: teacher key

Red-Bellied Piranhas, grade 9 edition, written for 9th grade. Scientists describe the red-bellied piranha's diet in different ways, and a shoal seems to calm a fish. Read what the evidence says about food, groups and nests.

Read the book. Print this page for the key.

Questions and answers

1. What does Steve Huskey say piranhas get most of their nutrients from?
   • Eating only fruit
   • Clipping the fins of other fish (answer)
   • Digging mud
2. According to a science writer, how do piranhas in larger shoals compare with those alone?
   • They are far less stressed (answer)
   • They are more stressed
   • They are no different
3. Where are the younger piranhas often found in a shoal?
   • In the center
   • Far away from the shoal
   • Toward the outside (answer)
4. What was Serrasalmus marginatus seen doing?
   • Building a nest
   • Taking crustacean parasites off red-bellied piranhas (answer)
   • Eating plants
5. Why do scientists describe the diet in different ways?
   • They describe a wide range of foods, and one stresses fins (answer)
   • The fish eats nothing
   • The fish changes color
6. What is a genome?
   • A kind of fish egg
   • A river bank
   • All the genes of a living thing (answer)

Words

• genome: all its genes
• piscivore: fish eater
• shoaling: group swimming
• parasites: tiny freeloaders
• spawn: fish eggs