Lots of surface area for O2 and CO2 exchange. Air comes in by abdominal slits. Silk is secreted from abdomen glands as liquid, then hardens as it leaves body. Nests, cocoon, trap, dragline, which is also used to communicate with other spiders of same species. Rocky Mountain Spotted Fever.
Krill feed baleen whales.
Antennae used for touch and taste. Usually gills for gas exchange. Fertilized eggs carried on female. Some hatchlings resemble adults, others have larval stages and successive molts. Barnacles are sessile and live in limestone cup they secrete.