The green tree frog has lungs. They absorb oxygen through their skin. For this to happen, their skin has to be moist. However, their skin can get infected by pathogens. Pathogens will live on the frog's skin. This makes them sick. The frog will then grow peptides. These will destroy the pathogens. The skin of the Green Tree Frog has caerins. Caerins is a group of peptides with antibacterial and antivirial protection. It also has caerulins. The caerulins have physiological effects. The CCK-8 is a digestive hormone and hunger suppressant. Several peptides from the skin of the green tree frog have been found to destroy HIV without harming healthy T-cells.