How do puffer fishes defend themselves when threatened?

When threatened, puffer fishes (members of the order tetraodontiform) employ a unique defense mechanism to deter predators. They swallow water or air to inflate their bodies into a globular, ball-like shape, which can reach up to five times their normal size. This rapid expansion makes it difficult for larger predators to consume them and serves to scare off potential threats.123

In addition to this physical transformation, puffers possess other defensive traits:

• Tough, Prickly Skin: Many species have skin that is difficult to handle or ingest.12
• Chemical Defense: Many puffers are poisonous, containing a highly toxic substance known as tetraodontoxin, which is concentrated in their internal organs.12

Once the fish perceives that the danger has passed, it slowly deflates to return to its normal size.3