Toadfish are a poorly known group of marine fishes, the vast majority of which live close to the shoreline but remain close to the sea bed. Unlike most fish, these animals are extremely vocal, with some authorities even reporting that their loud calls can be heard out of water. One North American genus, Porichthys, is more commonly known as the singing midshipman. The calls are produced by muscular contractions of the swimming bladder; the intensity of the sound is related to the degree of stimulation by the muscles. Toadfish are renowned for their territorial behavior, and it is likely that these loud calls have developed to warn off potential rivals through a series of grunts and postures. As an additional deterrent to potential attackers, toadfish have a number of venomous spines which can inflict an irritating, if not lethal, injection of toxins to a would-be predator.
Another peculiar adaptation of toadfish is the large number of light-emitting cells, or photophores, that are scattered around the body. A toadfish can have as many as 700 of these specialized glands. They are thought to contain large numbers of luminescent bacteria, but their purpose is not yet fully understood. In some species these lights, which may flash on and off, serve to attract prey or mates. However, these features are most often found in deep sea fishes and often those that inhabit the deepest and darkest reaches of the oceans.