Batrachoididae

The Batrachoididae family includes a group of fish commonly called toadfish or frogfish. Their names come from their physical appearance, which looks much like a toad or a frog. In scientific terms, the name comes from the Greek word "batrakhos," meaning frog. These fish are benthic ambush predators. This means they live on the bottom of the water and wait for prey to swim near them. They often use cryptic coloration to blend into their surroundings. This helps them stay hidden from the animals they want to eat.

Toadfish have several unique physical features. Most species are scaleless and possess large heads with eyes set high up. Their mouths are large and include both a maxilla and a premaxilla. Many species also have skin flaps or barbels near their mouths. They have two separate dorsal fins on their backs. The first dorsal fin is smaller and contains sharp spines. The second dorsal fin is larger and has between 15 and 25 soft rays. Their bodies can vary greatly in size. For example, the Thlassophryne megalops and the Pacuma toadfish represent different ends of this range.

Some members of this family have developed specialized defenses. All toadfish have sharp spines on their gill covers, also called the opercle. In the subfamily Thalassophryninae, these spines are actually hollow. These hollow spines connect to venom glands. If a predator is attacked, the fish can deliver a painful wound through this venom. Additionally, some species in the genus Porichthys, known as midshipman fishes, possess photophores. These are light-producing organs, and these fish also have four lateral lines along their bodies.

Toadfish are found in habitats all around the world. Most of these fish live in the salty ocean. However, some live in brackish water, which is a mix of salt and fresh water. One specific subfamily, the Thalassophryninae, lives only in freshwater. You can find species like Thalassophryne amazonica in the Amazon River. Another species, Daector quadrizonatus, lives in the Atrato River in Colombia. These fish can live in many areas, from near-shore spots to very deep waters. Some can even survive out of water for up to 24 hours.

One of the most famous behaviors of the toadfish is "singing." Male toadfish use a swim bladder, which is an internal gas-filled organ, to produce sound. They contract muscles to release air, creating a noise that sounds like a hum or a whistle. This sound can be loud enough for humans to hear from the surface of the water. Males use this singing to attract females to their nests. This process is a key part of their reproduction. After mating, the eggs are attached to the nest using a sticky side.

Toadfish exhibit a level of parental care that is very unusual for fish. After the eggs are laid, the male guards the nest against predators. During this time, he cannot leave the nest to hunt for food. He must survive on a very limited food supply while he protects the offspring. The eggs grow into embryos while attached to the nest for three to four weeks. Once they are larger, the young fish cluster around and hide behind the male. They stay close to him until they are large enough to survive on their own.

The history of the toadfish stretches back to the Late Cretaceous period. They are considered among the most basal percomorph orders. The earliest known toadfish is likely Bacchiaichthys from the Late Cretaceous of Italy. While some scientists have disputed its status, recent studies still classify it as a batrachoidiform. Other fossils have been found in France from the Early Eocene. In the Oligocene, a fossil called Louckaichthys was found in the Czech Republic. Finally, Zappaichthys fossils have been identified from the Miocene in Austria.