Sirenidae

Sirenidae is a family of aquatic salamanders belonging to the order Urodela (salamanders). Commonly known as sirens, these amphibians are characterized by their elongated, eel-like bodies, small forelimbs (in most species), and lack of pelvic fins and hind limbs. They are found exclusively in the southeastern United States and northern Mexico.

Sirens are obligate aquatic salamanders, meaning they spend their entire lives in the water. They inhabit slow-moving or stagnant freshwater environments such as swamps, marshes, ponds, and canals. They are primarily nocturnal and can be difficult to observe in the wild due to their secretive nature.

A distinguishing feature of sirens is the presence of external gills located on the sides of their necks. These gills are used for respiration, but sirens also possess lungs and can breathe atmospheric air when necessary, particularly in oxygen-poor waters. They also have the ability to breathe through their skin.

Sirens are carnivorous, feeding on a variety of aquatic invertebrates, including insects, crustaceans, and mollusks. They may also consume small fish and amphibians. They locate prey using a combination of sensory cues, including smell and mechanoreception.

The family Sirenidae includes two genera: Siren and Pseudobranchus. Siren species are typically larger, reaching lengths of up to 95 cm (37 inches), while Pseudobranchus species are smaller, rarely exceeding 25 cm (10 inches). Pseudobranchus species are also unique in having only one gill slit on each side, compared to the multiple slits found in Siren.

Sirens exhibit several unique adaptations to their aquatic lifestyle. They are able to aestivate, or enter a state of dormancy, during periods of drought or unfavorable conditions. During aestivation, they burrow into the mud and secrete a protective mucous cocoon to prevent desiccation.

The conservation status of siren species varies. Some species are relatively common and widespread, while others are considered to be threatened or endangered due to habitat loss and degradation.