Dipnoi

Dipnoi is a subclass of lobe-finned fishes known commonly as lungfish. These unique fish are characterized by their ability to breathe air using lungs, in addition to their gills. They are an important group in the study of vertebrate evolution due to their primitive features and their close relationship to the ancestors of tetrapods.

Taxonomy

The Dipnoi are divided into two orders:

• Ceratodontiformes
• Lepidosireniformes

Anatomy and Physiology

Lungfish possess both gills and lungs, allowing them to survive in environments with low oxygen levels. Their lungs are homologous to those of tetrapods, indicating a shared evolutionary origin. The heart of a lungfish is also more complex than that of other fish, with a partially divided atrium and ventricle, which allows for a more efficient separation of oxygenated and deoxygenated blood.

Habitat

Lungfish are found in freshwater environments in Africa, South America, and Australia. They typically inhabit slow-moving or stagnant waters such as swamps, marshes, and rivers. During dry seasons, some species can aestivate by burrowing into the mud and secreting a mucus cocoon to retain moisture.

Evolutionary Significance

Lungfish are considered living fossils, as they have retained many primitive features that were present in their ancient ancestors. Their ability to breathe air and their limb-like fins provide important insights into the transition from aquatic to terrestrial life in vertebrate evolution.

Species

There are six extant species of lungfish:

• Neoceratodus forsteri (Australian lungfish)
• Protopterus annectens (West African lungfish)
• Protopterus aethiopicus (East African lungfish)
• Protopterus dolloi (Central African lungfish)
• Lepidosiren paradoxa (South American lungfish)

Conservation Status

Many lungfish species are threatened by habitat destruction, pollution, and climate change. Conservation efforts are necessary to protect these unique and ancient fish.

Related Pages

• Sarcopterygii
• Tetrapod
• Evolution of fish
• Neoceratodus forsteri
• Protopterus annectens
• Protopterus aethiopicus
• Protopterus dolloi
• Lepidosiren paradoxa