Why these freshwater fish gulp air to survive in oxygen-poor tropical waters

Nature · Published 3 October 2026 Swipe more like this →

In short: Gouramis are not just colorful aquarium staples; they are evolutionary masters of low-oxygen environments. Equipped with a unique lung-like labyrinth organ, these fish can bypass the limitations of their habitat by breathing atmospheric air. From bubble-nest builders to devoted mouthbrooders, their survival strategies are as diverse as their temperaments.

Native to Asia, ranging from the Indian subcontinent to Korea, gouramis belong to the family Osphronemidae. Their most defining feature is the labyrinth organ, a specialized structure that allows them to gulp air at the water's surface. This adaptation is critical for survival in the warm, shallow, and often oxygen-depleted streams, canals, and rivers where they are naturally found. While they are often associated with the aquarium trade, their history stretches back to the early-mid Eocene epoch, with the fossil genus Ombilinichthys discovered in the Sangkarewang Formation of Sumatra, Indonesia.

The family is remarkably diverse, currently comprising about 133 recognized species across four subfamilies and roughly 15 genera. Their reproductive behaviors are equally varied; some species, such as the Siamese fighting fish, construct intricate bubble nests, while others, like the Krabi mouth-brooding betta, protect their young within their mouths. Regardless of the method, all living species exhibit parental care until their fry are capable of swimming freely. This intelligence extends to their social interactions, as many are known to recognize their owners and explore their surroundings with curiosity.

In the wild, gouramis are a significant food source in maritime Southeast Asia, where they are frequently fished and prepared in various spiced sauces. However, their reputation in the aquarium hobby is complex. While many are peaceful, others can be highly territorial or predatory. Compatibility depends heavily on the specific species and the tank environment. For instance, while some are shy and easily outcompeted, others like the paradise fish are known for their aggression. Because males often spar with one another, they are generally best kept apart to prevent injury, ensuring these fascinating labyrinth fish can thrive in captivity.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

Intellect Plus is a visual educational discovery platform for exploring fascinating facts and ideas. Brain Food, Not Brain Rot. What is Intellect Plus?

Related

• The evolution of fish that mastered the land
• These prehistoric survivors have been breathing air for over 150 million years
• These fish spend three-quarters of their lives on land, walking and climbing with fins.
• Hidden in acidic peat swamps, tiny fish are evolving in ways we barely understand.
• This living fossil breathes through a slit on its head
• Did the human lineage begin in the Mediterranean rather than in Africa?
• Before the saber-toothed cats, these Permian predators ruled with massive, specialized canine teeth
• The world's most farmed fish is a voracious herbivore with a global identity crisis.
• The goosefish uses a fleshy lure to hunt prey with its cavernous, toothy mouth
• Why the harmless grass snake mimics the deadly cobra to survive in the wild
• The most abundant vertebrate on Earth is a tiny, glowing, deep-sea predator.
• The original penguin was a flightless giant hunted to extinction by human greed

More in Vertebrates · More in Nature · Latest · A–Z · All topics