Fish
Brotula
Bythitidae · also called viviparous brotula
Sharing its elongated, eel-like shape with the cusk-eel yet giving birth to live young rather than laying eggs, a brotula quietly occupies habitats ranging from the open deep seafloor to the permanent darkness of underwater caves.
Overview
The brotula, family Bythitidae, is a live-bearing fish native to ocean habitat recorded across every major ocean basin. Its viviparous reproduction setting it apart from the closely related cusk-eel, specialised cave-dwelling members, and broad depth range make it one of the more quietly distinctive elongated fish families found across the world’s oceans.
A family defined by how it reproduces
While closely resembling the cusk-eel in overall body shape, the brotula follows a completely different reproductive path, carrying live young to birth rather than laying eggs, a distinction that separates the two otherwise similar-looking families at a fundamental level.
Status
Least Concern, though population trends remain largely unknown across much of the family’s range given the difficulty of surveying deep and cave-based habitat.
Brotula: common questions
How is the brotula different from the cusk-eel?
This family is viviparous, with young developing inside the mother and being born live, a trait that distinguishes it from its close relative the cusk-eel, which reproduces differently despite a broadly similar elongated body shape.
Do all brotulas live in caves?
No, only some species in this family spend their entire lives deep inside dark underwater cave systems, while others are found along the open seafloor at a range of ocean depths.
Why do cave-dwelling brotulas have such small eyes?
Cave-dwelling species within this family often have significantly reduced eyes, an adaptation to a habitat where vision offers little advantage in the permanent darkness found deep inside cave systems.
What does a brotula look like?
This family has an elongated, eel-like body plan, a shape shared broadly with its close relative the cusk-eel despite the two families having different reproductive strategies.