Fish That Lay Eggs Out of the Water: Freshwater Species of the Week

Splash tetra, Copella arnoldi, which lays its eggs out of the water
The splash tetra is the world’s only known fish that lays its eggs out of the water. Photo: Zikamoi, Wikimedia Commons

These fish are born out of water. 

freshwater species of the weekThe fish Copella arnoldi is commonly called the splash tetra or splashing tetra, due to its unique reproductive behavior. That is, it lays its eggs outside of water. It is one of few known species of fish in the world to do so.

When a male is ready to mate, it takes up position in the water below an overhanging leaf. It does a little display, and if a female is interested, she will sidle up next to him. Then, they will leap out of the water together. They latch unto the underside of a leaf with their fins.

The female releases six to eight eggs and the male quickly fertilizes them, before they fall back into the water. The pair repeat this process several times until they have deposited about 200 eggs onto the leaf.

The male then hides in aquatic vegetation near the leaf, where he keeps an eye on the eggs. He defends the territory and periodically splashes the eggs with his tail fin (which is asymmetrical, most likely for this purpose) to keep them moist. When the fry hatch, after about 48 hours, they fall into the water, where they hide as best they can.

Splash tetra live in slow-moving tributaries of the Amazon and other large South American rivers, especially in Guyana and Venezuela.

The fish grow to a length of about 2.7 inches (7 centimeters) and have a life expectancy of about three years.

“These really are amazing little fish with a totally unique method of reproduction,” Steven Chester told the Chester Chronicle. Chester is an aquarist at the Blue Planet Aquarium in Cheshire Oaks, United Kingdom, which just successfully bred the remarkable fish for display.

 

Brian Clark Howard covers the environment for National Geographic. He previously served as an editor for TheDailyGreen.com and E/The Environmental Magazine, and has written for Popular Science, TheAtlantic.com, FastCompany.com, PopularMechanics.com, Yahoo!, MSN, and elsewhere. He is the co-author of six books, including Geothermal HVACGreen LightingBuild Your Own Small Wind Power System, and Rock Your Ugly Christmas Sweater.

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