The Incredible Leaping Fish That Lay Eggs Out of Water

We’ve all heard the phrase, “a fish out of water,” but these fish take it literally. As you can see in this YouTube video, splash tetras lay their eggs on a leaf overhanging the water. Only 1% of the known fish species exhibit this type of reproductive process. So, how exactly do splash tetras do this, and why? Keep reading to learn more about splash tetras and their unique reproductive behavior.

The Leaping Fish of the Amazon

Splash tetras (Copella arnoldi) are freshwater fish native to the slow-moving tributaries of the Amazon River basin in South America. They typically inhabit shallow water with overhanging vegetation. Splash tetras are omnivores, primarily feeding on zooplankton, insects, and small invertebrates. They also consume some plant matter, such as algae and biofilm, especially when streams in the region dry up during the winter and other food sources are scarce.

Splash tetras are golden olive or silvery colored with paler bellies. These small fish have long, slim bodies averaging between 1.3 and 1.6 inches in length. However, a female that is ready to spawn will have a larger belly. Splash tetras are sexually dimorphic and dichromatic. The males are larger with longer, more colorful fins that appear yellow with red tips when they reach sexual maturity. Both sexes have white spots at the base of their dorsal fins. They are peaceful fish, often kept in aquariums, but they are most well-known for their incredible ability to leap from the water during spawning.

The Unique Reproductive Behavior of the Splash Tetra

When a splash tetra male reaches maturity and is ready to breed, he searches for a suitable leaf on which the female can lay her eggs. He does this by leaping out of the water and testing his ability to stick to the leaf. Once the leaf is chosen, he then positions himself under it and puts on a display for passing females. When a female shows interest, the couple aligns their bodies and they prepare to jump together.

When the female is ready, she nudges her mate with her head, then they flip their tails to propel themselves out of the water. They land together on the underside of the leaf, holding on by their fins. The female lays around 5-8 eggs and drops back down into the water. Then, the male fertilizes the eggs before he also falls back into the water. They repeat this process until all of the female’s eggs are laid and fertilized, which may result in a clutch of 50-200 eggs.

Hatching the Eggs

After the female has laid all of her eggs, she departs, leaving the male to care for the eggs. The male remains nearby and periodically uses his fins to splash water on the eggs, which is how the species got its name. This ensures the eggs remain oxygenated and keeps them from drying out. The eggs typically hatch within 48-72 hours. Scientists have found that the frequency of the splashing decreases daily, with mean splashing frequencies ranging from 38.5 to 0.2 splashes per hour. When the eggs hatch, the larvae fall down into the water and swim for safety.

Researchers believe that laying the eggs outside of the water keeps the eggs safe from predators and gives the offspring a better chance of survival. Scientists also note that an evolutionary adaptation for this type of water and air interaction during reproduction may offer splash tetra eggs the best oxygenation. As 59% of neotropical freshwater fish are currently threatened, any advantage in reproduction could mean the difference between preservation and extinction.

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