What are you looking at? Haven't you seen a fish that can build a nest?

Most of the fish we come into contact with in our daily lives expel eggs from their bodies during reproduction. The previous generation has fulfilled its responsibility to the next generation, and as for whether they can survive, grow and develop safely, they can only leave it to fate.

Often this method of reproduction relies on producing a huge number of eggs, hundreds of thousands, millions, or even hundreds of millions of eggs, to ensure that some of them can be fertilized, hatched, developed, and finally grown up, allowing the population to continue to reproduce.

But for some species, usually a female fish can only lay a few or dozens of eggs in a reproductive season. In order to ensure the continuation of offspring, these fish often have a certain degree of protection from their parents or one of them. This habit of protecting young fish is manifested in building nests, guarding the hatching of fish eggs, and caring for young fish . Today, I will introduce to you several "family-friendly" fish that can build nests.

01

Using local materials - building nests with water plants

During the reproductive period, the male stickleback first chooses a suitable location in the shallow water of the stream to build an ovary. The male stickleback picks up a thin stem of Potamogeton with its mouth, and secretes a transparent mucus from its kidneys. This secretion is discharged from the body through the ureter and solidifies when it comes into contact with water or air. The male stickleback uses this to stick the thin stem of Potamogeton to weave a nest suitable for laying eggs.

During work, the male stickleback swims towards the nest and splashes water from time to time, seemingly testing the solidity of the nest. He often rubs the small bed with his body, mixing the two with the mucus on the sides of his body, thus turning them into cement slurry for the water grass bricks. Next, he reaches into the sand at the bottom of the water with his snout, picks up a mouthful of sand, and spreads it on the foundation. He works repeatedly in this way until the small bed is pressed solid and stable.

Image source: Science Source

In order to test whether all the materials of this foundation are solid, it often pours water. The completed nest is a hollow and slightly round object, which is completely in line with a base surface fixed on the water plants. The entire nest is then sealed firmly with the mucus of the body. The plaster-like tissue inside the nest needs to be made as smooth as possible. This little builder tosses and turns his body in the nest, and the mucus is applied, and the inner wall is like a layer of solid false paint.

02

Civil Engineering Experts - Digging Mud and Building Nests

Some fish dig mud and build nests in the muddy bottom, such as yellow catfish, croaker, tilapia , etc. Male yellow catfish have the habit of building nests. During the reproductive period, male fish swim to the silt and clay with dense aquatic plants in the coastal area (water depth 8-40 cm), use the pectoral fins to rotate intermittently on the muddy bottom, and dig a small mud pit as a fish nest. Some are a few together, and some are in groups of dozens, forming a nest group not far apart.

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Similarly, some fish build nests on the bottom of gravel, such as salmon, lamprey, and naked carp of Qinghai Lake . After salmon arrive at the spawning grounds, they choose a secluded environment with clear water, fast current, moderate water temperature, and gravel on the bottom of the water. The male fish uses its tail fin to beat the gravel, and with the impact of the water flow, a pit with a diameter of 1 meter and a depth of about 20 centimeters is formed. This kind of nest is called a "wozi".

The female fish lays eggs in the nest and uses her tail fin to repeatedly move the gravel to bury the eggs. The spawning site of lampreys is similar to that of salmon. After the male fish arrives at the spawning site first, they choose a site and start to build a nest. The female fish arrive later and work together. They use their suction cup-shaped mouths to suck up small stones, use dragging and shaking methods to loosen them and drag them to the downstream of the nest, forming a pit with a diameter of 50-80 cm on the bottom of the river, which is an oval or round depression. This is the "love hut" they build together.

03

Safe and exquisite - hidden nest

There is a small goby that can build an exquisite hidden nest. The male fish first turns the empty shell over with the concave side facing down, then drills in and uses its tail fin to dig up the sand to form a small chamber, and finally digs a channel to connect to the outside world. Sand snakeheads use submerged shelters such as clams, tiles or broken pots as nests for laying eggs.

Image source: Phys.org

The darter 's nest is also very special. It chooses the space between the bottom of the rock in the water and the gravel at the bottom as the spawning place. The distance of this space is about 15-25 mm, which is exactly the same as the height of the fish body when the dorsal fin is vertical. The male fish first uses the end of the fleshy ball-shaped dorsal fin spine to clean the bottom of the rock so that the eggs can adhere. Many puffer fish (such as fighting fish) can create the most extraordinary nests. The male fish chooses a calm and sheltered place on the water surface, blows air and spits mucus to form small bubbles, and countless small bubbles adhere together to form a floating nest with a raised or slightly flat surface.

The parent fish that protect the young near the eggs and fry not only have to guard the eggs and fry and drive away invading enemies, some of them also have to constantly clear debris from the nest or stir up water flow to maintain a good environment in the nest, and even move the eggs out of the nest and clean and repair the nest. Compared with those fish that run away after giving birth, they are truly "model parents"!

Produced by | Science Popularization China

Author｜Life Pulse Team

Producer｜China Science Expo

Submitted by: Computer Information Network Center, Chinese Academy of Sciences

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