Seahorse dad can "give birth"

They are the only species where males give birth to offspring.

It's called "horse" but it's actually a fish

Seahorses are actually small fish in the ocean, but they don’t look like fish, they look like horses, hence the name “seahorse.” Most seahorses are 5 to 30 centimeters long, and the largest seahorse (the big-bellied seahorse) can only grow to about 35 centimeters.

Although seahorses have lived in the sea since they were young, their dorsal and pectoral fins are very small, and their caudal and pelvic fins are completely degenerate, which makes them not very good at swimming and they can only drift in the sea like seaweed. Seahorses usually use their tails to tightly "wrap" around corals or seaweed, for fear of being washed away by the current. Seahorses are also very lazy. During the day, they playfully hang upside down on floating seaweed or other objects, and stay still if possible. At night, they come to the top of the plants and stay upright. Even if they temporarily leave the object for feeding or other reasons, they will "wrap" around other objects after swimming for a distance.

Although seahorses swim slowly, their upright swimming posture is both special and beautiful. They are also good at camouflage and can deceive their prey, the fast-moving copepods. Once copepods find their natural enemies approaching them, they will flee at a speed, moving more than 500 times their own length per second. Even cheetahs, which are good at running, only run 30 times their own length per second. On the one hand, seahorses are extremely sensitive to the ripples caused by the approach of predators; on the other hand, when seahorses move towards their prey, they hardly disturb the seawater near their mouths and noses, thus not alerting copepods, etc., so their predation success rate exceeds 90%. Seahorses' eyes can turn independently like chameleons' eyes. But the most special thing about seahorses is their parenting process.

Bravely move forward for love

Seahorses are the only animals on Earth where males hatch and give birth to offspring. Seahorses are usually strictly monogamous, and they have unique and complex "marriage" behaviors and habits. Before reproducing, seahorses may spend several days courting. If a male seahorse finds a favorite object, he will immediately pursue it. Seahorses are usually timid and lazy, but when they meet a favorite object, they are bold and spare no effort.

During the courtship period, male and female seahorses will separate at night and reunite in a well-lit area after daybreak. The courtship dance usually lasts 2 to 38 minutes, and can last up to 8 to 9 hours. When the male seahorse approaches the female seahorse, not only does the male seahorse's body color become brighter, but it also begins to shake its body and dance. During this period, the male seahorse will show the female seahorse his empty brood pouch, sending a courtship signal that he is "single". If a female seahorse "takes a fancy" to the suitor, the female seahorse's body color will also become brighter, and the female seahorse will dance with the male seahorse.

During the dance, the tails of the two seahorses are kept within 1 cm of each other on the same attachment, and their bodies are tilted outward. The female seahorse will keep moving to keep a distance from the male seahorse, and the male seahorse will follow the female seahorse. If both parties feel it is suitable, they will officially "become a partner".

Seahorse father: I will give birth to the child

In order to successfully reproduce seahorse babies, male seahorses will personally "give birth", but the male seahorse's brood pouch is only an incubator, and the eggs still come from female seahorses. During mating, the female seahorse will discharge up to 1,500 eggs into the male seahorse's open brood pouch through the reproductive papilla and complete fertilization. The fertilized eggs are embedded in the male seahorse's pouch wall for development. After mating, the male seahorse with the fertilized eggs will choose a relatively less disturbed place to quietly nurture the fetus and wait for the children to come. The male seahorse will provide oxygen and nutrients to the embryo through blood vessels, while providing immune protection, osmotic regulation, gas exchange and waste transportation for the embryo. During embryonic development, as the male seahorse's brood pouch gradually grows larger, its color gradually deepens. The male seahorse with a big belly is more inconvenient to move, so it rarely swims and often lives at the bottom of the water. The appetite of the male seahorse in the gestation is also affected, and the amount of food intake decreases. In order to ensure the smooth birth of the child, the male seahorse is willing to suffer, which can be called the "good father" and "good husband" in the animal world. During the male seahorse's pregnancy, the female seahorse will visit to ensure that the male seahorse is taking good care of his offspring.

On the 50th to 60th day after mating, the male seahorse's brood pouch becomes noticeably larger and darker in color, indicating that the baby seahorses are about to be born. During the birthing process, the male seahorse hooks the strong seaweed with its tail, and repeatedly straightens and bends its body to squeeze out the baby seahorses in the brood pouch through muscle contraction. Seahorses can give birth to hundreds or even thousands of baby seahorses in one litter. After giving birth, the male seahorse is exhausted and needs to rest. But during the breeding season, male seahorses usually mate again within a few hours or days.

Small but loud

You may not think that seahorses are very noisy animals. When they are in danger, they will make extremely loud noises. Of course, they do not use their vocal cords, but the vibration of their muscles to produce a sound of up to 115 decibels, which is as loud as the siren of an ambulance. If they are caught by a predator, the seahorse will scare the predator in this way, and some predators will actually let go, and the seahorse will take the opportunity to escape.

Seahorses make clicking sounds when they are feeding, but the clicking sounds are louder during courtship, especially on the third and last day of their courtship. In general, males make the sounds during courtship, but in seahorses, both males and females make clicking sounds. During courtship, seahorses also make more complex sounds: low-frequency glissando followed by high-frequency knocking sounds, and female seahorses make higher-frequency knocking sounds than male seahorses. The knocking sounds can reach up to 105 decibels.

Hidden Master

In addition to hiding in seaweed, some seahorses have other stealth skills. The dwarf seahorse is one of the smallest seahorse species in the world, smaller than a paper clip. They use their tails to desperately grab seaweed or other aquatic plants to stabilize their bodies so as not to be washed away by the rapids. Their small size and poor swimming skills put them at a disadvantage in survival, making them prey or accidental food for many marine animals. In order to avoid predators and survive, dwarf seahorses have to resort to camouflage.

As adults, pygmy seahorses stay in gorgonians that are similar in color to themselves. Gorgonians are not fixed colors, so pygmy seahorses change color to match the color of the gorgonians. For example, pygmy seahorses living on orange gorgonians are orange, and pygmy seahorses living on red gorgonians are red. Pygmy seahorses also match the color and shape of their host corals by growing colored calcified bumps called "bulb tubercles," and the pygmy seahorse's body also resembles the stems of gorgonians.

In addition, the upright swimming posture of seahorses will cause many animals to mistake them for seaweed or corals, which helps them to remain invisible.

The tail is actually square

The tail of a seahorse is made up of a specialized tail fin, tail bones, and scales (but the tail fin is completely degenerate), which is both soft and strong. They have a curled, muscular tail that helps them wrap tightly around seaweed, mangrove roots, or coral reefs. The seahorse uses nerves to drive the outer bone plates to link the muscles in the center, allowing them to cooperate with each other to change the direction of the tail's movement. The most interesting thing is that the cross-section of the seahorse's tail is actually square.

The tail of a seahorse is made up of sections, each of which has a square cross section, and is surrounded by four "L"-shaped bone plates to form a square tail shape. When facing external impact, the bone plates can absorb the impact by sliding sideways to better protect the middle spine.

The square tail has a larger surface area than a round tail, which gives the seahorse's tail a stronger grip. The square tail of the seahorse is elastic, and the tail can quickly return to shape after being hit or bitten by a predator. The elastic tail can also help the seahorse quickly return to an upright swimming position.

High birth rate and low survival rate

Newly born seahorses are only about 1 cm long. They will drift with the sea water and start a new life journey in order to find a new habitat. In the process of looking for a new habitat, they will choose to "hold together" and move forward. The so-called holding together means using their tails to hook some seaweed or seaweed in the water layer. By taking this form of "hitchhiking", seahorse cubs can not only save energy, but also confuse natural enemies. Despite this, a large number of seahorse cubs will die of hunger or become prey to other animals during the drifting process. Therefore, although the birth rate of seahorses is high, less than 1% of seahorse babies can grow up.