Coral is just a hydra-shaped individual, hollow and cylindrical, with the lower end attached to the surface of the object and a mouth surrounded by one or more tentacles at the top. Tentacles are used to collect food and can be stretched to a certain extent. It has specialized cells (stinging cells). When the stinging cells are stimulated, they will turn out the stinging silk sac and paralyze their prey with stinging silk. Eggs and sperm are produced by gonads on the diaphragm and discharged into seawater through the mouth. Fertilization usually takes place in seawater,
Coral tentacles have a white cone-shaped protrusion in the center.
Sometimes it also occurs in the gastric circulatory cavity. Usually fertilization only occurs between eggs and sperm of different individuals. The fertilized egg develops into a floating larva, which is covered with cilia and can swim. After a few days to weeks, it is fixed on a fixed surface and develops into a hydra. It can also be propagated by budding. After the bud is formed, it is not separated from the original hydra. New buds keep forming and growing, so groups are formed. When the new hydra grows and develops, the old hydra dies, but its skeleton remains in the population. Soft corals, horny corals and blue corals live in groups. Each hydra in the population has eight tentacles, and there are eight diaphragms in the gastric circulation cavity, of which six diaphragms have cilia for introducing water into the gastric circulation cavity, and the other two diaphragms have cilia for guiding water out of the gastric circulation cavity. Bones are endoskeletons. Soft coral is widely distributed, and its skeleton is composed of calcium-containing spicules separated from each other. Some species are disc-shaped, while others have finger-like protrusions. Horned corals are abundant in shallow seas in tropical areas, and are banded or branched in shape, with a length of up to 3 meters. Horny corals, including so-called precious corals (red corals and rose corals), can be used as jewelry. Among them, the common species is red coral in the Mediterranean. Blue corals were found on coral reefs formed by stony corals in the Indian Ocean and the Pacific Ocean, forming a block with a diameter of 2 meters. Rock coral is the most well-known and widely distributed species, living alone or in groups. Like black coral and spiny coral, the number of septa is 6 or multiple of 6, and the tentacles are simple and have no feathers. Stone coral, black coral and spiny coral are different from related anemones mainly because of their exoskeletons. From the tidal zone to the depth of 6000 meters, there are rock corals in all oceans. For species living in groups, the diameter of hydra is 1 to 3 mm. Most of the existing stone corals are light yellow, light brown or olive, depending on the algae living on the corals. But its bones are white. The largest living stone coral belongs to the genus Shigella, with a diameter of about 25 cm. The skeleton of stone coral is cup-shaped, wrapped with hydra, and its composition is almost pure calcium carbonate. Its growth rate depends on age, food supply, water temperature and species. Ring coral islands and coral reefs are formed by the bones of stone corals. The average speed of its formation is about 5 mm to 28 mm per year. Common types of stony corals include brain coral, mushroom coral, star coral and staghorn coral, all of which are named according to their shapes. Black coral and spiny coral are whiplike, feathery, tree-like or bottle-brush-like, distributed in the coastal waters of the Mediterranean Sea, the West Indies or Panama.
Corals gather together to form a group, and their bones keep expanding, thus forming a coral reef with thousands of shapes, vitality and colors. This is how the famous Great Barrier Reef was formed. Corals live in groups, their bones are connected, and their intestinal cavities are also connected through the small intestine system, so these social corals have many "mouths", but they use a "stomach". There are about 500 kinds of coral reefs that can be built. These reef-building corals live in shallow waters with a water depth of less than 50 meters and a suitable temperature of 22 to 32 degrees. If the temperature is below 18 degrees, they can't survive. So people can't see coral reefs at high latitudes. Coral tentacles grow symmetrically. According to the number of tentacles, corals can be divided into two subcategories: 6 corals and 8 corals. Coral is generally a carnivorous species, using corals.
The antenna of the bud preys. In coral, there is a very small animal-zooxanthellae. Chlorella and coral are a pair of partners. If one side is destroyed, the other side cannot survive. In addition to corals, anemones also belong to corals. Most anemones live in a single body, and their posture is much larger than that of ordinary corals. They are also carnivores. They attract small animals with beautiful colors, and have stinging cells on their antennae, which can secrete toxic substances for hunting and defending against enemies.
Coral reproduction
When corals grow up, some species are hermaphroditic and some are hermaphroditic. Many kinds of corals release sperm and eggs for in vitro fertilization after the full moon in March and April of the lunar calendar. Because many species reproduce at similar times, a large number of sperm and eggs are suspended in the water, forming a wonder of nature.
Can everyone go to the coral reef to watch coral spawning at this time? Actually, it's a matter of opinion. Diving to the bottom of the sea to observe coral spawning itself will not interfere with coral reproduction behavior, but a group of people who are in the mood of joining in the fun and lack night diving experience may step on and destroy many corals because of poor sight at night. On the other hand, the safety of divers themselves is also worthy of attention.
Therefore, unless you are fully prepared, it is better to stay at home and watch the videos taken by experts and the explanations given by scholars. Sperm and eggs in water must be fertilized in a short time, but in fact, through the dilution of water flow and the decline of sperm vitality over time, most eggs may not have the opportunity to fertilize and develop into embryos, but become bait for fish and shrimp in water.
On the second day after coral lays a large number of eggs, a whole group of eggs can often be seen floating on the sea; These all represent the efforts made by corals to breed the next generation, and they are real soft coral communities.
Successful seedlings may be one in a million. Some corals not only release sperm and eggs, but also hatch embryos in the body, and then release them into the water layer after the embryos have developed to a considerable stage. These corals hatch embryos and release a batch of seedlings every month, usually in the warm season. According to our research, both the red-tube cup coral and the true-leaf coral in Taiwan Province Province put out seedlings around the new moon of the lunar calendar.
As for why corals release seedlings at this time of every month, is it because it is dark at night to escape being hunted? Or is the trend more appropriate? Is an unsolved problem.
In addition to the above sexual reproduction, corals can also reproduce asexually. Because many corals that make up a coral community can perform various life functions independently, when a community is divided into several blocks, each block has the ability to continue to survive, grow and reproduce, and the key factor for success lies in whether the block can be fixed on the substrate again and the size of the block itself. This characteristic of asexual reproduction has been paid more and more attention by biologists, and it has been used to restore coral reefs.
Coral growth
Coral growth mainly depends on the accumulation of bones, so the speed of bone accumulation often determines the speed of coral growth. Generally speaking, the growth rate of massive corals is very slow. For example, the fastest growing microporous coral in Taiwan Province Peninsula can increase its radius by about 2 cm per year, while others such as ammonite corals may be less than 0.5 cm.
So when we see a small ammonite coral with a diameter of about 30 cm at the bottom of the water, its life may have been 30 years. How long can the oldest coral live?
You can see micropore coral with a diameter of several meters, which is as big as a house in Green Island. According to calculations, these corals must be hundreds of years old. So it is no exaggeration to say that coral is the longest-lived animal.
As for why they can live so long, scientists are studying this subject. From these studies, we may discover the secret of longevity. The bones that have grown over the years have another meaning.
When coral bones are crystallized and accumulated, in addition to the main calcium carbonate component, some other ions in seawater are also crystallized in coral bones. Therefore, scientists can infer the composition of seawater in the past by analyzing the trace elements of coral bones in different ages, and then understand the past environmental conditions.
For example, the ratio of strontium to calcium in seawater can be used to infer the temperature of seawater in the past, some heavy metals can be used to infer the degree of pollution and river erosion in the past, and the ratio of oxygen isotopes can be used to infer the past rainfall.
The yellow spherical cells are * * * algae in small coral cells in Jiao Shan.
Transparent strips are stinging cells of coral, which can shoot poisonous needles.
What do corals do for a living?
When it comes to coral, most people's first confusion should be: "Is coral a plant or an animal?" Why does he seem to have the appearance of a plant, but he has the feeding characteristics of an animal? From a biological point of view, coral is an animal, and coral (the smallest living unit) is composed of many cells. It will use its swinging tentacles to catch small zooplankton in the sea for food. But because the body can't move, it must rely on the current to bring zooplankton near the body; Therefore, the sea area with strong current is usually the area where corals grow well.
Besides feeding on tentacles, most reef-building corals have surviving photosynthetic algae. These unicellular algae will transfer many nutrients into coral (host) while carrying out photosynthesis, thus providing another source of survival energy for coral. In fact, coral can indirectly get all the energy needed for metabolism from sunny algae in shallow water. Therefore, it is very important for corals to see whether the water quality of living waters is clear.
Many people want to put a coral jar at home after seeing the beautiful coral reefs. However, it is difficult for the small aquarium in the family to provide complete living conditions for corals. So, please don't keep corals at home. If you want to see live corals, you might as well work hard, go out for a walk, go to a large aquarium or go snorkeling in Kenting sea area!