Marine animals are mainly divided into three major categories: marine invertebrates, marine protochordates, and marine vertebrates.(I) Marine InvertebratesMarine invertebrates account for the majority of marine animals and have a wide variety of species. They mainly include protozoa, sponges, coelenterates, flatworms, nemerteans, nematodes, annelids, mollusks, arthropods, brachiopods, chaetognaths, pogonophores, echinoderms, and hemichordates. Common shrimp, crabs, shellfish, snails, octopuses, and cuttlefish all belong to invertebrates. For example, starfish and sea urchins belong to echinoderms. They have a spiny appearance, and their bodies are composed of symmetrical parts. They can move in any direction and move, breathe, and hunt by relying on the water pressure system of water-filled pipes in their bodies. According to statistics, there are about 140,000 species of marine invertebrates in the world. Compared with land, the animal phyla are more colorful.(II) Marine ProtochordatesMarine protochordates are a transitional group of animals from marine invertebrates to marine vertebrates. There are relatively few species and they only exist in the ocean. Protochordates are further divided into urochordates and cephalochordates. Urochordates such as salps and ascidians. Ascidians are somewhat like pineapples in shape and are also known as "pineapples in the sea." They are generally fixed on the backs of ships, rocks, or shellfish and crabs and feed mainly on plankton. At present, only one species of cephalochordate, amphioxus, has been discovered. It has a flat and elongated body with pointed ends. It is accustomed to burying its body in sand and only exposing the front half of its body for breathing and foraging. Widely distributed in temperate and tropical shallow waters, it is endangered due to being massively fished for its deliciousness and nutrition. Now it is a second-class protected animal in China.(III) Marine VertebratesMarine vertebrates can be divided into several major categories: fish, reptiles (such as sea turtles, sea snakes, hawksbill turtles), marine birds (such as albatrosses, petrels, puffins, etc.), and mammals (such as manatees, dolphins, seals, whales, etc.). Mammals are the most advanced category of marine vertebrates. They reproduce by viviparity and breathe with lungs. Some live in water for their entire lives. For example, whales will swim to the surface at regular intervals to breathe; some are semi-aquatic animals that move between the coast and the sea. For example, seals and sea lions need to go to the shore for mating and giving birth.II. The survival status of marine animals(I) Some species are facing threatsAs giants in the ocean, whales also face many survival challenges. Excessive commercial whaling has led to a sharp decrease in the number of some whale species. At the same time, they may also be trapped in fishing nets and be affected by marine pollution and sound pollution. For example, humpback whales and blue whales. Human activities pose a serious threat to their survival.
I. Classification of marine animal species
(1) Some species are threatened.
As giants in the ocean, whales also face many survival challenges. Excessive commercial whaling has led to a sharp decrease in the number of some whale species. At the same time, they may also be trapped in fishing nets and be affected by marine pollution and sound pollution. For example, humpback whales and blue whales. Human activities pose a serious threat to their survival.The survival of sea turtles is also a cause for concern. Their habitats are constantly being destroyed and they face problems such as commercial fishing, illegal fishing and habitat loss. Some sea turtle species, such as green sea turtles and flatback sea turtles, are listed as endangered or threatened species.Sharks occupy a key position in the marine food chain. However, due to overfishing and the shark fin trade, the population of sharks has declined. Some shark species have entered an endangered or threatened state.The survival status of dolphins varies by species and region. Some dolphin species are threatened by factors such as fishing nets, pollution and sound pollution. However, the population of some species such as common dolphins is relatively stable.(2) Impact of nuclear wastewater.The discharge of nuclear wastewater from Japan into the sea has had a great impact on marine life. Taking the appearance of eel and sea turtle corpses on the beach as an example, after the discharge of nuclear wastewater, a sea turtle corpse was found on a beach in Japan. On August 27, on the beach in Chiba Ninety-nine Miles, Japan, a sea turtle corpse was washed up by the sea. On August 29, in Kamakura, Japan, Chinese tourists took pictures of eel corpses everywhere on the local beach. Although it cannot be determined whether the deaths of these eels and sea turtles are entirely caused by the discharge of nuclear wastewater, there is no doubt that the discharge of nuclear wastewater will have many impacts on marine life. First, there is a reduction in biodiversity. The discharge of nuclear wastewater may affect various organisms in the marine ecosystem, from plankton to fish and marine mammals. Some organisms may be more sensitive to radioactive substances, which may lead to the death or reduction of certain species, thus affecting the balance of the entire ecosystem. Second, there are diseases and deformities. Long-term exposure to radioactive substances may cause diseases and physiological deformities in marine organisms, which may affect their survival ability and reproductive health.(3) Hazards of "ghost fishing gear" and climate warming."Ghost fishing gear" has caused serious harm to marine life. Every year, more than 640,000 tons of "ghost fishing gear" are discarded into the ocean, causing the death of 136,000 marine organisms such as seals, sea lions and whales. "Ghost fishing gear" will change the living environment of benthic microorganisms and have a negative impact on benthic organisms. The fine sediments they carry will block the gaps in coral reefs, causing local hypoxia and leading to the death of marine organisms. It is estimated that the pollution of discarded fishing gear generated in the ocean within Brazil can reach 580 kilograms per day.Climate warming has led to a gender imbalance in sea turtles. In sand with a temperature exceeding 31 degrees Celsius, female sea turtles will hatch from sea turtle eggs. Now in Florida, the United States, there are no male sea turtles born, only female sea turtles. In the past four years, all the sea turtles born are female, and the ratio of male to female is 1:10. As the climate warms, the sand becomes hotter and hotter, and there will be fewer and fewer male sea turtles while the number of females will increase. New research shows that due to the "feminization" of green sea turtles caused by climate change, up to 93% of newborn green sea turtles may be female by 2100. Sea level rise will also submerge some nesting areas of green sea turtles. In the future, green sea turtles will face troubles brought by habitat loss and rising temperatures.III. Unique habits of marine animals.(1) The swarm dance of nereis.In late spring or early autumn, nereis will carry out a unique reproductive activity - a group marriage dance. Female nereis put on blue-green "wedding dresses", and male nereis put on pink or milky white "formal clothes". Some dance in the light of the bright full moon (photophilic reproduction), and some gather in the quiet moonlight (photophobic reproduction). They roll in the water, as if holding a festival dance. Male and female nereis discharge a large amount of eggs and sperm into the water respectively, making the clear sea water immediately turn milky white and turbid. Sperm and eggs meet and combine to form new little lives.
(1) The group dance of nereis.
In late spring or early autumn, nereis will carry out a unique reproductive activity - a group marriage dance. Female nereis put on blue-green "wedding dresses", and male nereis put on pink or milky white "formal clothes". Some dance in the light of the bright full moon (photophilic reproduction), and some gather in the quiet moonlight (photophobic reproduction). They roll in the water, as if holding a festival dance. Male and female nereis discharge a large amount of eggs and sperm into the water respectively, making the clear sea water immediately turn milky white and turbid. Sperm and eggs meet and combine to form new little lives.(2) The brief love of prawns.Prawns have a brief love affair in their lives. Usually, mature males and plump females behave politely and interact gracefully. But when a female prawn molts and exposes her skin, the male prawn will suddenly notice the presence of the opposite sex, act out of character, and become emotionally impulsive. It will gently stroke the other with its antennae and walking legs, approach the female lying on her side, and take the opportunity to embrace her. At this time, the exhausted female after molting instinctively snuggles in the arms of the male and opens her genitalia to receive the male's sperm. After a one-night stand, they dissolve their marital relationship and live separately.(3) The love of cichlids for their offspring.When the water temperature is above 20°C, the male cichlid (commonly known as tilapia) will leave the group and dig mud with its mouth to create a pit-like "bridal chamber". After completion, it swims around to guard and does not allow other fish to approach or invade. At this time, the male is dressed in a red robe, and its head is even more vivid, luring the female to "get married". After mutual kissing, flapping of the caudal fin, and chasing each other, the female is forced into the "bridal chamber". When estrus reaches its peak, the female begins to lay eggs and sucks the eggs into her mouth. The male then ejaculates, and the semen is sucked into the female's mouth with the water and she becomes pregnant. Then, they leave the "bridal chamber" respectively. From fertilization to hatching, it takes 10-12 days and all occurs inside the female's mouth. After the fry hatch, they still stay in the mouth for protection. When the environment is suitable, the female opens her mouth and spits out the fry to play beside her. If there is any disturbance, she immediately opens her mouth and sucks the fry back into her mouth and leaves. Its love for its offspring is touching.(4) The peculiar diet of bottlenose dolphins.The peculiar eating habit of bottlenose dolphins liking to eat yellow-bellied sea snakes has attracted great attention. The reasons may be as follows: First, yellow-bellied sea snakes are beneficial to the health of bottlenose dolphins. Yellow-bellied sea snakes feed on fish and other small aquatic animals, indirectly providing food resources for bottlenose dolphins. At the same time, the existence of yellow-bellied sea snakes helps maintain the balance of the marine ecosystem, reduces competition for fish resources, and makes it easier for bottlenose dolphins to find food. In addition, yellow-bellied sea snakes are rich in a special nutrient - tanshinone. This is a powerful antioxidant with multiple health benefits such as anti-aging, anti-inflammatory, and prevention of cardiovascular diseases. Bottlenose dolphins can obtain this special nutrient by swallowing yellow-bellied sea snakes to meet the challenges of environmental factors such as high temperature, ultraviolet rays, and oxidative stress in tropical and subtropical sea areas.In terms of predation skills, bottlenose dolphins are the only dolphin species that use sounds emitted from their mouths to prey on sea snakes. When a bottlenose dolphin discovers a sea snake, it will open its mouth and emit special high-frequency sound waves. These sound waves will produce a reaction after hitting the body surface of the sea snake, making the sea snake feel confused and puzzled. Bottlenose dolphins take advantage of this opportunity to quickly swallow the sea snake. Studies have shown that the frequency and amplitude of this sound wave are closely related to the body shape and movement mode of the sea snake. Bottlenose dolphins can judge the position and speed of the sea snake according to the emitted sound waves, so as to better capture the target. It is worth mentioning that bottlenose dolphins need to be very careful when preying on sea snakes. Sea snakes are very poisonous marine organisms. If bitten by a sea snake, they may lose their ability to move and eventually die. To counteract the toxicity of sea snakes, bottlenose dolphins usually rinse the sea snake with a large amount of water before preying. In addition, they will also specially choose sea snakes with lower toxicity content in their bodies. Bottlenose dolphins often form small groups with other members when foraging. They coordinate their actions through sound and body movements to improve the efficiency of predation. This clustering behavior also helps protect bottlenose dolphins from potential threats.IV. Protective measures for marine animals.(1) Laws and actions.China attaches great importance to the protection of marine organisms and actively signs the Convention on Biological Diversity, becoming one of the first countries to sign it. To protect marine biodiversity, China has successively issued a series of protection policies. For example, in 1994, the "China Biodiversity Conservation Action Plan" was issued and implemented. In the "China Agenda 21", biodiversity is listed as one of the important contents. Successive action plans such as the "Yangtze Finless Porpoise Rescue Action Plan (2016 - 2025)", the "Chinese White Dolphin Protection Action Plan (2017 - 2026)", and the "Spotted Seal Protection Action Plan (2017 - 2026)" have been issued. These action plans further strengthen the protection of marine habitats, standardize artificial breeding, strictly regulate business utilization, effectively protect marine biodiversity, and promote the harmonious development of humans and nature.
(1) Law and Action
China attaches great importance to the protection of marine organisms and actively signs the Convention on Biological Diversity, becoming one of the first countries to sign it. In order to protect marine biodiversity, China has successively introduced a series of protection policies. For example, in 1994, the "China Biodiversity Conservation Action Plan" was issued and implemented. In "China Agenda 21", biodiversity is listed as one of the important contents. Successive action plans such as the "Yangtze Finless Porpoise Rescue Action Plan (2016 - 2025)", the "Chinese White Dolphin Protection Action Plan (2017 - 2026)", and the "Spotted Seal Protection Action Plan (2017 - 2026)" have been issued. These action plans further strengthen the protection of marine habitats, standardize artificial breeding, strictly regulate business utilization, effectively protect marine biodiversity, and promote the harmonious development of humans and nature.(2) Construction of nature reservesMarine nature reserves are crucial for protecting marine biodiversity. It can protect fragile ecosystems and endangered biological resources and provide a safe living environment for marine organisms. For example, China has established many national marine nature reserves and national marine special reserves, providing a good protection platform for rare marine species. "Red Beach" in Panjin, Liaoning Province is a national marine nature reserve, where more than 200 species of birds inhabit, and there are national first- and second-class rare protected animals such as red-crowned cranes and Saunders's gulls. The national nature reserve for sea turtles in Huidong, Guangdong Province provides spawning, migratory, and breeding grounds for sea turtles. Since its establishment, it has cumulatively protected 741 nests of wild sea turtles coming ashore to lay eggs and released more than 64,000 sea turtles.(3) Adjusting the protection listAdjusting the list of key protected organisms according to national conditions and resource situations is an important measure to protect marine animals. The new version of the "List of National Key Protected Wild Animals" officially promulgated on February 5, 2021 is a huge review of China's current wild animal protection situation. Compared with the 1989 version, a total of 517 species (categories) of wild animals have been added. The five species of sea turtles distributed in China have been upgraded from national second-class key protected wild animals to first-class. The spotted seal has been promoted from a national second-class protected wild animal to a national first-class protected wild animal. These adjustments reflect China's attention and determination to protect marine organisms.(4) Protecting the marine ecologyProtecting the marine ecology requires a series of specific measures. First, sewage discharge needs to be treated. Domestic garbage, sewage, and industrial wastewater are dumped into the sea without treatment, adding a large number of bacteria, viruses, and parasites to the ocean and also causing eutrophication of seawater. Industrial wastewater contains substances that are not easily biodegradable by organisms and also contains toxic elements. To improve the marine environment, attention should be paid to the management of industrial and agricultural wastewater discharge and the treatment of domestic sewage in coastal cities, and attention should be paid to reforming the problem of self-pollution caused by sewage discharge from coastal marine aquaculture. Secondly, overexploitation should be prohibited. On the basis of ensuring the sustainable use of marine resources, strengthen the depth and breadth of development, increase the scientific and technological content of development, continuously improve the technical level in the fields of marine development and marine services, accelerate the promotion and application of advanced and applicable technologies, and strive for the maximization of the added value of the marine economy. Comprehensively develop and utilize marine resources and improve the utilization efficiency of resources; continuously discover new resources, use new technologies, form and develop new marine industries, and promote the sustained, rapid, and healthy development of the marine economy. For marine renewable resources, it is necessary to improve the utilization efficiency of resources, not only make use of them as much as possible, but also maintain a strong recovery ability of the ecosystem and maintain its sustainable reproduction ability; for marine non-renewable resources, they should be developed moderately and plannedly without affecting the interests of future generations. Finally, marine science and technology should be developed. Tianjin is the first city in China to carry out scientific and technological innovation and scenario application of seawater desalination. Based on marine renewable energy and combined with the seawater desalination industry, it can not only alleviate the problem of water shortage but also reduce energy consumption and protect the ecological environment. At present, Tianjin is the only region in China where all three mainstream technologies of seawater desalination have been applied. Nearly 200 related patents have been applied for, and many technologies have entered the international advanced ranks.V. Famous marine animals(1) Ten major marine organismsPortuguese man-of-war: The Portuguese man-of-war is actually not a warship but a combination of hydroids. Its appearance is similar to that of a jellyfish. The tentacles are generally about 10 meters long, and the longest can reach 22 meters. The stinging cells on the tentacles are highly poisonous. If accidentally stung by it, there is a high risk of life-threatening.Ocean sunfish: The ocean sunfish, also known as Mola mola, Mambo fish, and head fish, is a large marine fish. The adult body length is generally 3.0 - 5.5 meters, and the weight is usually 1.4 - 2.5 tons, with the heaviest reaching 3.5 tons. It is the heaviest existing bony fish. It is widely distributed in temperate and tropical waters around the world, and also in the South China Sea and East China Sea of China. The ocean sunfish is the only known thermostatic fish so far. It is extremely addicted to the moon jellyfish. Other small fish and turtles are just daily snacks. The reproductive capacity of the ocean sunfish is astonishing. One spawning can reach 300 million eggs, but only less than thirty can grow up safely.Giant clam: Giant clams can be seen in oceans, rivers, and even ponds. The largest giant clam discovered by humans is 1.3 meters long and weighs 500 catties. The attack power of giant clams should not be underestimated. If you put your hand in, it is difficult to pull it out without a struggle. Nowadays, many species of clams are on the verge of extinction.Spider crab: Spider crabs have eight long legs and look like spiders, hence the name spider crab. When its two legs are straightened, the distance between the two ends can reach four meters. Not only is it large in size, but the meat is also very delicious.Basking shark: The basking shark is one of the gentlest sharks in the ocean. Generally, it only eats plankton, fish eggs, and larvae and swims very slowly. Due to its slow swimming speed and gentleness, it is easily over-hunted by humans, and its number has dropped sharply.Giant squid: The giant squid is a deep-sea giant squid. In legends, it has long and large tentacles and can easily overturn ships. At present, the legend of the giant squid has been confirmed by humans. They are more than 20 meters in size and mostly inhabit the deep sea around 2,000 meters in the Antarctic waters. However, due to living in the deepest part of the ocean for a long time, few people have seen it with their own eyes.Oarfish: The oarfish is the longest bony fish in the world. Generally, its body length is 300 centimeters, and its maximum weight is 272.0 kilograms. Its body is slender and ribbon-like. It has a strange appearance, with a protruding mouth. It is fierce in temperament and even cannibalizes its own kind. Many people think it is the original form of a deep-sea monster.Whale shark: The whale shark is the largest shark in the world. Usually, its body length is 9 - 12 meters, and the largest individual can reach 20 meters in length and a maximum weight of 12,500 kilograms. They are gentle in temperament and like to swim with humans. They mainly feed on small organisms in the ocean.Blue whale: The blue whale is the largest mammal in the ocean. Its body length can reach 33 meters, and its maximum weight can reach 181 tons. It mainly feeds on small fish, shrimps and other crustaceans and is gentle in temperament. However, due to over-hunting by humans, its number has锐减.Lion's mane jellyfish: The lion's mane jellyfish is the largest jellyfish in the world. Its body is umbrella-shaped, with a diameter of more than two meters. There are up to 150 tentacles, and the longest tentacle alone is 40 meters long. They like to live in the cold waters of the Arctic Ocean all year round. Their swimming speed is slower than that of a snail. Some even need to rely on ocean currents to move.(2) Ten oldest marine organismsFrilled shark: The frilled shark has six gill slits on both sides of its body, and there are folds between the gills. Its appearance is similar to that of an eel. It is one of the most primitive shark species on Earth. It has a history of 150 million years and has basically not evolved much. Because of its terrifying appearance, it is called the most terrifying marine organism in the world.Tadpole shrimp: The tadpole shrimp is scientifically known as Triops longicaudatus and has many common names in China. They have lived on Earth for more than 200 million years. Their life cycle is about 90 days, but the diapause period is at least 25 years. The eggs can still hatch when they encounter a suitable environment after 25 years.Sturgeon: Sturgeon is one of the earliest existing vertebrates in origin. It can be traced back to about 200 million years ago. It has a long lifespan, and some sturgeon species can even live up to 100 years.Horseshoe shrimp: The horseshoe shrimp is bent in a horseshoe shape and is a typical "living fossil". Even after 200 million years, its appearance has not changed at all.Lamprey: The lamprey looks very similar to an eel. It is a parasite and lives by parasitizing on other fish. It has existed since 360 million years ago. When its mouth opens, it looks like a huge circular suction cup. Its mouth is full of sharp teeth, and there are also sharp tongue teeth on its tongue.Coelacanth: The coelacanth first appeared about 360 million years ago and was once thought to be completely extinct. This idea was broken only after the discovery of Latimeria chalumnae in South Africa in 1938. Now it is listed as an endangered species.Horseshoe crab: The horseshoe crab belongs to primitive arthropods. The earliest fossils were found in the Ordovician period, about 445 million years ago. Since its appearance, it has basically retained its original ancient appearance.Nautilus: The nautilus has lived on Earth for more than 500 million years. In the Ordovician period, its body length could reach 11 meters. It was once the strongest霸主 in the ocean. Now it is facing the danger of extinction.Jellyfish: There are many kinds of jellyfish with different shapes. Their survival history has reached 500 million years. At present, the number in warm waters is increasing.Sponge: No one knows exactly how many years sponges have existed, but scientific research shows that a sponge species has at least a history of 760 million years and is the oldest existing marine organism.
