Mammals of the water. Marine mammals and their diversity

Thanks to their warm-blooded nature and high level of organization, mammals have spread across the Earth from the tropics to high latitudes. Depending on the habitat animals are divided into several ecological groups:

land animals,
underground mammals,
aquatic Mammals,
flying mammals.

Each group includes small groups. So, among there are groups of terrestrial mammals that lead:

typically terrestrial
woody,
tree climbing or other way of life.

Land animals - the most numerous group in terms of the number of species, which is divided into two subgroups:

forest animals,
animals of open spaces.

For animals inhabiting the forest and leading a terrestrial lifestyle (elk, deer, roe deer, wolverine, brown bear), is characteristic limited vision, well-developed hearing and sense of smell. They get all their food on the ground. Babies are born on the forest floor (elk, roe deer), in burrows (badger), in dens (brown bear).

Arboreal mammals(squirrels, flying squirrels, some species of martens, most monkeys) spend most of their lives in trees, where they get food, make nests, and hide from enemies. They are characterized elongated slender body and very mobile limbs. There are often special adaptations for climbing trees:

sharp curved claws,
hapal type paws with well-developed toes,
prehensile tail, etc.

Animals leading a terrestrial lifestyle (sable, chipmunk) feed mainly on the ground, and make nests under the roots of trees, in hollows located not high from the ground, in fallen trees.

TO land animals open spaces include ungulates, lagomorphs, some carnivores, etc. They are characterized by:

slim body,
ability to run fast,
protective body coloring,
well developed vision,
have hooves or thick, blunt claws.

In large herbivorous animals (antelope, camels, horses), newborn babies immediately get to their feet and move behind their parents. Small animals (gophers, marmots, hamsters), although they spend a significant part of their time on the surface of the earth, where they find food, live in burrows, serve as a place of rest, feeding their offspring, and summer and winter hibernation. They have flattened body, short legs with large but blunt claws; the fur is short and rough.

Terrestrial animals that are common in various habitats. Some species of animals, for example, the wolf and the fox, live both in forests and in steppes, deserts, and mountains. The nature of their food, methods of obtaining, and breeding conditions are different and associated with specific places of residence. So, wolves that live in forests give birth to babies in dens, and sometimes dig holes in the desert and tundra.

Underground Beasts (moles, mole rats, blind men, armadillos) spend their entire life (or most of it) in the soil, finding shelter and food there. Their body is flattened; the neck is weakly defined, thick, legs and tail are short. The hairline is short, often without lint. The eyes are reduced to one degree or another. There are no auricles. Some dig the ground with their forelimbs, others loosen with their incisors.

Aquatic mammals They spend their entire life (or most of it) in an aquatic environment. Cetaceans and sirenians lead an exclusively aquatic lifestyle. Their hair completely disappears, and the layer of subcutaneous fat is well developed. There are no hind limbs. The organ of movement is the caudal fin. Pinnipeds lead a predominantly aquatic lifestyle - only reproduction and molting occur outside the water. The hair cover of pinnipeds is reduced to one degree or another and the function of thermal insulation is performed by a layer of subcutaneous fat. With the help of their hind limbs (flippers), moved far back, they swim and dive.

Half aquatic Mammals live both in water and on land (otter, nutria, beaver, muskrat, muskrat). Their limbs are short, there is a swimming membrane between the toes of the hind legs; the tail of some is flat, covered with scales and is used as a rudder when swimming; the auricles are shortened or completely reduced, the ear openings and nostrils are closed by valves when animals are immersed in water; the hair is thick, slightly wetted by water.

Flying animals are a highly specialized group, whose representatives have adapted to flight (the Chiroptera series). In connection with the flight they developed keel, as well as muscles that move the wings; the bones of the skull have fused, the chest has become stronger.

It is no secret that the seas and oceans are places of distribution and habitat of the most unusual, beautiful and simply amazing animals. Until now, the seas still present surprises to researchers. Discoveries of incredible animals are made, their way of life and interactions with each other are studied.

Among the marine and ocean inhabitants there are representatives of all classes of animals, except perhaps birds. And even then, depending on what point of view you look at them from. After all, many birds hunt in water, and penguins generally live in the ocean. But in this article I would like to focus specifically on those who fit the definition of “marine mammal.”

Fauna of seas and oceans

The organoleptics and chemical composition of water in the seas and oceans are almost the same. Water differs only in the content of certain elements and in the concentration of salts. Therefore, their fauna is also extremely similar. Animals of the seas easily go into the ocean, and animals of the oceans feel great in the seas.

The fauna of these reservoirs is represented by animals of the following classes:

Shellfish of all kinds.
Crustaceans.
Fish.
Polyps.
Sponges.
Hydroid.
Insects.
Amphibians.
Reptiles.
Mammals.
Birds.

It is obvious that the organic world of the oceans and seas is extremely diverse and large in terms of biomass. Among all the fauna, the marine mammal deserves special attention. Most often they live both on land and in water. However, there are also purely aquatic inhabitants.

Species diversity of mammals in the seas

The species of mammals living in the seas and oceans are very interesting and diverse both in their lifestyle and in appearance. Let's look at the main representatives.

Whales. These include different species: blue, gray, bowhead, sperm whales, humpbacks, beaked whales, minke whales and others.
Killer whales. Animals very close to whales, dangerous killers of sea and ocean spaces.
Dolphins. Different species: bottlenose dolphins, beaked dolphins, short-headed dolphins, porpoises, beluga whales and others.
Seals. Animals of the seal genus, the most common being the ringed seal.
Seals. They include several varieties: lionfish, spotted seals, eared seals, true seals, bearded seals and others.
There are two types of elephant seals: northern and southern.
Sea lions.
Sea cows are today a marine mammal almost exterminated by humans.
Walruses.
Seals.

In total, there are over 120 species of various marine mammals.

Signs of mammals

Like land species, sea and ocean animals also have distinctive features that allow them to be classified as mammals. What animals are classified as mammals?

Like all representatives of this class, marine and ocean mammals are characterized by feeding their offspring with milk through special mammary glands.
These animals bear offspring within themselves (fetal development) and reproduce through the process of viviparity.
These are poikilothermic animals (warm-blooded), they have sweat glands, a thick layer of subcutaneous fat glycogen.
There is a diaphragm available to allow breathing.

These devices make it possible to confidently classify all of the above animals as marine and ocean mammals.

Features of the lifestyle of marine animals

Animals of the seas and oceans have a number of adaptations in order to feel confident and safe in the expanses of water. For example:

limbs transformed into flippers for fast movement;
many of them have powerful sharp teeth (predators and carnivores);
large body size with a thick layer of subcutaneous fat;
streamlined body shape, increasing speed of movement;
the ability to give each other sound signals (for the majority).

Thanks to such adaptations, marine animals of the ocean coexist perfectly with each other and the surrounding world. Most often, sea mammals try to stay in a herd. This is typical for those who cannot protect themselves from large predators other than fleeing otters, seals, lions, seals).

Others, on the contrary, prefer loneliness. This is more convenient for hunting and pursuing prey (sperm whales, killer whales, predatory species of dolphins and whales).

Marine mammals, with rare exceptions, are diurnal. At night they usually rest. However, there are exceptions (some seals are nocturnal).

Mammals of the seabed

A marine mammal that moves along the very bottom of the depths of oceans and seas - dugong or (siren). This animal is completely harmless; it fully lives up to its name, as it feeds exclusively on bottom vegetation.

The sizes are average compared to other mammals of the seas: about 4 m in length, weight approximately 600-650 kg. A person can calmly swim next to a sea cow and even touch and stroke it. The animal is very affectionate, obedient and harmless, like a child.

In addition, this animal is one of the oldest on our planet (it appeared about 50 million years ago), it is listed in the Red Book. This is perhaps the only representative belonging to the category “animals of the seabed”.

Other representatives of marine mammals prefer to spend time at the surface or in the water column, rarely sinking to the bottom.

The most dangerous animals of the oceans

The most dangerous ocean animals include:

Killer whales (killer whales). They weigh more than 8 tons and reach 10 m in length. They are merciless killers that feed on large fish, mammals and their own relatives - whales.
Sperm whales. They attack squid, octopuses and giant mollusks, and can eat large fish. The weight of the animal is about 50 tons, and its length is over 20 m.
Sea lions. Seemingly cute and completely harmless animals often attack humans, as they strictly guard their possessions. In addition, they are carnivorous and feed on fish and small animals.

Of course, there are many more dangers hidden in the oceans. However, among mammals and representatives of marine fauna, the most dangerous are those listed above. The rest are either herbivores or feed on plankton or small animals.

The largest animals of the oceans

The largest mammals include the following representatives:

Blue or - reaches 33 m in length. Its weight varies from 90 to 120 tons. The heart alone weighs more than 600 kg!
Southern elephant seal - reaches a length of 6 m. Weight is from 5 to 6 tons. In addition to their enormous size, these animals are also predators - dangerous and ferocious. They are capable of diving into water to a depth of over a thousand meters if they set themselves the goal of catching up with the victim at all costs.
Walruses reach a length of 4 m and weigh up to 2 tons. Very impressive in size for a completely harmless disposition - they feed on small invertebrates, tearing them out of the silt and sand at the bottom of coastal zones. Large dormouse spend a lot of time sleeping in groups on the banks of water bodies.

The most harmless animals of the seas and oceans

Which are the most harmless mammals of the sea and ocean? The answer is known to every schoolchild: of course, bottlenose dolphins! Lovers of swimming with people, friendly and beautiful - they rejoice and play, splash, jump (up to 6 m in height!) and bring a lot of fun and pleasure to people.

Also harmless marine animals include seals, otters, fur seals and some whales.

Among mammals, only cetaceans are true aquatic animals. They live in almost all seas and oceans of the globe and in some rivers and lakes of Asia and South America. Constant living in the aquatic environment left a strong imprint on the appearance of cetaceans and led to the emergence of very special adaptations in them.

The sizes of these animals range from 1 to 33 meters, and weight - from 30 kilograms to 140 tons. Their body shape is elongated, torpedo-shaped, and well streamlined. The hind limbs have disappeared, only in some representatives they are found in the form of rudimentary formations, and the front limbs have turned into paddle-shaped pectoral fins - rudders for depth, turns and brakes. The main organ of movement is the tail, equipped with powerful muscles, slightly flattened on the sides, the “stem” of which ends in a triangular caudal fin with horizontally located blades. In addition, most species develop a dorsal fin. All whales are devoid of hair, sebaceous, sweat, and salivary glands; Due to the aquatic lifestyle, their auricle also disappeared and other changes occurred in the structure of the body.

Systematically, cetaceans are divided into two suborders - baleen and toothed whales. The differences between them are significant and quite distinct. They relate to a number of structural features of the skull and skeleton, the protein composition of blood serum, and features of the respiratory and digestive systems. This gives grounds for some researchers to consider baleen and toothed whales to have originated from different roots and to elevate them to the rank of independent orders. However, ultramicroscopic examination of the structure of their cell nuclei showed great similarity in chromosome morphology, which definitely supports the hypothesis of the origin of cetaceans from a single root. The ancestors of cetaceans were undoubtedly some very ancient land mammals. Whether these were ancient insectivores or primitive carnivores (creodonts), or ungulates is difficult to say. Paleontologists and taxonomists are still arguing about this. Cetaceans as an order may have become isolated in the Cretaceous, that is, about 100 million years ago.

115. The bowhead whale is a representative of the baleen whales. The huge head makes up at least a third of the animal's body. Numerous horny plates, or whalebone, are visible in the mouth, which serve as a filtering apparatus for the whale.

Baleen whales are characterized primarily by the complete absence of teeth (they are present only in embryos) and the development in the oral cavity on the expanded palatine processes of the maxillary bones of one hundred and thirty to four hundred horny plates on each side of the jaw. In right whales, these plates hang into the oral cavity and, thanks to the horny fringe that turns them off along the lower edge, they serve as a filtering apparatus. With the help of this “sieve” and a powerful tongue that acts like a piston, animals filter out various planktonic organisms from the water mass that enters their mouths, which they feed on. Baleen whales include nine species, comprising three families: gray whales, right whales and minke whales.

Marine mammals are a collective group of aquatic and semi-aquatic mammals whose life is spent entirely or a significant part of their time in the marine environment. This category includes representatives of various systematic groups of mammals: sirenians, cetaceans, pinnipeds - eared seals, true seals, walruses. In addition to these animals, marine mammals also include single representatives of the mustelidae (sea otter and sea otter) and ursidae (polar bear) families. In total, marine mammals include about 128 species, representing 2.7% of the total number of mammals.

Marine mammals are animals descended from land animals that secondarily connected their lives at a certain stage of evolutionary development with the sea water element. Sirens and cetaceans descended from ungulate ancestors, while pinnipeds, sea otters and the polar bear originated from ancient canids.

Long before people appeared on our planet, the sea and ocean were developed by marine mammals - cetaceans and pinnipeds. Findings by paleontologists confirm the existence of whales 26 million years ago in the Cenozoic period. During the process of evolution, the species composition of marine mammals has undergone significant changes. Epochs changed and, along with them, the conditions of existence, some species became extinct, others, on the contrary, managed to adapt and increase their numbers.

The species of mammals living in the seas and oceans are very interesting and diverse both in their lifestyle and in appearance. Let's look at the main representatives.

1. Whales. These include different species: bowheads, sperm whales, beaked whales, minke whales and others.

2. Orcas. Animals very close to whales, dangerous killers of sea and ocean spaces.

3. Dolphins. Different species: bottlenose dolphins, beaked dolphins, short-headed dolphins, porpoises, beluga whales and others.

4. Seals. Animals of the seal genus, the most common being the ringed seal.

5. Seals. They include several varieties: lionfish, spotted seals, eared seals, true seals, bearded seals and others.

6. Elephant seals two types: northern and southern.

7. Sea lions.

8. Sea cows- today, a marine mammal almost exterminated by humans.

9. Walruses.

10. Navy SEALs.

Like land species, sea and ocean animals also have distinctive features that allow them to be classified as mammals. What animals are classified as mammals? Like all representatives of this class, marine and ocean mammals are characterized by feeding their offspring with milk through special mammary glands. These animals bear offspring within themselves (fetal development) and reproduce through the process of viviparity. These are poikilothermic animals (warm-blooded), they have sweat glands, a thick layer of subcutaneous fat glycogen. There is a diaphragm available to allow breathing. These devices make it possible to confidently classify all of the above animals as marine and ocean mammals.

Sea lion

Order Pinnipeds

These are large animals with a spindle-shaped body, a short neck and limbs turned into flippers. They spend most of their time in the water, coming ashore only to breed or for short-term rest. About 30 species are known, among them the harp seal, fur seal and.

harp seal- This is a pinniped animal that does not have ears, the rear flippers are short, extended back and are not used for movement on land. They crawl on land, raking the surface with their front flippers. Adult seals have thin fur, without undercoat. Juveniles, who cannot yet swim, have thick fur, usually white.

The harp seal is an inhabitant of the Arctic seas. Seals spend most of the year in the open sea, feeding on fish, shellfish and crustaceans. In winter, herds of seals come to the shores and get out onto large, flat ice fields. Here the female gives birth to one large, sighted calf. The white skin of a baby seal with thick fur protects it from frost and makes it invisible among the snow. With the beginning of spring, the herd migrates north. Seals are hunted for their skins and fat.

Fur seal has ears and rear flippers used for locomotion. On land, the hind flippers bend under the body, then straighten - the cat makes a jump.

The fur seal lives in the Far Eastern seas. Its body is covered with thick fur with a dense, waterproof undercoat. At the beginning of summer, seals come to the shores of the islands in large herds to breed. The female gives birth to one young, covered with black hair. In the fall, when the cubs grow up and learn to swim, the seals leave the islands until spring. Seals have valuable fur.

Walrus- the largest of all pinnipeds, up to 4 m long and weighing up to 2,000 kg. The walrus has bare skin and no hair. It is characterized by huge fangs, 40-70 cm long, hanging vertically down from the upper jaw. Walruses use them to scavenge at the bottom, extracting from there various large invertebrates - mollusks, crayfish, worms. Having eaten, they like to sleep on the shore, gathered in a tight group. When moving on land, the hind legs are tucked under the body, but due to the enormous mass they do not go far from the water. They live in the northern seas.

Order Cetaceans

These are completely aquatic mammals that never go onto land. They swim using a caudal fin and a pair of forelimbs modified into flippers. There are no hind limbs, but from two small bones located at the site of the pelvis, one can judge that the ancestors of cetaceans also had hind limbs. Cetacean calves are born fully formed and can immediately follow their mother.

Blue whale- the largest modern mammal. Some specimens reach a length of 30 m and a mass of 150 tons. This corresponds to the mass of at least 40 elephants. The blue whale is a toothless whale. It has no teeth and feeds on small aquatic animals, mainly crustaceans. Numerous elastic horny plates with fringed edges hang from the upper jaw of the animal - whalebone. Having filled the huge oral cavity with water, the whale filters it through the oral plates and swallows the stuck crustaceans. A blue whale eats 2-4 tons of food per day. Whales that have baleen instead of teeth are classified as baleen or toothless whales. There are 11 known species of them.

The other group is toothed whales having numerous teeth, some with up to 240 teeth. Their teeth are all the same, cone-shaped, and serve only to capture prey. Toothed whales include dolphins and sperm whales.

Dolphins- relatively small (1.5-3 m long) cetaceans, the snout of which is elongated, like a beak. Most have a dorsal fin. There are 50 types in total. Dolphins find prey using ultrasounds. In water, they make clicking sounds or an intermittent high-pitched whistle, and the echo reflected from the object is picked up by the hearing organs.

Dolphins can exchange sound signals with each other, thanks to which they quickly gather where one of them has discovered a school of fish. If any misfortune happens to one dolphin, the others come to its aid as soon as they hear alarm signals. The dolphin brain has a complex structure, with many convolutions in its cerebral hemispheres. In captivity, dolphins quickly become tamed and are easy to train. Dolphin hunting is prohibited.

The common dolphin, no more than 2.5 m long, lives in the northern and Far Eastern seas, as well as in the Baltic and Black seas. Its slender body is black on top, its belly and sides are white. On the elongated jaws of the white sided there are more than 150 teeth of the same conical shape. With them the dolphin grabs and holds the fish, which it swallows whole.

Sperm whale- large toothed whale. The length of males is up to 21 m, females - up to 13 m and weight up to 80 tons. The sperm whale has a huge head - up to 1/3 of the body length. His favorite food is large cephalopods, for which he dives to depths of up to 2,000 m and can stay under water for up to 1.5 hours.

Marine mammals can stay underwater for varying amounts of time. For example, whales can go from 2 to 40 minutes without breathing underwater. A sperm whale can not breathe underwater for up to an hour and a half. How long a mammal can stay underwater is affected by the volume of its lungs. The content of a special substance in the muscles, myoglobin, also plays an important role.

Marine mammals, like land mammals, are predators and herbivores. For example, manatees are herbivorous mammals, while dolphins and killer whales are carnivores. Herbivorous mammals feed on various algae, while predators need animal food - fish, crustaceans, mollusks and others.

Most common Among the marine mammals, this is the Larga seal, which lives off the coast and hunts fish, and for this it swims considerable distances from the shore. After hunting, he returns to the shore to feed the cubs and rest himself. The Larga seal is gray in color with brown spots. That's why it got its name. Larga seals can form entire settlements, where from several hundred to several thousand individuals live.

The largest marine mammal - blue whale. Due to its size, it is listed in the Guinness Book of Records. The average length of a giant is 25 meters. And the average weight is 100 tons. Such impressive sizes distinguish it not only among marine animals, but also among mammals in general. Despite their terrifying appearance, whales are not dangerous to people, as they feed exclusively on fish and plankton.

The most dangerous marine mammal- This . Despite the fact that it does not attack humans, it is still a formidable predator. Even whales are afraid of her. It’s not for nothing that the killer whale is called a whale killer. In addition to whales, she can hunt dolphins, sea lions, seals and fur seals, as well as their calves. There have been cases of killer whales attacking elk and deer that swam across narrow coastal channels.

When killer whales hunt seals, they ambush them. In this case, only the male hunts, and the rest of the killer whales wait in the distance. If a seal or penguin is swimming on an ice floe, then the killer whales dive under the ice floe and hit it. The victim falls into the water as a result of the blows. Large whales are attacked mainly by males. They unite and all together attack the prey and bite it by the throat and fins. When killer whales attack a sperm whale, they do not give it the opportunity to hide in the depths of the sea. As a rule, they try to separate the whale from the herd or separate the baby from its mother.

Manatees

The friendliest to humans, the marine mammal is the dolphin. There are many cases where dolphins saved people from shipwrecks. They swam up to people, and they clung to their fins, so the dolphins brought people to the nearest shore. There are no known cases of dolphin attacks on humans. Both children and adults love these peace-loving animals. In dolphinariums you can watch dolphins perform in the water. By the way, dolphins are very smart and scientists have found that their brains can be even more developed than the human brain.

Killer whale is fastest marine mammal. It can accelerate to 55.5 kilometers per hour. Such a record was recorded in 1958 in the eastern Pacific Ocean. The killer whale is distributed throughout the world's oceans. It can be found near the coast and in open waters. The killer whale does not enter only the East Siberian, Black and Laptev Seas.

An animal that lives in water for a period of time or its entire life. Many insects, such as mosquitoes, mayflies, dragonflies and caddisflies, begin their life cycle as aquatic larvae before developing into winged adults. Aquatic animals can breathe air or obtain oxygen dissolved in water through specialized organs called gills or directly through the skin. Natural conditions and the animals that live in them can be divided into two main categories: aquatic or.

Groups of aquatic animals

Most people only think of fish when asked about aquatic animals. However, there are other groups of animals that live in water:

mammals, for example (whales), sirenians (dugongs, manatees) and pinnipeds (seals, eared seals and walruses). The concept of "aquatic mammal" also applies to animals with a semi-aquatic lifestyle, such as river otters or beavers;
shellfish (eg sea snails, oysters);
(for example, corals);
(eg crabs, shrimp).

The term "aquatic" can apply to animals that live in both fresh water (freshwater animals) and salt water (marine animals). However, the concept of marine organisms is most often used for animals that live in seawater, that is, in oceans and seas.

Aquatic fauna (especially freshwater animals) are often of particular concern to conservationists due to their fragility. They are exposed to overfishing, poaching, pollution, etc.

Frog tadpoles

Most are characterized by an aquatic larval stage, for example, tadpoles in frogs, but adults lead a terrestrial lifestyle near bodies of water. Some fish, for example, the arapaima and the walking catfish, also breathe air to survive in oxygen-poor water.

Do you know why the hero of the famous cartoon "SpongeBob SquarePants" (or "SpongeBob Square Pants") is depicted in the form of a sponge? Because there are aquatic animals called marine animals. However, sea sponges do not look like a square kitchen sponge like the cartoon character, but have a more rounded body shape.

Fish and Mammals

School of fish near a coral reef

Did you know that there are more species of fish than amphibians, birds, mammals and reptiles combined? Fish are aquatic animals because their entire lives are spent in water. Fish are cold-blooded and have gills that receive oxygen from the water to breathe. In addition, fish are vertebrates. Most fish species can live in either fresh or saltwater, but some fish, such as salmon, live in both environments.

Dugong is an aquatic mammal from the order of sirens.

While fish live only in water, mammals can be found on land and in water. All mammals are vertebrates; have lungs; They are warm-blooded and give birth to live young instead of laying eggs. However, aquatic mammals depend on water to survive. Some mammals, such as whales and dolphins, live only in water. Others, such as beavers, are semi-aquatic. Aquatic mammals have lungs but no gills and are unable to breathe underwater. They need to come to the surface at regular intervals to breathe air. If you've ever seen what a fountain of water looks like coming out of a whale's blowhole, it's an exhalation followed by an inhalation before the animal dives back underwater.

Molluscs, cnidarians, crustaceans

The giant tridacna is the largest representative of bivalve mollusks

Molluscs are invertebrate animals that have soft, muscular bodies without legs. For this reason, many shellfish have a hard shell to protect their vulnerable bodies from predators. Sea snails and oysters are examples of shellfish. Squids are also classified as mollusks, but they do not have shells.

Swarm of jellyfish

What do jellyfish, sea anemones and corals have in common? All of them belong to cnidarians - a group of aquatic animals that are invertebrates and have a special mouth and stinging cells. The stinging cells around the mouth are used to catch food. Jellyfish can move around to catch their prey, but sea anemones and corals are attached to rocks and wait for food to approach them.

Red crab

Crustaceans are aquatic invertebrate animals with a hard chitinous outer shell (exoskeleton). Some examples include crabs, lobsters, shrimp and crayfish. Crustaceans have two pairs of antennae that help them receive information about their environment. Most crustaceans feed on the floating remains of dead plants and animals.

Conclusion

Aquatic animals live in water and depend on it for survival. There are various groups of aquatic animals, including fish, mammals, molluscs, cnidarians and crustaceans. They live either in freshwater bodies (streams, rivers, lakes and ponds) or in salt water (seas, oceans, etc.), and can be either vertebrates or invertebrates.