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In today's article we will learn about the curious world of Fish and how much these animals contribute to human beings.
They are animals that live in water and have a series of adaptations to live in this environment, such as fins and a fusiform body.
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In the most varied aquatic environments we find fish, which are characterized by being a numerous and diverse group of vertebrates.
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Including in this group cartilaginous fish: skeleton formed by cartilage, and bony fish: bony skeleton.
Many changes occurred in the classification of animals after the adoption of cladistic methodology and improvement of DNA analysis techniques.
Fish and their characteristics
Vertebrate animals that live exclusively in the aquatic environment. They have different sizes, shapes and colors.
They are of great economic importance, as they are used for food, sport fishing and breeding in aquariums.
Digestive and excretory system
With a complete digestive system, it has an intestine ending in a cloaca in cartilaginous fish and an anus in bony fish.
Their excretory system is formed by a pair of kidneys. In the cartilaginous ones, urea is mainly excreted, and in the bony ones, ammonia is eliminated.
Circulatory system
The heart has two cavities: atrium and ventricle and the circulatory system is closed.
Therefore, in the blood pumping organ, only blood rich in carbon dioxide, venous blood, circulates.
The blood travels through the heart through the atrium, continues to the ventricle and runs towards the gills, where it is oxygenated. The oxygenated blood goes to the animal's body.
There are lungfish, a group of only six species, which are found only in fresh water in South America, Africa and Australia.
In Brazil, the species of lungfish: piramboia.
These animals are able to build galleries, which they use as shelter to protect themselves from drought and predators.
Sensory organs
The lateral line is a sensory organ present in fish, which is very important.
Located laterally, they allow the animal to capture movements in the water and avoid predators.
In addition to these, fish have developed olfactory lobes, allowing them to perceive smells.
The ampullae of Lorenzini, which capture electrical currents produced by other animals, are found only in cartilaginous fish.
Endotherms and Ectoderms
The fish are ectotherms, means being unable to maintain a constant body temperature using physiological mechanisms.
Tuna and Sharks keep parts of their body warmer than others, raising the temperature by endothermic of heat.
Fish reproduction
Reproduction varies between groups. Cartilaginous fish have internal fertilization, while most bony fish have external fertilization.
Bony fish have indirect development, with the formation of larvae, and a phase called fry.
Adaptations of fish to live in water
Fish have great adaptations to live in the aquatic environment, highlighting the presence of gills.
These blade-shaped, vascularized organs exchange gases between the animal's water and blood, constituting gill respiration.
Water enters through the mouth, passes through the slits in the pharynx, goes to the gills, and leaves the animal's body.
The movements of the operculum and jaws allow water to reach the gills.
The way they swim serves to ensure ventilation of the gills.
Fusiform body that aids swimming
Fish have a hydrodynamically shaped body, which helps them move through the water.
They have a fusiform body: elongated and with tapered ends, enabling swimming. This shape allows them to swim at high speeds.
The mucus on their skin helps reduce friction with water.
And with mucus, scales play an important role in protecting fish against pathogens.
The fins stand out in their shapes, sizes and positions in each species of fish.
Their main functions are: to maintain the fish's balance, to help change direction and depth, and to act as propellers.
Swim bladder
In addition to adaptations to facilitate swimming, they have strategies to avoid sinking, as they have a greater density than water.
In cartilaginous animals, what guarantees buoyancy is the presence of a developed liver with an abundance of fat.
And bony fish have a swim bladder, a hydrostatic organ that allows the fish to swim to the bottom and to the surface.
Cartilaginous and bony fish
Fish are divided into two large groups: cartilaginous fish (Chondrichthyes) and bony fish (Osteichthyes).
Cartilaginous animals are given this name because they do not have bones forming their skeleton, which is predominantly made up of cartilage.
Stingrays, sharks, and chimeras are representatives of these schools, making up the majority of marine species.
This group is characterized by the presence of tooth-like plates that cover their bodies, the so-called placoid scales.
The difference between this group and bony fish are: ventral mouth, presence of cloaca, excretion of urea and absence of swim bladder.
Bony fish have a bony skeleton. In them, the gills are covered by the operculum, a type of bony flap that protects these structures.
Some characteristics: mouth at the anterior end, intestine ending in anus and excretion of ammonia.
Important!
- Fish are very important for human nutrition, as they provide vitamin D and omega 3, which are essential for human health.
- They also provide essential amino acids: retinol, iron, zinc, vitamin E, calcium, iodine and selenium.
- The benefits of fish for human health are associated with protection against cardiovascular diseases and stroke.
