Embryonic development of fish

To get into the embryonic development of fish, we must first know some basic concepts of embryology such as the types of eggs and the phases that make up early embryonic development.

We can find different types of eggs , according to how the yolk is distributed and how much it contains.To begin with, we will call the cell resulting from the union of an egg and a sperm and, vitellum, the set of nutritional elements found in inside the egg and will serve as food for the future embryo.

Types of eggs according to the organization of the vitello inside:

Isolecite eggs : the vitello is uniformly distributed throughout the interior of the egg.Typical of poriferous animals, cnidarians, echinoderms, nemertines and mammals.
Telolecitos eggs : the vitello is displaced towards an area of the egg, being opposite to The place where the embryo will develop.Most animals develop from these types of eggs, for example, mollusks, fish, amphibians, reptiles, birds, etc.
Little center eggs : the vitello is surrounded by cytoplasm and, in turn, envelops the nucleus that will give rise to the embryo.It occurs in arthropods.

Types of eggs according to the amount of vitelo:

Oligolecitos eggs : they are small and have little vitello.
Mesolecyte eggs : medium size with a moderate amount of vitello.
Macrolecitos eggs : they are large eggs with a large amount of vitello.

Typical phases of embryonic development

Segmentation : in this phase a series of cell divisions take place that increase the number of cells needed for the second phase.It ends in a state called blastula.
Gastrulacion : there is a reorganization of the blastula cells giving rise to blastoderms (primitive germ layers) that are ectoderm, endoderm and, in some animals, mesoderm.
Differentiation and organogenesis : the tissues and organs will form from the germ layers, the structure of the new individual being fixed.

The temperature is closely related to the incubation time of eggs in fish and their embryonic development (the same occurs in other animal species).Generally there is an optimal temperature range for incubation, which varies by about 8ÂºC.

Eggs incubated within this range will have a higher probability of developing and hatching.Also, those eggs incubated for long periods of time at extreme temperatures ( out of the last range of the pecie) will have a lower probability of hatching and, if they do, born individuals may suffer serious abnormalities .

Now that you know the basic concepts of Embryology, we will enter the embryonic development of the fish.The fish are telolecitic, that is, they come from telolecyte eggs, those that had the vitellas displaced to an area of the egg.

Zygotic phase

The newly fertilized egg remains in zygote status until the first division, the approximate time at which this split occurs depends on the species and the temperature of the medium.In the zebrafish, Danio rerio (fish most used in research), the first segmentation occurs around 40 minutes after fertilization.Although it seems that there are no changes in this period, In the interior of the egg, decisive processes are taking place for further development.

Phase of s egmentation

The egg enters the segmentation phase when the first division of the zygote occurs.In fish, the segmentation is meroblastic, because the division does not completely pass through the egg since it is prevented from vitelus, but rather It is limited to the area where the embryo is located.The first divisions are vertical and horizontal to the embryo, they are very fast and synchronous.They give rise to a mound of cells seated on the vitellus, constituting the discoid blastula.

Phase of gastrulation

During the gastrulation phase there is a rearrangement of the cells of the discoid blastula by morphogenetic movements, that is, the information contained in the nuclei of the different cells already formed, is transcribed so that forces the cells to obtain a new spatial configuration.In the case of fish, this reorganization is called involvement.Also, this stage is characterized by a decrease in the rate of cell division and little or no cell growth.

During involvement, some cells of the discoblastula or discoid blastula migrate to the vitellum, forming a layer on it.This layer will be the endoderm.The layer of cells that remain on the mound will form the ectoderm.At the end of the process , the gastrula will be defined or, in the case of fish, discogastrula with its two primary germ layers or blastoderms, the ectoderm and the endoderm.

Phase of differentiation and organogenesis

DuringIn the phase of differentiation, in fish, the third embryonic layer appears, located between the endoderm and the ectoderm, called the mesoderm.

The endoderm is invaded forming a cavity called archaenteron.The entrance to this cavity will be called blastoporo and will give rise to the anus of the fish.From this point, the cephalic vesicle (encephalon in formation) can be distinguished and, on both sides, the vesiculasopticas (future eyes).Next the cephalic vesicle will form the neural tube and, on either side, the Somites, structures that will eventually form the bones of the spine and ribs, muscles and other organs.

Throughout this phase, each germ layer will eventually produce several organs or tissues, so that:

Ectoderm :

Epidermis and nervous system
Beginning and end of the digestive tract

Mesoderm :

Dermis
Musculature, excretory and reproductive organs
Celoma, peritoneum and circulatory system

Endoderm :

Organs involved in digestion: internal epithelium of the digestive tract and attached glands.
Organs responsible for gas exchange.

Comments

How to know what size a mongrel dog will be?

When we talk about a mixed breed dog or mixed breed dog , generally we refer to a dog whose ancestry is unknown and that has typical characteristics of two or more breeds.This is usually the result of a non-selective breeding, but generally fortunate, since a mongrel dog can be exactly as good companion as a dog of a certain breed. Due to numerous factors, although here it is worth highlighting the great genetic variability, there are many advantages of having a mongrel dog and it is important to emphasize this point since unfortunately it is usually grant a lower value to a dog of these characteristics.If you are thinking of adopting a mixed breed dog, you are surely gathering all the necessary information, if you are wondering how to know what size a mongrel dog will be I didn't leave It is to read this article of Animals and Pets Online. Is it possible to know the size of a mongrel dog? Of course, estimating the exact size of a mongrel dog is not an easy task, although ...

Garlic and onion poisoning in dogs

Decide to share our home with a dog means to We are responsible for guaranteeing a complete state of well-being, which includes multiple care, some of the most important is to provide adequate socialization, sufficient company and affection, and optimal food. The feeding of the dog is of great importance, because it directly interferes with your health.In fact, improper nutrition acts as a trigger for multiple diseases.Many owners also decide to provide homemade food to their pet as a complement to feed and, by In this way, they are informed about what foods can be toxic, but it is also necessary to know how to interpret this information. In this article of Animal Expert we talk about the garlic and onion poisoning in dogs , two vegetables that do not have to stop being present in the diet of our pet. The toxicity of garlic and onion For many years and even today it is strongly stated that garlic and onion are toxic to dogs, but it turns out that is only so in excessive qua...

Why does my dog have arches?

The arcades in the dogs It is common for a dog to have arches as precedents of vomiting , which can indicate, if the episode is repeated or we find another symptomatology, that is suffering from some disorder digestive that we should consult with our veterinarian. Many times a dog that has vomited several times arches without vomiting when it no longer has any content to eliminate in its stomach.But, sometimes, These indicate another type of problem.In the following sections we will explain the most likely causes of why our dog has arches. The presence of foreign bodies One cause that can explain to us why a dog has arcades is that has swallowed a foreign body and it is lodged in the mouth, throat or esophagus.We talk about objects such as bone fragments, splinters, thorns, threads, needles, hooks, spikes, balls and other toys, ropes, etc. If these bodies have sharp or sharp edges can complicate the picture by producing perforations.If our dog begins to show hypersaliva...

American Akita dog: features, photos and videos

The American Akita is a variant of the akita inu from the northern and mountainous regions of Japan.The American strain is known simply as akita.This variant of the breed shows all kinds of colors unlike the Japanese akita.It is a very cold-resistant breed. If you are thinking of adopting an American akita, you have entered the right place, in ExpertAnimal we will do a general review of everything you have to know about the American akita including useful information about the character, the training, food, education and obviously about weight and height, something to consider. Physical appearance As a main difference we will see that it is thicker and more imposing than the akita inu , it is even somewhat higher in height and weight.It has a triangular head and formed with triangular ears also splitz type The nose truffle is completely black.The eyes are black and small.As a Pomeranian breed, the American Akita has a double layer coat, which protects it very well from the c...

The language of the horses

Like humans, horses are social animals that need to be part of a community in which to communicate and express themselves freely, with a verbal and body communication system. For this system to work, since horses don't speak, horses have different Ways to communicate information to other members of your own species, as well as to other species, including humans. Are you a horse lover and want to know more about them? We invite you to read the following article of Animals and Pets Online where, this time, we will talk about the language of horses . Corporal lenguage Despite their great size, in nature, horses are considered as animals of prey, this means that it is an animal species that can be hunted or caught in some way or another.For this reason In order not to attract predators, horses at the evolutionary level have developed a communication system based on body language mainly.It is also said that this is one of the reasons why horses have a very limited range of...

Why do cats make a lot of noise when they mate?

If you have seen the mating of two wise cats that do a lot of noise.The truth is that the meows begin when the cats enter into heat, to attract the attention of the males .They also respond with meows and so the procession begins. But it is during the copula that the screams are more obvious and scandalous.Many people wonder why do cats make a lot of noise when they mate? In Animal Expert we will answer your question, you will be surprised. Sexual maturity and zeal Females reach sexual maturity between 5 and 9 months of age.Males, meanwhile, somewhat later, between 9 and 12 months .It is quite evident when cats are in heat.In addition to the characteristic meowing, there are many other signs that a cat is in heat, such as licking, tail lifting, etc. The heat in cats has an average of 5 to 7 days and is repeated once a month .This interval will depend on whether the cat has crossed or not with a male during the heat Other factors that may intervene are the season of the a...

Start in Agility

Agility is a very fun and complete sport, suitable for all types of dogs over 18 months of age.It consists in the combination of a guide (owner) that leads the dog along a pre-established route while overcoming various obstacles following a fixed order and time.Finally the judges determine the winning dog based on his skill and dexterity. This sport develops the intelligence, obedience, agility and concentration of the dog in addition to strengthening their muscles and promoting your understanding. Everyone can practice Agility if they are predisposed, want to pass it on.well and enough time, you do not have to have advanced knowledge or a great capacity as a trainer.Read on to know how to start in Agility . FCI Regulation Agility is a type of competition that has an international regulation prepared by the FCI (the Federation Cynologique Internationale ) who is responsible for organizing the championship official and set the basic rules, although around the world there ar...

The best toys for parrots

Parrots are very active animals, they need to exercise every day and face mental challenges positively stimulate.In nature, parrots are gregarious animals with very complex relationships with their relatives.They spend the day communicating, playing, climbing trees, feeding and creating new bonds. In this article of Animals and Pets Online we will talk About the toys for parrots, we will see how they should be, what types exist, we will even learn how to make toys for parrots since we can not always afford to visit a specialized store. The importance of parrot toys The lack of physical activity, new challenges, absence of more parrots or other animals with which I empathize can end up causing health problems in our parrot.Symptoms of stress or discomfort in parrots are not usually evident in a principle, then, being prey animals they know how to hide their weaknesses perfectly. If you have one or several parrots at home, you should know that one of the strategies to reduce yo...

Why do whales explode?

When a dead whale is run aground on the beach, the countdown is activated, late or early, if not acted correctly, the whale will explode, but why do the whales explode when they die? In this article of Animals and Pets Online we will explain the reason for this fact, although many readers may find it somewhat unpleasant. Strandings of whales It is common to see news about whales or other cetaceans stranded on the beaches.Unfortunately, a large number of them die because they fail to return to the water , even if the human being tries to help.Their sensitive skin and the weight they support are not able to withstand the environmental conditions outside the water. The reasons why stranding occurs, whether massive and individual, are still being studied. They can occur for behavioral reasons, such as when seek refuge on the shore fleeing from some danger in the open sea.Bad weather conditions can also attract cetaceans to In addition, sick individuals can separate themselves...

My chinchilla doesn't drink water

If you have recently adopted a chinchilla as a pet you may have doubts about the behavior or the habits of this.The chinchilla is a somewhat reserved and scary rodent, especially the first few days. If you have observed that your chinchilla does not drink water , calm down, then we will explain some possible causes and what you should do to solve this problem. Keep reading this article from Animal Expert to answer your questions: Knowing the chinchillas To begin with, you should know that the chinchillas don't drink a lot of water , on the contrary they usually take small sips occasionally and especially at night.If you observe urine, your chinchilla is probably drinking. Animals and Pets Online advises you to mark with a marker the water line in the drinking fountain to find out if you are really drinking or not. Anyway, it is essential to explain that these animals They are especially suspicious when they arrive at our home.Stress and excessive noise will cause you to...

Animals and Pets Online

Search This Blog