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 ...

Can you eat shellfish during pregnancy?

Seafood is one of the most exquisite foods out there, but also one of the worst known in the diet of a pregnant woman.Can you eat shellfish and fish during pregnancy? The truth is that it has many benefits for the future breast and the fetus, but as long as the appropriate varieties are chosen, they are cooked well and in a healthy way and not excessive consumption is made.Especially, during this stage, it is essential to avoid consumption of raw fish or shellfish and opt for those varieties with a lower amount of mercury so as not to endanger the health of the baby or the pregnant woman.Read this ONsalus article to know all the details about the issue: Can seafood be eaten during pregnancy? Can I eat shellfish in pregnancy? The fats that seafood has are mostly healthy, in addition to also having omega-3, an element that lowers cholesterol, especially if taken on a regular basis, which also helps decrease the risk of heart disease.Therefore, seafood has very significant benefits ...

Differences between a Persian cat and an angora

Although both breeds are known and popular, for some lovers of cats the differences between a Persian cat and an angora are not entirely clear, perhaps because they both have a spectacular long coat, but the differences between both races are remarkable and, if we want to adopt any of these cats, it is important that we have them in order for our new cat to adapt as well as possible to our home. This is why in this article of Animals and Pets Online we will expose the differences between a Persian cat and an angora .If you intend to adopt any of these cats, this article of Persian cat vs Angora is essential! Physical differences between Persian and Angora cats We begin this review of the differences between a Persian cat and an angora for the most obvious, that is, those that refer to physical aspects.These are going to be the following: The nose: it is, perhaps, the most important and significant, in addition, at first glance it will allow us to differentiate a Persian cat a...

Bach flowers for cats

In the last few years we hear frequent talk of Bach flowers, also applied to our Companion animals.There are more and more numerous cases treated with this therapy, as well as veterinary professionals who are trained in this discipline.In this article of Animals and Pets Online we will focus on cats to discover what Bach flowers are, which These are the benefits and uses they can have for our cats.If you've ever heard of these Bach flowers for cats , you're interested in reading! What are Bach flowers? The 38 extracts of flowers and plants discovered by the English doctor Edward Bach in the early twentieth century are called.This doctor chose plants that acted on different conditions that could experience the human beings, such as fear, sadness, anger or hyperactivity.Prepared these plants in the form of dilutions that conserved with alcohol in a dropper to facilitate their use.Various drops were administered directly several times a day or put in the water or even in t...

Cetaceans - Meaning, Types and Features

The cetaceans are the marine animals most famous for their presence in ancient tales and legends.They are animals that have always aroused great interest on the part of the human being.These animals, in general, are great strangers that, little by little, are disappearing without, apparently , let's do nothing. In this article of Animals and Pets Online we will talk about cetaceans, which are, their characteristics, where they live and other curiosities .Do you want to know more about these inhabitants of the sea depths? Keep reading! What are cetaceans? The order of the cetaceans is composed of two suborders, the myxicets, formed by the bearded whales, and that of the odontocetes, composed of cetaceans with teeth, such as sperm whales, dolphins and killer whales. The evolution of the cetaceans has resulted in a similarity between these two living suborders, being the result of evolutionary convergence.The common structural characteristics between the two groups, suc...

10 reasons to walk your dog

The dog is an animal that needs to walk 2 to 3 times a day, But do you know why that is so? In this article of Animals and Pets Online we will explain why it is so important to walk with your dog, why the garden does not replace the walk and many other things that, perhaps you do not know. Do not forget This is a very important habit that you must carry out on a daily basis.Not doing so can be very harmful for your pet, do not forget it.Keep reading and discover 10 reasons to walk with your dog . 1.They must make their needs The first reason, and the most important , to take a dog for a walk, is to allow him to do his needs until he is satisfied. Apart from puppies that are not yet able to go outside or who are learning to urinate, it is very negative to allow our dog to urinate and defecate at home.In addition to causing a bad smell, we will be creating an unhealthy environment important that can lead to serious health problems in dogs and humans. 2.It allows them to ...

The raccoon dog as a pet

The raccoon dog, better known as Nursery dog or Tanuki It is an animal of Asian origin that resides in China and Japan.Its scientific name is: Nyctereutes procyonoides . It is a very old breed, but until recently there has been no interest for domesticate it as a pet.It is considered as an invasive species in many countries.For example, in Spain it is prohibited as a pet, as well as its trade or introduction into nature. Even if it were tendered its Tenure, I would never advise adopting a Tanuki as a pet.If you continue reading Animals and Pets Online, I will explain the arguments that support my opinion.And I believe you will convince yourself that it is not sensible to have the raccoon dog as a pet .Then I explain why: Tanuki, the ancestral dog The Tanuki is the oldest breed of wild dogs on the planet, leaving aside its morphology that reminds the naked eye more of a raccoon that to any dog, it is their habits that make it too difficult for them to live alongside th...

Urinary incontinence in cats - Causes and treatment

Who has a cat at home knows how careful they are with their personal hygiene , especially when it comes to using its waste box correctly.When the cat gets dirty outside its rightful place, this is an unequivocal sign that something is wrong, whether it is done intentionally or not. Keep reading this Animals and Pets Online article so you can find out everything about urinary incontinence in cats, their causes and treatment. What do we call urinary incontinence? It receives this name the inability that develops the animal to control the muscles of the urethra, so the sphincter does not remain closed , causing the cat can not decide at what time urinating, but continually suffers accidental spills or losses. Incontinence is never manifested for a casual reason nor should it be ignored, as it indicates that something is wrong in the feline's health, either emotionally or physical. When it has been confirmed that it is incontinence and not land marking, in no case should...

Colicos in horses - Symptoms and treatment

The equine colic is the first cause of mortality in horses and many horse owners have to face it once since it is the most frequent disease of the adult horse.Colic syndrome is defined as a abdominal pain of varied origins . The horse is a hypersensitive animal and the external manifestations of the colic can be impressive.Some specificities of the horse can complicate the situation: a horse cannot vomit, so that the food that has reached the stomach is forced to follow its path in the digestive tract.In addition, certain parasites such as strongils cause a narrowing of the arteries of the digestive system, which can make the condition worse. Fortunately less than 10% of horses with colic require surgery.case colic syndrome is a of the most important equine pathologies for their severity and frequency, in this article of Animals and Pets Online we will tell you everything you need to know about the colic in horses . Symptoms of colic on the horse Colic or colic syndrome is...

Flying mammals - Examples, characteristics and images

Usually, when we think of flying animals the first thing that comes to us head are images of birds.But in the animal kingdom there are many other flying animals, from insects to mammals.It is true that some of these animals do not fly, only plan or have body structures that allow them to jump from great heights without damaging when they arrive to the ground. Even so, there are flying mammals that really have the ability to fly, not just plan, like bats.In this article of Animals and Pets Online we will show you the curious characteristics of flying mammals.list with photos of the most representative species. Characteristics of flying mammals At a glance, the wings of a bird and a bat can look very different.The birds have wings covered with feathers and bats with hair but, nevertheless, observing their structure we will see that they have the same bones : humero, radio, cubito, carpales, metacarpal and phalanges. In birds, some of the bones corresponding to the wrist and hand...

Animals and Pets Online

Search This Blog