Polyembryony Polyembryony is the development of more than one embryo from one zygote in animals or the formation of several embryos in one seed in plants. Zygotes are the first cells of new organisms. Stages of zygote development Development of several embryos

Lit.: Kanaev I.I., Twins, M. - L., 1959; Ivanova-Kazas O. M., Polyembryony in animals, "Archive of anatomy, histology and embryology", 1965, v. 48, c. 3; Tokin B.P., General Embryology, Moscow, 1970.

A. V. Ivanov, K. M. Kurnosov.

In plants P. - the formation of several embryos in 1 seed. They can occur in 1 embryo sac (true P.) or in different embryo sacs (false P.). With true P., several embryos develop from one zygote as a result of its incorrect division (for example, in some tulips) or as a result of splitting of the pre-embryo or its apical cell (in the adventive water lily, etc.), as well as from suspension cells (in lobelia, etc. ). Often, with true P., embryos arise from 1 or 2 synergids (See Synergids) (for example, in iris, lily, mimosa) or antipodes (See Antipodes) (scented onions, etc.). Additional embryos can arise without fertilization - from cells of Nucellus and Integuments. With false P., embryos are formed either as a result of the development of several embryo sacs in the ovule (strawberry, feverfew, etc.), or due to the development of not 1 of 4 megaspores, as usual, but several (for example, in a lily, cuff), or due to the development additional aposporic (from vegetative cells) embryo sacs along with normal (eg, hawkweed, sagebrush).

Lit.: Mageshwari P., Angiosperm Embryology, trans. from English, M., 1954; Poddubnaya-Arnoldi V. A., General Embryology angiosperms, M., 1964.

- the appearance in the embryo sac of only one embryo, in which the number of the embryo sacs themselves, capable of simultaneously developing normally in the same ovule nucellus, is equal to two or more ...
Glossary of botanical terms
- see nucellar polyembryony...
Glossary of botanical terms
- the formation of additional embryos from the same zygote or pre-embryo ...
Glossary of botanical terms
- see monozygotic polyembryony ...
Glossary of botanical terms
- the presence in the seed of several embryos, which are formed either during the fragmentation of the embryo developing from the zygote, or as a result of adventitious embryonic ...
Plant anatomy and morphology
- polyembryony - . Development of several embryos from one zygote, resulting in the formation of identical twins ; distinguish between specific and random P. ...
Molecular biology and genetics. Dictionary
- exit from the egg of not one, but several embryos. The phenomenon is observed both as pathological and as normal ...
encyclopedic Dictionary Brockhaus and Euphron
- the formation of several embryos in one testicle ...

Pregnancy begins with fertilization and ends with the birth of a mature fetus. In agricultural mammals, the ovum released from the ruptured follicle enters the expanded part of the oviduct and retains the ability to fertilize for an average of 5-6 hours.

The process of fertilization occurs in the anterior third of the oviduct, where a new cell (zygote) is formed as a result of the fusion of sperm with eggs. Within 2 - 2.5 days, the zygote moves into the uterine cavity.

The development of an individual goes through four stages:

1. stage of the blastocyst (vesicle);

2. embryonic (embryonic), characterized by the laying of organisms;

3. fetal (fetal);

4. post-fetal - from birth to the onset of maturity of the body.

The vascular and amniotic (water) membrane develops from the outer germ layer, and the urinary membrane is formed from the final section of the blind protrusion of the primary intestine. From the embryoblast (inner leaf), the embryo mainly develops, and then the fetus.

On the surface of the choroid, villi (baby placenta) grow, which are embedded in crypts in the mucous membrane of the uterus (maternal placenta).

The formed placenta (connection of villi with crypts) also has important functions:

1. nutritional function - supplying the fetus with nutrients;

2. respiratory function - the supply of oxygen to the fetus and the release of carbon dioxide by the fetus;

3. excretory function - excretion of metabolic products from the blood of the fetus;

4. hormonal function - the formation of hormones that are present in the adult body of the female;

5. barrier function, consisting in the fact that the placenta does not allow harmful substances, microbes and some viruses to pass to the fetus.

A large amount of biliverdin (green pigment) accumulates in the placenta, which does not give a green color in a normal placenta. When the placenta decomposes under the action of enzymes or microbes, the pigment is released from the tissues and green or dark green discharge appears. Green discharge is a diagnostic indicator of retention of the placenta, and in case of prolonged childbirth, it is an indication for the use of a caesarean section.

With the onset of pregnancy, the female stops sexual cycles, there are significant changes in the hormonal balance, metabolic and energy processes. The most pronounced changes in the genitals: one or more corpus luteum is formed in the ovaries, which ensure the development and maintenance of pregnancy; the weight of the uterus (without a fetus) increases 5-20 times, and its size - hundreds of times (mainly due to hypertrophy of muscle fibers). The average duration of pregnancy in animals (in days): cow 285, mare 340.

Pregnancy can be singleton (usually in large animals) and multiple (in small ones), due to the maturation and ovulation of several eggs during one hunt.

In the embryonic and postembryonic development of animals (ontogenesis), there are several periods that differ in the rate of growth and differentiation of individual tissues, organs, parts and proportions of the body.

The period of embryonic development of animals begins with the formation of a fertilized egg - a zygote and ends with birth.

The embryonic period begins with the formation of the embryo and lasts until the formation of the fetus (with the rudiments of all organs). The fertile period ends with the birth of the animal.

Embryo, embryo, an organism at an early stage of development occurring in the egg membranes or in special bodies maternal organism. Biologists include in the embryonic, or embryonic, development (embryogenesis) in animals the entire period of development - from fertilization to the beginning of the independent existence of a new organism.

On the other hand, they are divided into the embryonic period, when organs are laid down, and the fetal period, when organs grow and the body is completed. The first period in cattle lasts 4 weeks.

In the embryonic period, the following stages are distinguished:

fertilization, culminating in the formation of a zygote, due to the fusion of the male and female nuclei;

crushing - division of the zygote into blastomeres, which at first seem to be a homogeneous massive accumulation of cells (morula);

restructuring of the morula into a single-layer embryo - the blastula;

isolation from it of the germinal (embryoblast) and extra-embryonic (trophoblast) parts; the formation of a two-layer embryo from the embryoblast - gastrula from two germ layers (ectoderm and endoderm);

isolation from the material of the primary ectoderm (in higher vertebrates) of the third germ layer - the mesoderm, the formation of a three-layer embryo;

the formation on its dorsal side of the neural tube, at its anterior end of the embryo, and later five cerebral vesicles, under the neural tube - the strand of the chord; this stage is sometimes called neurula;

primary differentiation of the mesoderm: on both sides of the neural tube and chord, the mesoderm is divided into 3 sections. Its medial parts give massive mesodermal accumulations (somites); the next, very small section of jade is the rudiment of the excretory system. Laterally, between the ecto- and endotherm, the lateral sheets of the mesoderm are located;

secondary differentiation of the mesoderm, affecting primarily somites; the ventral-medial part separates from them, dividing into loose tissue surrounding the neural tube and chord.

Then begins the allocation of the primary tissue - the mesenchyme, which fills the spaces between the germ layers and the rudiments of organs. After the sclerotome (skeletal sheet) is isolated, a musculocutaneous sheet remains from each somite, which in turn divides into a dorsal mesenchymal part - the dermatome (future connective tissue section of the skin) and a deep part - the myotome, which grows strongly and gives skeletal muscles.

Organogenesis is the transition to fetal development. The lateral sheets of the mesoderm split into a parietal and visceral sheet, and between them a secondary cavity of the whole body is formed. From the ectoderm, the epidermis and its derivatives are formed - the nervous system, sensitive cells of the sense organs.

From the endoderm develops the lining of the middle and hind intestines, respiratory organs, liver and pancreas. From the mesoderm, the muscular system, excretory organs, and the reproductive system are formed. The mesenchyme, which is released mainly from the mesoderm, is the source of the development of supporting-trophic tissues: blood, connects different types. tissue, cartilage and bone tissue. Each type of tissue undergoes its own histogenesis and participates in organogenesis. In addition, the germ layers form fetal membranes: the ectoderm and parietal mesoderm participate in the development of the amnion and chorion; in the development of allantois and the yolk sac - the endoderm and the visceral sheet of the mesoderm.

Polyembryony Polyembryony is the development of more than one embryo from one zygote in animals or the formation of several embryos in one seed in plants. Polyembryony is the phenomenon of the development of more than one embryo from one zygote in animals or the formation of several embryos in one seed in plants. The word comes from the Greek "poly" many and "embrion" germ The word comes from the Greek "poly" many and "embrion" germ

Animal polyembryony In animals, a specific (inherent) this species) polyembryony, and sporadic, or random. Specific polyembryony is found in animals of various systematic groups (bryozoans, insects, armadillos, etc.). Specific polyembryony is found in animals of various systematic groups (bryozoans, insects, armadillos, etc.). Its biological meaning is to increase the number of offspring developing from one fertilized egg. Its biological meaning is to increase the number of offspring developing from one fertilized egg. Sporadic polyembryony is caused by exposure to random factors and occurs in many animal species, including humans. As a result of polyembryony, two organisms develop that are absolutely identical in genotypes, but have differences in phenotype (consequences of environmental exposure). Sporadic polyembryony is caused by exposure to random factors and occurs in many animal species, including humans. As a result of polyembryony, two organisms develop that are absolutely identical in genotypes, but have differences in phenotype (consequences of environmental exposure).

Polyembryony of plants Polyembryony of plants can be true and false. True polyembryony all embryos develop in the same embryo sac, false in different embryo sacs, respectively. Polyembryony of plants is true and false. True polyembryony all embryos develop in the same embryo sac, false in different embryo sacs, respectively.

Monozygotic twins Monozygotic twins are formed from one zygote, divided into two (or more) parts during the crushing stage. They have the same genotypes. Monozygotic twins are always of the same sex. Monozygotic twins are formed from one zygote, divided into two (or more) parts at the stage of crushing. They have the same genotypes. Monozygotic twins are always of the same sex.

Monozygotic twins A special group among identical twins are unusual types: two-headed (usually non-viable) and xifopagi ("Siamese twins"). Most famous case Born in 1811 in Siam (now Thailand), Siamese twins Chang and Eng. They lived for 63 years. They were connected by a fabric jumper about 10 cm wide from the sternum to the navel. Later it was found that the bridge connecting them contained liver tissue that connected the two livers. Any surgical attempt to separate the brothers would not have been successful at the time. Currently sever and more complex connections between twins. A special group among identical twins are unusual types: two-headed (usually non-viable) and xifopagi (“Siamese twins”). The most famous case was born in 1811 in Siam (now Thailand) Siamese twins Chang and Eng. They lived for 63 years. They were connected by a fabric jumper about 10 cm wide from the sternum to the navel. Later it was found that the bridge connecting them contained liver tissue that connected the two livers. Any surgical attempt to separate the brothers would not have been successful at the time. More complex bonds between twins are currently being severed.

Conclusion Polyembryony - a method asexual reproduction, in which new individuals are formed from fragments of parts into which the embryo breaks up. This mode occurs during embryonic development. Polyembryony is a method of asexual reproduction in which new individuals are formed from fragments of parts into which the embryo breaks up. This mode occurs during embryonic development.

Polyembryony

Polyembryony- a method of asexual reproduction of organisms, when there is a development of more than one embryo from one zygote in animals or the formation of several embryos in one seed in plants.

The word comes from the Greek poly" - a lot and " embryo"- germ.

Animal polyembryony

In animals, a specific (peculiar to a given species) polyembryony, and sporadic, or random, are distinguished. Specific polyembryony is found in animals of various systemic groups (bryozoans, insects, armadillos, etc.)

Its biological meaning is to increase the number of offspring developing from one fertilized egg.

Sporadic polyembryony is caused by exposure to random factors and occurs in many animal species, including humans. As a result of polyembryony, two organisms develop that are absolutely identical in genotypes, but have differences in phenotype (consequences of environmental exposure).

Plant polyembryony

It happens true and false. True polyembryony - all embryos develop in the same embryo sac, false - in different embryo sacs, respectively.

The emergence of the term "zygote"

The appearance of the term "zygote" is the merit of the German scientist Edward Strasburger, who devoted his whole life to the study of cytology and the chromosome theory of heredity. It is he in late XIX century for the first time came to the conclusion that in plant, animal and human body proceeds in much the same way.

Zygote: definition

direct development. In this case, the child is similar in external and internal signs to the parents. The differences are in the size and underdevelopment of some organs. It is typical for birds and mammals, including humans.
Indirect development. With this type of development, the child (larva) has many differences from its parents. Typical for frogs and insects.

Zygotes are cells that duplicate the genotype of the parents. But in the process of development of the embryo, the cells begin to differ in structure and perform various functions. This is due to the fact that some types of genes function in some cells, while others in others. Thus, the body is a complex system, which is based on the zygote.

Polyembryony Polyembryony is the development of more than one embryo from one zygote in animals or the formation of several embryos in one seed in plants. Zygotes are the first cells of new organisms. Stages of zygote development Development of several embryos

Animal polyembryony

Plant polyembryony

see also

See what "Polyembryony" is in other dictionaries:

The emergence of the term "zygote"

Zygote: definition