Mammal animals habitat. The city as a habitat for small mammals
Hydra movements. Epithelial-muscle cells of the ectoderm have fibers that can contract. If they contract at the same time, the entire body of the hydra shortens. If the red tape in the cells is reduced on one side, then the hydra tilts in that direction. Thanks to the work of these fibers, the tentacles of the hydra move and its entire body moves (Fig. 13.4).
Reactions to Hydra irritation. Thanks to nerve cells located in the ectoderm, hydra perceives external stimuli: light, touch, some chemicals. The processes of these cells close together, forming a mesh. This is how the simplest nervous system in structure is formed, called diffuse (Fig. 13.5). Most of the nerve cells are located near the sole and on the tentacles. Manifestation of work nervous system and epithelial muscle cells is unconditioned reflex Hydra - bending of tentacles in response to touch.
Rice. 13.4. Hydra movement diagram |
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Rice. 13.5. Hydra nervous system |
The outer layer also contains stinging cells containing capsules with a twisted thin tube - the stinging thread. A sensitive hair sticks out from the cell. It is enough to touch it lightly, and the thread is ejected from the capsule and pierces the body of the enemy or prey. Poison reaches it through the stinging thread, and the animal dies. Most stinging cells are located in the tentacles.
Hydra regeneration. Small, round intermediate ectoderm cells are capable of transforming into other types of cells. Due to their reproduction, the hydra quickly rebuilds the damaged part of the body. The ability to regenerate this animal is amazing: when the hydra was divided into 200 parts, a whole animal was restored from each!
Hydra nutrition. The endoderm contains glandular cells and digestive cells equipped with flagella. Glandular cells supply substances called digestive juices to the intestinal cavity. These substances destroy prey, breaking it down into microscopic pieces. With the help of flagella, digestive cells push them towards themselves and capture them, forming pseudopodia. Internal cavity It is no coincidence that the hydra is called intestinal: food digestion begins in it. But the food is finally broken down in the digestive vacuoles of the digestive cells. Undigested food remains are removed from the intestinal cavity through the mouth.
Selection harmful substances formed during the life of the hydra occur through the ectoderm into the water
Cell interaction. Among the hydra cells, only the digestive cells digest food, but they provide nutrients not only to themselves, but also to all other cells. In turn, the “neighbors” create best conditions life for nutrient suppliers. Think about the hydra hunting - now you can explain how the coordinated work of nerve, stinging, epithelial-muscular and glandular cells ensures the functioning of the digestive cells. And these cells share the results of their labor with their neighbors. Material from the site
How does hydra reproduce? During asexual reproduction, a bud is formed as a result of the division of intermediate cells. The bud grows, tentacles appear on it, and a mouth breaks out between them. At the opposite end the sole is formed. The small hydra separates from the mother’s body, sinks to the bottom and begins to live independently.
Hydra also reproduces sexually. Hydra is a hermaphrodite: in some protrusions of its ectoderm sperm are formed from intermediate cells, in others - eggs. Having left the body of the hydra, the sperm follow the water to other individuals. Having found the eggs, they fertilize them. A zygote is formed, around which a dense membrane appears. This fertilized egg remains in the hydra's body. Usually sexual reproduction occurs in the fall. In winter, adult hydras die, and the eggs survive the winter at the bottom of the reservoir. In the spring, the zygote begins to divide, forming two layers of cells. From them a small hydra develops.
On this page there is material on the following topics:
Sponge reproduction state
Irritation and movement biology report
Features of the structure and functioning of the cells of the hydra body
Features of the life processes of hydra
Compare the structure of the hydra stinging cell and the skin of a nettle leaf.
Questions about this material:
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On the reaction of freshwater hydra to exogenous biologically active (hormonal) compounds
CM. Nikitina, I.A. Vakolyuk (Kaliningrad State University)
The functioning of hormones as the most important regulators and integrators of metabolism and a variety of functions in the body is impossible without the existence of systems for specific signal reception and its transformation into the final beneficial effect, that is, without a hormone-competent system. In other words, the presence of a reaction at the organismal level to exogenous compounds is impossible without the presence of cytoreception to these compounds and, accordingly, without the existence in these animals of endogenous compounds related to those with which we act. This does not contradict the concept of universal blocks, when the basic molecular structures in the functional systems of living organisms are found in almost a complete set already at the very early stages evolutions, which are only accessible to study, are represented by a limited number of molecules and carry out the same elementary functions not only among representatives of one kingdom, for example in different groups mammals or even different types, but also in representatives of various kingdoms, including multicellular and unicellular organisms, higher eukaryotes and prokaryotes.
However, it should be noted that data on the composition and functions of compounds that act as hormones in vertebrates in representatives of taxa of a fairly low phylogenetic level are just beginning to appear. Of the groups of animals of a low phylogenetic level, hydra, as a representative of the coelenterates, is the most primitive organism with a real nervous system. Neurons differ morphologically, chemically, and probably functionally. Each of them contains neurosecretory granules. A significant diversity of neuronal phenotypes in Hydra has been established. In the hypostome there are orderly groups of 6-11 synaptically connected cells, which can be considered as evidence of the presence of primitive nerve ganglia in hydras. In addition to providing behavioral reactions, the hydra nervous system serves as an endocrine regulatory system, providing control of metabolism, reproduction, and development. In hydras, there is differentiation of nerve cells according to the composition of the neuropeptides they contain). It is assumed that the molecules of oxytocin, vasopressin, sex steroids and glucocorticoids are universal. They are also found in representatives of the coelenterates. Head and plantar activators (and inhibitors) are isolated from methanol extracts of the body of hydra. The head activator, isolated from sea anemones, is similar in composition and properties to the neuropeptide found in the hypothalamus and intestines of cows, rats, pigs, humans and in the blood of the latter. In addition, it has been shown that in both invertebrates and vertebrates, cyclic nucleotides are involved in ensuring the response of cells to neurohormones, that is, the mechanism of action of these substances in two phylogenetically different lines is the same.
The purpose of this study, taking into account the above, we chose to study the complex effect of exogenous biologically active (hormonal) compounds on freshwater hydra.
Material and research methods
Animals for the experiment were collected in June-July 1985-1992. at a hospital (channel of the Nemonin River, village of Matrosovo, Polesie district). Adaptation to content in laboratory conditions- 10-14 days. Volume of material: type - Coelenterata; class - Hydrozoa; species - Hydra oligactis Pallas; quantity - 840. The number of animals is reflected at the beginning of the experiment and the increase in number is not taken into account.
The work used water-soluble hormonal compounds of the oxytocin series, the anterior lobe of the pituitary gland with an initial activity of 1 ml (ip) (hyfotocin - 5 units, pituitrin - 5 units, mammophysin - 3 units, prefisone - 25 units, gonadotropin - 75 units) and a steroid - prednisolone - 30 mg , which in vertebrates provide three-tier endocrine regulation, including the hypothalamic-pituitary complex and epithelial glands.
In preliminary experiments, drug concentrations from 0.00002 to 20 ml ip/l of the animal housing environment were used.
There were three study groups:
1st - determination of the “+” or “-” reaction in all concentrations accepted by us;
2nd - determination of the range of concentrations that ensure work in a chronic mode of varying duration;
3rd - chronic experiment.
The experiment took into account the budding activity of Hydra. The obtained data were subjected to standard statistical processing.
Research results
When determining the "" reaction of hydras in a wide range of concentrations of compounds, three were selected (0.1 ml IP/L medium, 0.02 ml IP/L medium and 0.004 ml IP/L medium).
In the control group of hydras, budding remained at the level of 0.0-0.4 buds/hydra (Pa) for five days. In the environment of the minimum concentration of prefisone, the increase was 2.2 individuals/hydra, pituitrin - 1.9 individuals/hydra (the significance of the differences with the control is extremely high - with a significance level of 0.01). At medium concentrations, hyfotocin, mammophysin and prefisone performed well (1.8-1.9 individuals/hydra). Prednisolone in minimal, and especially in average concentration, caused an increase in the number of 1.1-1.3 individuals/hydra, which significantly exceeds the control.
In the following experiment, only optimal concentrations of hormonal compounds were used. The duration of the experiment was 9 days. At the beginning of the experiment, the control and experimental groups were not reliably distinguished by the Pa value. After nine days of the experiment, the Pa values were significantly different in experimental groups and control with a significance level of 0.05 (Table 1).
Table 1
The influence of hormonal drugs on hydra budding (Ra) and the likelihood of the significance of their differences (p)
Environment RaChange1 day9 daysRa1 day9 daysControl1,20,81,50,90,30,1-Gonadotropin2,11,25,10,33,00,80,710,95Prefisone1,10,74,92,03,81,30,130,97Hyphotocin1,80 ,86,12,24,31,40,580,99Pituitrin0,80,54,52,03,71,50,470,98Mammophysin1,10,35,32,04,21,70,150,99Prednisolone1,50,47,12,25,61 ,80,430,99
As can be seen from the table, highest value Ra was obtained when animals were kept in prednisolone. All peptide preparations give approximately similar Pa values (average 3.80.5). However, there is also variation here. The best effect (4.31.4) is achieved when animals are kept in an environment with a purified extract of the neurohypophysis - hyphotocin. Close to it in terms of impact is mammophysin. In the experimental groups with pituitrin and prefisone, the Ra values are 3.71.5 and 3.81.3, respectively. The least effect is achieved by affecting hydra with gonadotropin. Unreliable differences in Ra occur by the end of the first day after placing hydras in solutions of hormonal drugs. During the nine days of the experiment, Ra in the control did not change. Starting from the third day, Ra in all experimental groups significantly exceeds Ra in the control. It should be noted that there was a gradual significant increase in this indicator in the experimental groups by the ninth day.
To assess the statistical reliability of the effects, the values of the F criterion (ratio of mean squares) obtained for each of the two factors separately (A - factor of duration of detention; B - factor of influence) and for their interaction (A + B), and the tabulated values of the criterion were compared for two significance levels P=0.05 and P=0.01 (Table 2).
table 2
Results of variance analysis of the influence of hormonal drugs and duration of detention on the intensity of asexual Hydra breeding oligactis
Fact-Factual in groupsTable RtorsPituitrinMammophysinGifotocinGonadotropinPrefisonePrednisolone0.050.01A3.441.402.272.173.621.301.922.50B8.374.048.094.738.2612.704.007.08A+B1 ,120,960,560,371,071,031,922,50As can be seen from the table, Ffact for the impact factor at a significance level of 0.05 in all experimental groups is greater than Ftable, and at a significance level of 0.01, this pattern is observed in the groups with pituitrin, hyfotocin, prefisone and prednisolone, and the degree of effect in the group with prednisolone is the highest, much greater than in the groups with pituitrin, hyfotocin and prefisone, which have a similar effect strength (Fact values very close). The influence of the interaction of factors A and B in all experimental groups has not been proven.
For factor A, Ffact is less than Ftable (at both significance levels) in the groups with mammophysin and prednisolone. In the groups with hyfotocin and gonadotropin, Fact is greater than Ftable at P = 0.05, that is, the influence of this factor cannot be considered conclusively proven, in contrast to the experimental groups with pituitrin and prefisone, where Ffact is greater than Ftable both at P = 0.01 and at P=0.05.
All hormonal drugs, except gonadotropin, delay the onset to varying degrees. asexual reproduction. However, this turns out to be statistically significant only in the group with prefisone (P = 0.01). The hormonal preparations used in the experiment do not reliably affect the duration of development of a single kidney, they change the mutual influence of the first and second kidneys: pituitrin, mammophysin, prefisone, gonadotropin - in the presence of only the formed head section of the developing kidneys; pituitrin, gonadotropin and prednisolone - in the presence of at least one formed plantar section of the developing kidneys.
Thus, the sensitivity of hydras to a wide range of vertebrate hormonal compounds can be considered established and it can be assumed that exogenous hormonal compounds are included (as synergists or antagonists) in the endocrine regulatory cycle inherent in the hydra itself.
Bibliography
1. Pertseva M.N. Intermolecular fundamentals
In the article, readers will be able to find out what hydra is. You will also get acquainted with the history of the discovery, the characteristics of this animal and its habitat.
History of the discovery of the animal
First of all, a scientific definition should be given. Freshwater hydra is a genus of sessile (in lifestyle) coelenterates belonging to the hydroid class. Representatives of this genus live in rivers with relatively slow flow or stagnant bodies of water. They are attached to the soil (bottom) or plants. This is a sedentary single polyp.
The first information about what a hydra is was given by the Dutch scientist, microscope designer Antonie van Leeuwenhoek. He was also the founder of scientific microscopy.
More detailed description, as well as the processes of nutrition, movement, reproduction and regeneration of the hydra were revealed by the Swiss scientist Abraham Tremblay. He described his results in the book “Memoirs on the history of a genus of freshwater polyps.”
These discoveries, which became the subject of conversation, brought great fame to the scientist. It is currently believed that it was the experiments in studying the regeneration of the genus that served as the impetus for the emergence of experimental zoology.
Later, Carl Linnaeus gave the family scientific name, which came from ancient Greek myths about Lernaean Hydra. Perhaps the scientist associated the name of the genus with mythical creature due to its regenerative abilities: when a hydra's head was cut off, another grew in its place.
Body structure
Expanding the topic “What is a hydra?”, one should also give external description kind.
The length of the body ranges from one millimeter to two centimeters, and sometimes a little more. The hydra's body has cylindrical shape, in front there is a mouth surrounded by tentacles (their number can reach twelve). There is a sole at the back, with the help of which the animal can move and attach to something. There is a narrow pore on it, through which liquid and gas bubbles are released from the intestinal cavity. The individual, together with this bubble, detaches from the support and floats up. In this case, the head is in the water column. In this way, the individual disperses throughout the reservoir.
The structure of the hydra is simple. In other words, the body is a bag whose walls consist of two layers.
Life processes
Speaking about the processes of respiration and excretion, it should be said: both processes occur over the entire surface of the body. In selection important role cell vacuoles play main function which is osmoregulatory. Its essence lies in the fact that vacuoles remove residual water that enters cells due to one-way diffusion processes.
Due to the presence of a nervous system with a mesh structure, freshwater hydra carries out the simplest reflexes: the animal reacts to temperature, mechanical irritation, illumination, the presence chemical substances V aquatic environment and other environmental factors.
Hydra's diet consists of small invertebrates - cyclops, daphnia, oligochaetes. The animal captures prey with the help of tentacles, and the venom of the stinging cell quickly affects it. Then the food is brought by the tentacles to the mouth, which, thanks to body contractions, is, as it were, put on the prey. The hydra throws out the remaining food through its mouth.
Hydra reproduction in favorable conditions occurs asexually. A bud forms on the body of the coelenterate and grows for some time. Later she develops tentacles and also breaks out her mouth. The young individual separates from the mother, attaches to the substrate with tentacles and begins to lead an independent lifestyle.
Sexual reproduction Hydra begins in the fall. Gonads are formed on her body, and germ cells are formed in them. Most of individuals are dioecious, but hermaphroditism also occurs. Fertilization of the egg occurs in the body of the mother. The formed embryos develop, and in winter the adult dies, and the embryos overwinter at the bottom of the reservoir. During this period they fall into a process of suspended animation. Thus, the development of hydras is direct.
Hydra nervous system
As mentioned above, the hydra has a mesh structure. In one of the body layers nerve cells form a scattered nervous system. There are not many nerve cells in the other layer. In total, there are about five thousand neurons in the animal’s body. The individual has nerve plexuses on the tentacles, sole and near the mouth. Recent studies have shown that the hydra has a perioral nerve ring very similar to the hydromedusa's nerve ring.
The animal does not have a specific division of neurons into separate groups. One cell perceives irritation and transmits a signal to the muscles. There are chemical and electrical synapses (the point of contact between two neurons) in her nervous system.
Opsin proteins were also found in this primitive animal. There is an assumption that human and hydra opsins common origin.
Growth and ability to regenerate
Hydra cells are constantly renewed. They divide in the middle part of the body, then move to the sole and tentacles. This is where they die and flake off. If there is an excess of dividing cells, they move to the kidneys in bottom part bodies.
Hydra has the ability to regenerate. Even after a cross-section of the body into several parts, each of them will be restored to its original form. The tentacles and mouth are restored on the side that was closer to the oral end of the body, and the sole is restored on the other side. The individual is able to recover from small pieces.
Body parts store information about the movement of the body axis in the structure of the actin cytoskeleton. A change in this structure leads to disturbances in the regeneration process: several axes can form.
Lifespan
Speaking about what hydra is, it is important to talk about duration life cycle individuals.
Back in the nineteenth century, it was hypothesized that the hydra was immortal. Over the course of the next century, some scientists tried to prove it, and some tried to refute it. Only in 1997 was it finally proven by Daniel Martinez through an experiment that lasted four years. There is also an opinion that the immortality of the hydra is associated with high regeneration. And what is in the rivers in winter middle zone adult individuals die, most likely due to a lack of food or exposure to unfavorable factors.
- Type: Cnidaria = Coelenterates, cnidarians
- Subphylum: Medusozoa = Jellyfish-producing
- Class: Hydrozoa Owen, 1843 = Hydrozoans, hydroids
- Subclass: Hydroidea = Hydroids
- Squad: Hydrida = Hydras
- Genus: Hydra = Hydras
Genus: Hydra = Hydras
Hydras are characterized by a primitive diffuse nervous system, formed in the ectoderm by nerve cells in the form of a scattered nerve plexus. The endoderm contains only individual nerve cells, but in total Hydra has about 5,000 neurons. Nerve plexuses are located on the sole, around the mouth and on the tentacles. There is evidence that hydra has a perioral nerve ring similar to that of the umbrella of hydromedusas. Although the hydra does not have a clear division into sensory, intercalary and motor neurons, it nevertheless has sensory and ganglion nerve cells. The bodies of sensitive cells are located across the epithelial layer; they have a stationary flagellum surrounded by a collar of microvilli that sticks out into the external environment and is able to perceive irritation. The processes of ganglion cells are located at the base of the epithelial-muscular cells and do not extend into the external environment. Hydra is the most primitive animal in nerve cells which discovered light-sensitive opsin proteins, which have a common origin in hydra and humans. In general, the presence of a nervous system in the hydra allows it to carry out simple reflexes. Thus, hydra reacts to mechanical irritation, temperature, lighting, the presence of certain chemicals in water and a number of other environmental factors.
Stinging cells are formed from intermediate cells only in the torso area. There are about 55,000 stinging cells in Hydra and they are the most numerous of all cell types. Each stinging cell has a stinging capsule, which is filled toxic substance, and a stinging thread is screwed inside the capsule. On the surface of the cell, only a sensitive hair rips, and when irritated, a thread is immediately thrown out and hits the victim. The stinging cell dies after the thread is fired, and in its place new ones are formed from intermediate cells.
Hydra has four types of stinging cells. When hydras hunt, the first to shoot are the desmonemas (volvents): their spiral stinging threads entangle the outgrowths of the prey’s body and ensure its retention. When the victim tries to jerk free, the vibration caused by them triggers stenoteles (penetrants), which have a higher threshold of irritation. And the spines present at the base of their stinging threads are anchored in the body of the prey, and poison is injected into its body through the hollow stinging thread. Large glutinants (their stinging thread has spines, but, like volventas, does not have a hole at the top) are apparently mainly used for protection. Small glutinants are used only when the hydra moves to firmly attach its tentacles to the substrate. Their firing is blocked by extracts from the tissues of Hydra victims.
On the tentacles of the hydra there is the most a large number of stinging cells that form stinging batteries here. The stinging battery usually includes one large epithelial-muscular cell in which the stinging cells are immersed. In the center of the battery there is a large penetrant, around it there are smaller volvents and glutinants. Cnidocytes are connected by desmosomes to the muscle fibers of the epithelial muscle cell.
Ultra-high-speed filming of the firing of the Hydra penetrant showed that the entire firing process takes about 3 ms. Moreover, in the initial phase of firing, the speed reaches 2 m/s, and the acceleration is about 40,000 g; which apparently is one of the fastest cellular processes of those known in nature. In the early phase of nematocyst firing, the speed of this process is 9-18 m/s, and the acceleration ranges from 1,000,000 to 5,000,000 g, which allows a nematocyst weighing about 1 ng to develop a pressure of the order of magnitude at the tips of the spines (the diameter of which is about 15 nm 7 hPa, which is comparable to the pressure of a bullet on a target and allows it to pierce the fairly thick cuticle of victims...