Hydra reacts to irritation. Topic: "Type of coelenterates
About reaction freshwater hydra on 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 various functions in the body is impossible without the existence of systems for the specific reception of a signal and its transformation into a final signal. beneficial effect, that is, without a hormone-competent system. In other words, the presence of a reaction at the organismic 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 that we influence. This does not contradict the concept of universal blocks, when the basic molecular structures in functional systems living organisms are found in almost complete set already at the earliest stages of evolution, which are only available for 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, higher eukaryotes and prokaryotes.
However, attention should be paid to the fact that data on the composition and functions of compounds that act as hormones in vertebrates are only just beginning to appear in representatives of taxa of a rather low phylogenetic level. Of the groups of animals of a low phylogenetic level, hydra, as a representative of the intestinal cavities, 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 ordered 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 responses, the hydra nervous system acts as an endocrine regulatory system, providing control of metabolism, reproduction, and development. Hydra has differentiation nerve cells according to the composition of the neuropeptides contained in them). It is assumed that the molecules of oxytocin, vasopressin, sex steroids and glucocorticoids are universal. They are also found in representatives of the coelenterates. The head and plantar activators (and inhibitors) are isolated from methanolic extracts of the hydra body. 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 was 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.
aim this study Considering the foregoing, 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 the station (a channel of the Nemonin River, the village of Matrosovo, Polessky District). Adaptation to the content in the laboratory - 10-14 days. Volume of material: type - Coelenterata; class - Hydrozoa; view - Hydra oligactis Pallas; number - 840. The number of animals is reflected at the beginning of the experiment and the increase in numbers is not taken into account.
We used water-soluble hormonal compounds of the oxytocin series, the anterior pituitary with an initial activity of 1 ml (ip) (hyphotocin - 5U, pituitrin - 5U, mammophysin - 3U, prephysone - 25U, gonadotropin - 75U) and a steroid - prednisolone - 30 mg , which in vertebrates provide three-link 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 environment were used.
There were three study groups:
1st - definition of "+" or "-" reactions in all concentrations accepted by us;
2nd - determination of the range of concentrations that ensure the work in chronic mode of different duration;
3rd - chronic experiment.
The experiment took into account the activity of hydra budding. The obtained data were subjected to standard statistical processing.
Research results
When determining the "±" hydr reaction 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 hydr control group, budding remained at the level of 0.0-0.4 buds/hydru (Pa) for five days. In the medium with the minimum concentration of prephysone, the increase was 2.2 ind./hydra, pituitrin - 1.9 ind./hydru (significance of differences with control is extremely high - with a significance level of 0.01). Hyfotocin, mammophysin and prephyson performed well in medium concentrations (1.8-1.9 individuals/hydra). Prednisolone in the minimum, and especially in the average concentration, caused an increase in the number of 1.1-1.3 individuals / hydra, which significantly exceeds the control.
AT next experiment used only optimal concentrations hormonal compounds. The duration of the experiment is 9 days. By the beginning of the experiment, according to the value of Ra, the control and experimental groups were not reliably distinguishable. After nine days of the experiment, the Pa values significantly differed in the experimental groups and control with a significance level of 0.05 (Table 1).
Table 1
Influence of hormonal preparations on hydra budding (Ra) and the probability of reliability of their differences (p)
As can be seen from the table, highest value Ra obtained by keeping animals in prednisolone. All peptide preparations give approximately similar Pa values (average 3.8±0.5). However, there is also variation here. Best effect(4.3±1.4) is achieved when animals are kept in a medium with a purified extract of the neurohypophysis - hyphotocin. Mammophizin is close to it in terms of the degree of influence. In the experimental groups with pituitrin and prephyson, the Pa values were 3.7±1.5 and 3.8±1.3, respectively. The least effect is given by the effect on hydra by gonadotropin. Unsignificant differences in Ra appear by the end of the first day after placing hydras in solutions of hormonal preparations. 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 a gradual significant increase in this indicator in the experimental groups by the ninth day.
To assess the statistical significance of the impacts, the values of the criterion F (ratio of mean squares) were compared, obtained for each of the two factors separately (A - duration factor; B - impact factor) and for their interaction (A + B), and table values criterion for two significance levels P=0.05 and P=0.01 (Table 2).
table 2
The results of analysis of variance of the effect of hormonal preparations and the duration of maintenance on the intensity of asexual reproduction of Hydra oligactis
As can be seen from the table, F fact 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 groups with pituitrin, hyphotocin, prefizone and prednisolone, and the degree of exposure in the group with prednisolone the highest, much more than in the groups with pituitrin, hyphotocin and prephysone, which have a similar effect (Ffact values are very close). The influence of the interaction of factors A and B in all experimental groups is not proven.
For factor A, Fact is less than Ftabl (at both levels of significance) in groups with mammophysin and prednisolone. In groups with hyphotocin and gonadotropin, Fact is greater than Ftabl at P=0.05, that is, the influence of this factor cannot be considered definitively proven, in contrast to the experimental groups with pituitrin and prephysone, where Fact is greater than Ftabl at P=0.01 and at P=0.05.
All hormonal preparations, except for gonadotropin, to one degree or another delay the onset of asexual reproduction. However, this is statistically significant only in the group with prephyson (P=0.01). The hormonal preparations used in the experiment do not significantly affect the duration of the development of a single kidney, they change the mutual influence of the first and second kidneys: pituitrin, mammophysin, prephyson, gonadotropin - in the presence of only a formed head section of developing kidneys; pituitrin, gonadotropin and prednisolone - in the presence of at least one formed plantar section of developing kidneys.
Thus, we can consider the established sensitivity of hydra to a wide range hormonal compounds of vertebrates and suggest that exogenous hormonal compounds are included (as synergists or antagonists) in the endocrine regulatory cycle inherent in the hydra itself.
Bibliography
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Hydra movements. The epithelial-muscular 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 leans in this direction. Thanks to the work of these fibers, the tentacles of the hydra move and its entire body moves (Fig. 13.4).
Reactions to irritation of the hydra. Thanks to the nerve cells located in the ectoderm, the hydra perceives external stimuli: light, touch, and some chemicals. The processes of these cells interlock with each other, forming a grid. This is how the simplest nervous system is formed, called diffuse (Fig. 13.5). Most nerve cells are located near the sole and on the tentacles. A manifestation of the work of the nervous system and epithelial-muscle cells is the unconditioned hydra reflex - bending the tentacles in response to touch.
| Rice. 13.4. Hydra movement scheme |
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| Rice. 13.5. Nervous system hydra |
In the outer layer there are also stinging cells containing capsules with a twisted thin tube - a stinging thread. A sensitive hair sticks out of the cell. It is enough to touch it lightly, as the thread is ejected from the capsule and pierces the body of the enemy or prey. Poison comes to him along the stinging thread, and the animal dies. Most of the stinging cells are located in the tentacles.
Hydra regeneration. Small rounded intermediate cells of the ectoderm 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 food. 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, decomposing it into microscopic pieces. With the help of flagella, digestive cells adjust them to themselves and capture them, forming pseudopodia. internal cavity Hydra is not accidentally called intestinal: it begins the digestion of food. But finally, the food is 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, occurs through the ectoderm into the water
Cell interaction. Among hydra cells, only digestive cells digest food, but they provide nutrients not only to themselves, but to all other cells. In turn, the "neighbors" create best conditions life for nutrient providers. Think of the hydra's hunt - now you can explain how the coordinated work of nerve, stinging, epithelial-muscular and glandular cells provides digestive cells with work. And these cells share the results of their work with their neighbors. material from the site
How does hydra reproduce? At asexual reproduction as a result of the division of intermediate cells, a kidney is formed. The kidney grows, tentacles appear on it, a mouth erupts between them. A sole is formed at the opposite end. A small hydra is separated from the mother's body, sinks to the bottom and begins to live on its own.
Hydra also reproduces sexually. Hydra is a hermaphrodite: in some protrusions of its ectoderm, spermatozoa are formed from intermediate cells, in others, eggs. Leaving the body of the hydra, spermatozoa follow the water to other individuals. Having found eggs, they fertilize them. A zygote is formed, around which a dense shell appears. This fertilized egg remains in the hydra's body. Sexual reproduction usually occurs in autumn. In winter, adult hydras die, and the eggs survive the winter at the bottom of the reservoir. In spring, the zygote begins to divide, forming two layers of cells. From them, a small hydra develops.
On this page, material on the topics:
State of reproduction of sponges
Irritation and movement biology report
Features of the structure and functioning of the cells of the hydra body
Features of the vital processes of hydra
Compare the structure of the stinging cell of the hydra and the skin of the nettle leaf.
Questions about this item:
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From this article you will learn everything about the structure of freshwater hydra, its lifestyle, nutrition, reproduction.
The external structure of the hydra
A polyp (meaning "many-legged") hydra is a tiny translucent creature that lives in the clear clear waters of slow-flowing rivers, lakes, and ponds. This coelenterate animal leads a sedentary or attached lifestyle. The external structure of freshwater hydra is very simple. The body has an almost regular cylindrical shape. At one of its ends is a mouth, which is surrounded by a crown of many long thin tentacles (from five to twelve). At the other end of the body is the sole, with which the animal is able to attach to various subjects under the water. The body length of freshwater hydra is up to 7 mm, but the tentacles can be greatly stretched and reach a length of several centimeters.
Beam symmetry
Let us consider in more detail the external structure of the hydra. The table will help to remember their purpose.
The body of the hydra, like many other animals leading an attached lifestyle, is inherent. What is it? If we imagine a hydra and draw an imaginary axis along the body, then the tentacles of the animal will diverge from the axis in all directions, like the rays of the sun.
The structure of the hydra's body is dictated by its lifestyle. It is attached to an underwater object with a sole, hangs down and begins to sway, exploring the surrounding space with the help of tentacles. The animal is hunting. Since the hydra lies in wait for prey that can appear from any direction, the symmetrical radial arrangement of the tentacles is optimal.
intestinal cavity
Let's consider the internal structure of the hydra in more detail. The body of the hydra looks like an oblong bag. Its walls consist of two layers of cells, between which there is an intercellular substance (mesogley). Thus, inside the body there is an intestinal (gastric) cavity. Food enters through the mouth. It is interesting that the hydra, which in this moment does not eat, the mouth is practically absent. Ectoderm cells close and fuse in the same way as on the rest of the body surface. Therefore, every time before eating, the hydra has to break through the mouth again.
The structure of the freshwater hydra allows it to change its place of residence. On the sole of the animal there is a narrow opening - the aboral pore. Through it, liquid and a small bubble of gas can be released from the intestinal cavity. With the help of this mechanism, the hydra is able to detach itself from the substrate and float to the surface of the water. In such a simple way, with the help of currents, it settles in a reservoir.
ectoderm
The internal structure of the hydra is represented by ectoderm and endoderm. The ectoderm is said to form the body of the hydra. If you look at the animal through a microscope, you can see that several types of cells belong to the ectoderm: stinging, intermediate, and epithelial-muscular.
The most numerous group is skin-muscle cells. They are in contact with each other by the sides and form the surface of the body of the animal. Each such cell has a base - a contractile muscle fiber. This mechanism provides the ability to move.
With the contraction of all fibers, the body of the animal contracts, lengthens, and bends. And if the contraction occurred only on one side of the body, then the hydra leans. Thanks to this work of cells, the animal can move in two ways - “tumbling” and “walking”.
Also in the outer layer are star-shaped nerve cells. They have long processes, with the help of which they come into contact with each other, forming single network - nerve plexus, braiding the entire body of the hydra. Nerve cells are also connected with skin-muscle cells.
Between the epithelial-muscular cells are groups of small, round-shaped intermediate cells with large nuclei and a small amount of cytoplasm. If the body of the hydra is damaged, then the intermediate cells begin to grow and divide. They can transform into any
stinging cells
The structure of the hydra cells is very interesting, the stinging (nettle) cells with which the entire body of the animal, especially the tentacles, are strewn, deserve special mention. have a complex structure. In addition to the nucleus and cytoplasm, the cell contains a bubble-shaped stinging chamber, inside which is the thinnest stinging thread rolled into a tube.
A sensitive hair comes out of the cell. If the prey or the enemy touches this hair, then there is a sharp straightening of the stinging thread, and it is thrown out. The sharp tip pierces the body of the victim, and poison enters through the channel passing inside the thread, which can kill a small animal.
As a rule, many stinging cells are triggered. Hydra captures prey with tentacles, draws to the mouth and swallows. The poison secreted by stinging cells also serves to protect. Larger predators do not touch painfully stinging hydras. The poison of the hydra in its action resembles the poison of the nettle.
Stinging cells can also be divided into several types. Some threads inject poison, others wrap around the victim, and still others stick to it. After triggering, the stinging cell dies, and a new one is formed from the intermediate one.
Endoderm
The structure of the hydra also implies the presence of such a structure as the inner layer of cells, the endoderm. These cells also have muscular contractile fibers. Their main purpose is to digest food. Endoderm cells secrete digestive juice directly into the intestinal cavity. Under its influence, prey is split into particles. Some endoderm cells have long flagella that are constantly in motion. Their role is to pull food particles up to the cells, which in turn release prolegs and capture food.
Digestion continues inside the cell, which is why it is called intracellular. Food is processed in vacuoles, and undigested residues are thrown out through the mouth opening. Respiration and excretion occurs through the entire surface of the body. Consider again cellular structure hydras. The table will help visualize this.
reflexes
The structure of the hydra is such that it is able to feel changes in temperature, chemical composition water, as well as touch and other irritants. Animal nerve cells are capable of being excited. For example, if you touch it with the tip of a needle, then the signal from the nerve cells that have felt the touch will be transmitted to the rest, and from the nerve cells to the epithelial-muscular ones. The skin-muscle cells will react and contract, the hydra will shrink into a ball.
Such a reaction - bright This is a complex phenomenon, consisting of successive stages - the perception of the stimulus, the transmission of excitation and the response. The structure of the hydra is very simple, and therefore the reflexes are uniform.
Regeneration
The cellular structure of the hydra allows this tiny animal to regenerate. As mentioned above, intermediate cells located on the surface of the body can transform into any other type.
With any damage to the body, intermediate cells begin to divide very quickly, grow and replace the missing parts. The wound heals. The Hydra's regenerative abilities are so high that if you cut it in half, one part will grow new tentacles and a mouth, and the other a stem and sole.
asexual reproduction
Hydra can reproduce both asexually and sexually. At favorable conditions in summer time a small tubercle appears on the body of the animal, the wall protrudes. Over time, the tubercle grows, stretches. Tentacles appear at its end, a mouth erupts.
Thus, a young hydra appears, connected to the mother's organism by a stalk. This process is called budding because it is similar to the development of a new shoot in plants. When a young hydra is ready to live on its own, it buds off. Daughter and mother organisms are attached to the substrate with tentacles and stretch in different sides until they separate.
sexual reproduction
When it starts to get colder and adverse conditions are created, the turn of sexual reproduction comes. In the fall, hydras from intermediate germ cells begin to form, male and female, that is, egg cells and spermatozoa. Hydra egg cells are similar to amoebas. They are large, strewn with pseudopods. Spermatozoa are similar to the protozoan flagella, they are able to swim with the help of a flagellum and leave the body of the hydra.
After the sperm cell enters the egg cell, their nuclei fuse and fertilization occurs. The pseudopods of the fertilized egg cell retract, it rounds, and the shell becomes thicker. An egg is formed.
All hydras in the fall, with the onset of cold weather, die. The mother organism disintegrates, but the egg remains alive and hibernates. In the spring, it begins to actively divide, the cells are arranged in two layers. With the onset of warm weather, a small hydra breaks through the egg shell and begins an independent life.
Topic: "Type Coelenterates".
Choose one correct answer
A1. The response of the hydra organism to the action of external stimuli
1) regeneration
2) fertilization
3) reflex
4) budding
A2. Coral colonies are formed by animals that belong to the type
1) shellfish
2) coelenterates
3) lancelets
4) protozoa
A3. The body wall of the hydra consists of ... layers
4) four
A4. Hydra is not part of the ectoderm
1) skin-muscle cells
2) stinging cells
3) nerve cells
4) digestive cells
A5. Between the ectoderm and endoderm, the hydra is located
1) base plate
2) mesoglea
3) hypodermis
4) mesoderm
A6. largest cluster stinging cells in hydra
1) at the mouth and on the sole
2) at the mouth and on the stem of the body
3) at the mouth and on the tentacles
4) at the mouth and on the walls of the intestinal cavity
A7. belongs to the intestinal type
1) sea anemones
2) sea squirts
4) holothurians
A8. Hydra lives in
4) fragmentation
A12. The early free-floating stage of jellyfish development, shortly after they are formed, is called
1) morula
4) planula
A13. According to the way the jellyfish feed
1) predators
3) filter feeders
4) herbivores
A14. Coral reefs are formed
1) in polar seas
2) in the seas of temperate latitudes
3) in tropical seas
4) everywhere in the oceans
A15. Not typical for corals
1) symbiosis with other organisms
2) the formation of the medusa stage
3) budding
4) sexual reproduction
A16. Body coelenterates
1) does not have a cellular structure
2) consists of one cell
3) consists of ectoderm, endoderm and mesoderm
4) consists of ectoderm and endoderm
A17. has radial symmetry
1) river hydra
2) planaria
3) lancelet
4) daphnia crustacean
A18. There are no stinging cells
1) Nereid annelids
3) sea anemones
4) aurelia jellyfish
A19. The response to irritation of the river hydra is possible due to the presence of
1) neural tube
2) nerve chain
3) intermediate cells
4) nervous network
A20. The ability to restore damaged and lost body parts or whole organism from the part called
1) degeneration
2) regeneration
3) sexual reproduction
4) reflex
A21. The belonging of the jellyfish aurelia to the type of coelenterates is evidenced by
1) the ability to swim in the water column
2) the presence of a larval stage
3) two-layer body structure
4) the ability to form colonies
A22. Medusa doesn't have
1) ectoderm
2) mesoderm
3) endoderm
4) nerve cells
A23. often reproduce asexually
1) amphibians
2) intestinal
3) insects
4) crustaceans
A24. Hydra breathes
1) with air bags
2) using the trachea
3) gills
4) absorbing oxygen dissolved in water by the entire surface of the body
A25. Which intestinal animal leads an attached lifestyle
1) aurelia
2) cornerot
3) stalked hydra
4) red coral
A26. Among the coral polyps there are hermaphrodites, that is, animals
1) with signs of a female body
2) with signs of a male body
3) bisexual
4) same-sex
A27. What is the function of stinging cells
1) respiratory
2) movement
3) protective
4) digestive
A28. belongs to the class Hydroid
1) aurelia
2) cornerot
4) sea anemone
A29. belongs to the Scyphoid class.
1) aurelia
2) red coral
4) sea anemone
A30. belongs to the class Coral polyps
1) aurelia
2) cornerot
4) sea anemone
IN 1. Select the traits that apply only to coelenterates
A) three-layer structure of the body
B) bilateral symmetry
B) two-layer body structure
D) there is a polyp stage in the development cycle
E) the body consists of ectoderm, endoderm, mesoderm
IN 2. Establish a correspondence between the features of the lifestyle and structure and different intestinal cavities, for which these features are characteristic
A) dwelling in the thickness sea water 1) jellyfish
B) living in the surf 2) coral polyps
B) form colonies
D) do not form colonies
D) have a calcareous skeleton
E) do not have a calcareous skeleton
IN 3. Establish a correspondence between function and cell type
A) defeat of the victim 1) skin-muscular
B) protecting the body from enemies 2) nervous
C) the body's response to irritation 3) stinging
D) the formation of the body cover
D) movement
C1. Find the errors in the given text, correct them, indicate the numbers of the sentences in which they are made, write down these sentences without errors.
1. Intestinal - three-layer, invertebrate animals.
2. Among them, there are both free-floating forms and those attached to the substrate.
3. They reproduce only asexually.
4. Include classes: Hydroid, Scyphoid, Flagellates.
C2. Give a complete detailed answer to the question.
Coral polyps live at relatively shallow depths. With what it can be connected?
Answers to level A tasks
Answers to level B tasks
Respiration and excretion of metabolic products occurs through the entire surface of the animal's body. Probably, the vacuoles that are in the cells of the hydra play some role in the selection. Main function vacuoles, probably osmoregulatory; they remove excess water, which constantly enters the cells of the hydra by osmosis.
Irritability and reflexes
The presence of a nervous system allows the hydra to carry out simple reflexes. Hydra reacts to mechanical irritation, temperature, light, presence in the water chemical substances and a number of other environmental factors.
Nutrition and digestion
Hydra feeds on small invertebrates - daphnia and other cladocerans, cyclops, as well as naidid oligochaetes. There is evidence of hydra consumption of rotifers and trematode cercariae. Prey is captured by tentacles with the help of stinging cells, the poison of which quickly paralyzes small victims. With coordinated movements of the tentacles, the prey is brought to the mouth, and then, with the help of contractions of the body, the hydra “puts on” the victim. Digestion begins in the intestinal cavity, ends inside the digestive vacuoles of the epithelial-muscular cells of the endoderm. Undigested food remains are expelled through the mouth.
Since the hydra has no transport system, and the mesoglea is quite dense, there is a problem of transport nutrients to ectoderm cells. This problem is solved by the formation of outgrowths of cells from both layers, which cross the mesoglea and connect through gap junctions. Small organic molecules can pass through them, which provides nutrition to the cells of the ectoderm.