CATDOLL : CATDOLL: How do fish embryos develop? Discuss the process of fish embryo development?

1. How do fish embryos develop?

Thanks for the invitation!

There are three types of fish reproduction: oviparous, ovoviviparous and viviparous.

1. Oviparity is the reproductive method of most fish. Fish lay eggs outside the body, and the embryonic development takes place outside the body. The embryonic development process completely relies on the nutrients in the eggs.

2. Ovoviviparous fertilized eggs develop in the female reproductive tract, mainly relying on yolk nutrition during development, and have no nutritional relationship with the mother, or the mother's reproductive tract mainly provides water and minerals, and finally the mother produces fry. Such as guppies.

3. The embryos of some viviparous elasmobranch fish are connected to the mother through blood circulation. The nutrients needed for embryonic development are not only provided by the yolk of the embryo itself, but also by the mother. There are some protrusions on the wall of the oviduct where the embryo develops, which are connected to the embryo, forming a structure similar to the placenta. The mother sends nutrients to the embryo through this structure. For example, the gray star shark.

2. Discuss the embryonic development process of fish?

The embryonic development of fish can be divided into two periods: pre-embryonic development and post-embryonic development, with the period before and after the embryo hatches as the boundary. It is also called early development.

Pre-embryonic development takes place within the egg membrane, gradually developing from a fertilized egg into an active larva, and finally breaking the egg membrane to hatch. This period is often called hatching.

Post-embryonic development refers to the period from hatching to the ability to begin to ingest external nutrients or the differentiation of major organs.

1. Pre-embryonic development

It takes place inside the egg membrane and uses the yolk as nutrition.

Three major stages: cleavage stage, embryo formation stage, organ differentiation stage

(I) Temperature and incubation speed

Within the suitable temperature range, the lower the water temperature, the slower the development.

The four major fish species are sensitive to temperature changes around the blastopore closure period.

2. Hatching

Hypoxia often causes the embryo to hatch early, while increasing oxygen saturation inhibits hatching.

Within the range of normal oxygen content, the higher the oxygen content, the more normal embryos will hatch.

3. What is fish developmental biology?

Developmental biology is one of the important basic branches of biological sciences. Its research content is interpenetrating and interconnected with many other disciplines, especially genetics, cell biology, and molecular biology. It uses modern scientific technology and methods to study and analyze the processes and mechanisms of organisms at the molecular level, submicroscopic level, and cellular level.

A discipline that studies the mechanism of individual development using the methods of molecular biology and cell biology. It was developed from experimental embryology. Experimental embryology studies the relationship and properties of the various parts of the developing embryo, and how they affect each other. Developmental biology investigates the essence of this relationship, what substances (or substances) are at work, how the substances that work make embryonic cells differentiate in a certain direction, how the differentiating cells form tissues or organs to ensure the development of tissues and organs, how the normally developing embryo grows, matures, and becomes a growing individual, why the latter gradually ages after developing to a certain stage, and how to complete the entire development of the individual in a specified time and space sequence.

4. How to control the reproductive development of sows?

Sympathetic estrus control technology for sows

Synchronized estrus means making sows estrus at a predetermined time.

1. Use exogenous hormone preparations to artificially control and adjust the progress of the sow's estrus cycle

Commonly used exogenous hormones for estrus synchronization: pregnant mare serum (PMSG); human chorionic gonadotropin (HCG); PG600 (each dose contains 400 U of PMSG and 200 U of HCG).

2. Adjust the weaning time of lactating sows

Sows with similar lactation periods are concentrated and weaned on the same day. Through the regulation of their own hormones, the purpose of concentrated estrus is achieved.

3. Methods to promote estrus in sows

Mixed breeding of empty-stomach sows is the simplest method of inducing estrus. Through contact between different individuals, such as possible mounting behavior or even fighting, the release of sow sex hormones is promoted, thus producing a certain estrus induction effect.

5. How to control soil development?

However, as the time of vegetable planting increased, various problems appeared in the soil. The soil quality became worse and worse, with serious compaction, acidification, shallow tillage layer, poor ventilation, and various serious soil-borne diseases. Therefore, the vegetables grew worse and worse, seedlings were difficult to emerge after sowing, the root system grew slowly after transplanting, the seedlings were slow to grow, the plants were weak, and various diseases and insect pests were serious.

I envy those who can balance vegetable growing and soil improvement. Even after growing vegetables for many years, they still have dark and fertile soil that makes vegetables grow particularly strong. Soil improvement or keeping the soil in good condition is not something that can be achieved in a short period of time, nor is it something that can be achieved by using a certain method.

This requires us to pay attention to many details in daily cultivation management so as not to damage the soil or improve the soil.

We have a piece of land with very poor soil. There are always big clods in it, and the chives we planted don't grow well.

1. Why is the soil for growing vegetables easy to deteriorate, while the soil for growing field crops is relatively much better?

This is mainly because vegetables consume more nutrients.

Among all crops, vegetables consume relatively more nutrients. They require more fertilizer than fruit trees and flowers, which are also horticultural crops, and also more fertilizer than field crops, because vegetables grow fast and produce more.

Except for fast-growing leafy vegetables, most vegetables have a long growing period. They continue to grow and be harvested during this period, and require a large amount of nutrient absorption. Therefore, when planting such long-season vegetables, we often apply fertilizer multiple times.

Most of them are topdressed with chemical fertilizers. Although chemical fertilizers have a quick effect, they will have a bad impact on the soil environment, reduce the content of humus, destroy the soil aggregate structure, reduce the organic matter content of fertile soil, etc. The negative impact of chemical fertilizers, especially nitrogen fertilizers, on the soil is greater than the positive impact.

Improper or insufficient fertilization will lead to excessive consumption of soil by vegetables, resulting in a decrease in soil organic matter and poor air permeability.

More manure is always good

2. In the daily management of vegetable planting, we should at least pay attention to the following 3 points for soil improvement

1. Apply more organic fertilizer

Although the impact of chemical fertilizers on agriculture cannot be ignored and is huge, because the yield of chemical fertilizer crops has been greatly improved, with the development of modern agriculture, the transformation from high yield to high efficiency and high quality has been achieved. To produce high-quality vegetables, a good soil environment is required. If the soil conditions are good enough, the corresponding fertilizer and pesticide input will be reduced.

Therefore, in actual planting, we should reduce the dependence on chemical fertilizers and apply more organic fertilizers. Many vegetable growers do not like to apply organic fertilizers, the reason is nothing more than that it takes a long time to take effect and is relatively expensive. In fact, the application of organic fertilizers is not as troublesome as we think. Organic fertilizers are not only manure, but also stable manure, soil fertilizer, cake fertilizer, etc. are all organic fertilizers. If you are a family planting vegetables in a small area, you can pull a few trucks of farmyard manure and apply it to the field, and the effect is also very good.

Returning straw to the field is also a way to apply organic fertilizer. The decomposed straw can increase the content of organic matter in the soil and improve the soil's ability to retain water and fertilizer. We often see the return of crop straw to the field. Now there are also vegetable plant crushers that crush the plants to be pulled directly into the ground and apply it after turning the soil.

6. Summarize the types of fish fertilization, reproduction and development?

Fertilization in fish can be external or internal; reproduction can be oviparous, viviparous, or ovoviviparous.

Oviparous: fertilized and developed outside the body. Some species are fertilized inside the body, but the fertilized eggs are hatched outside the body, so they are still oviparous, such as the medaka.

Ovoviviparous: Fertilization and hatching inside the body, the young fish are expelled from the mother as lively ones, but they do not use the mother's nutrition, so it is called ovoviviparous, such as guppy.

Pseudoviviparity: The oviduct of some cartilaginous fish has developed into a structure similar to the uterus of mammals, and is connected to the embryo by blood circulation through a "yolk placenta" structure, supplying nutrients for embryonic development.

The developmental stages of fish: embryonic stage - larvae stage - juvenile stage - young fish stage - adult stage - aging stage.

Development includes embryonic development and post-embryonic development.

7. How do dancers control their development?

In addition to controlling their diet every day, high-intensity physical training also helps them stay in shape. They do physical training every morning, and rehearse dances or practice solo dances in the afternoon. After a day of training, they are so tired that they can't even lift their legs. Dancing is very caloric, and the continuous dance training every day is even more so.

When the intake is far less than the consumption, there is no need to deliberately maintain the body shape.

8. How do fish control the amount of water they displace?

Fish control this through their swim bladders, which inflate and deflate to adjust their size, so the fish can adjust the amount of water they displace as needed.

The volume of a submarine is fixed and it has no swim bladder, so the buoyancy it experiences is fixed. At this time, the only way to achieve free ascent and descent is to adjust the submarine's own weight.

The volume of a submarine is fixed and it has no swim bladder, so the buoyancy it experiences is fixed. At this time, the only way to achieve free ascent and descent is to adjust the submarine's own weight.

9. Why do dancers need to control their development?

If a dancer grows too fast, is too tall, or has large bones, then they will not be able to practice dancing, and will not be able to perform some difficult movements. Therefore, for some dancers, there are strict requirements for body shape and height. If you are dancing in a group, you must be about the same height. If you are too short or too tall, you may be eliminated.

10. The cell nucleus controls the development and?

The cell nucleus controls the cell's life activities and metabolic processes.

The genetic material (genes) on the chromosomes in the cell nucleus can affect the development process of organisms, but cannot control it.

The individual development of organisms is the interaction between cells, cells and the environment, and organisms and the environment, and is controlled by regulating life activities such as hormone regulation.