CATDOLL : CATDOLL: Are mature fish eggs single-celled?

1. Are mature fish eggs single-celled?

It means that when a single cell matures, it is no longer a single cell after it combines with sperm.

2. What is the difference between growth maturity and physiological maturity of fish?

(1) Growth and maturation

After the micro-growth period and the macro-growth period, the primary oocyte of fish has grown fully, the ovum is completely filled with yolk material, and the nucleus or germinal vesicle (GV) is obviously biased towards the position below the fertilization hole at the animal pole (Ⅱ-17, 18). The oocyte in the IV+++ phase in this condition can be considered to have reached growth maturity.

(2) Physiological maturity

The germinal vesicle (GV) of the primary oocyte that has reached growth maturity (Ⅳ+++) undergoes chromosomal meiosis, expel the first polar body, and is in the second meiotic metaphase (Ⅱ-22, 23); the cytoplasm dispersed in the yolk space and around the egg is concentrated toward the animal pole to form the blastema (Ⅱ-21). Ovulation refers to the oocyte being freed from the surrounding follicular cell layer, the micropylar cell embedded in the fertilization pore (micropyle) disintegrating and disappearing, and the fertilization pore opening (Ⅱ-24, 27, 28), preparing for the sperm to enter the egg.

3. What do the male gonads of animals refer to?

The male gonads of animals refer to the male reproductive system.

The male reproductive system is the general term for the organs in male animals that complete the reproductive process, including gonads and reproductive ducts. Some vertebrates also have accessory glands and copulatory organs. Generally, the male reproductive system of male higher vertebrates includes testes, epididymis, vas deferens, accessory glands and penis.

for example

Amphioxus

The gonads are arranged in segments, about 25 to 26 pairs, and the males and females are dioecious. They do not have reproductive ducts. Mature reproductive cells pass through the gonad walls and body walls, enter the peribranchial cavity, and are discharged from the abdominal holes with the water flow, and fertilization is carried out in seawater. The reproductive organs are not connected to the excretory organs, which is a feature different from most vertebrates.

Cyclostomata

Although there are concentrated gonads, there are no reproductive ducts. Mature reproductive cells fall into the body cavity, enter the cloaca through the abdominal hole, and then are discharged from the body through the cloaca. The eggs are fertilized outside the body in the water. Lampreys are dioecious. The reproductive organs of hagfish are hermaphroditic in structure, but the two sexes are still separate in physiological function. The front part of the larval gonad is the ovary, and the back part is the testis. If the front part is well developed and the back part is degenerated, it will become a female, otherwise it will become a male. This situation shows that the differentiation of sex in this type of animal is late and it shows a primitive state.

Chondrichthyes

The situation is rather special. Sharks are animals that undergo internal fertilization, and males have copulatory organs - flippers. During mating, the male inserts his flippers into the female's uterus, and the semen flows directly into the female shark's uterus along the groove on the inside of the flippers. The sperm ascends along the oviduct, remains in the front section of the oviduct, and meets the egg there for fertilization. Male sharks have a pair of testes. Many sperm ducts extend from the front of the testes, and these small tubes pass to the front of the kidney to transport sperm through the mesonephric duct. Since there is another accessory renal duct dedicated to urination, the mesonephric duct is only used for sperm transport and is called the vas deferens. The front end of the vas deferens coils in front of the kidney, and the back end of the vas deferens swells into a seminal vesicle that can store semen. The lower ends of the left and right seminal vesicles fuse into urogenital sinuses, which open into the cloaca through the urogenital process.

Osteichthyes

Fertilization is carried out in vitro, and males do not have copulatory organs. The ovaries of female fish are white and increase in size to almost the same length as the body cavity during the reproductive season. The reproductive system of bony fish does not have a special reproductive duct, nor does it use the mesonephric duct to transport sperm like cartilaginous fish do. Instead, the reproductive gland wall itself continues into a tube, which is rare in vertebrates.

Amphibia

Most tailless amphibians (such as frogs) perform external fertilization, and males do not have copulatory organs. Caecilians (such as caecilians) perform internal fertilization, and the male frog's cloaca is very long and can protrude outward, so that during mating, the semen can be directly injected into the female's cloaca. Male frogs have a pair of oval testes, while toads have long columnar testes. Many tiny sperm ducts extend from the testes to the front end of the kidneys and connect to the mesonephric duct. Male frogs do not have separate sperm ducts, and the mesonephric duct is used for both urine and sperm.

Reptiles

All are internally fertilized. Except for tuatara, males have copulatory organs. The copulatory organs of snakes and lizards are called hemipenes, which are formed by a pair of expandable sacs extending from the back wall of the cloaca. Normally, the hemipenes are retracted inside the body. During mating, the hemipenes stand upright, the inner surface of the sacs is turned outward from the body, and inserted into the female cloaca. There are many small spines on the inner wall of the hemipenes of snakes. The size and number of spines vary depending on the type of snake, and the shape of the hemipenes also varies from species to species. Turtles and crocodiles have only one copulatory organ, which contains spongy tissue and can also erect like the penis of mammals. Reptiles have a pair of testes. The vas deferens is transformed from the mesonephric duct. For amniotic animals above reptiles, the kidneys of adults are metanephric ducts, which have the function of urination. The mesonephric ducts degenerate into some accessory structures of the reproductive system, such as the paradidymis and epididymal appendages, while the mesonephric ducts are used exclusively for sperm delivery.

Aves

All fertilization is internal. Only a few birds, such as ostriches, ducks, and geese, have copulatory organs. The penis of ducks and geese is a spiral protrusion protruding from the abdominal wall of the cloaca.

4. What is the function of the gonad system?

The gonadal system refers to a group of organs in the human body that are responsible for reproductive function, including the testicles in men and the ovaries in women. They have the following main functions:

1. Production of reproductive cells: The gonadal system is responsible for the production of reproductive cells, namely sperm (in males) and eggs (in females). These cells contain genetic information and are the basis for the genetic characteristics of offspring.

2. Hormone secretion: The gonadal system also secretes hormones, including testosterone (in the testicles of men) and estrogen and progesterone (in the ovaries of women). These hormones regulate sexual development, sexual characteristics, sexual desire, and reproductive function throughout the reproductive cycle.

3. Sexual development: The gonadal system plays an important role in the development of the human body. At puberty, the gonads begin to produce sex hormones, which promote the development of secondary sexual characteristics, such as deepening of the voice (in males), breast development (in females), growth and development, and body hair growth.

4. Reproductive capacity: The gonadal system is the key to achieving reproduction. Through gamete fusion and fertilization, the male and female gonadal systems cooperate to produce new life.

In summary, the gonad system is a key organ in the human body related to reproduction and gender. It is responsible for producing germ cells, secreting hormones, regulating sexual development and realizing reproductive ability.

5. What are the morphological characteristics of the gonads of male crucian carp?

The gonads of male fish are called "testes" and those of female fish are called "ovaries". In the sexual maturity period of fish, the gonads are relatively large. For example, the female ovaries of grass carp, silver carp and bighead carp account for 14% to 22% of their body weight during their maturity period (this number is usually called the mature ovary coefficient).

The testes are milky white in color, commonly known as "fish white", and the ovaries are blue-gray or orange-yellow in color, located on both sides of the swim bladder in the fish's abdominal cavity.

6.What does gonad secretion mean?

Gonadal secretion refers to the role of gonads in the reproductive system, such as testicles and ovaries, in secreting hormones and reproductive cells. It is an important factor affecting the physiological and psychological development of the human body. The testicles secrete testosterone, sperm, etc., while the ovaries secrete estrogen, progesterone, etc. Gonadal secretion plays an important role in the reproductive function of both men and women, the development of secondary sexual characteristics, and mental health. Therefore, it can be said that gonadal secretion plays a vital role in the physiological and psychological development of the human body.

7. What are the characteristics of boar’s accessory glands?

The accessory glands include the prostate, paired seminal vesicles, and bulbourethral glands. The secretions of the accessory glands and the secretions of the ampulla of the vas deferens have the functions of diluting sperm, nourishing sperm, and improving the vaginal environment. Together with the sperm produced by the testicles, they constitute semen.

1. Prostate: The body of the prostate is located above the urethral opening, and the diffuse part is wrapped around the pelvic part of the urethral sponge. The prostate secretes a thin, grayish white, fishy-smelling weakly alkaline liquid that can neutralize the acidity of urine, change the dormant state of sperm, and enhance its vitality.

2. Seminal vesicle: Located on the outside of the ampulla of the vas deferens, it is a lobed gland. The seminal vesicle and bulbourethral glands of boars are well developed, so the amount of ejaculation is large.

3. Bulbourethral glands: Located on both sides of the end of the pelvic part of the urethra, behind the seminal vesicles, with triangular ischiocavernosus muscles on the surface. The secretion is sticky and jelly-like, light white.

4. Ampulla of the vas deferens: underdeveloped. The terminal and the seminal vesicle excretion duct on the same side open on the seminal caruncle on the dorsal wall of the urethra.

8. What do the dog’s accessory glands include?

The accessory sex glands of dogs include the prostate gland, seminal vesicle glands and bulbourethral glands. Their development is directly affected by sex hormones. In young castrated animals, the glands are not fully developed. When the testicles are removed after sexual maturity, the glands gradually atrophy.

The secretions of the accessory glands have the functions of diluting sperm, nourishing sperm and improving the vaginal environment, which are beneficial to the survival and movement of sperm.

9. Where is gonadotropin produced?

Gonadotropin is a type of hormone that stimulates the gonads and is secreted by the posterior pituitary gland, placenta, and endometrium, including follicle-stimulating hormone, luteinizing hormone, human menopausal gonadotropin, prolactin, and human chorionic gonadotropin.

10. What parts does the animal accessory gland include?

The accessory glands of animals include the seminal vesicles, prostate gland and bulbourethral glands.

Its degree of development is directly affected by sex hormones. In animals that are castrated at a young age, the glands are not fully developed. When the testicles are removed after sexual maturity, the glands gradually atrophy.

The secretions of the accessory glands have the functions of diluting sperm, nourishing sperm and improving the vaginal environment, which are beneficial to the survival and movement of sperm.