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Reproductive System Evolution
REPRODUCTIVE SYSTEM EVOLUTION
by EM, GA and SM
Meet our female fetal pig, Roxanne. She was taken from the uterus of a pregnant sow in a slaughterhouse. Her blood has been removed but her organs remain quite intact. Let's take a look at her reproductive system.
^The picture above is the outer reproductive system on the posterior end of Roxanne.
The urethral orifice can be found on the ventral surface of the vagina at its junction in the urethra. The clitoris can be located near the opening of the urogenital sinus, which is the homolog of the penis. The labia majora, folds of skin, can be found on either side of the urogenital aperture, which is ventral to the anus. The urogenital aperture and labia majora are what make up the culca. The urogenital papilla (what identifies the pig as female) projects from the urogenital aperture.
Internal Urogenital System:
Ovaries are paired, small bean-shaped structures located posterior to the kidneys and are the female gonads. Oviducts (fallopian tubes) are located dorsal to the anterior portion of the ovary.
Uterine Horns (Cornua):
The uterine horns are dorsal to the ovary and join to form the uterus. In pigs and other mammals, unlike in humans, fetuses are formed in the uterine horns extending from the uterus rather than the uterus body itself, allowing multiple births. It's kind of like the Texas Longhorn symbol.
Uterus and Vagina:
The vagina is a continuation of the uterus and lies dorsal to the urethra. Cervix lis between body of uterus and the vagina.
The vagina and urethra unite to form a passageway that opens to the exterior urogenital sinus (vestibule). In humans, the vagina and urethra do not connect and is part of the external genitalia.
This picture was taken from the following link. (
Here is a picture of the same region in Roxanne. The other picture gives a clearer view of the organs.
UNITY AND DIVERSITY OF REPRODUCTIVE SYSTEMS
Pictured above is the reproductive system of a
Like a pig it has a
. However, the method in which this urogenital opening is used differs between the two species. The female perch releases its eggs into open water to allow them to be fertilized by sperm from the male perch (external fertilization). In pig reproduction, the male releases sperm directly into the female's
. Also, the female pig has two ovaries. While the female perch starts with two ovaries in its embryonic stage, the two organs fuse together during development to form one organ (information taken from the above link).
Pictured above is the reproductive organs of a starfish, vaguely described as "gonads" (
There is no way to determine whether the gonads are male or female with the naked eye. The gonads are located in each arm of the stafish where gametes are manufactured. Like the perch, the starfish gametes are extrenally fertilized. The gametes are released from gonoducts in the center of the starfish. Starfish may also reproduce asexually. If an arm is torn off (and some of the central body is still connected to the arm) then the arm may grow into a new starfish. This may counter their fairly unreliable method of sexual reproduction. To find out more check out this site (
Pictured above is a ventral view of the female crayfish reproductive system (
During crayfish reproduction, sperm are released into the seminal receptacle by the male and eggs from the ovaries are released from the female's genital opening. The eggs pass through the sperm in the seminal receptacle and thus become fertilized. The eggs then pass towards the female's posterior end (tail) where they remain until they hatch (
Unlike perch or a starfish eggs, the crayfish eggs receive some protection from predators from their mother. The tail almost acts as an external uterus, sheltering the eggs until they hatch.
Pictured above is the female and male grasshopper's reproductive system (
Like many of the other animals, grasshoppers have differing male and female reproductive systems. The male grasshoppers have testes made up of follicles that are located dorsal to the intestines, that each connect to the vas deferens (like in male pigs). The vas deferens joins the ejaculatory duct that is involved in the internal fertilization of the female’s eggs. The female grasshoppers have two ovaries made up of ovarioles that converge into a oviduct that carries the eggs to be fertilized. The grasshopper’s reproductive system is similar to that of other organisms we studied such as the pig and crayfish since it uses internal fertilization. It differs in that the female then lays its fertilized eggs below the ground using its oviposter and abdomen. Guys, check this out for more info: (
Pictured above is the reproductive system of a female frog: (
Picture above is the male frog reproductive system:
Like the grasshopper and the perch, the frog uses external fertilization. The female frog lays a clutch of eggs and then the male sheds semen on top of them. The male reproductive system is made up of the following organs: The sperm is produced in the testes (similar to all of the other animals). The urethra is where the ejaculatory ducts empty and the prostate is a gland which produces milky fluid that mixes with the sperm. The penis is an organ that pushes the urine and semen the the urethra and out of the body. The parts of the female reproductive system are as follows: The vagina ia the canal that leads from the uterus to the outside of the body. The cervic is a knob of flesh with a small hole in the middle the protects the inside of the uterus. The uterus recieves eggs and supports a growing embryo's development. The fallpian tubes transport the eggs to the uterus and the ovaries produce and store the eggs.
Pictured below are the major organs of the mussel, including the reproductive organs such as the siphons and rectum:
The siphons in a mussel have multiple purposes. On a daily basis the siphons serve to draw water in and bring it to the bronchial chamber and eventually the food substances get funneled into the mouth which marks the beginning of the digestion process. A similar process in the freshwater mussel occurs during reproductive fertilization. However, during reproduction sperm enters the female's body through the intake siphon.
Pictured above is the reproductive (and life) cycle of mussels:
Like each of the other animals studied, mussels have separate male and female reproductive systems. Similar to the perch, the male mussels release their sperm into the water, and the females must siphon the sperm to
its eggs. The female then stores thousands of eggs on her gills for one to ten months until the larva of mussels, called
, fully develop. Unlike the other animals studied, the mussel has to rely on another organism in order to undergo its full reproductive cycle. The fully developed glochidia are released into the water until they find a fish (different species of mussels use different fish) to serve as a host for up to four weeks. The glochidia attach themselves to the gills of the fish, where a cyst is formed, and the larvae are safe and able to feed without harming the fish until they are fully developed and break through the cyst and fall to the sea bottom. For more information, visit
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