The Open Door Web Site
Part VI : Animal Reproduction
Mating on Land Homepage
Mating can be a dangerous business
Female moths send a strong perfume into the air
Some penguins have difficulty in recognizing each other and in distinguishing males from females
Many cows are fertilized by artificial insemination
MATING AND FERTILIZATION II
To avoid being stung or injured the male scorpion has to quickly hold the female's pincers with his own during mating. The two scorpions then "dance" backwards and forwards, which has the effect of clearing an area on the ground. The male then places a packet of sperm cells from underneath his thorax onto the cleared ground. Then he has to pull and push the female until the sexual pouch underneath her thorax is above the packet of sperm.
When the eggs hatch inside the pouch, the young scorpions crawl out and onto their mother's back. They stay on her back for fourteen days.
Mating can be a dangerous business for a male spider. He prepares himself before he meets a female. He spins a triangle of silk a few millimetres long and puts a drop of sperms from a gland underneath this body onto the silk triangle. This packet of sperms is then sucked into a hollow pouch in a special leg called the pedipalp.
The male signals with his front legs to attract the female. His pedipalp is often brightly coloured to catch her attention. It is important that the female recognizes the male or she will attack him as she would any prey. The male carefully approaches the female and positions himself to squirt the packet of sperms from his pedipalp into her sexual opening. Once this has been achieved he has to escape very quickly. If he is not quick enough the female will eat him.
Crickets and Cicadas
Crickets and cicadas use sounds to attract the opposite sex. Other insects, such as the firefly, use light signals. The male firefly risks his life by flying through the air on warm summer nights, signalling to females with his flashing light. The females return their signals from the safety of the vegetation. Different species of fireflies are thought to have different codes of flashing lights.
Female moths send a strong perfume into the air. The male emperor moth is able to detect the perfume of a female at a distance of 11 km when the wind is blowing the perfume towards him. The male moths use their antennae to detect the female's perfume. A female emperor moth releases only 0,0001 mg of perfume into the night air.
Most penguins have difficulty in recognizing each other and in distinguishing males from females. They are not able to dance or sing to attract a male, (although they do make a lot of noise!).
The male penguin makes his intentions known to another penguin by offering it a pebble. This is done to suggest building a nest. If the pebble is rejected, the other penguin was either an unready female or another male!
Amongst humans, giving birth to two or more babies at once is not common, so we regard twins as rare but in the animal world it is quite common. This type of twin, from the fertilization of two eggs by separate sperms, is called a fraternal twin because the babies are all brothers or sisters of one another. There is another type of twin called an identical twin. This is quite different and to understand it we need to know what happens to the egg after fertilization.
After the sperm cell fuses with the egg cell no more sperm cells can enter the egg cell. After a few hours the fertilized egg cell divides into two, then into four, then into eight and so on until a ball of cells develops. This is the beginning of the embryo. If at this stage the ball of cells breaks in two - which can happen - two separate babies can form and they will be identical to one another.
In conjoined twins the ball of cells does not completely separate and the babies are born attached to each other. If the attachment between the twins is not too great they can be separated. They are often called Siamese twins because the first pair of this type of twin to be described in 1820 came from Siam, which is called Thailand today. This does not mean that there are a lot of twins joined together in Thailand. There are no more there than anywhere else. Conjoined twins are very rare amongst humans and other animals.
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