Spiders. Part 2. Sex, and Spiders’ Next of kin.
Recap, from the Introduction, that spiders and their kin have no penis, thereby I like to think that these members of the Arachnids learned to reproduce on land before sex as we know it was invented.
Ancient Spider Reproduction.
How Arachnids (spiders’ next of Kin) reproduce on land. This is a good illustration of the various methods used for sperm transfer.
Recall that spiders and their kin have no penis, thereby I like to think that these members of the Arachnids learned to reproduce on land before sex as we know it was invented.
The following post is an extract from a talk given to Naturalist Societies on Valentines Day Ha, Ha.
Let us start with the tiny Pseudoscorpion, a common creature of the forest floor litter. This is one of the laziest lovers in the animal kingdom. When ready to reproduce a male will simply deposit a drop of sperm on the ground, and leave it for the female to find and impregnate herself.
Promenade a deux Dance.
The mating ritual of scorpions.
The Scorpions, on the other hand, the male produces a spermatophore. This is a jelly-like stalk fixed to a solid object, on top of which is a cup containing the sperm. This cup has a lid with a trigger mechanism attached. The male on finding a female will sting her to subdue her then drag her over the spermatophore until the trigger releases the sperm in a spray, thereby fertilizing the female.
The Solifugae, or Wind Scorpions transfer sperm as a packet deposited on the ground, then will pick it up with his chelicerae. Followed by throwing the female onto her back he places the sperm into her genital opening using the chelicerae.
As you will see from the above examples there is a progression of improvements as natural selection refines the sperm transfer.
Let us view a few of the other none-spider Arachnids.
Tailless Whip Scorpion.
Amblypygids or Tailless Whipscorpions have usually eight legs but only walk on six of them. The first pair are drawn-out into a very long length and are fantastic adaption, used as antennae-like organs.
Like the true scorpions, reproduction involves the male depositing a stalked spermatophore on the ground. Again like the scorpions he will his pedipalps to guide the female into position. The fertilized eggs are carried under her body. When the young hatch they climb up onto her back to be carried around until their next molt, if one was to fall off, she will eat it.
True Whip Scorpion.
The true Whip Scorpion or Vinegaroons have a tail-like whip at the rear of the abdomen and have the ability to spray a mist vinegar-like smell of acetic acid, hence their other name. This is also found among some ants which are able to spray an acid. Whip Scorpions have no venom glands like true scorpions.
Whip Scorpions also secrete a spermatophore attached to the ground. By dragging the female about by her first legs he will maneuver her over it, if that does not work, he will pick up the packet of sperm with his pedipalps and insert it into her genital opening.
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Harvestmen.
Harvestmen fossils are known to be some 400 million years old. Yet, they reproduce sexually involving direct copulation. Some species males offer the female a nuptial gift before mating. The female lays her eggs with the aid of an ovipositor, which can be mistaken for a penis.
In some cases, a nest is built, and the male of some species takes on the parental role of guarding and cleaning the eggs. Guarding them quite often by preventing a female from eating the eggs given half a chance.
One can never make hard and fast rules as far as the animal kingdom is concerned, there is always an exception. In this case that of the harvestmen where both sexes have a penis. The male has a very long penis while the female has a very similar organ with which she deposits her eggs
Conclusion.
In an aquatic environment like the sea, the male gametes can swim to the female’s egg.
Yet in a dry land environment, the sperm needs to be placed inside the female’s body where it is stored. only later to be mixed with her eggs.
Question, How is this transfer carried out?
Read-on
Enjoy reading on- JohnH.
