Amniotes are tetrapods with special characteristics that enable them to produce an amniotic egg. In the majority of species this egg is adapted to be laid on land and survive. However there are mammals, such as eutherian mammals that utilize a similar structure for reproduction.
An amniotic egg is made up of an amnion, which is a fluid-filled sac that protects the embryo. This type of egg also has membranes that develop outward from the embryo and are not part of it. Extra-embryonic membranes include an amnion, chorion, yolk sac, and an allantois.
The amnion embraces the embryo and proportions it with an aqueous habitat, known as the amniotic fluid. While amphibians have the necessity to lay their eggs in water, the amniotic egg enables the animal to place its egg on land because it contains the water inside of it.
Attached to the embryo are the allantois and the yolk sac. The yolk sac, which is concentrated with nutrients, feeds the embryo as it grows. As the embryo matures, the yolk sac reduces. All of the embryo´s metabolic wastes are stored in the allantois. This last membrane also functions as a gas exchanger along with the chorion. The overall enclosure of the membranes and embryo is provided by the chorion. It is in charge of exchanging gases, retaining moisture, and diffusing carbon and oxygen across the membrane.
Finally, there is the albumen or outer shell of the egg. This one protects the whole egg and is around the chorion. The shell prevents dry circumstances for the embryo, while still permitting the creature to receive air.
Mammals use a type of modified egg structure, normally within their uterus called placenta. The young of these mammals are developed inside the mother from fertilization, when the sperm of the male joins with the ovum, or “egg” of the female. Placental mammals are viviparous, which means that they give birth to fully developed offspring that was carried by the mother through its growth.
The membranes in placental mammals are like the ones of the laid egg, but modified in a certain manner. Surrounding the embryo is the amnion filled with the amniotic fluid. The yolk sac and the allantois are joined to become the umbilical chord, where food is supplied to the fetus and the waste of it is also removed. All of these membranes, including part of the chorion, compose the placenta. This one in turn physically attaches the embryo to uterine wall of its mother. The placenta also protects the embryo and the mother by separating their blood.
Fear is what gets into the minds of most people when they hear the word “venom”. We imagine these horrible creatures that are tiny or large, but can probably kill you. Consciously or unconsciously we think of words like “toxic, poison, snake, spider, scorpion, sting, bite, sickness, death, ect.” Nevertheless, in contrast to their unwanted reputation, venom and its producers can be used to benefit mankind greatly.
Because of their venom and other special features, one of the most studied type of creatures are arthropods, specifically those which belong to the groups hymenoptera (ants, bees, and wasps) and chelicerata (spiders, scorpions, and other arachnids). Arthropods are invertebrates and they are extremely vital in the survival of many ecosystems and important for the success of agriculture.
Numerous arthropods are natural pollinators, pest controllers, and can be a supply of food, either directly or indirectly. These animals are characterized by their external skeleton (exoskeleton), segmented body, jointed appendages, jointed limbs, and cuticles. They are perhaps the most versatile and diverse animals on earth. Nearly 80% of all described living animal species belong to the group Arthropoda.
Their venomous feature has been subject of horror and wonder throughout the centuries. Spiders use fangs, centipedes use modified feet, scorpions and other similar animals use a sting, bees or wasps utilize a unique egg-laying device, some caterpillars have defensive venom glands associated with bristles on the body, and many others have adapted bodies to create and apply their venom. It is commonly known that their venom is used for defense, however, it is also employed by animals to paralyze prey and even for sterilization of pathogens.
All of these venomous arthropods contain active principles that can be used for the development of new drugs to treat diseases such as cancer, arthritis, strokes, and many others. They have active molecules that are capable of interfering in human cellular physiology, without damaging the body. This also signifies that their venom can be used widely enough to rejuvenate the body. Therefore, arthropods and their venom are a potential use in natural and composed medicine. Who knows, maybe someday they might be helping save thousands of lives. That is a more virtuous way to see venom and its producers.