Showing posts with label Spider. Show all posts
Showing posts with label Spider. Show all posts

Jun 26, 2015

Horsehoe Crabs and Spiders

Horseshoe crabs were misidentified as crabs hundreds of years ago. They spend most of their time crawling on the sea floor and have a crab-like shell roughly resembling a horseshoe. However, they are grouped with arachnids.

Horseshoe crabs date back 500 million years as a species. These prehistoric survivors, who perhaps never evolved to flourish on land like the rest of their cousins, can grow up to 0.6 meters (2 ft) wide and use their long tails as a tool to dig for food or to turn over. The horseshoe crab has 10 eyes on its back and sides, can replace lost body parts, and has blue blood. The blood is medically valuable and is used to detect bacteria, for cancer research, diagnosing leukemia, and vitamin B12 deficiency.

Feb 1, 2014

Venomous or Poisonous

Fish, snakes, and spiders are often described as either being venomous or poisonous. The difference is in the delivery system. Those that are venomous inject their target with their toxin through a bite, sting, or sharp body protrusion. Those that are poisonous have toxins that must be swallowed or inhaled in order to be dangerous.

Venomous animals need to get their toxins beneath the skin and then into the bloodstream to be effective. Some have a venomous bite, but are safe to eat. Many caterpillars have defensive venom glands associated with specialized bristles, known as urticating hairs, which can be lethal to humans. There are about six venomous snake and about seven venomous spider fatalities in the US each year. Venoms are usually not lethal if swallowed.

Poisonous fish can be potentially deadly if eaten. Poisons work mostly through the digestive system and mucous membranes of the body. Some poisons can be transferred easily to humans by merely touching or handling.

The yellow-bellied sea snake has both a venomous bite and poisonous flesh.

There are several types of venom. Neurotoxins attack the brain and the nerves. Animals whose bite results in paralysis use this type of venom. Cytotoxins are a type of venom that causes the most pain, as this venom attacks cells directly, causing them to rupture and release their contents into the body. Hemotoxins attack blood cells directly and most kill red blood cells, which interrupts the flow of oxygen throughout the body. Not all poisonous or venomous creatures are fatal to humans, but they are all discomforting.