Creepy, Crawly, Scaly and Slimy

There are over 30 different major groups of animals.  Only one of these groups includes the vertebrate animals.  All of the others are invertebrates.  The invertebrate group that includes insects, spiders, scorpions, crabs, and lobsters is the Arthropods.  All Arthropods have their skeleton on the outside of their body and it also serves as their skin.  This type of skeleton is called an exoskeleton. When the Hissing Cockroach sheds, the skin that is left behind looks just like the cockroach.  This is because its skin is also its skeleton.     

Insects are the most important group of animals on earth.  There are more species of insects than there are species of all other animals combined.  In fact, if you could gather up all of the insects on earth and weigh them, they would weigh more than all the other animals on earth combined!   If insects suddenly disappeared the food chain would break down and all other animals would die!

Spiders, ticks, mites and scorpions are Arachnids.  Arachnids have eight legs, two body segments, and special mouth parts called chelicera.  In spiders the chelicera form the fangs, in ticks they form the blood sucking mouthparts.

My spider is a Rose Hair Tarantula from South America.  It has what looks like hair covering most of its body.   This helps to increase its sense of touch the same way the fine hair on your arms helps you feel a mosquito when it lands on you.

Spiders have eight tiny eyes.  They produce silk from silk glands in their abdomen.  It comes out as a liquid but it quickly dries into a thin thread that is one of the strongest materials known.  The silk is used to make webs that have sticky strands to capture prey.  It is used like rope to climb up and down.  Spiders make egg cases from silk and some small spiders even use their silk to sail long distances with the wind.  

Spiders use their fangs to inject venom into their prey.  In some spiders the venom paralyzes the prey without killing it.  This allows the spider to store its food and eat it later.  Spiders are beneficial to people because they are predators of insects that cause problems for us. 

Rose Hair Tarantula

My scorpion is an Emperor Scorpion.  These are the largest scorpions in the world; They can grow up to 8 inches long!  They live around giant termite mounds in tropical rainforests of Africa where they dig to find termites for food. 

Scorpions use their pincers to grab and tear apart smaller prey.  They have a long flexible abdomen that ends in stinger which they can use to inject venom into larger prey.   Both the stinger and the pincers can be used in self defense.  The pincers of an Emperor Scorpion can draw blood and the sting is about like a bee sting.  

Scorpion babies are born alive and the mother protects them by carrying them around on her back.  Scorpions are one of one of the oldest of arthropods adapted for living on land.  Scientists have found scorpion fossils that are 425 million years old!  The "Southern Devil" is a species of scorpion that is found in Kentucky.  They are small, timid, and nocturnal so they are rarely seen.

Emporer Scorpion

Crabs, lobsters, crayfish and shrimp belong to a group of arthropods called Crustaceans.  Crustaceans have 10 legs and are mostly aquatic.  Many crustaceans are tiny animals that are a part of the plankton that makes up the bottom of the food chain in aquatic ecosystems. 

Hermit crabs find a shell from the body of a snail-like mollusk and use it for protection.  The Hermit Crab's body is adapted to fit inside the shell and carry it around.  At first glance, you only see six legs.  Four legs are missing!  In order to see them the crab must come out of its shell.  The other four legs are much smaller and are especially adapted for holding on to the shell and moving in and out of it.  Only Hermit Crabs have these specialized legs. 

The vertebrate animals I have are amphibians and reptiles.  These animals are cold-blooded which means that their body temperature depends on the temperature of their environment.  Cold-blooded animals don’t need to eat as much as warm-blooded animals since they don’t use energy to keep their bodies warm.  Most snakes go at least a week between meals!

There are two main groups of amphibians, the salamanders and the frogs.  Amphibians were the first vertebrate animals to evolve adaptations for living on land.  These adaptations include legs and lungs.  Amphibians also have two things that limit them as land animals. 

For one thing, most amphibians must go back to the water to reproduce.  They lay their eggs in water and the eggs hatch into larvae that must live in the water.  These larvae gradually go through metamorphosis to change into an adult amphibian.  Toad and frog larvae are tadpoles.  They are more like fish than they are like adult frogs.  They even have gills like fish.  Salamander larvae are similar but they have gills that are outside of their bodies.    While all toads and frogs develop into adults with lungs, some salamanders still have gills as adults.

                       Frog egg

                        Amphibian larvae

The second thing that limits amphibians is that their skin is not waterproof.  It stays moist and allows the water in their bodies to dry out if they do not stay in a moist environment.  The Tiger Salamander is an example of this.  It lives on land but must stay under rocks or leaves where it is moist.   Tiger Salamanders are the largest land salamanders in the world and get over a foot long.

Bullfrogs are the largest frogs in North America.  They are what are raised to make the frog legs that people eat.  Bullfrogs are semi-aquatic.  They spend most of their time on land sitting perfectly still waiting for prey but they are never far from water because they escape from predators by jumping into the water.  The Bullfrog’s feet are adapted for both land and water.  They are webbed for swimming but they have bumps on the bottom that give them traction on land like tire treads or the treads of your shoes.  Most frogs eat mainly insects but Bullfrogs eat things much bigger, including other frogs! 

                Bullfrog

Webbed feet for swimming and bumps for traction on land

Lizard eggs hatching

Baby Box Turtle's belly button

There are three main groups of reptiles living today.  The lizards and snakes make up the largest group followed by the turtles and then the crocodilians.  

Turtles are the oldest group of reptiles still in existence.  They have a bony shell that is makes up most of their skeleton.  This is an adaptation for protection.  The top part of the shell is formed by the backbone and ribs while the bottom part is formed by the breastbone or sternum.    Turtles do not have teeth but their jawbones are very strong and sharp. 

The Box Turtle is the only turtle in our area that lives on land.    If you look at one of the scales, you can see little rings where a new scale has grown in each year.  By counting these rings you can tell how old a box turtle is.  The newborn turtle below has no rings, the two year old turtle has two rings, and the adult turtle has about 10. 

                              One year old                        Two years old                        Ten years old

The crocodilians are the modern reptile group most closely related to the dinosaurs.  The only one other animal group more closely related is birds.  There are only 22 species of crocodilians.  Alligators, caimans and crocodiles belong to this group. 

All crocodilians are aquatic with a flat tail they use to paddle and eyes and nostrils that stick up on top of their heads above the water.  They even have a flap in the back of their throat to prevent water from getting inside when they eat.  They have huge mouths, long teeth and powerful jaws to capture their prey and rip it into pieces. 

The largest and most dangerous crocodilian is the Saltwater Crocodile of Asia and Australia.  It gets over 20 feet long and is responsible for killing hundreds of people of each year.  The head I have is from an American Alligator that was about 12 feet long.  Although Alligators do not prey on humans, they can grow to 18 feet long.

American Alligator head

Lizards and snakes are in the same group because snakes evolved from lizards about 100 million years ago.  The Savannah Monitor Lizard is probably very similar to the ancestors of snakes.  Monitors lizards also have a tongue that they use to help them with their sense of smell just like snakes.  Monitor lizards are like the ancestors of modern snakes and that snakes got their tongue from these lizards.

                     Savannah Monitor Lizard

Snakes inherited their tongue from their lizard ancestors that were like the monitor lizards.

 .Most but not all lizards have legs.  Lizards also have ears and eyelids but snakes do not.  Snakes' flexible jaws are adapted for swallowing prey that is much larger than their heads.  They have special scales on their bellies that they use to move.  The common Boa Constrictor lives in the tropical rainforests of South and Central America.  It captures its prey by grabbing with its mouth, wrapping around, squeezing it to death, then swallowing it whole. 

The Boa Constrictor belongs to a family of snakes that includes the largest snakes in the world.  My male Boa is nearly full grown at a mere 6 feet long and 20 pounds but some of its relatives can grow to over 30 feet long including the Green Anaconda of South America and the Reticulated Python of Southeast Asia. 

All members of this family of snakes have a pair of tiny bones near their tail that are left over from the leg bones of snakes’ lizard ancestors.  This is further proof of the close relationship between lizards and snakes.  Body parts left over from evolution like this are called vestiges or vestigial structures.  Vestiges are fairly common and include the hip bones found in whales and dolphins and the appendix of humans.