Which arthropods are the most diverse

They won't bite. Watch the way they roll up into a ball when disturbed. Not all isopods can do this, but rolling up into an armored ball is a great defensive tactic. Compare our teeny tiny terrestrial version with the enormous preserved marine isopods.

Look at the live brine shrimp, hermit crabs and fiddler crabs. Treat them gently more pets. Watch the way they use their legs, including the modified legs that form their mouthparts. You may see the male fiddler crabs raise their large claw and wave it about to claim a territory inside the tank, in the hopes of attracting a mate Can you blame them?

Observe the live crayfish. What does the crayfish do when it feels threatened? How does it use its swimmerets when it is stationary? Observe the diversity in insect mouthparts etc. Don't worry about being able to identify the individual slides.

Try to get a feel for the way modified legs are employed in these animals for a wide variety of sucking, sponging, piercing and biting. Observe the insects on display. You should be familiar for lab and lecture with the common orders of insects listed in this guide. Crayfish are relatively easy to dissect. Many of you have had ample practice dissecting them at Jazz Fest. Your first task is to determine whether you have a male or female crayfish.

Turn the animal on its back, and examine the area of the thorax where the legs join the body. Female crayfish have a circular opening, like a tiny doughnut, which is their seminal receptacle. Male crayfish have a hardened pair of swimmerets legs on the abdomen that extends back towards the head, and fits neatly into the groove between the walking legs.

These modified legs are stiff, like hard plastic. They are curved like half a soda straw, and when they are joined together, they make a tiny tube through which the sperm travel during copulation. Crayfish literally copulate with their legs. Observe their external anatomy. Identify the following structures: rostrum, antennae, eyes, thorax, carapace, chelae claws , cheliped, walking legs, abdomen, swimmerets, telson, and uropod.

Examine the various appendages and modified appendages closely. Note that some are biramous ex. The uniramous appendages result from the evolutionary loss of the second branch. Note that each pair of antennae are biramous appendages. Examine the telson and uropod. How does the crayfish use these biramous appendages to escape predators?

Using a probe, try to find the mouth and anus. Note the thick triangular mandibles , a primary trait of crustaceans. Place the crayfish in the pan with its dorsal side up. Carefully cut the carapace just to one side of the midline with your scissors, and down along both sides.

Peel it back to expose the gills. Notice how the gills interface with the legs, and observe the second underlying row of gills. Cut away the gills where they join the body. Try to find the tiny heart good luck! Just under the heart are the gonads ovaries or testes. Look for the esophagus and stomach you can always insert a probe through the mouth to see where it emerges. Carefully remove the internal organs, and look for the tiny brain near the base of the antennae.

Ecologically, they are critically important herbivores. Arthropods are the primary converters of plant tissue to animal tissue on the planet! Trilobites were among the most successful arthropods on Earth, once numbering over 10, species. They are known to have a painful pinch. Along with its 21 to 23 pairs of legs, this particular centipede has appendages known as gnathopods that will inject venom in their prey that can cause instant pain in its victim.

They are very effective predators and will feed on lizards, frogs, rodents, insects, and sometimes flying critters. They can even reach into the air to snatch a non-suspecting victim. Just like most crawling critters, they are not usually interested in people as prey: you can breathe a sigh of relief, they are not out to get us! There are no known marine myriapod species. They have a single pair of antennae and mouthparts roughly similar to those found in chelicerates.

The main distinguishing feature of myriapods is the multiple jointed legs that extend from their elongated worm-liked bodies. The subphylum name comes from Greek root words meaning countless feet. Myriapods have between 10 to legs. The class Insecta is another primarily terrestrial group of arthropods, although insects have been reported from nearly all environments with the exception of deep-sea habitats.

Insects are the most diverse members of the subphylum Hexapoda Fig. Hexapods have a distinct body plan, which includes three large sections: a head, thorax, abdomen with three pairs of thoracic legs and one pair of antennae Fig.

Hexapods have three sets of jaws called mandibles, maxillae, and labium Fig. Insects breathe by taking in air through spiracles into trachea tubes. Unlike in the arachnids, these tubes do not terminate at book lungs, but branch into smaller networks of tubes called tracheoles that branch directly into the tissues of the insect for gas exchange Fig.

There is no active pumping of air, but any small movement in the insect body leads to airflow throughout the trachea. Along with their close relatives the centipedes and millipedes, insects have appendages that are unbranched. Their bodies are developed into three distinct segments of head, thorax and abdomen. The wings usually two pairs are contained on the thorax segment along with three pairs of legs. Insect wings and legs are modified in many ways depending upon the lifestyle of the insect.

In most insects, though, the legs include sensory receptors. Other sensory receptors are found on the body, and insects have compound eyes and light sensing ocelli on their heads. Most marine arthropods belong to the subphylum called Crustacea Fig. Some species of shrimp, called krill, spend their lives as plankton, drifting in the surface waters of the open oceans.

Some species of crustaceans, such as crayfish, are common in freshwater lakes and streams; a few—isopods and pill bugs, for example—live on land. Many crustaceans are used as food, both by larger animals and by humans. While most crustaceans are mobile, one exception is the barnacle. Barnacles are free swimming as larvae, but when they metamorphose, the head reduces and is cemented to the substrate with a strong chemical glue.

The barnacle secretes a hard protective shell around itself and filter feeds from inside this shell, using elongated appendages to collect food particles. Due to their lack of mobility, barnacles are one of the few arthropods that are hermaphroditic. The crustacean body is clearly divided into a head, an abdomen, and a thorax. While the insects have a flexible joint between the head and thorax, crustaceans tend to have the two sections fused together.

Crustaceans have two antennae on the head, followed by mandibles , maxillae , and maxillipeds , all structures for handling food Fig. The thorax contains the walking and swimming legs. The front pairs of appendages are often modified into claw-bearing appendages.

The abdominal section contains appendages called swimmerets Fig. These appendages produce water currents that pass over the gills for respiration. Female crustaceans typically use swimmerets to hold onto eggs for brooding , or keeping the eggs with them until they are ready to hatch. Insects are the largest group of arthropods but can be distinguished from other arthropods by certain characteristics.

Insects have three body regions head, thorax and abdomen , three pairs of legs and a pair of antennae. One gift most insects have that other arthropods lack is the ability to fly.

When it comes to sex, mammals and other vertebrates are predictable compared to insects. Some insects even reproduce by parthenogenesis where no males exist.

Surprisingly, attentive parental care actually occurs in some species. But are insects really important or just annoying picnic guests? To answer this question, first consider the number of described insects. Such a large, diverse group should suggest that ecosystems are extremely complex. Consequently, insects fulfill many important roles in these ecosystems.