Ch. 38 - Arthropods Phylum: Arthropoda Means “jointed legs” 75% of all animals belong to this phylum Insects, lobsters, crabs, spiders, millipedes, & centipedes

Characteristics of Arthropods 1. Appendages – legs, antennae 2 appendages per segment 2. Open circulatory system 3. Digestive system 4. Ventral nervous system 5. Exoskeleton – protection & desiccation Made of chitin

What is molting? Shedding of the exoskeleton Why do animals molt? Every time an animal molts it enlarges or grows

What are some advantages & disadvantages of molting? Protection, prevents desiccation Must molt to grow, vulnerable after it molts

Crustacea subphylum Crayfish, lobsters, crab, sow bugs, daphnia. Mainly aquatic Crayfish Characteristics 2 main body parts 1. Cephalothorax – head & thorax 2. Abdomen – 7 segments Last segment is the telson

Appendages of the Crayfish 1. Chelipeds – pinchers 2. Antennules – smaller (inside) 3. Antenna – larger (outside) 4. Walking legs – 4 along the thorax 5. Swimmerets – along the abdomen 6. Uropod – outside the telson

Digestive & Excretory Systems First the crayfish tears the food with their maxillae & maxillipeds. They chew their food with their mandibles The food passes through the esophagus to the stomach.

The digestive glands absorb nutrients, then the undigested material enters the intestine, and then exits the anus. Green glands are also used in the excretory system to remove waste; much like kidneys.

Circulatory & Respiratory Systems Open Circulatory System Dorsal heart that pumps blood to the body cavity to bath the organs. It is then pumped to the gills. What do the gills do? Large surface area for gas exchange The gills are attached to each walking leg

Nervous System Ventral nerve cord Brain Sense receptors  antennules, antennae, & compound eyes A compound eye has many lenses Do you have a compound eye?

Usually mate in the fall Reproductive System Usually mate in the fall The male uses its swimmerets to transfer sperm to the female, where she keeps the sperm until spring. The eggs are then fertilized and kept along the female’s swimmerets until they hatch.

Chelicerae - subphylum Class: Arachnida Spiders, mites, scorpions Many use stingers or fangs with poison. How do spiders catch their prey? with webs or “trap doors” Scorpions hunt at night and hide during the day.

Only a few scorpions are poisonous to kill humans Mites and ticks are the most abundant in this class. Ticks are parasitic and some carry diseases. Lyme’s disease Rocky mountain spotted fever. Spider mites can damage and wipe out fruit trees or other trees.

Structure of a spider 2 segments 1. Cephalothorax 2. Abdomen Chelicerae – hollow fangs Pedipaps – aid in chewing 8 legs & eyes Spiracles – openings for respiration

Book lung – air sacs in the abdomen for respiration. Malpighian tubules – kidney-like excretory system. Removes wastes. Spinnerets – spins silk for webs Can also be used as silk balloons to fly away in young spiders. Black widow & Brown Recluse 2 poisonous spiders in Kansas

Uniramia - subphylum 2 classes 1. Diplopoda – millipedes Means “thousand feet” 2 pair of legs per segment 2. Chilopoda – centipedes Means “hundred feet” 1 pair of legs per segment Some are poisonous