Arthropods Chapter 28

Animal Classification Sponges Cnidarians Worms Mollusks Arthropods Echinoderms Invertebrates Class Arachnida Class Crustacea Class Insecta Arthropods Animals Fishes Amphibians Reptiles Ectotherms (cold-blooded) Vertebrates Birds Mammals Endotherms (warm-blooded)

28-1: Characteristics of Arthropods

Characteristics Arthropod comes from the Greek words “arthron” – joint “pod” – foot Typical arthropods: Segmented Coelomate Bilateral symmetry Exoskeleton

Characteristics Appendages – any structure (a leg or an antenna) that grows out of the body of an animal

Why Arthropods Must Molt Exoskeletons cannot grow, so they must be shed periodically Molting – shedding the old exoskeleton Before an arthropod molts, a new, soft exoskeleton formed beneath the old one Cicada

Segmentation in Arthropods Arthropods do not have as many segments as segmented worms In most groups, arthropods are consisted of three segments Head Thorax Abdomen

Segmentation in Arthropods Some arthropods have two sections Cephalothorax – A fused head and thorax Abdomen

Arthropods Have Acute Senses Movement, sound, and chemicals can be detected with great sensitivity by antennae Antennae are also used for sound and odor communication; can detect pheromones Atlas moth

Arthropods Have Acute Senses Pheromones – chemical odor signals given off by animals Some pheromones are used as scent trails (example: the group-feeding behavior of ants) Many pheromones are important in the mating behavior of arthropods

Arthropods Have Acute Senses Most arthropods have one pair of large compound eyes and three to eight simple eyes A simple eye is a visual structure with only one lens that is used for detecting light

Arthropods Have Acute Senses A compound eye is a visual structure with many lenses Compound eyes can detect the movements of prey, mates, or predators, and can also detect colors

Arthropods Have Other Complex Body Systems Arthropods have open circulatory systems and complete digestive systems Mouth, stomach, intestine, and anus

Arthropods Have Other Complex Body Systems Mandibles – the mouthparts of most arthropod groups include one pair of jaws The mandibles are adapted for holding, chewing, sucking, or biting

Arthropods Reproduce Sexually Some species (bees, ants, and wasps) exhibit parthenogenesis – a form of asexual reproduction in which a new individual develops from an unfertilized egg In bees, drones are developed from unfertilized eggs

28-2: Diversity of Arthropods Diversity of All Animals About 85% of all known animals are arthropods

Additional information http://evolution.berkeley.edu/evolibrary/article/_0_0/arthropods_intro_05

Arachnids Spiders, scorpions, mites, and ticks belong to the class Arachnida Spiders are the largest group of arachnids An arachnid has a cephalothorax and an abdomen with six pairs of jointed appendages

Arachnids Chelicerae [kuh-lis-er-uh] – the first pair of appendages located near the mouth (modified pinchers or fangs) Pincers are used to hold food, and fangs inject prey with poison

Arachnids Pedipalps – the second pair of appendages that is adapted for handling food and for sensing In male spiders, pedipalps are used to carry sperm during reproduction The four remaining appendages are adapted as legs

Arachnids – Black Widow

Crustaceans Class Crustacea include crabs, lobsters, shrimps, crayfishes, pill bugs, and barnacles Most crustaceans are aquatic and exchange gases over gills

Crustaceans – Red Crab Mating

Crustaceans – Red Crab Offspring

Centipedes and Millipedes Centipedes and millipedes have tracheal tubes for gas exchange Centipedes are carnivorous and eat soil arthropods, snails, slugs, and worms A millipede eats mostly plants and dead material on damp forest floors

Insects Class Insecta is the largest group of arthropods Insects have three body segments and six legs

Insects – Giant Asian Hornets (Invasive Species) vs Insects – Giant Asian Hornets (Invasive Species) vs. European Honey Bees

Insects – Giant Asian Hornets (Invasive Species) vs Insects – Giant Asian Hornets (Invasive Species) vs. Japanese Honey Bees

Insects – Botfly

Metamorphosis Metamorphosis – the series of changes, controlled by chemical-substances in the animal Two types of metamorphosis: 1. Complete metamorphosis consists of four stages: Egg Larva – the free-living, wormlike stage of an insect Pupa – a period of reorganization in which the tissues and organs of the larva are broken down and replaced by adult tissues Adult

Metamorphosis Examples: ants, beetles, flies, and wasps

Metamorphosis With each molt, it begins to resemble the adult more 2. Incomplete metamorphosis – insects go through only three stages of development Egg Nymph – hatches from an egg, has the same general appearances the adult but is smaller Adult With each molt, it begins to resemble the adult more Grasshoppers and cockroaches undergo incomplete metamorphosis

Picture of incomplete metamorphosis

Collecting Arthropods 1. Pitfall Traps 2. Flying Traps

Pitfall Trap Cup Water Soap Paper plate Sticks Labels

Flying Trap Water bottles Scissors Twine or yarn Labels