Arthropods Chapter 36 Chapter 36

Phylum Arthropoda Section 36.1

Arthropods Examples: lobsters, crabs, spiders, millipedes, centipedes, insects Arthropod means “jointed foot” Appendages: body segments with jointed extensions Used in feeding, moving, & mating

Characteristics: Exoskeleton Compound eye Open circulatory system Protection, support, prevents desiccation 3 layers excreted by epidermis Made of chitin Compound eye Optic nerves send impulse to the ventral nerve cord Open circulatory system

Molting: Video Periodic shedding of the exoskeleton to allow growth Few day process to develop hard exoskeleton – extremely vulnerable times! Hormone, pressure, and enzyme induced enzymes digest old exoskeleton while synthesizing new one Video

Evolution: 545 million years ago All from a common ancestor Tagmata: fused segments that perform a specialized function of modern arthropods 5 subphlya

Classification: 5 Subphyla Trilobita: (trilobites) Extinct! Crustacea: (shrimp, lobster, crayfish, pill bugs, barnacles) Chelicerata: (spiders, scorpions, ticks, horseshoe crab) Myriapoda: (centipedes, millipedes) Hexapoda: (insects, springtails) Page 725

Subphylum Crustacea Section 36.2

General Information: “Crusta” means shell Most are aquatic Defining characteristic = 2 pairs of antennae Exoskeleton: Made up of chitin (protein) or CaCO3 Carapace has waxy coating 16 to 20 body segments that fuse to form tagmatas

General Information: Many have mandibles jawlike mouthparts Usually each segment has at least 1 pair of appendages Open circulatory system Many respire with gills (aquatic only) Nauplius Free swimming larvae

Crustacean Diversity Aquatic: Terrestrial: Isopods Plankton – collection of small animals that drift near the surface of the water Copepods (crustaceans) are a part of plankton Water flea Barnacles Shrimp Lobster Crabs Crayfish Terrestrial: Isopods Pill and sow bugs Lose water quickly

Crayfish Decapods – “ten feet,” five pairs of legs

THIS IS WHAT WE WILL BE DISSECTING – WEAR CORRECT SHOES! Video

External Structure Two major sections: Cephalothorax: two tagmata Head – 5 segments Thorax – 8 segments posterior to head Carapace – dorsal exoskeleton Abdomen: 7 segments Telson – 7th segment, flat paddle at posterior

Appendages: Antennules – touch, taste, equilibrium Antennae – touch, taste Mandible – chewing Maxilla – manipulate food, draw water over gills Maxilliped – touch, taste, manipulate food

Cheliped (claws) – capture food, defense Walking legs – locomotion over solid surfaces Swimmeret – create water currents, transfer sperm (male), carry eggs and young (female) Uropod – propulsion during tailflips

Digestion: Digestive System: mouth  esophagus  stomach  enzymes secreted by digestive gland  intestine & digestive gland  anus

Respiration: Respiratory System: gills Base of each walking leg under carapace Diffusion of gases

Excretion: Excretory System: green glands Acts like a kidney Eliminate excess water due to hypotonic environment

Circulation: Circulatory System: open system baths organs in hemolymph Pumping organ: heart (dorsal)

Neural Control: Brain = pair of ganglia above esophagus Ventral nerve cord Sensory hairs on exoskeleton 2,000 light sensitive units on each eye Statocyte at base of antennae for balance

Reproduction: Video Sexual: mate in fall Male’s first 2 hollow legs transfer sperm Female holds sperm until eggs laid, then fertilize; mated previous fall Eggs laid in spring (100) carried by female on swimmerets 6-8 weeks; “berried” regenerate missing parts Video

Female Male