arthropods chapter 36 phylum arthropoda section 36.1
TRANSCRIPT
Arthropods
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
– Protection, support, prevents desiccation– 3 layers excreted by epidermis
• Compound eye– Optic nerves send impulse to the ventral
nerve cord
• Open circulatory system
Molting:• 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
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 Subphyla1. Trilobita:
– (trilobites) • Extinct!
2. Crustacea: – (shrimp, lobster, crayfish, pill bugs,
barnacles)
3. Chelicerata: – (spiders, scorpions, ticks, horseshoe
crab)
4. Myriapoda: – (centipedes, millipedes)
5. Hexapoda: – (insects, springtails)
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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:
– 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 WEWILL BE DISSECTINGON MONDAY – WECORRECT SHOES!
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 tail flips
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:
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
Female
Male
Subphyla Chelicerata & Mryiapoda
Section 36.3
Subphyla Chelicerata
• Examples: spiders, scorpions, mites, horseshoe crab
• Typically 6 pair of appendages– 1st pair = chelicerae (modified pincers or
fangs)
Class Arachnida:• Arachnids include spiders, scorpions,
mites, and ticks• Cephalothorax has 6 pairs of jointed
appendages:– one pair of chelicerae (pincers or fangs)– one pair of pedipalps (aid in holding food
& chewing)– Four pairs of walking legs
Anatomy of a spider:• Chelicerae = modified fangs• 8 simple eyes• Spinnerets = produce silk
Respiratory System• Book lungs = paired sacs with
parallel folds• Tracheae = system of tubes carrying
air directly to tissues– Air in through spiracles in exoskeleton
Some have one or the otherSome have both!
Excretory System• Malpighian tubules = hollow
projections of digestive tract– Collect body fluids & waste– Waste leaves as feces– Helps conserve water in spider
Feeding:• Use webs to capture prey• Inject venom to paralyze animal
• Two harmful spiders to humans = black widow & brown recluse
Reproduction:1. Transfer of sperm to tip of pedipalps2. Sperm place into seminal receptacles
on female3. Male flees to avoid being eaten4. Eggs fertilized as passed out of
female5. Fertilized eggs into silken case6. Female carries eggs or attaches to
plant7. Young spiders hatch in two weeks
Scorpions• Large, pincerlike pedipalps in forward
position• Large stinger on last segment of
abdomen curled over body– Hunt insects & spiders at night– Inject venom into prey video
Mites
• Completely fused cephalothorax & abdomen
• Many are free living, some are parasitic
• Causes mange in dogs
Chiggers• Larvae of harvest mites• Break vertebrae skin, feed on blood• Causes swelling & itching• Can attack humans
Ticks• Many parasitic• Pierce host’s skin, feed on blood• Transmits bacteria & microorganisms
– Lyme disease– Rocky Mountain spotted fever
Subphylum Myriapoda• Myriapods = “many feet”• Examples: millipedes & centipedes• First animals on land• Segmented bodies• Live in damp environments
Class Diplopoda• Examples: millipedes• Round bodies• Appendages:
– Two pair of legs on each segment– Short antennae– Two groups of simple eyes
• When threatened: coil up & secrete noxious fluid with cyanide
• Food source: decaying plant material
Class Chilopoda• Example: Centipedes• Flat bodies• Appendages:
– Long, jointed legs– Poison claws– Long antennae– Two clusters of simple eyes
• Prey = earthworms, insects, NOT humans!
Video