Understanding Arthropods: Anatomy, Classification, and Functions

1. Arthropod Unit: Learning Target Objectives (I can…): Identify body systems and their components, body structures (anatomy) and functions (physiology), and label arthropod appendages. Distinguish between types (classes, etc) of arthropods and the 4 subphyla based on arthropod characteristics and give examples of each. Determine the type of symmetry seen in arthropods. Evaluate the role of arthropods in disease/illness transmission and relate the arthropod to the disease it carries. Vocabulary: Arthropod * invertebrate * appendages * exoskeleton * chitin * ventral nervous system * open & closed circulatory systems * molt * isopods * cephalothorax * carapace * antennules * antennae * mandibles * maxillae * maxillipeds * chelipeds * walking legs * compound eyes * swimmerets * uropods * telson * chitinous teeth * digestive glands * green glands * gills * statocyst * cephalothorax * chelicera * pedipalps * book lungs * spiracles * trachea * malpighian tubules * spinnerets * herbivores

2. Vocabulary: Arthropod * invertebrate * appendages * exoskeleton * chitin * ventral nervous system * open & closed circulatory systems * molt * isopods * cephalothorax * carapace * antennules * antennae * mandibles * maxillae * maxillipeds * chelipeds * walking legs * compound eyes * swimmerets * uropods * telson * chitinous teeth * digestive glands * green glands * gills * statocyst * cephalothorax * chelicera * pedipalps * book lungs * spiracles * trachea * malpighian tubules * spinnerets * herbivores

3. Phylum Arthropoda Kingdom: Animalia Subkingdom: Invertebrata (no backbone) Phylum: Arthropoda (jointed feet) Characteristics * - jointed appendages (extensions of the body, including legs, arms, antennae) - segmented body (like annelids), segments are often fused (joined) *- exoskeleton (external or “outside” skeleton) provides protection & support. It’s secreted by the epidermis. Made of chitin. - ventral nervous system (lower side of body) with brain and sense organs - open circulatory system – blood flows out of vessels into cavities - digestive system (complete) with mouth & anus - coelom - sensory receptors (for sight, hearing, touch & chemicals)

4. Because the exoskeleton can’t grow, as an arthropod gets bigger, it must molt (shed its skeleton & grow a new one). This leaves it unprotected from predators & unprotected from drying out. Advantages of ExoskeletonDisadvantages of Exoskeleton Protective, like armor Heavy Prevents drying out Doesn’t grow Jointed for mobility Susceptible during molting Arthropods make up 75% of ALL animals!! 4 Subphyla of Arthropods: (Subphylum Trilobita are all extinct, once lived in Wis. ocean waters!)

6. 4 Subphyla of Arthropods: 1) Subphylim Crustacea: Includes: crayfish, lobsters, pill bugs, sowbugs, water fleas, barnacles - most are aquatic except for the isopods (pill bugs and sow bugs) - chewing mouth parts - 2 pair of antennae/antennules - 5 or more pairs of legs Ex: Crayfish: - 2 body sections 1) Cephalothorax (head & chest combination) – 13 segments covered by a hard carapace (part of exoskeleton covering cephalothorax) Includes these appendages: a) antennules for touch, taste, & balance b) antennae – longer than antennules, used for touch & taste c) mandibles – crush food by moving side to side d) maxillae (2 pairs) hold on to food e) maxillipeds (3 pairs) for touch, taste, & food handling f) chelipeds – large front legs with claws used in defense & to catch food g) walking legs (4 pairs) h) compound eye on stalks

8. 2) abdomen - 7 segments Includes these appendages: a) swimmerets – used in swimming. First pair of swimmerets are used by males to transfer sperm. Last three pairs on females are used to hold eggs. (Sex differences: males have larger 1st pair of swimmerets than females. Males have opening at base of 4th walking leg. Females have opening at base of 3rd walking leg.) b) uropods (6th segment) Together these can flip ventrally to quickly c) telson (7th segment) propel the crayfish backward. Internal (inside) Structures: Digestive System: Maxillae & maxillipeds tear up food. Mandibles chew up pieces. Food moves through mouth and esophagus. Chitinous teeth in the stomach grind food (insect larva, worms, dead organisms) digestive glands absorb food Undigested food passes through intestines and out anus.

9. Excretory System: Green glands in the head region remove liquid wastes from blood and then excrete them through an opening at the base of the ANTENNAE! Circulatory System: - open system - dorsal sinus (cavity)  heart  vessels  body cavity (soaks organs in blood)  large ventral sinus  vessels  gills (for oxygenation)  dorsal sinus - Blood is colorless when oxygen deprived & blue-green when oxygenated. This is because their blood is copper based. (No iron) Respiratory System: Gills - for CO2 release and O2 uptake - located on each walking leg. Movement of 2nd maxillae & walking legs forces water over gills.

11. Nervous System & Senses: - brain located behind the eyes - ventral nerve cord runs from brain to tail - nerves behind the compound eye carry images of light & movement - statocysts contain grains of calcium carbonate & hairs that are used in balance (much like our ears). The grains are lost & replaced at each molt. (Any lost appendages such as walking legs are regrown at the next molt.) Reproduction: Male transfers sperm to female in Fall. Sperm is stored until Spring when it fertilizes eggs. Eggs are attached to the last 3 pairs of swimmerets where they hatch 4-6 weeks later. The young cling on for several weeks after that. Uses for Chitin: Varnish, seed coating (prevents fungus growth), protective contact lens for injured eyes, artificial skin, dissolving sutures (stitches), electrical filters, “plastic” wrap

12. 2) Subphylum Chelicerata: - have no antennae - pincer-like mouthparts (chelicera) Class Arachnida Ex: spiders, scorpions, mites, ticks - have a cephalothorax & an abdomen (these are fused in mites and ticks) - appendages may include: a) chelicera – fang-like structures used to pierce prey. These may have poison glands used to paralyze prey. b) pedipalps – sensitive to chemicals & touch, hold food, used by male in reproduction for sperm transfer c) walking legs (4 pairs) (insects only have 3 pairs) All of the above appendages are found on the cephalothorax.

14. Respiration: Book lungs for gas exchange (located in abdomen) with blood vessels. Spiracles are openings in the cuticle (of thorax region) that allow air into the body. Tracheae carry air directly to the tissues Excretory System: Malpighian tubules carry liquid wastes to the intestines. Liquid wastes are then either reabsorbed if needed or discharged with solid wastes out the anus Reproduction: Male transfers sperm (using his pedipalps) to the female’s seminal receptacle. Sperm is stored. Eggs are fertilized as they pass through the genital pore. The first spider molt occurs while still in the eggs! * Scorpions have LIVE births – they’re the only arthropod that does this.

15. Anatomy of a Spider Pumpingstomach Heart Brain Intestine Ovary Eyes Malpighiantubules Poisongland Anus Pedipalp Spiracle Fanglikechelicera Spinnerets Bases ofwalking legs Silk glands Airflow Section 28-2 Cephalothorax Abdomen Book Lung

16. Other Information: Spiders have 8 simple eyes. Spinnerets, at the end of the abdomen, are used to make silk-like thread for webs, etc. Health Ticks carry Rocky Mountain Spotted Fever and Lyme disease Spider mites are a major plant problem. Dog mites cause mange People have 2 types of mites on their face that have been linked to possibly introducing acne to susceptible people. Chigger mites do not burrow under the skin but cause a reaction that can leave quite a tall bump – by this time the mite has dropped off.

17. Brown Recluse Spider Bite

18. 3) Subphylum Uniramia - have antennae - mandibles present Includes: millipedes, centipedes, and insects Myriapods – “many feet” a) Class Diplopoda: (“diplo” = 2; “poda” = feet) Ex: Millipedes – “thousand feet” - 2 pairs of legs on each segment except the last 2 (and 1st four segments have only 1 pair) but don’t have even close to 1000 feet. - legs good for burrowing When threatened, millipedes coil up and release cyanide gas - they are herbivores (eat plants) and decaying material (detritivores) - rounded body Do they have antennae?

19. b) Class Chilopoda: Centipedes – “100 feet” - flattened body - 1 pair of legs per segment (except for 1st segment and last 2 segments) - they have between 15 and 175 pairs of legs - they are predators that eat earthworms and insects - 1st segment has claw-like appendages that inject venom into prey Do they have antennae? c) Class Insecta

21. Arthropoda means 4 Subphyla All are extinct Have 5 or more Have 4 pair Have many legs pairs of legs of legs Exs:

22. Crayfish Anatomy Body Regions Abdomen appendages For touch/taste “legs” mouth parts hold for swimming eggs/sperm Large claws 4 pairs