The Arthropods Zoology: Part 2

Transcription

1 Biology Chapter 15 The Arthropods Zoology: Part 2 14A Introduction to Arthropods The Malacostracans arthropods - invertebrates with jointed appendages Greek: arthro - "jointed" & pod - "feet" Make up more than 3/4 of all species in the animal kingdom over 891,000 species includes: insects, spiders, crayfish, centipedes, milllipedes range in size: from giant king crab (10 ft. leg spans) to microscopic mites and tiny marine crustaceans found in all climates found in every conceivable environment: 20,000 ft. high in the Himalayas at the surface of the world's oceans deep in the frozen tundra of the Arctic on the burning sands of the deserts burrowed underground Common Characteristics: 1. Exoskeleton a. composed of chitin (ki tin) chemically similar to cellulose or starch gives the body covering toughness & flexibility b. also composed of mineral salts gives it hardness c. advantages disadvantages protect support weight limits size of animal obstacle to body growth must be shed periodically (vulnerable) 2. jointed appendages 3. segmented body three major body segments: a. head (head and thorax are often united b. thorax into a cephalothorax) c. abdomen 4. open circulatory system (with a dorsal heart) not as efficient as the closed circulatory system because it depends in part on gravity for its proper operation (is one of the reasons most insects try to right themselves quickly if they're turned over) 5. ventral nervous system Class Malacostraca lobsters, crabs, crayfish, brine shrimp, sow bugs, barnacles range in size: from the tiny sow bugs and minute water fleas

2 10 th Biology Chapter 15 / Arthropods 2 to lobsters and giant crabs largest species of lobster - American lobster (may weigh over 20 lbs. and reach a body length of 20") giant spider crab of Japan - measures up to 12' long crayfish "crawfish" "crawdads" They inhabit lime-containing lakes, ponds, rivers, & streams. They are on every continent except Africa & Antarctica. Movement: swimmerets and tail are used for swimming walk forward slowly using 4 pairs of walking legs can shoot backward rapidly in the water by contracting powerful abdominal muscles (25 feet in less than 1 sec. which equals 17 mph) Support: exoskeleton Protection: by body covering - hard exoskeleton cephalothorax is covered by the carapace abdomen composed of 6 segments and covered by plates has a number of paired appendages: 1. antennules (shorter feelers) - balance, taste & touch 2. antennas (longer feelers) - organs of touch and taste 3. mandibles - "true jaws" - pulverizing the food 4. maxillae - "smaller jaws" - aids in chewing (chews from side to side rather than up and down) 5. maxillipeds - "jaw feet" - holds food in place 6. chelipeds (KEE luh pedz) - pincers 7. walking legs - for locomotion 8. swimmerets - swimming and reproduction 9. uropods - (flipper) for swimming 10. telson - (the last abdominal segment) for swimming Nutrition: mouth esophagus stomach (has tooth-like structures made of chitin; the gastric mill) finely ground particles filtered into the digestive gland (chemical digestion and absorption) undigested food intestine anus

3 10 th Biology Chapter 15 / Arthropods 3 Respiration: gills gills are covered by the lateral portions of the carapace (God has so designed the crayfish's gills that they are protected by its carapace, which extends over them and forms a chamber. Because this chamber retains water moisture, a crayfish can survive out of water for a short period of time. They can "hold their water" on land like you "hold your breath" in the water.) Circulation: open circulatory system heart pumps colorless blood into 7 large arteries which bathe the major organs blood collects in large sinuses (some small crustaceans have no heart - their body movements circulate the blood throughout their body) Excretion: green glands lie in front of the stomach and open to the outside near the base of the antennae function like kidneys they also store lime and make it available to the crayfish when the animal is ready to molt Response: nervous system - brain nerves several sensory structures: 1. antennae - smell and touch 2. compound eyes on stalks 3. small sensory bristles on appendages for touch 4. statocysts - at the base of antennules for balance 5. antennules - taste and touch Reproduction: only sexually does regenerate for repair Male transfers sperm to the body of the female with his swimmerets. She stores the sperm until she lays her eggs in the spring. Eggs are fertilized as they pass out of the oviduct. Egg clusters remain attached to swimmerets until they hatch in 5-6 weeks. Release young crayfish closely resembling their parents. (Young lobsters differ greatly from an adult in appearance and passes through several larval stages.)

4 10 th Biology Chapter 15 / Arthropods 4 Class Arachnida spiders, daddy longlegs, mites, ticks, scorpions, & horseshoe crabs range in size: from microscopic mite to a giant South American tarantula (5" long body and leg span 8-10") NOT INSECTS spiders insects 2 distinct body regions 3 distinct body regions (cephalothorax & abdomen) (head, thorax, abdomen) 4 pairs of legs 3 pairs of legs no antennae antennae only simple eyes (4 pairs) both single & compound eyes no wings usually 1 or 2 pairs of wings respiration by book lungs & no book lungs, just tracheae tracheae Spiders Silk: not all spiders produce silk spinnerets - the organs which the spider uses to spin silk uses of silk: 1. primary is to capture food web - is made of two kinds of silk (sticky & nonsticky) different kinds of webs irregular sheet funnel orb 2. build a nest for itself 3. build cocoons for its eggs 4. guide to find its way home 5. ballooning Nutrition: The spider's mouth and stomach are designed for sucking liquids. A spider cannot chew. bites food & immobilizes it with its venom injects digestive juices into its prey sucks up the partially digested liquid through its muscular pharynx liquid is transported to the digestive gland in the abdomen where it is stored and used Respiration: uses book lungs some spiders have trachea that transport 0 2 (spiracles)

5 10 th Biology Chapter 15 / Arthropods 5 The book lungs are located in tiny cavities in the spider's abdomen; tarantulas have two pairs of book lungs, while most other spiders have only a single pair. Each book lung is made up of at least 15 extremely thin, flat folds of tissue forming parallel air pockets that are arranged like the pages of a book. Air enters the cavities where the book lungs are located through slits in each side of the body wall near the front of the spider's abdomen. As air circulates between the sheets of the book lungs, an exchange of gases takes place and 0 2 passes into a blood-filled chamber. Reproduction: female is usually larger than the male The male places his sperm in a web sac which he stores in cavities in his pedipalps. He transfers the sperm sac to seminal receptacles on the ventral surface of the female's abdomen. This act is usually preceded by some courtship ritual. Afterwards, some female spiders devour the smaller male. As females lay eggs, they are fertilized by stored sperm and usually placed within a silk cocoon, attached to the female's body or the web. Depending upon the size of the species, the female may lay as few as 1 egg or an many as 2,000 eggs. In some species, the female dies after making the egg sac. in other species, she remains with the eggs until they hatch. Tiny spiderlings hatch inside the silken cocoon and remain inside until the arrival of warm weather. As soon as they leave the egg sac, the spiderlings begin spinning draglines. Many spiderlings climb to the top of a tall object, such as a fence post, tilt their spinnerets toward the wind, and balloon their way over long distances - sometimes even 100's of miles. Life span: many species live only about 1 year others, such as the large wolf spider, live for several years Tarantulas are the longest-lived of all spiders; certain species live over 20 years. Six North American spiders whose bites are harmful to man: (1) Black widow male is smaller and is harmless female: shiny black body, red "hourglass" on its underside "widow" implies she eats the male after mating (not true)

6 10 th Biology Chapter 15 / Arthropods 6 mortality rate for black widow poisoning in man is approximately 5% Read page 415 (2) Brown recluse small brown spider with a dark, violin-shaped marking on its cephalothorax may be fatal (3) Brown widow (4) Red-legged widow (5) Sack spider (6) Varied widow Other Arachnids: Scorpion: stinging arachnids long, segmented abdomen which ends in a venomous stinger (painful but not usually fatal) Mites & Ticks: dangerous arachnids transmit diseases (man - Rocky Mt. spotted fever & Lyme disease; cattle - Texas fever) Harvestman (daddy longlegs): long-legged arachnids Chiggers (red bugs): larval stage of mites Class Chilopoda (kye LAHP uh duh) Class Diplopoda (duh PLAHP centipedes millipedes uh duh) flattened body rounded body a pair of long, jointed antennae shorter antennae poisonous harmless single pair of legs attached to 2 pairs of legs per segment each body segment fast movers rather slow creatures do not necessarily have 100 feet, anywhere from legs may be Class Insecta The most varied and numerous of all God's living creatures. Makes up more than 70% of all animal species. Entomologists - scientists who study insects Entomology - The study of insects Life Cycle of Insects metamorphosis- a change in shape or form that an animal undergoes in it's development from egg to adult incomplete metamorphosisstages: egg -> nymph -> adult

7 10 th Biology Chapter 15 / Arthropods 7 nymph- an immature form of the insect that looks much like the adult but has different body proportions & lacks wings Examples: dragonflies, mayflies, cricket, grasshoppers, locusts, roaches, termites complete metamorphosisstages: egg -> larva -> pupa -> adult used by almost 90% of the insects larva- a wormlike eating and growing stage beetles- grubs flies- maggots butterflies & moths- caterpillars mosquitoes- wigglers pupa- resting stage; larva forms a cocoon or chrysalis. The insect stops feeding & rests while its body experiences near-miraculous changes which transform it into the adult insect. The Grasshopper: A Typical Insect Movement: jointed legs and wings 1st two pairs of legs - for crawling, clinging & climbing (fore) front wings - flying 3rd pair of legs & hind wings - jumping Body Covering: exoskeleton Support: exoskeleton Nutrition: mandibles - chew plant material maxillae - bring chewed food to the mouth salivary glands - lubricate food passing into the esophagus crop - stores food gizzard - grinds foods with chitinous plates stomach - absorbs particles digested by juices from the gastric ceca ` intestine - passes unabsorbed particles to the rectum & out anus Respiration: tracheae - complex network of tubules, bring air directly to the cells spiracles - opening; air goes in and out with abdominal contractions Circulation: open circulatory system

8 10 th Biology Chapter 15 / Arthropods 8 dorsal heart Excretion: malpighian tubules - absorb wastes from blood flowing through the abdomen pour wastes into digestive tract for elimination Response: brain ventral nerve cord sensory organs: antennas (smell) receptors on the mouth parts (taste) tactile hairs (touch) *compound & simple eyes **tympanum (hearing *Three simple eyes are located respectively above the base of each antenna and in the groove between them. These structures can detect only light and shadow. Projecting from the front and sides of the grasshopper's head is a pair of large compound eyes. Each of these eyes is composed of 100's of 6-sided lenses that are sensitive to different colors. They enable the creature to see in several directions at the same time. **Tympanums are found almost anywhere on the body of an insect except the head; these membranes are located on the front legs of a cricket. Most insects do not have tympanums but hear by means of hairs located on their antennae or other parts of their body. Reproduction: no asexual ovaries/testes (are in the abdomen) separate sexes seminal receptacle (female's stores sperm) ovipositor - female deposits fertilized eggs through her ovipositor eggs are laid in the fall and hatch in the spring ptera - a Greek word for "wing" Major Orders of Insects Coleoptera (ko lee AHP tur uh) means "sheath wings" beetles, firefly, June bug, ladybug Diptera (DIP tur uh) means "two wings"

9 10 th Biology Chapter 15 / Arthropods 9 flies, mosquitoes, gnats Two of the plagues on Egypt involved dipterans. (gnats and flies) The Hebrew word translated "lice" literally means "gnats". Read pages It is the female mosquito that "bites;" she is in search of animal or human blood, which she needs for the proper development of the eggs within her body. Hymenoptera (HYE muh NAHP tur uh) means "membrane wings" social insects: ants, bees, wasps three classes seen in social insects (1) Queens - reproductive females that maintain population lays all the eggs for the colony (in 1 day she may lay up to 3,000 eggs) unfertilized eggs develop into drones fertilized eggs develop into queens or workers Queens have long lives (frequently live 5 or 6 years and sometimes 10 years) Read page 424 (2) Drones - haploid, reproductive males that fertilize the queen (It appears that their only function is to fly with the queen so that one of the drones can mate with her. The drone that successfully mates with the queen soon dies, and the other drones are allowed to return to the colony. In the fall, all drones are stung to death by workers (which also die). (3) Workers - non-egg laying females (immature females) jobs: tend the queen care for eggs feed larvas search for food build and maintain the hive stinger: when a bee stings you the bee then rips off its last abdominal segment, leaving it to pump more venom when a worker uses her stinger, the stinger is ripped from the worker's body along with certain internal organs, and the worker bee dies honey: 240 million lbs. of honey are harvested each year each pound represents 20,000 bee trips from flowers to hive Lepidoptera (Lep uh DAHP tur uh) means "scale wings" butterflies and moths

10 10 th Biology Chapter 15 / Arthropods 10 butterfly moth lighter body heavier body smooth outer covering hairy outer covering smooth, rodlike antennae feathery antennae holds its wings vertically holds its wings horizontally when at rest pupa rests in a hard chrysalis pupa rests in a soft cocoon active during the day fly about at night extremely beneficial - pollination usually harmful - devour food and clothing Orthoptera (or thop ter uh) means "straight wings" crickets, grasshoppers, locusts, roaches Odonata (O do na ta) means "toothed wings" dragonflies and damselflies capable of speeds up to 60 mph (because they cannot walk, dragonflies do almost everything while flying, including mating and catching and eating insect prey in mid-air) Five factors which help in the survival of insects: (1) body color and shape - camouflage (2) weapons - stingers piercing mouth parts chemicals that produce irritating odors and gases (3) forming large colonies - provides safety and shelter (4) reproducing in great numbers (5) behavior - fly to escape play dead fight back Methods of control (pages ): 1. Quarantine Control - materials are carefully inspected before being permitted to enter the country to be sure that they do not carry harmful insects and organisms 2. Chemical Control - insecticides are used to poison insects 3. Agricultural Control - involves rotating crops, rescheduling the times of planting and harvesting, and other agricultural techniques to minimize insect damage to particular crops 4. Environmental Control - if the life cycle of an insect is known, changes can be made to prevent its development; destruction of places where insects breed 5. Biological Control - predators and parasites are introduced