Lecture 1. Arthropods - Its Definition, Groups, Characteristics and Importance of Each Group.pdf

LECTURE 1 ARTHROPODS: Definition, Groups, Characteristics and Importance Marife S. Sayat Faculty, Crop Protection Department BS Agriculture Program Course: CC 411: Beneficial Arthropods a...

LECTURE 1 ARTHROPODS: Definition, Groups, Characteristics and Importance Marife S. Sayat Faculty, Crop Protection Department BS Agriculture Program Course: CC 411: Beneficial Arthropods and Microorganisms  What is Arthropods? The Basics: “Arthro” means joints and “podos” means foot or limb. Arthropods are animals that have jointed legs. The most successful animals on Earth – found in air, land, sea and make up > 75% of known living and fossil species. Appeared 545 millions years ago Course: CC 411: Beneficial Arthropods and Microorganisms Major Groups of Arthropods? Course: CC 411: Beneficial Arthropods and Microorganisms  Subphylum Chelicerata (Class Arachnida) The class arachnid includes spiders, ticks, mites, and scorpions. Key features of Arachnids These animals have: 2 body parts: a head-chest region called the cephalothorax and an abdomen; have several pairs of simple eyes; all have piercing jaw since they are all predator; chelicerae (pointed mouthparts) for biting and poisoning prey; and they do not have wings or antennae. Course: CC 411: Beneficial Arthropods and Microorganisms  Crustaceans include sow bug (also called pill bugs and roly-poly) Subphylum Crustacea shrimp, crayfish, crabs, lobsters, and barnacles. Body Parts of the Crustaceans Course: CC 411: Beneficial Arthropods and Microorganisms  Subphylum Myriapoda This include the centipede with worm like bodies, segmented bodies, one pair of legs on each body segment and one pair of (Class Chilopoda) antennae or none. Body Parts of the Centipede Nocturnal Flattened bodies in cross section Poison claws Course: CC 411: Beneficial Arthropods and Microorganisms  Subphylum Myriapoda This include the millipedes with worm like bodies, segmented bodies, two pairs of legs on each segment, and one pair of (Class Diplopoda) antennae or none. Body Parts of the Millipede 11-100 trunk segments Glands produce Hydrogen Cyanide to repel other animals Round bodies in cross section. Course: CC 411: Beneficial Arthropods and Microorganisms  Subphylum Hexapoda This include insects, mostly live on land, contain 3 pairs of legs and 2 pairs of wings. (Class Insecta) Course: CC 411: Beneficial Arthropods and Microorganisms  Subphylum Hexapoda (Class Insecta) Course: CC 411: Beneficial Arthropods and Microorganisms  The Five most Diverse Insect Orders Course: CC 411: Beneficial Arthropods and Microorganisms  A. Evolution of the Body Parts 1. Jointed, Paired Legs Extremely diverse and modified for different functions. Segmentation allowed for this specialization Course: CC 411: Beneficial Arthropods and Microorganisms  Evolution of the Body Parts 2. Segmentation Evolved from segmented Body Plan usually has three major sections: head, thorax, ancestors. Segments have been abdomen: lost or fused together. HEAD: Has sensory/food manipulation appendages. THORAX: Section with jointed limbs for movement ABDOMEN: Contains vital organs (heart, reproductive organs, digestive organs) Course: CC 411: Beneficial Arthropods and Microorganisms  Evolution of the Body Parts 3. Exoskeleton An outer skeleton found in arthropods. Protects internal muscles, blood vessels, etc. Made of chitin (material made up of modified glucose. Also found in fish scales, cell walls in fungi, squid beaks). Has be thick, heavy and inflexible – Lobsters/crabs or thin, light, and flexible – Grasshopper joints/wings. Course: CC 411: Beneficial Arthropods and Microorganisms  What are some advantages of having an exoskeleton? Full protection Provide structure (muscle can connect) Keeps heat in What are some disadvantages of having an exoskeleton? Heavy – limits size Cannot grow Course: CC 411: Beneficial Arthropods and Microorganisms  Size limitations Largest Aquatic Arthropod: (Japanese Spider Crab Macrocheira kaempferi ) 19 kg (42 pounds) / 5.5 m (18 feet) claw-to-claw Largest Terrestrial Arthropod: Coconut Crab! 4.1 kg (9.0 lb) / 1m (3.3 ft) claw-to-claw Course: CC 411: Beneficial Arthropods and Microorganisms  So how do arthropods grow if their exoskeleton cannot grow? Molting – The process of shedding, or losing, the rigid exoskeleton to let the organism grow. – In arthropods this is known as Ecdysis. Dangers of Molting: 1. Arthropods shed not just their outer body covering, but their eye surfaces, and even the lining of the internal passageways leading to the respiratory system – body parts can get stuck and ripped off. 2. Arthropods can get stuck leaving their old exoskeleton. 3. Arthropods are soft and vulnerable for many weeks while the new exoskeleton hardens. Course: CC 411: Beneficial Arthropods and Microorganisms  4. Bilateral Symmetry The body plan of arthropods can be divided in half making a right and left side that are mirrors of each others. Course: CC 411: Beneficial Arthropods and Microorganisms  B. Feeding and Excretion Arthropods have a very diverse diet due to their extremely high variation of specialized appendages. Course: CC 411: Beneficial Arthropods and Microorganisms  Have a one-way digestive system (runs mouth to anus where undigested food is excreted) Developed system: Contains a foregut (pharynx and esophagus to the stomach), midgut (stomach), and hindgut (colon, anus) – much like humans. Excretion: Terrestrial arthropods have malpighian tubules, which collect waste from the blood and add it to undigested food to be excreted. This saves water since the liquid and cellular waste is added to the digestive waste and is dry Course: CC 411: Beneficial Arthropods and Microorganisms  C. Respiration and Circulation Arthropods possess an open circulatory system consisting of heart and a system of arteries. Open Circulatory System – Blood is pumped by a heart into the body cavities, where tissues are surrounded by the blood. The blood eventually diffuses back in the circulatory system. Course: CC 411: Beneficial Arthropods and Microorganisms  Respiration: 1. Aquatic arthropods possess gills for respiration. They vary in structure and location but are all outgrowths of integument (skin) and are therefore covered by the exoskeleton (which is thin enough that gas exchange can occur). 2. Terrestrial Arthropods use book lungs and trachea as respiratory organs. Trachea – Tiny tubes that run around the body to transport gases. (insects) Spiracles – Opening to the Tracheae from the outside. How gases enter/exit Course: CC 411: Beneficial Arthropods and Microorganisms  Respiration: Book Lungs – Found in arachnids. Gases still enter/exit through spiracles, but gas is exchanged in the blood in the “pages” of the lung area, rather than filling a system of trachea (as in insects). Course: CC 411: Beneficial Arthropods and Microorganisms  D. Reproduction  Typically Sexual Reproduction Note: Some insects (like Stick Insects) can  Separate sexes in arthropods asexually reproduce through parthenogenesis. Growth and development can occur without  Paired sex organs, or gonads, are fertilization – i.e. female lays eggs that become connected directly to ducts that open female without fertilization onto the ventral surface (front/belly)  Internal Fertilization – Sperm is transferred into the female via packets called spermatophores. Course: CC 411: Beneficial Arthropods and Microorganisms  E. Importance of Arthropods Course: CC 411: Beneficial Arthropods and Microorganisms  E. Importance of Arthropods  Ants  Ants are important components of ecosystem and acts as biological indicators.  Acts as decomposers by feeding on organic waste, insects or other dead animals.  Carpenter ants, which make their nests in dead or diseased wood, considerably accelerate the decomposition process of timber.  Ants also use as food. Course: CC 411: Beneficial Arthropods and Microorganisms Course: CC 411: Beneficial Arthropods and Microorganisms Course: CC 411: Beneficial Arthropods and Microorganisms Course: CC 411: Beneficial Arthropods and Microorganisms Course: CC 411: Beneficial Arthropods and Microorganisms  Class Arachnids Course: CC 411: Beneficial Arthropods and Microorganisms  Class Chilopoda and Diploda  Millipede generally have little impact to human economically.  Appears in folklore and traditional medicine around the world.  Have also inspired and played roles in scientific research.  Chilopods are feed on slug, cockroaches and worms. Course: CC 411: Beneficial Arthropods and Microorganisms  Thank you… Course: CC 411: Beneficial Arthropods and Microorganisms References https://blogs.ubc.ca/mrpletsch/2019/03/07/phylum-arthropoda/ https://www.slideshare.net/slideshow/economic-important-of-arthropods/118840538