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Myriopods: “myriad of legs”
Centipedes Millipedes Myriapods and (Chilopoda) (Diplopoda) Insects CH 14 Subphylum Mandibulata Similar to insects in many ways: (continued from Crustacea) --Uniramous appendages, trachea, excretory system --Antenna, mandibles, 1st &2nd maxilla, maxilliped as poison gland in centipedes --Two distinct body regions: head-trunk -- Millipedes and centipedes found in late Cambrian marine fauna; considered two independent invasions of land
More on Myriapods: Super Class Hexapoda (6 legged arthropods) Class Entognatha All terrestrial, mostly nocturnal, relegated to moist conditions in forest, moist soils rotting logs Class Insecta
The cuticle is not waxy and allows considerable water A. Introduction loss. Also, spiracles of tracheal system are unable to B. Basic characteristics close during respiration What distinguishes insects? C. Insect Reprod. & Early Development Millipedes: herbivores; fused segments, 2 pr of leg per E. Metamorphosis Centipedes: maxillipeds as fangs; night hunters F. Exoptergygota and Endopterygota G. Hormonal Control of Metamorphosis H. Insect Societies
Class Entognatha (two-pronged bristletails) Class Insecta
Diplura (questionable affinity)
Thysanura (silverfish) Protura
Collembolla -Wingless - Considered the most primitive true insects - Mouthparts within a special pouch on the head - Wingless -Without metamorphosis - Without metamorphosis - Branched off before the evolution of insects
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Great diversity of Flying Insects (Pterygota) Less Familiar Organisms biting lice (black fly) (Japanese beetle) (secondarily Familiar wingless parasites) Animals
Order Mallophaga (2500 species) Order Coleoptera Order Diptera (360,000 species) (150,000 species)
Diversity Exotic animals Success of Insects - 35 to 40 orders, 0.75 - 1.5 million species 2-3 thousand described every year; outnumber all other animal species combined
-# of individuals in most species is high e.g. locust
- found in practically every major habitat (one exception is the deep sea)
- great economic importance Order Lepidoptera Meets the Order Mantoidea (160,000 species) (2,000 species)
Reasons for Success …as pests ...Vectors of disease Female Anopholes -High reproductive potential
-example: termite queen lays 200,000 eggs/day
- Small size: most insects 1-2.5 mm in length large numbers for any given food supply
Mountain pine beetles Malaria, plague, typhoid and - Metamorphosis: larva or nymph and the adult yellow fever……. stage do not compete for food Benefits: • as predators of other insects -Wings and Flight: gain in dispersal, escape predation, (parasitoid dipterans, hymenopterans) exploit resources • as producers…honeybees, silkworms - Exoskeleton • as pollinators of plants
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Class Insecta = Hexapoda Characteristics
A. Introduction B. Basic characteristics What distinguishes insects? C. Insect Reprod. & Early Development E. Metamorphosis Uniramous F. Exoptergygota and Endopterygota appendages G. Hormonal Control of Metamorphosis
H. Insect Societies - Four cephalic appendages: antenna, mandibles 1st maxilla, labium (fused 2nd maxilla)
- Most appendages are uniramous (but evolved from polyramous, possibly even biramous types)
Insect Body Plan Respiratory system of spiracles and trachea
• System of tubes that deliver oxygen directly to - 3 Tagma: Head, thorax, abdomen; flight muscles and other cells!! thorax as 3 segments, pro, meso, metathorax • Air taken into spiracles (by action of abdominal - 1 pair of legs per thoracic segment; wings in meso and muscles) into tracheal tubes then to tracheoles and metathorax (1 pair on each) finally to individual cells. • - Abdomen usually with 11 segments; repro. structures; Respiration is independent of blood circulation - Compared to crustacea, Abdominal appendages have been lost
Excretory and osmoregulatory Malpighian tubules Tracheoles Hollow tubes between Highly Trachea hemocoel, (where waste is Acidic alkaline collected) and the gut where waste is removed.
Spiracle Distally K Urate in dissolved form enters the tubule.
As pH drops proximally, uric acid is formed, water Muscle and potassium is reabsorbed.
fibers Waste is in the form of a crystal, uric acid and water is thus conserved.
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Class Insecta = Hexapoda Reproduction •Insects are dioecious (separate sexes) A. Introduction B. Basic characteristics •Sperm transferred in a specialized container (spermatophore) What distinguishes insects? •Fertilized Eggs Require protection: C. Insect Reprod. & Early Development oviposition in water E. Metamorphosis or in other insects F. Exoptergygota and Endopterygota or in plant tissues G. Hormonal Control of Metamorphosis
H. Insect Societies
Reproduction and Development
- - After fertilization, nuclei duplicate and migrate to the perimeter of the embryo, , cellularize and form a blastula
Link to Video - Segments begin to develop in sequence resulting in formation of head, thorax and abdominal region
http://www.cals.ncsu.edu/course/ent425/ tutorial/embryogenesis.html
Class Insecta = Hexapoda Types of Post-Embryonic Development (metamorphosis) A. Introduction 1. Ametabolous: no larva or nymph Examples : B. Basic characteristics wingless primitive insects bristletails What distinguishes insects? such as springtails and collembolans silverfish C. Insect Reprod. & Early Development Miniature adult; without any major change in form E. Metamorphosis F. Exoptergygota and Endopterygota G. Hormonal Control of Metamorphosis H. Insect Societies
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2. Hemimetabolous mayfly Dragonfly naiad
•Immature aquatic stage, or naiad; similar to the adult but the wings are not fully developed. •Wing pads can be seen on advanced instars •Common orders : Ephemeroptera (mayflies) Dragonfly emerging Odonata (Dragon Flies, damsel flies), Plecoptera (stone flies)
4. Holometabolous 3. Paurometabolous: similar to hemimetabolous mosquito Usually involves terrestrial forms -- Young is different from adult such as grasshopper. in nearly every respect. The immature stage is the nymph -- Called a larva; it must pupate pupa larva and undergo a profound metamorphosis to the adult stage or imago.
-- The pupa in beetles is called a grub, in flies a maggot, crysallis for butterflies
Why Imago? “Apparition” ?
Imaginal Discs in Holometabolous Development Class Insecta = Hexapoda
A. Introduction B. Basic characteristics What distinguishes insects? C. Insect Reprod. & Early Development E. Metamorphosis F. Exoptergygota and Endopterygota G. Hormonal Control of Metamorphosis Imaginal discs have not been H. Insect Societies found in animals with incomplete metamorphosis
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Class Insecta = Hexapoda
A. Introduction Order Diplura Apterygotes B. Basic characteristics (silverfish) What distinguishes insects? Exopterygotes C. Insect Reprod. & Early Development Endopterygotes E. Metamorphosis F. Exoptergygota and Endopterygota No longer used in G. Hormonal Control of Metamorphosis H. Insect Societies Taxonomy as they were paraphyletic taxa
Insect hormonal control of metamorphosis Insect Social Systems
- PTTH produced by cells in the brain JH in red --Truly Social Insects (Eusocial) include: enters the corpora cardiaca (neurohemal Prothoracicotrophic organs associated with the aorta) hormone (PTTH) -- all ~9500 ant species -- honeybees, a few wasps Hymenoptera -Increasing PTTH levels in the blood induce the Prothoracic gland to produce -- termites ecdysone -- Colonies are made up of Castes in all 3 groups: -Action of ecdysone is modified by juvenile hormone (JH) from the corpora bees: workers (all sterile females), queen, drones allata; JH suppresses expression of “adult genes”
- What triggers cessation of JH production? Genetics.
Insect Social Systems Insect Social Systems --Truly Social Insects (Eusocial) include: male -- all ~9500 ant species -- honeybees, a few wasps Hymenoptera -- termites
-- Colonies are made up of Castes: worker ants: workers, soldiers, queen, males Flying female queens control sex of offspring by pheromones soldier
Waggle dance of the honeybee
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Insect Social Systems Inclusive fitness:
Haplodiploidy:
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Males are 1N, females 2N There is an asymmetrical degree of relationship Mothers are 1/2 related to daughters Sisters are 3/4 related to each other
But termites, snapping shrimp also eusocial yet not haplodiploid so other adaptive values may exist
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