4/5/15. Myriopods: myriad of legs. Myriapods and Insects CH 14 Subphylum Mandibulata. More on Myriapods:

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Griffin Williams
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Similar to insects in many ways: --Uniramous appendages, trachea, excretory

centipedes --Two distinct body regions: head-trunk -- Millipedes and

invasions of land More on Myriapods: All terrestrial, mostly nocturnal,

is not waxy and allows considerable water loss.

Millipedes: herbivores; fused segments, 2 pr of leg per Centipedes:

Class Entognatha Class Insecta Class Entognatha (two-pronged bristletails)

Wingless - Mouthparts within a special pouch on the head - Without

1 Myriopods: myriad of legs Myriapods and Insects CH 14 Subphylum Mandibulata (continued from Crustacea) Centipedes (Chilopoda) Millipedes (Diplopoda) Similar to insects in many ways: --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: All terrestrial, mostly nocturnal, relegated to moist conditions in forest, moist soils rotting logs The cuticle is not waxy and allows considerable water loss. Also, spiracles of tracheal system are unable to close during respiration Millipedes: herbivores; fused segments, 2 pr of leg per Centipedes: maxillipeds as fangs; night hunters Super Class Hexapoda (6 legged arthropods) Class Entognatha Class Insecta Class Entognatha (two-pronged bristletails) Class Insecta Diplura (questionable affinity) Protura Thysanura (silverfish) - Wingless - Mouthparts within a special pouch on the head - Without metamorphosis - Branched off before the evolution of insects Collembolla - Considered the most primitive true insects - Wingless - Without metamorphosis (springtails) 1

Great diversity of Flying Insects (Pterygota) (black fly) Familiar

(secondarily wingless parasites) Order Diptera (150,000 species) Order

Exotic animals Success of Insects - 35 to 40 orders, 0.75-1.

other animal species combined - # of individuals in most species is

exception is the deep sea) Order Lepidoptera (160,000 species) Meets

reproductive potential - example: termite queen lays 200,000 eggs/day

5 mm in length large numbers for any given food supply Mountain pine

Benefits: as predators of other insects (parasitoid dipterans,

2 Great diversity of Flying Insects (Pterygota) (black fly) Familiar Animals (Japanese beetle) Less Familiar Organisms biting lice (secondarily wingless parasites) Order Diptera (150,000 species) Order Coleoptera (360,000 species) Order Mallophaga (2500 species) Diversity Exotic animals Success of Insects - 35 to 40 orders, 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) Order Lepidoptera (160,000 species) Meets the Order Mantoidea (2,000 species) - great economic importance as pests...vectors of disease Female Anopholes Reasons for Success - High reproductive potential - example: termite queen lays 200,000 eggs/day - Small size: most insects mm in length large numbers for any given food supply Mountain pine beetles Malaria, plague, typhoid and yellow fever. Benefits: as predators of other insects (parasitoid dipterans, hymenopterans) as producers honeybees, silkworms as pollinators of plants - Metamorphosis: larva or nymph and the adult stage do not compete for food - Wings and Flight: gain in dispersal, escape predation, exploit resources - Exoskeleton 2

Characteristics Uniramous appendages - Four cephalic appendages: antenna, mandibles 1st maxilla, labium (fused 2nd maxilla)

system of spiracles and trachea - 3 Tagma: Head, thorax, abdomen; thorax as 3 segments, pro, meso, metathorax - 1 pair of

structures; - Compared to crustacea, Abdominal appendages have been lost System of tubes that deliver oxygen directly to

! Air taken into spiracles (by action of abdominal muscles) into tracheal tubes then to tracheoles and finally to

Respiration is independent of blood circulation Trachea Tracheoles Excretory and osmoregulatory Malpighian tubules Hollow

3 Characteristics Uniramous appendages - 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 - 3 Tagma: Head, thorax, abdomen; thorax as 3 segments, pro, meso, metathorax - 1 pair of legs per thoracic segment; wings in meso and metathorax (1 pair on each) - Abdomen usually with 11 segments; repro. structures; - Compared to crustacea, Abdominal appendages have been lost System of tubes that deliver oxygen directly to flight muscles and other cells!! Air taken into spiracles (by action of abdominal muscles) into tracheal tubes then to tracheoles and finally to individual cells. Respiration is independent of blood circulation Trachea Tracheoles Excretory and osmoregulatory Malpighian tubules Hollow tubes between hemocoel, (where waste is collected) and the gut where waste is removed. Acidic Highly alkaline Spiracle Distally K Urate in dissolved form enters the tubule. Muscle fibers As ph drops proximally, uric acid is formed, water and potassium is reabsorbed. Waste is in the form of a crystal, uric acid and water is thus conserved. 3

Reproduction Insects are dioecious (separate sexes) Sperm transferred in a specialized container (spermatophore) Fertilized Eggs Require protection: oviposition in water or in other insects or

begin to develop in sequence resulting in formation of head, thorax and abdominal region http://www.cals.ncsu.edu/course/ent425/ tutorial/embryogenesis.

4 Reproduction Insects are dioecious (separate sexes) Sperm transferred in a specialized container (spermatophore) Fertilized Eggs Require protection: oviposition in water or in other insects or in plant tissues 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 tutorial/embryogenesis.html Types of Post-Embryonic Development (metamorphosis) 1. Ametabolous: no larva or nymph wingless primitive insects such as springtails and collembolans Miniature adult; without any major change in form Examples : bristletails silverfish 4

2. Hemimetabolous Dragonfly naiad mayfly Immature aquatic stage, or

Wing pads can be seen on advanced instars Common orders : Ephemeroptera

forms such as grasshopper. The immature stage is the nymph 4.

-- Called a larva; it must pupate and undergo a profound metamorphosis

pupa mosquito larva -- The pupa in beetles is called a grub, in flies a

5 2. Hemimetabolous Dragonfly naiad mayfly 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) Odonata (Dragon Flies, damsel flies), Plecoptera (stone flies) Dragonfly emerging 3. Paurometabolous: similar to hemimetabolous Usually involves terrestrial forms such as grasshopper. The immature stage is the nymph 4. Holometabolous -- Young is different from adult in nearly every respect. -- Called a larva; it must pupate and undergo a profound metamorphosis to the adult stage or imago. pupa mosquito larva -- The pupa in beetles is called a grub, in flies a maggot, crysallis for butterflies Why Imago? Apparition? Imaginal Discs in Holometabolous Development Imaginal discs have not been found in animals with incomplete metamorphosis 5

Order Diplura (silverfish) Apterygotes Exopterygotes Endopterygotes

hormonal control of metamorphosis - PTTH produced by cells in the

the aorta) - Increasing PTTH levels in the blood induce the

modified by juvenile hormone (JH) from the corpora allata; JH

hormone (PTTH) --Truly Social Insects (Eusocial) include: -- all

-- Colonies are made up of Castes in all 3 groups: bees: workers (all

made up of Castes: ants: workers, soldiers, queen, males queens

6 Order Diplura (silverfish) Apterygotes Exopterygotes Endopterygotes No longer used in Taxonomy as they were paraphyletic taxa Insect hormonal control of metamorphosis - PTTH produced by cells in the brain enters the corpora cardiaca (neurohemal organs associated with the aorta) - Increasing PTTH levels in the blood induce the Prothoracic gland to produce ecdysone - Action of ecdysone is modified by juvenile hormone (JH) from the corpora allata; JH suppresses expression of adult genes JH in red Prothoracicotrophic hormone (PTTH) --Truly Social Insects (Eusocial) include: -- all ~9500 ant species -- honeybees, a few wasps Hymenoptera -- termites -- Colonies are made up of Castes in all 3 groups: bees: workers (all sterile females), queen, drones - What triggers cessation of JH production? Genetics. --Truly Social Insects (Eusocial) include: -- all ~9500 ant species -- honeybees, a few wasps Hymenoptera -- termites -- Colonies are made up of Castes: ants: workers, soldiers, queen, males queens control sex of offspring by pheromones worker male Flying female soldier Waggle dance of the honeybee 6

7 Inclusive fitness: Haplodiploidy: 1 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 7

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