Lecture 7+8 quiz (end of 7)

Mandibulata

• mouth parts → mandibles

  • from segmented appendages (3rd/4th head segments)

• antennae

  • chemosensory

  • homologous to chelicerates

  • help mate and manipulate food

• organisms

  • centipedes, millipedes, “crustaceans” and insects

Myriapoda

• organisms

  • centipedes and millipedes

• swinging tentorium (internal head structure)

  • movable, provides attachment site for muscles/mandibles/other mouth parts

• Ultrabithorax gene

  • Hox gene that determines the gradients in body

Myriapoda clades

1. diplopoda - millipedes

   1. head (8 embryonic segments fused together) + trunk

   2. 1 segment is 2 fused together

   3. herbivorous

2. chilopoda - centipedes

   1. head + trunk

   2. predatory → long legs for fast running

Pancrustacea (Crustacea and Insecta)

• neuroanatomical features → for smell

• strong molecular support

• 4 crystalline cone cells in ommatidia of compound eye

  • dense, shape and number important for vision

  • light has to hit right on

  • hexagonal shape → modification of simple eye

  • ommatidium → single unit

Crustacea

• organisms

  • lobsters, crayfish, crab, krill, shrimp, isopods, barnacles

• 2 pairs of antennae

• variable number of legs

• compound eyes

• gills

• many with calcium deposition in exoskeleton

• cephalothorax → sensory structures & walking legs

• abdomen → other appendages (not for walking)

• carapace: the sideward extension of the cephalothorax going down around the top part

Insecta

• 3 body regions

  • head → sensory material, antennae, eyes, mouth

  • thorax → 3 segments each with pairs of legs

  • abdomen → visceral function, reproductive organs, excretory

• most with wings (Pterygota)

  • leg sclerites → expand and attached to tergum and sternum (whole thing is a solid box → distortion = flight

  • tergum → dorsal plate

  • sternum → ventral plate

• ancestrally wingless: silverfish & kin

• evolved from winged ancestors: ants, fleas, lice)

ametabolous

• postembryonic development in insects

• young → differ in proportions

• looks like adult

• only sexually immature

• continues to molt after maturity

hemimetabolous

• young resembles adult (lacking wings, external wing pads)

• cease molting at maturity

• immatures = nymphs (NOT larva)

• ex.) grasshopper, cockroach, aphid

homometabolous

• young quite different from adult

• egg → larva → pupa → adult

  • pupal stage → wing pads outward

  • resting stage = last molt → pupa formation

• e.g) mosquitoes, beetles, moths

• advantage

  • lava and adults dont feed on the same thing → less competition

disease vectors

• mosquitoes → malaria, yellow fever

• anopheles mosquitoes → sleeping sickness

• fleas → bubonic plague

• nematodes → filarial diseases

beneficial impact of insects

• biological control → integrated pest management

  • cottony cushion scale on citrus, vedalia beetle

    • maintains low populations of the scales

  • parasitoid wasps

    • Females have long needle-like structures where eggs will hatch into other insects

• honey, silk (moths), food (locusts), pollination (butterflies/bees)