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Ecdysozoans adult polyphemus moth (Antheraea polyphemus). Copyright Peter J. Bryant/BPS. red-kneed tarantula; Mexico. Copyright Barbara J. Miller/BPS. Green Darner dragonfly has just emerged from its larval exoskeleton and is pumping fluids into its expanding wings. Planktonic cyclopoid copepod (Cyclops strenuus). LM. Copyright Robert Brons/BPS. Monophyly of Ecdysozoa supported by molecular and genetic evidience,including a common set of homeobox genes Cuticle and molting arose in the common ancestor to this clade Discussion will focus on adaptive significance of the various exoskeletons in this lineage,and of the ability to shed that exoskeleton Ecdysozoa includes a dozen or more phyla; we will concentrate on two: Arthropoda primarily, and Nematoda to some extent. Family Culicidae: mosquito (Culex sp.), engorged with blood. Copyright Robert Brons/BPS. Nematoda Roundworms Trichinella, a parasitic roundworm that infects mammals Trichinella -thick, multi-layered cuticle secreted, related to characteristic locomotion -exchange oxygen and nutrients with environment through both cuticle and complete gut (two openings - mouth and anus) -free-living and parasitic forms -among the most abundant and universally distributed organisms -- tremendous ecological importance Pinworms Filarial Worms Filarial heart worm Structure of a nematode as illustrated by Ascaris female Source: Raven et al (2002) Chelicerates Trilobites Insects Crustaceans Sources: Freeman (2002), Campbell (2002) Above; the four main lineages of arthropods Flexor muscle Extensor muscle Head Joint between leg segments Thorax Right; important Abdomen features of arthopod body plan jointed limbs Exoskeleton The tremendous success -- diversification, adaptive radiations-- of Arthropods is related to: Fundamental design features in their body plan -rigid exoskeleton -segmentation -jointed appendages Specialization of groups of body segments and appendages for many different functions About 2/3 of all described species are arthopods; about half of those arthropods are insects; about half of those insects are beetles Phylum Uniramia (= “one branch”) -Myriapods (below). ~20,000 species in four groups, including centipedes and millipedes, with relatively undifferentiated segments and appendages -Insecta (right)~1.5 million described species (small fraction of actual diversity) Apterygotes insects lacking wings Pterygotes winged insects; includes lineages that lack metamorphosis, undergo incomplete metamorphosis, or undergo complete metamorphosis John Meyer UNC http://www.cals.ncsu.edu/course/ent425/tutorial/integ.html Several differentiated layers of cuticle Epidermis and underlying basement membrane 0672 Exocrine Gland Setae Pile Joint Skeletal muscles Keaton & Gould 1993 Grasshopper launching into flight Direct flight muscles (attached to wings) are responsible for downstroke and indirect flight muscles for upstroke in grasshoppers Flight is a key adaptation that contributed to the adaptive radiation of insects Genes in the homeotic complex encode regulatory proteins that affect embryonic pattern formation Expressed segmentation genes in fruit flies. Antibody staining shows the location of segmentation gene products in fly embryos Insect Onychophoran Distal-less expression in protostomes. These embryos have been stained with an antibody to theproteing produced by Dll. In each case, the Dll gene product is localizd in cells that will become part of an outgrowth from the body, such as a limb Segmented worm Crustacean 0683 Arthropods have open circulatory systems hemolymph is pumped by one or more hearts through arteries and into sinuses (pockets) surrounding tissues and organs. Hemolymph reenters the circulatory vessels through pores Cuticle Various mechanisms of gas exchange have evolved in Arthropods Valve Commissural tracheae -Gas exchange in terrestrial arthropods typically occurs in specialized internal surfaces Ventral trachea Gas exchange in aquatic arthopods typcially occurs across gill surfaces Dorsal trachea Spiracles Tracheoles Raven (2002) Book Gills Keaton & Gould (1993) A group of spawning horseshoe crabs Source: Campbell (2002) Molting and Metamorphosis Molt; Periodic shedding and replacement of exoskeleton to allow growth Metamorphosis; change from juvenile to adult body form; Both processes are controlled by the interaction of two neurosecretory hormones: ecdysone and juvenile hormone Hatching Hatching Molt Molt Molt Larvae Molt Juveniles Molt Molt Pupation Pupa Pupation Metamorphosis Adult All insects metamorphose. Some lineages undergo partial metamorphosis, and some complete metamorphosis Source: Freeman (2002), Hickman et al (2001) Molt and Metamorphosis are regulated by neurosecretory hormones; juvenile hormone and ecdysone Pulse of Ecdysone when JH is high causes molting Pulse of Ecdysone when JH is low causes metamorphosis Source: Freeman (2002) Sgs-3 Lsp-1a IMP-E1 FTZ-F1 Usp Changes in gene expression during insect metamorphosis are caused by ecdysone Genes Crustaceans Uniramians Remipedia Cephalocarida Branchiopoda Maxillopoda Malacostraca Chelicerates Extra slides L320652Family Theraphosidae: red-kneed tarantula; Mexico. Copyright Barbara J. Miller/BPS. L320653Family Lycosidae: a wolf spider (Lycosa sp.). Copyright Peter J. Bryant/BPS. L320654Family Thomisidae: female crab spider (Misumenoides formocipes), on lantana blossom. Copyright Peter J. Bryant/BPS. L320655Family Oxyopidae: female green lynx spider (Peucetia viridans), with fresh egg case. Copyright Peter J. Bryant/BPS. L320656An immature daddy long-legs (Leiobunum sp.). Copyright BPS. L320657An adult pseudoscorpion (species unknown). Copyright Peter J. Bryant/BPS. L320658A wood tick (Ixodes ricinus), piercing human skin. Copyright Robert Brons/BPS. L320659Wind scorpion (Eremobates sp.). Copyright BPS. L320660Adult brine shrimp (Artemia salina). Copyright David J. Wrobel/BPS. L320661Tadpole shrimp (Triops sp.). Copyright David J. Wrobel/BPS. L320662Water flea (Daphnia sp.), with embryos. Copyright Peter J. Bryant/BPS. L320663Calanoid copepod group (Calanus sp.); Monterey Bay, CA. Copyright David J. Wrobel/BPS. L320664Planktonic cyclopoid copepod (Cyclops strenuus). LM. Copyright Robert Brons/BPS. Flatworms (Platyhelminthes) Simple Lophtrochozoans -bilateral symmetry -cephalization -lack organs for oxygen transport -simple organs for excreting metabolic waste -gut with single exterior opening -relationship between oxygen transport, waste elimination and flat, high surface area to volume ratio, body plan -free-living and parasitic forms Annelida Segmented worms Polychaeta Oligochaeata Acanthobdellida Branchiobdellida Hirudinea -radiations in terrestrial, freshwater and marine habitats -segmentation;septa dividing coelomiccavity alters function of hydrostatic skeleton Earthworms - Oligochaetes Feather duster - marine annelid -most lack rigid, external body covering; gas exchange occurs across body wall in most spp. Australian Tiger Leech Polychaetes living around thermal vent Monoplacophorans Cephalopods Scaphopods Gastropods Bivalves Chitons Polyplacophorans Giant Clam Slug Snail Octopus -extensive adaptive radiations related to variations on body plan based on foot, mantle, and visceral mass Mollusca Nautilus