Preview 2/22 Dr. Kopeny

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1 Preview 2/22 Dr. Kopeny 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 -most lack rigid, external body covering; gas exchange occurs across body wall in most spp. Feather duster - marine annelid Earthworms - Oligochaetes Australian Tiger Leech Polychaetes living around thermal vent

2 Monoplacophorans Gastropods Cephalopods Scaphopods Bivalves Chitons Polyplacophorans Slug Giant Clam Snail Octopus -extensive adaptive radiations related to variations on body plan based on foot, mantle, and visceral mass Mollusca Nautilus 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.

3 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 nturients with environment through both cuticle and complete gut (two openings - mouth and anus) -among the most abundant and universally distributed organisms -- tremendous ecological importance Pinworms Filarial Worms Filarial heart worm

4 Structure of a nematode as illustrated by Ascaris female Source: Raven et al (2002)

5 Chelicerates Trilobites Insects Crustaceans Above; the four main lineages of arthropods Right; important features of arthopod body plan Head Thorax Abdomen jointed limbs Sources: Freeman (2002), Campbell (2002) Flexor muscle Extensor muscle Joint between leg segments 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

6 Phylum Uniramia (= one branch ) -Myriapods (below). ~20,000 species in four groups, including centipedes and milipedes, with relatively undifferentiated segments and appengades -Insecta (right)~1.5 million described species (small fraction of actual diverisity) Apterygotes insects lacking wings Pterygotes winged insects; includes lineages that lack metamorphosis, undergo incomplete metamorphosis, or undergo complete metamorphosis John Meyer UNC Several differentiated layers of cuticle Exocrine Gland Epidermis and underlying basement membrane 0672 Setae Pile Joint Skeletal muscles

7 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

8 Insect Onychophoran 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

9 Cuticle Valve Commissural tracheae Ventral trachea Dorsal trachea Spiracles Various mechanisms of gas exchange have evolved in Arthropods -Gas exchange in terrestrial arthropods typically occurs in specialized internal surfaces Gas exchange in aquatic arthopods typcially occurs across gill surfaces Tracheoles Raven (2002) Book Gills Keaton & Gould (1993) A group of spawning horseshoe crabs

10 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 Pupation Molt Metamorphosis Pupa Adult Pupation All insects metamorphose. Some lineages undergo partial metamorphosis, and some complet metamorphosis

11 Source: Freeman (2002), Hickman et al (2001) Molt and Metamorphosis are regulated by neurosecretory hormones; juvenile hormone and ecdysone Sgs-3 Lsp-1a IMP-E1 FTZ-F1 Usp Genes Source: Freeman (2002) Changes in gene expression during insect metamorphosis are caused by ecdysone

12 Crustaceans Uniramians Remipedia Cephalocarida Branchiopoda Maxillopoda Malacostraca Chelicerates