ecdysozoans planktonic cyclopoid copepod (cyclops strenuus). lm. copyright robert brons/bps....

Ecdysozoans

Planktonic cyclopoid copepod (Cyclops strenuus). LM. Copyright Robert Brons/BPS.

red-kneed tarantula; Mexico. Copyright Barbara J. Miller/BPS.adult polyphemus moth

(Antheraea polyphemus). Copyright Peter J. Bryant/BPS.

Green Darner dragonfly has just emerged from its larval exoskeleton and is pumping fluids into its expanding wings.

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.

NematodaRoundworms

Pinworms

Filarial heart worm Filarial Worms

Trichinella

Trichinella, a parasitic roundworm that infects mammals

-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

Structure of a nematode as illustrated by Ascaris female

Source: Raven et al (2002)

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

Head

Thorax

Abdomen

Flexor muscleExtensor muscle

Joint between leg segments

Exoskeletonjointed limbs

Chelicerates Trilobites Insects Crustaceans

Above; the four main lineages of arthropods

Right; important features of arthopod body plan

Sources: Freeman (2002), Campbell (2002)

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

Exocrine Gland

Setae PileJoint Skeletal muscles

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Keaton & Gould 1993

Flight is a key adaptation that contributed to the adaptive radiation of insects

Direct flight muscles (attached to wings) are responsible for downstroke and indirect flight muscles for upstroke in grasshoppers

Grasshopper launching into flight

Expressed segmentation genes in fruit flies. Antibody staining shows the location of segmentation gene products in fly embryos

Genes in the homeotic complex encode regulatory proteins that affect embryonic pattern formation

Insect Onychophoran Segmented worm Crustacean

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

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

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Cuticle

Valve

Commissural tracheae

Ventral trachea

Dorsal trachea

Spiracles

Tracheoles

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

Raven (2002)

A group of spawning horseshoe crabs

Keaton & Gould (1993)

Book Gills

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

Molt

Molt

Molt

Molt

Metamorphosis

Hatching

Molt

Molt

Pupation

Pupation

Pupa

Adult

Larvae

Juveniles

All insects metamorphose. Some lineages undergo partial metamorphosis, and some complete metamorphosis

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), Hickman et al (2001)

Sgs-3

Lsp-1a

IMP-E1 Genes

FTZ-F1

Usp

Changes in gene expression during insect metamorphosis are caused by ecdysone

Source: Freeman (2002)

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

AnnelidaSegmented worms

Polychaeta Oligochaeata Acanthobdellida Branchiobdellida Hirudinea

Feather duster - marine annelid

Earthworms - Oligochaetes

Australian Tiger LeechPolychaetes living around thermal vent

-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.

Mollusca

Monoplacophorans

Gastropods

Cephalopods

Bivalves

Scaphopods

Polyplacophorans

-extensive adaptive radiations related to variations on body plan based on foot, mantle, and visceral mass

Chitons

Snail

Giant Clam Slug

Octopus

Nautilus