4/12/2011 Ecdysozoa Ecdysozoa • Ecdysis = molt • Phylum Nematoda (Roundworms) – Shed outer covering: cuticle (exoskeleton) – Body not segmented – Longitudinal muscles – Pseudocoelomate – Sexual reproduction 100,000 eggs/day Zygotes resistant Ecdysozoa Ecdysozoa • Phylum Nematoda (Roundworms) • Phylum Arthropoda – Found in most • 1,000,000,000,000,000,000 aquatic environments • Over 1 million described species – Caenorhabditis elegans model organism – Segmented Body – m – Parasites – Hard Exoskeleton • Example: Trichinella spiralis – Jointed Appendages • Commandeer host cell function • First noted in Cambrian Explosion Ecdysozoa Ecdysozoa • Phylum Arthropoda • Chitinous Exoskeleton • Must shed to grow – Dangerous, energetica lly expensive • Benefits – Protection – Muscle attachment – Prevents desiccation – Structural support 1 4/12/2011 Ecdysozoa Ecdysozoa • Phylum Arthropoda • Phylum Arthropoda • Open Circulatory System • Subphylum Cheliceriformes – Hemolymph into hemocoel – Spiders, ticks, scorpions, horseshoe crabs – HlHemocoel replaces coelom • Subphylum Myriapoda – Millipedes, centipedes • Gas Exchange • Subphylum Hexapoda – Gills in aquatic species – Insects, springtails – Holes for respiration in • Subphylum Crustacea terrestrial species – Crabs, lobsters, shrimp Ecdysozoa Ecdysozoa • Subphylum Cheliceriformes • Subphylum Cheliceriformes – Have chelicerae (feeding appendage) – Arachnids • Often pincers or fangs • Pedipalps – No antennae – Most have simple eyes • Single lens – Most are arachnids Ecdysozoa Ecdysozoa • Subphylum Cheliceriformes • Subphylum Cheliceriformes – Arachnids – Arachnids • Book Lungs Horseshoe 2 4/12/2011 Ecdysozoa Ecdysozoa • Subphylum Myriapoda • Subphylum Hexapoda (insects etc.) – Millipedes and Centipedes – Most speciose group of life – Terrestrial; have antennae – Mainly terrestrial and freshwater – Flight • Wings from exoskeleton • Evolved once – Flowering plants Ecdysozoa Ecdysozoa • Subphylum Hexapoda (insects etc.) • Subphylum Hexapoda (insects etc.) – Metamorphosis – Importance to humans Incomplete • Disease vectors • Plant pests Complete Ecdysozoa • Subphylum Crustacea – Marine counterpart to insects • Also freshwater and terrestrial members – Up to 19 pairs of appendages • Including on abdomen – 2 pairs of antennae 3.