Ecdysozoa and Arthropods Overview

Lobster Industry
  • Declining Catch: U.S. lobster catch is decreasing due to environmental and economic challenges driven by climate change.
  • Migration: Warmer waters cause lobsters to migrate from traditional fishing grounds.
Learning Objectives
  • Superphylum Ecdysozoa: Understand characteristics and significance.
  • Nematodes: Analyze their ecological roles and health impacts.
  • Arthropoda: Study structure, nutrition, and reproductive systems.
  • Insect Metamorphosis: Describe the processes involved in insect development.
Phylogenetic Tree of Animals
  • Classification from Metazoa to specialized groups:
    • Eumetazoa: Organisms with specialized tissues.
    • Bilateria: Animals with bilateral symmetry and three germ layers (triploblastic).
    • Ecdysozoa: Includes organisms that undergo molting.
    • Major Phyla: Include Arthropoda, Nematoda, Platyhelminthes, etc.
Superphylum Ecdysozoa
  • Definition: Named for the process of ecdysis, or molting.
  • Physical Characteristics:
    • Cuticle offers support and protection.
    • Internal fertilization through amoeboid sperm to adapt to dry environments.
  • Diversity: 8 major phyla, notably Nematodes and Arthropods as the most common.
Nematodes (Roundworms)
  • Diversity: Over 20,000 species documented, e.g., $C. elegans$ (1 mm).
  • Ecological Role: Predators or saprophytes, essential in soil ecosystems.
  • Model Organism: $C. elegans$ used in genetics and neurobiology studies.
Parasitic Nematodes
  • Common Species:
    • Ascaris lumbricoides: Human intestinal parasite, segmented; infects through ingestion of eggs.
    • Hookworm: Infects humans via skin contact; affects over 500 million individuals globally.
  • Transmission and Lifecycle:
    • Larval stages penetrate skin, affecting lungs and intestines.
Common Parasitic Nematodes and Their Lifecycle**
  • Infection Routes:
    • Hookworm: Juveniles through soil; suck blood from intestines.
    • Pinworm: Contaminated surfaces, most common in U.S. children.
    • Trichina worm: Through infected food, occasional human infections.
  • Disease Examples: River blindness, Guinea worm disease, Elephantiasis.
Phylum Tardigrada (Water Bears)
  • Characteristics:
    • Tiny (0.3-0.5 mm), reside in moist environments.
    • Unique morphology with four pairs of stubby legs.
    • Capable of cryptobiosis, surviving extreme conditions.
Phylum Arthropoda (Arthropods)
  • Diversity: Accounts for 85% of known species with jointed appendages (legs and mouthparts).
  • Body Structure:
    • Segmentation into head, thorax, abdomen.
    • Rigid exoskeleton molted as the organism grows.
    • Open circulatory system and sophisticated nervous system.
Major Subphyla of Arthropoda
  • Crustacea: Includes shrimp, lobsters, crabs, characterized by gills and antennates.
  • Chelicerata: Features spiders and scorpions, with specialized mouthparts (chelicerae).
  • Myriapoda: Includes centipedes (carnivorous) and millipedes (herbivorous).
  • Hexapoda: Insects characterized by three pairs of legs and wings.
Insect Metamorphosis
  • Types:
    • Ametabolous: No metamorphosis, simple growth.
    • Hemimetabolous: Gradual change from nymph to adult.
    • Holometabolous: Complete metamorphosis (egg, larva, pupa to adult).
  • Implications: Development strategies influence survival and adaptation to environments.