Coelomate Ecdysozoans

This section covers Chapter 14 and 15, focusing on coelomate ecdysozoans.
Key groups include Protists, Basal Phyla, Spiralia, Animalia, Ecdysozoa, and Deuterostomia.

Ecdysis: The process of molting the cuticle.
Coelomate: Possessing a coelom.
Protostome Development: Undergoing protostome development.
Metamerism: Segmented body structure.
- With tagmatization (specialization of body regions).
Hemocoel: A body cavity containing blood.
Open Circulatory System: Circulatory system where blood is not always confined to vessels.

Most diverse and successful animal group.
Classification is continuously studied.
Exoskeleton:
- Chitinous and molted.
- Jointed.
Paired Appendages: Highly varied and specialized.
Metamorphosis: Common, with distinct larval forms.
- Hemimetabolous: Incomplete metamorphosis.
- Holometabolous: Complete metamorphosis.
Subphyla:
- Trilobitomorpha: Extinct trilobites.
- Chelicerata
- Myriopoda
- Pancrustacea
  - Crustacea
  - Hexopoda

Panarthropoda includes Arthropoda, Onychophora, and Tardigrada.
Onychophora: Velvet worms.
- Slime glands, oral papillae.
Tardigrada: Water bears.
- Cryptobiosis: a state of dormancy.
- Stylets used in feeding.
Arthropoda
- Chelicerata
  - Euchelicerata
    - Pycnogonida: Sea spiders
    - Xiphosura: Horseshoe crabs
    - Opiliones: Harvestmen
    - Acarina: Ticks and mites
    - Scorpionida: Scorpions
    - Araneae: Spiders
- Myriapoda
- Mandibulata
  - Pancrustacea
Hemocoel, metamerically arranged paired appendages, nonsclerotized cuticle shed by ecdysis are characteristics of Panarthropoda.
Chelicerae are characteristic of Chelicerata.
Compound eyes, sclerotized exoskeletal plates separated by nonsclerotized joint membranes, jointed legs are characteristics of Arthropoda.
Mandibles are characteristic of Mandibulata.

Characteristics:
- 2 tagmata (body sections):
  - Prosoma (Cephalothorax)
  - Opisthoma (Abdomen)
- Chelicerae: First pair of appendages, often pincher-like.
- Pedipalps: Second pair of appendages, often sensory, sometimes used in feeding or reproduction.
- Dioecious: Having separate sexes.

Horseshoe Crabs (Xiphosura):
- Now often considered within Arachnida.
- 4 living species.
- 2-part body: Prosoma & Opisthoma, with elongate telson.
- Book gills.
Eurypterids (extinct):
- Some gigantic, “sea scorpions”.

Sea Spiders:
- Short body, long legs.
- Organs extend into legs.
- Feed on cnidarians on the ocean floor.
- May be a distinct Subphylum “Cheliceriformes”.

Mouth appendages project from head, Malpighian tubules.
Myriapoda:
- Two tagmata, paired appendages on most segments
Pancrustacea:
- Appendages modified for crawling, swimming, feeding
Hexapoda:
- Three tagmata, three pairs of uniramous appendages, five pairs of head appendages
Head and abdomen reduced, thoracic appendages used in filter feeding.
Carapace absent, cephalothorax, four or five pairs of swimming legs.

Diplopoda- Millipedes
- 2 pair legs per “segment”.
- Scavengers.
- Repugnatorial glands.

Characteristics
- Biramous appendages
  - Exopodite/endopodite
- 2 pair antennae
- Compound eyes
- Cephalothorax
- Mandibles, maxillae, maxillipeds, Pereopods
- Abdomen
  - Pleopods
  - Uropod & Telson

Malacostraca
- Best known
  - Order Decapoda
    - Named for 10-legs (5 pairs of walking legs, starting with Cheliped
    - Lobsters, crayfish, crabs, shrimp, stomatopods
  - Order Isopoda
    - Dorsoventrally flattened, scavengers- pillbugs, etc.
  - Order Amphipoda
    - Laterally compressed sand fleas, etc.

Branchiopoda
- Mostly freshwater
- “Gill-foot”- feathery appendages
- Fairy shrimp & water fleas
Maxillopoda
- Diverse orders, 2 distinct subclasses:
  - Copepods- abundant, mostly planktonic. Swim with antennae
  - Barnacles- modified sessile adults, filter feed with legs

Characteristics
- Distinct 3 tagmata structure
  - Head: compound eyes, 1 pair antennae, mouthparts
  - Thorax: 3 pair legs + wings
  - Abdomen: spiracles, genitals and ovipositors (females)
- Flight- BIG DEAL!
  - Single greatest key to insect success
- Development- Metamorphosis
- Social behavior- eusociality
  - Bees, ants & wasps; termites

Coleoptera- Beetles
- Most diverse group
- Forewings=elytra (hardened)
Lepidoptera- butterflies & Moths
- Important pollinators
- Some store toxins from plants
Diptera- flies
- Single pair of wings
- Fluid diets
- Diverse, but many important to humans
Hymenoptera- bees, ants, wasps
- Many eusocial (basis of sociobiology)
- Haplodiploidy
- Important pollinators