Arthropoda

ARTHROPODA Classification

  • Phylum Arthropoda includes a diverse range of organisms known as arthropods, characterized by their jointed appendages and segmented bodies.

Classification of Phylum Arthropoda

  • Sub-Phylum I: Trilobitomorpha

    • Trilobita: Extinct group.

  • Sub-Phylum II: Chelicerata

    • Includes:

      • Arachnida: Spiders, Scorpions

      • Merostomata: Horseshoe crabs

      • Pycnogonida: Sea spiders

  • Sub-Phylum III: Myriapoda

  • Sub-Phylum IV: Crustacea

    • Includes:

      • Branchiopoda: Brine shrimp

      • Remipedia: Blind crustaceans

      • Cephalocarida: Horseshoe shrimp

      • Maxillopoda: Barnacles

      • Ostracoda: Seed shrimps

      • Malacostraca: Lobsters, crabs, shrimp

  • Sub-Phylum V: Hexapoda

    • Insecta: Winged insects

    • Entognatha: Wingless insects

TRILOBITOMORPHA

  • Trilobites are part of a larger group called Artiopoda, mainly marine organisms with fossil evidence commonly found alongside salt-water species such as brachiopods and corals.

CHELICERATA

  • Characterized by:

    • Two body segments

    • Six pairs of appendages

    • Four pairs for walking, two for feeding (chelicerae and pedipalps)

    • No mandibles or antennae

    • Segmented body with jointed appendages

    • Reduced coelom and presence of hemocoel for blood circulation.

ARACHNIDA

  • Class Arachnida includes spiders, daddy longlegs, scorpions, and mites/ticks.

  • The body consists of the cephalothorax and abdomen, with variations in sternites and tergites.

  • Possess simple eyes.

Examples of Arachnids

  • Black widow- Pholcus phalangioides

  • Daddy long legs- Latrodectus mactans

  • Ticks- Dermacentor variabilis

  • Dessert scorpion- Hadrurus arizonensis

MEROSTOMATA

  • Commonly known as horseshoe crabs, once abundant, now limited to four species.

  • Notable features include:

    • Adapted for marine environments

    • External fertilization

    • Bottom-dwelling, nocturnal habits

    • Diet includes worms, molluscs, and other small invertebrates.

PYCNOGONIDA

  • Sea spiders belong to Pycnogonida and typically have four pairs of legs and reduced bodies.

  • They possess a long proboscis and inhabit underwater environments.

MYRIAPODA

  • Characterized by many pairs of legs, two body sections (head and trunk), one pair of antennae, and simple eyes.

  • Classes include:

    • Chilopoda (centipedes)

      Centipede- Lithobius forficatus

    • Diplopoda (millipedes)

      African millepede- Archispirostreptus gigas

    • Pauropoda

      Trachypauropus britannicus

    • Symphyla

      Scutigerella immaculata

CHILOPODA

  • Long, segmented predaceous arthropods, known for one pair of legs per segment.

  • Nocturnal hunters feeding on small invertebrates.

DIPLOPODA

  • Segmented animals, each segment with two pairs of legs (diplosegments).

  • Approximately 10,000 described species in this class.

PAUROPODA

  • Small, millipede-like arthropods with nine pairs of legs.

  • Primarily found in soil and leaf mold, feeding on fungi and organic matter.

SYMPHYLA

  • Also known as garden centipedes, resembling centipedes, they are small and primarily herbivores.

  • They can harm crops by consuming roots and seeds.

CRUSTACEA

BRANCHIPODA

Primitive aquatic crustaceans including brine shrimp and water fleas.

  • 800 species recognized, with a long fossil record traced back to the Devonian period.

    • Notable species: Branchinecta gigas (largest living branchiopod).

    • Anomopods-water fleas

    • Artemia salina-brine shrimp

REMIPEDIA

  • Ancient class of blind Crustacea, totaling around 10 known living species.

  • Found in underwater caves and characterized by elongated bodies and biramous legs.

  • Speleonectes lucayensis

CEPHALOCARIDA

  • Class comprising 12 species, commonly referred to as horseshoe shrimp.

  • Discovered in 1955, benthic creatures with little known about their behaviors.

MAXILLOPODA

  • Diverse class of crustaceans including barnacles and copepods.

  • Characterized by five pairs of head appendages and up to 23,000 species.

  • Stygotantalus stocki

  • Coronula diadema

OSTROCODA

  • Small crustaceans with a bivalved carapace, typically 0.5 to 2.0 mm in size.

  • Known for being common microfossils, with reduced trunk segmentation.

MALACOSTRACA

  • Largest class of crustaceans with over 40,000 species including shrimp, krill, and crabs.

  • Notable for high adaptability across marine and freshwater environments.

  • Pagurus samuelis-hermit crab

  • Scylla serrata-mud crab

HEXAPODA

  • Largest clade of arthropods, encompassing true insects and wingless arthropods (Entognatha).

  • Differentiated body regions: head, thorax, and abdomen; often present with wings.

INSECTA

  • Class Insecta is the largest within Arthropoda, characterized by segmented bodies and jointed legs.

  • Body divided into three regions: head, thorax (with legs and wings), and abdomen.

  • Schistocerca americana

  • Ischnura senegalensis

  • Aeshna mixta

ENTHOGNATHA

  • Class of wingless arthropods with retracted mouthparts.

  • Comprises three orders: Collembola, Diplura, and Protura, recognized as paraphyletic.

  • Pediculosis capitis