Mr.Bastin-ZooBot-Arthropods

Taxonomy

Domain: Eukarya

Kingdom: Animalia

Phylum: Arthropoda

Basics (meaning, %, includes)

• Greek for “jointed foot” (jointed appendages)

• Largest animal phylum, over 75% of known species

• Have exoskeletons made of chitin

• Segmented bodies and bilateral symmetry

• Includes insects, crustaceans, arachnids, and myriapods

Structure

• Bilateral symmetry

• Complex organ systems

• Triploblastic

• Coelomates (coelom not used for hydrostatic support)

• Hard external exoskeleton made of chitin

Exoskeletons

structural support, prevents water loss

composed of chitin

varies by taxa

must molt (shed) as body grows

Feeding/digestion

-range from filter feeders to predators

-one way digestive tract (mouth to anus)

Circulation

Open system

Respiration

Terrestrial taxa:

• Most breathe through branching tracheal tubes

  • Air enters and exits through spiracles in the exoskeleton

• Some have book lungs

  • Stacked respiratory tissue like book pages (ex. spiders)

Aquatic taxa:

• Most use feather-like gills (ex. crabs, lobsters)

Excretion

Terrestrial taxa:

-typically use Malpighian tubules

>sac-like organs which extract waste from blood and add to feces

Aquatic taxa:

-waste diffuses out of body

Response

brains

-although most behaviors genetically preprogrammed

Movement

• Muscles attach to the exoskeleton and generate force by contracting

• Different muscles flex (bend) or extend (straighten) joints

Reproduction

• Most species have separate sexes (male or female)

Terrestrial taxa:

• Internal fertilization

  • Some males directly inseminate females

  • Others use appendages or leave sperm packets for females to pick up

Aquatic taxa:

• External fertilization

  • Females release eggs and males shed sperm into the water

• Most species lay eggs

Parthenogenesis example

• Parthenogenesis in aphids

  • Females produce clones in summer

    • Born already pregnant

    • Rapid colony growth

  • Sexual reproduction in fall

    • Genetic recombination

Arthropod Groups (Subphyla and classes)

Subphylum Chelicerata

• Class Arachnida (spiders, scorpions, ticks, mites)

• Class Merostomata (horseshoe crabs)

• Subphylum Uniramia

  • Class Insecta (insects)

  • Class Diplopoda (millipedes)

  • Class Chilopoda (centipedes)

• Subphylum Crustacea

  • Class Malacostraca (crabs, lobsters, crayfish, shrimp, isopods)

  • Class Branchiopoda (brine shrimp, water fleas)

  • Class Maxillopoda (copepods, barnacles)

Subphylum Chelicerata

Includes Class Arachnida (spiders, scorpions, ticks, mites), Class Merostomata (horseshoe crabs)

Class Merostomata

Subphylum: Chelicera

(horseshoe crab)

-found in shallow marine environments (eastern US)

Class Arachnida

(spiders, scorpions, ticks, mites)

• Two pairs of appendages near the mouth

• Eight walking legs

• No antennae

• Body divided into two regions

  • Cephalothorax (head + thorax)

  • Abdomen

Scorpions

Subphylum Chelicerata
Class Arachnida (scorpions)

• Tail with a venomous stinger

• Chew food using chelicerae

• Nocturnal (active at night)

Subphylum Uniramia

Includes Class Insecta (insects), Diplopoda (Millipedes), and Chilopoda (centipedes)

Class Diplopoda

Subphylum Uniramia (millipedes)

• Many body segments

• Two pairs of legs per segment

• Herbivores

Class Chilopoda

\Subphylum Uniramia (centipedes)

• Many body segments

• One pair of legs per segment

• Carnivores with venomous claw

Subphylum Crustacea

• Class Malacostraca (crabs, lobsters, crayfish, shrimp, isopods)

• Class Branchiopoda (brine shrimp, water fleas)

• Class Maxillopoda (copepods, barnacles)

Class Malacostraca

Subphylum Crustacea (crabs, lobsters, crayfish, shrimp, isopods/pill bugs)

• Two pairs of branched antennae

• Chewing mouthparts called mandibles

Crayfish

Subphylum Crustacea
Class Malacostraca

• Five pairs of legs (Order Decapoda)

  • First pair are chelipeds with claws

• Swimmerets

  • Flipper-like swimming appendages

  • Differ by sex

  • Allow backward swimming using tail flap

Coconut Crab

Subphylum Crustacea
Class Malacostraca (coconut crab)

• Largest crustacean (legs span ~3 ft)

• Lives on South Pacific islands

• Eats coconuts; can climb trees

• Mates on land, then migrate to sea to release eggs

Pistol shrimp

Subphylum Crustacea
Class Malacostraca (pistol shrimp)

• Shoots a jet of water to stun prey

• Creates a bubble

• Bubble collapses with a loud snap

Class Branchiopoda

Subphylum Crustacea

(Brine shrimp and water fleas (Cladocera))

Brine Shrimp

Subphylum Crustacea
Class Branchiopoda

• Eggs survive extreme conditions

  • Can dry out or endure boiling water

  • Hatch within hours in saltwater

• Important to aquatic food chains (e.g., Mono Lake)

Cladocera (water fleas)

Subphylum Crustacea
Class Branchiopoda

• Part of zooplankton (animal plankton)

• Free-swimming with a two-valved carapace

• Females brood young in a pouch

• Commonly used in toxicity studies

Class Maxillopoda

Subphylum Crustacea

(Copepods and barnacles)

Copepods

Subphylum Crustacea
Class Maxillopoda

• Dominant members of zooplankton

• Mostly transparent

• Many species are parasitic

Barnacles

Subphylum Crustacea – Class Maxillopoda (barnacles)

• Sessile; attach to surfaces

• Feed with appendages

• Mostly hermaphroditic