Greek root: arthron
Joint
Greek root: pous or podos
Foot
Phylum Arthropoda
(General description)
-most diverse phylum
-more species than all other forms of life combined
-occur in literally all habitats and every place on earth
-chitinous, segmented exoskeleton a major innovation in morphology
-highly developed sense organs
Subphylum Myriapoda
Centipedes, millipedes
Subphylum Hexapoda
Insects
Subphylum Cherlicerata
Spiders, ticks, scorpions, horseshoe crabs
Subphylum Crustacea
Lobsters, crabs, barnacles
Subphylum Trilobita
Trilobites (all extinct)
Versatile exoskeleton
Protective while flexible for mobility CaCO3
Segmentation and appendages
Very efficient for locomotion, allows for division of labor
Air piped directly to cells
Tracheal air tube system, high metabolic rate possible also limits body size
Complex behavior patterns
Incredible diversity of behaviors, sociality, understand symbolism
Limit intraspecific competition through metamorphosis
Larval forms do not compete for resources
Arthropod
(Characteristics)
-jointed appendages ancestrally, often modified
-bilateral & segmented
-triploblastic
-complete digestive system
-complex muscular system
-open circulatory
Paired excretory glands in Arthropods
Coxal, antennal, or maxillary
Excretory organs in arthropods
Malpighian tubules
Subphylum Trilobita
-Probably evolved from Cambrian
-extinct for over 200 mya
-dorsally flattened bottom dwellers (scavengers)
-no true mouthparts
Three tagmata in trilobita
Head (cephalon), trunk, pygidium
Cephalon in Trilobita
Pair of antennae, compound eyes, mouth, four pairs of leg like appendages
Class Merostomata
Subclass Eurypterida
-giant water scorpions (up to 3m)
- from Cambrian to Permian
-head with 6 fused segments , simple & compound eyes, chelicerae and pedipalps
-dominant predators at the time
-anterior appendages modified into crushing claws to dent the dermal armor of early
Subclass Xiphosaurida
Horseshoe crabs
Used in xiphosaurida for respiration?
Book gills
Body characteristics of Xiphosaurida?
-cephalothorax with a pair of chelicerae, one pair of pedipalps, four pairs of walking legs
-unsegmented, horseshoe shaped carapace, broad abdomen, long tail spike called a telson
What do Xiphosaurida feed on?
Worms and small molluscs
Xiphosaurida reproduction cycle
Eggs laid in a small burrow in the sand, larvae resembling trilobites, hatch and are washed into the sea with another high tide
Class Pycnogonida
Sea spiders
Class Pycnogonida characteristics
-about 100 species, shallow to deep
~0.75 m across
-small, thin with four pairs of walking legs
-circulatory system simple
-absent
What is unique to Arthropods?
(Class Pycnogonida)
Some segments duplicated, some males have extra legs called ovigers
Greek root Arachne
Spiders
Class Arachnida
(Species)
Spiders, scorpions, pseudoscorpions, whip scorpions, ticks, mites, daddy longlegs,
Class Arachnida
(Characteristics)
-more than 80,000 species
-two tagmata: a cephalothorax and an abdomen
-most predaceous
-chelicerae sometimes modified into fangs
-claws are modified pedipalps
Order Araneae
Spiders
-pair of chelicerae on abdomen, have terminal fangs to transfer venom
-leglike pedipalps, used by males to transfer sperm
-feed on insects
Cephalothorax in Araneae is called
Prosoma
Abdomen in Araneae is caled
Opisthosoma
Araneae organs and senses
-Breathe through book lungs, trachea or both
-malpighian tubules work with unique resorptive cells in intestinal epithelium, some have coxal glands which are modified nephridia
-usually 8 eyes (but vision is poor )
-many mechanoreceptors on body, sensory
Web spinning and prey capture
-2/3 spinnerets run to silk glands
-spider silk is stronger than steel
-used for prey, nest or burrow, wrapping prey items or throwing silk nets onto prey
Spider reproduction
-males usually spins a small web, deposits sperm then picks it up in pedipalps
-inserts pedipalps into female's genital opening
-Females lays eggs in silken net, may carry it or attach it to something, young usually remain in cocoon for a few weeks, then
Dangerous spiders in US
-black widows (neurotoxic)
-brown recluses (hemotoxic)
Both very rarely fatal
Order Scorpiones
Scorpions
-most ancient of the arachnids
-predatory to insects and spiders, seizing with pedipalps and shred with chelicerae
Order Scorpions (characteristics)
-short cephalothorax with chelicera, pedipalps walking legs, one pair of big median eyes, 2-5 pairs of small lateral eyes
-postabdomen or metasoma of 5 segments w/ stinger on the end of the tail
-comblike lectures that serve as tactile organs
Scorpion reproduction
-males perform complex mating dance, holding females chelae as he steps back and forth
-sometimes sting her on edge of cephalothorax
-male deposits spermatophore on substrate, females walks over and picks it up
-scorpions brood and nourish young in female
Order Solpugida
Sun or camel spiders
-nonvenomous, shred prey with large chelicerae
-up to 15 cm across
-usually in desert habitats, very high metabolism
Order Opiliones
Harvestmen (daddy long legs)
Order Opiliones
(Characteristics)
-abdomen and cephalothorax rounded and broadly joined, no pedicel
-external segmentation
-four pairs of legs that end in claws, can be lost and regenerated
-carnivorous and scavengers
-nonvenomous
Daddy long leg myth?
The idea that they are ultra venomous but cannot bite humans
Order Acari
-most medically important arachnids
~about an inch long
-most habitats on earth
-many species parasitic for at least part of their life cycle
Acarian Anatomy
-complete fusion of cephalothorax and abdomen
-no division or segmentation
-chelicera for gripping and tearing food
-base of pedipalps forms hypostome, rostrum or tectum extends dorsally over mouth
-usually four pairs of legs
-most transfer sperm directly
Mouthparts on anterior projection in acarians
Capitulum
Human parasites
Chiggers
Itch mites
Deer ticks
Wood ticks
Chiggers (Trombicula)
Feed on dermal tissue
Itch mites (Sarcoptes)
Cause scabies
Deer ticks (ixodes)
Carry Lyme disease
Wood ticks (dermacentor)
Carry tularemia and Rocky Mountain spotted fever
Subphylum Myriapoda
(Characteristics)
-many footed
-two tagmata: head and trunk, paired appendages on each truck segment
-use trachea to carry respiratory gasses to and from all body cells, another independent evolutionary event from arachnids and insects
-excretion through Malpighian tubules
Greek root cheilos
Margin or tip
Class Chilopoda
The centipedes
Class Chilopoda
(Characteristics)
-extremely carnivorous
~30 cm long
- few very venomous to humans
~170 segments, each segment except one behind head and last todo had one pair of jointed legs
-appendages of first segment make venomous claws
-one pair of antennae, mandibles, one of two pa
Class Chilopoda
(Digestive, Respiration & reproduction)
-Digestive system straight tube
-respiration through a pair of spiracles in each segment
-sexes separate, unpaired gonads and pair ducts
-some lay eggs, other give birth to live young, no metamorphosis
Greek root diploo
Double
Class Diplopoda
Millipedes
Class Diplopoda
(Characteristics)
-move with slow, graceful motion, not active like centipedes
-most eat detritus, some eat living plants
-some secrete toxic or repellant fluids from repugnatorial glands on sides of body
~25-100 segments, each with two pairs of legs and two pairs of spira
Class Diplopoda
Females lay eggs in a nest and guard them, larval forms only have one pair of legs per segment
Greek root pauros
Small
Class Pauropoda
-soft bodied, about 599 species, live in moist soil or leaf litter
-small head with branched antennae, no true eyes, 12 trunk segments, one dorsal plate covering two segments
-no tracheae, spiracles, or circulatory system
Greek roots sym
Together
Class Symphyla
(Characteristics)
-Small, centipede like bodies, live in led litter
-often pests on horticultural and agricultural
-soft bodied with 14 segments, 12 of which bear legs legs antennae long and unbranched
-eyeless, but have sensory pits at base of antennae l, tracheal system
Class Symphyla
(Characteristics)
In one genus, male puts spermatophore on stalk female puts in her mouth, storing it, pulls eggs from her gonopore with her mouth, attaches them to substrate by smearing them with semen, development direct