Unit III: Protostomes Flashcards
What are the two Protostomes - Ecdysozoa?
- Nematoda
- Arthropoda
List Nematoda characteristics
- Round, unsegmented worms (roundworms)
- Outer cuticle is rich in collogen and chitin
- Molt during growth
- Widespread and can be abundant
- Free-living and parasitic species
List Arthropoda characteristics
- Grow by molting an outer exoskeleton (made of chitin, provides protection, and structure for muscle attachment)
- Body is segmented into discrete regions
- Movement due to jointed appendages
- Homocoeal (central body cavity) with open circulatory system in which no distinction between blood and interstitial fluid
- Gas exchange occurs spiracles (pores) in exoskeleton, while aquatic crustaceans use gills
Arthropoda - Chelicerate
- horseshoe crabs, spiders, mites, ticks, and scorpions
- Chelicerae: a pair of appendages in front of the mouth
- Loss of antennae, usually two magmata with no discernible head
- Pedipalps: the second pair of appendages attached to the cephalothorax
Chelicerae
modified first pair of appendages often form specialized claw-like or fang-like mouthparts
Pedipalps
second pair of appendages that often have roles in sensing environment or manipulating food
Arthropoda – Crustacea
- Most dominant aquatic arthropods; includes shrimp, lobsters, krill, crabs, and crayfish
– But also terrestrial groups like isopods (“pill bugs”) - Typically have…
– Head and thorax fused into a cephalothorax
– Two antennae
– Biramous (two-branched) appendages
Arthropoda – Hexopoda
- Insects; Largest group of arthropods
- Typically have…
– Six legs
– Three tagmata (head, thorax, abdomen)
– Wings (secondarily lost in some groups)
What are the defining traits of Arthropods?
- Chiton exoskelton
- Jointed appendages
- Tagmata
- Hemocoel with open circulatory system
What are the 2 Protostomes - Lophotrochozoa?
- Mollusca
- Annelida
What is Mollusk body plan ?
3 major parts:
- Foot: large muscles at base of individual, usually used for movement
- Visceral mass: region containing most of the internal organs as well as external gill
- Mantle: specialized epidermis that encloses all visceral organs and secretes shells
And Radula
Radula
tongue-like organ with chitinous ornamentation
How do Snails, Bivalves, Cephalopods move?
Snails - waves of muscle contraction along foot allows individuals to “crawl”
Bivalves - digging appendage
Cephalopods - forms tentacles for crawling and grasping
Bivalvia characteristics
- Bivalvia = “two-valves”
- Clams, oysters, mussels, scallops
- Modified foot for digging
- Poorly developed head area with no defined mouth
- Loss of radula
Gastropoda characteristics
- Gastropoda = “stomach-foot”
- Snails, slugs, conches
- During development undergoes torsion: rotation of the mantle and visceral mass 180
- Creates space in visceral mass that allows withdrawal of head
Cephalopoda body plan
Octopuses, squid, cuttlefish, and nautiluses
- Foot typically modified to tentacles
- Many display and rapidly change an array of colors
- Chromatophores
Chromatophores
specialized pigment cells in that expand and contract to produce different color patterns
Annelida characteristics
Segmented worms, earthworms, leeches, polychaete
- Metamerism: series of body structures that are similar internally and externally, such as segments
- During development, the segments behind the head arise sequentially from a growth region anterior to the tail, a pattern called teloblastic growth
- Two opening in digestive tract and closed circulatory system
- Setae
- Clitellum
- Filter feeders
- Some live around deep sea hydrothermal vents
- Secrete mineral “tube” around body
Setae
chitinous hairs that are attached to muscle, extend through epidermis, and provide traction
Clitellum
specialized band of fused segments, which aids in reproduction
What are the defining traits of Lopotrochozoa?
Mollusks:
- Body plan: foot, visceral mass, mantle
- Radula
Annelida:
- Metamerism with teloblastic growth
- Setae
- Citellum
