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Invertebrate Zoology

Invertebrate Zoology. Lecture 2: Bauplans (cont.). Lecture outline. Animal Bauplans Key features of body plans (cont.) Locomotion and support Feeding. Bauplans: key features. Locomotion and support Type of locomotion limited by type of support system

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Invertebrate Zoology

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  1. Invertebrate Zoology Lecture 2: Bauplans (cont.)

  2. Lecture outline • Animal Bauplans • Key features of body plans (cont.) • Locomotion and support • Feeding

  3. Bauplans: key features • Locomotion and support • Type of locomotion limited by type of support system • Example: Peristaltic movement requires a hydrostatic skeleton • Locomotion depends upon medium through which an animal moves as well as its size • Reynold’s number Re = • Large animals: high Re(>1.5): Inertial forces rule • Small animals: low Re(<1.5): Viscous forces rule

  4. Bauplans: key features • Locomotion and support • Four key locomotory methods • Amoeboid • Cilia/flagella • Hydrostatic propulsion • Use of limbs

  5. Locomotion and support: amoeboid movement Many cell types move this way Amoebocytes of sponges Extension of pseudopodia Fluid “endoplasm” pushes the more viscous “ectoplasm” in a particular direction. Endoplasm and ectoplasm are the same… ∆ viscosity Movement involves actin and myosin Bauplans: key features

  6. Bauplans: key features • Locomotion and support: cilia/flagella • Operate effectively at low Re • Sometimes associated with secreted mucus • Several Functions • Propulsion of larvae and small adults • Create fluid currents for feeding and gas exchange • Propel food particles and/or waste particles • Role in sensory structures

  7. Locomotion and support: cilia/flagella Structure 9 + 2 microtubule arrangement Dynein arms ATP-powered Microtubules slide past each other slightly Protein cross-links limit sliding  bending Bauplans: key features

  8. Bauplans: key features • Locomotion and support: cilia/flagella • Patterns of movement • Flagella: may beat back and forth, or may move in a helical (or “rotary”) motion • Push or pull along axis of flagellum

  9. Bauplans: key features • Locomotion and support: cilia/flagella • Patterns of movement • Cilia: oar-like movement • Power stroke vs. recovery stroke • Metachronal waves • Coordination of metachronal waves is usually mechanical • Cilia and flagella are very specific terms (not “hairs!”)

  10. Bauplans: key features • Locomotion and support: hydrostatic • Key principle: body fluids are not compressible: • can be pushed into structures  expansion. • can provide support/structure • Complementary action of circular and longitudinal muscles • Circular: decrease diameter with contraction • Longitudinal: shorten with contraction • Fluids move in response to muscle contraction • Helical muscles prevent twisting and kinking • Anchor points important

  11. Bauplans: key features • Locomotion and support: hydrostatic • Peristalsis of earthworm

  12. Phylum Echiura • Fat innkeeper worm: also moves by peristalsis within tube

  13. Bauplans: key features • Locomotion and support: limbs • Involves rigid skeleton • Exoskeleton: usually epidermally-derived • Endoskeleton: usually mesodermally-derived • Some are articulated: with joints • Did skeletons arise “by chance” from accumulation of metabolic wastes? (nitrogenous waste  chitin)

  14. Bauplans: key features • Locomotion and support: limbs • Muscles attach to and push against skeletal elements in order to move • Origin vs. insertion points • Often in pairs of antagonistic muscles (i.e. flexor/extensor pairs) • Note interior attachment points for exoskeleton

  15. Bauplans: key features • Feeding • Digestion • Extracorporeal digestion: occurs outside body • Example: some sea stars open up mussel shell and secrete enzymes to liquefy tissue • Use cilia and mucus to draw fluids into mouth

  16. Bauplans: key features • Feeding • Digestion • Intracellular digestion: occurs within cells • Phagocytosis (particles) • Pinocytosis (fluids) • Role of lysosomes • Absorption of DOM

  17. Bauplans: key features • Feeding • Digestion • Extracellular digestion: within gut chamber • Incomplete • single opening • Complete • two openings • Advantages of complete digestive system?

  18. Bauplans: key features • Feeding • Modes of feeding (briefly) • Suspension feeding: remove food particles from the water column • Deposit feeding: obtain nutrients from the sediments • Herbivory • Carnivory • Scavenging • Direct intake of dissolved organic materials

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