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  Example: Peristaltic movement requires a hydrostatic skeleton  Locomotion depends upon medium through which an animal moves as well as its size  Reynold’s number R e =  Large animals: high R e (>1.5): Inertial forces rule  Small animals: low R e (<1.5): Viscous forces rule

Bauplans: key features  Locomotion and support  Four key locomotory methods  Amoeboid  Cilia/flagella  Hydrostatic propulsion  Use of limbs

Bauplans: key features  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  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

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

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

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!”)

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

Bauplans: key features  Locomotion and support: hydrostatic  Peristalsis of earthworm

Phylum Echiura  Fat innkeeper worm: also moves by peristalsis within tube

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)

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

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

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

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

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