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Invertebrate Zoology
Lecture 2: Bauplans (cont.)
Lecture outline
Animal BauplansKey features of body plans (cont.)
Locomotion and supportLocomotion and support FeedingFeeding
Bauplans: key features Locomotion and support
Type of locomotion limited by type of support system Example: Peristaltic movement requires a hydrostatic Example: Peristaltic movement requires a hydrostatic
skeletonskeleton
Locomotion depends upon medium through which an animal moves as well as its size Reynold’s number Reynold’s number RRee = =
Large animals: high Large animals: high RRee (>1.5): Inertial forces rule(>1.5): Inertial forces rule
Small animals: low Small animals: low RRee (<1.5): Viscous forces rule(<1.5): Viscous forces rule
v
plU
Bauplans: key features Locomotion and support
Four key locomotory methods AmoeboidAmoeboid Cilia/flagellaCilia/flagella Hydrostatic propulsionHydrostatic propulsion Use of limbsUse of limbs
Bauplans: key features Locomotion and support: amoeboid movement
Many cell types move this way Amoebocytes of spongesAmoebocytes of sponges
Extension of pseudopodia Fluid “endoplasm” Fluid “endoplasm”
pushes the more pushes the more viscous “ectoplasm” in viscous “ectoplasm” in a particular direction. a particular direction.
Endoplasm and Endoplasm and ectoplasm are the ectoplasm are the same… same… ∆ viscosity∆ viscosity
Movement involves Movement involves actin and myosinactin and myosin
Bauplans: key features Locomotion and support: cilia/flagella
Operate effectively at low Re Sometimes associated with secreted mucusSometimes associated with secreted mucus
Several Functions Propulsion of larvae and small adultsPropulsion of larvae and small adults Create fluid currents for feeding and gas exchangeCreate fluid currents for feeding and gas exchange Propel food particles and/or waste particlesPropel food particles and/or waste particles Role in sensory structuresRole in sensory structures
Bauplans: key features Locomotion and support: cilia/flagella
Structure 9 + 2 microtubule 9 + 2 microtubule
arrangementarrangement Dynein armsDynein arms
ATP-powered Microtubules slide past Microtubules slide past
each other slightlyeach other slightly Protein cross-links limit Protein cross-links limit
sliding sliding bending bending
Bauplans: key features Locomotion and
support: cilia/flagella Patterns of movement
FlagellaFlagella: may beat back and : may beat back and forth, or may move in a helical forth, or may move in a helical (or “rotary”) motion(or “rotary”) motion
Push or pull along axis of Push or pull along axis of flagellumflagellum
Bauplans: key features Locomotion and support:
cilia/flagella Patterns of movement
Cilia: oar-like movementCilia: oar-like movement Power stroke vs. recovery
stroke Metachronal waves
Coordination of Coordination of metachronal waves is metachronal waves is usually mechanical 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 can be pushed into structures expansion. expansion. can provide support/structurecan provide support/structure
Complementary action of circular and longitudinal muscles Circular: decrease diameter with contractionCircular: decrease diameter with contraction Longitudinal: shorten with contractionLongitudinal: 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
ExoskeletonExoskeleton: usually : usually epidermallyepidermally-derived -derived
EndoskeletonEndoskeleton: usually : usually mesodermallymesodermally-derived -derived
Some are articulated: Some are articulated: with jointswith 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 Note interiorinterior attachment attachment
points for exoskeletonpoints for exoskeleton
Bauplans: key features Feeding
Digestion Extracorporeal digestionExtracorporeal digestion: occurs outside body: 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 Intracellular
digestiondigestion: occurs : occurs within cellswithin cells Phagocytosis
(particles) Pinocytosis (fluids) Role of lysosomes Absorption of DOM
Bauplans: key features Feeding
Digestion Extracellular digestionExtracellular digestion: :
within gut chamberwithin gut chamber Incomplete
single openingsingle opening Complete
two openingstwo openings Advantages of
complete digestive system?
Bauplans: key features Feeding
Modes of feeding (briefly) Suspension feedingSuspension feeding: : remove food particles
from the water column Deposit feedingDeposit feeding: : obtain nutrients from the
sediments HerbivoryHerbivory CarnivoryCarnivory ScavengingScavenging Direct intake of dissolved organic materialsDirect intake of dissolved organic materials