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

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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