Invertebrate Zoology

Lecture 3: Bauplans (cont.)

Lecture outline

Animal BauplansKey features of body plans (cont.)

Excretion and osmoregulationExcretion and osmoregulation Circulation and Gas ExchangeCirculation and Gas Exchange

Bauplans: key features Excretion and osmoregulation: overview

Excretion, defined: ridding body of metabolic wastes Carbon dioxideCarbon dioxide Water (if in excess)Water (if in excess) Nitrogenous and other wastes (=many are toxic)Nitrogenous and other wastes (=many are toxic)

Excretion usually tied to osmoregulationCO2 often excreted separatelyExcretion ≠ removal of solid waste

Bauplans: key features Excretion and osmoregulation

Nitrogenous wastes & water conservation Protein digestion Protein digestion nitrogenous wastes nitrogenous wastes

Excess amino acids are “deaminated”

Amine groups incorporated into waste molecules

Bauplans: key features Excretion and osmoregulation

Osmoregulation and habitat

Bauplans: key features Excretion and

osmoregulation Osmoregulation

and habitat What if osmolarity What if osmolarity

changes? changes? Osmoconformers Osmoregulators

Estuary: fresh water seawater

Bauplans: key features Excretion and osmoregulation

Osmoregulation and habitat What if osmolarity changes (cont.)?What if osmolarity changes (cont.)?

Most osmoconformers can osmoregulate (a bit)Most osmoregulators have limits to

osmoregulationOsmoregulation can occur at the cellular level

Example: Cell placed in hypotonic solution Example: Cell placed in hypotonic solution might initially swell, then respond by excreting might initially swell, then respond by excreting salts. (Why would this help?)salts. (Why would this help?)

Bauplans: key features Excretion and osmoregulation

Specialized structures Water expulsion vesicles (as in various Protista)Water expulsion vesicles (as in various Protista)

Accumulate water expel it to the outside Requires energy. Mechanism? Possibly in Porifera?

Bauplans: key features Excretion and osmoregulation

Specialized structures Nephridia: Nephridia:

Tubules acquire water/and or ions at one end and excrete wastes through pores

Bauplans: key features Excretion and osmoregulation

Specialized structures NephridiaNephridia

Protonephridia: proximal end closed

Metanephridia: proximal end open

Bauplans: key features Circulation and gas exchange

Overview Nutrients, wastes, and gases move through Nutrients, wastes, and gases move through

the bodythe body Transport systems allow for movement Transport systems allow for movement

beyond diffusionbeyond diffusion Origin of fluid for transportOrigin of fluid for transport

Internal body fluids; external fluids (i.e. Porifera)

Movement of fluids through/within body cavity may occur instead of or in addition to movement within a “true” circulatory system.

Bauplans: key features Circulation and gas exchange

Circulatory systems (true) CLOSED: blood remains within vesselsCLOSED: blood remains within vessels

Associated with well-developed coelomic cavity Composition of blood vs. coelomic fluid differs Exchange of dissolved materials occurs within

capillary beds (single cell layer to promote diffusion)

Bauplans: key features Circulation and gas exchange

Circulatory systems (true): OPEN: vessels exist, but open into hemocoelOPEN: vessels exist, but open into hemocoel

Associated with reduced coelom,peritoneum Less efficient than closed system?

Additional functions (i.e. hydrostatic)Additional functions (i.e. hydrostatic) Secondary systems have evolved to compensateSecondary systems have evolved to compensate

Bauplans: key features Circulation and gas

exchange Hearts and other pumping

mechanisms Pump blood/hemolymph; Pump blood/hemolymph;

maintain blood pressuremaintain blood pressure Several typesSeveral types

Contractile vessels (Annelida) Ostiate hearts (Arthropoda)

Allows entry of hemolymph Allows entry of hemolymph back into heart from the back into heart from the hemocoelhemocoel

Chambered hearts (Mollusca)

Bauplans: key features Circulation and gas exchange

Other key concepts (circulation) Myogenic vs. neurogenic control of contractionMyogenic vs. neurogenic control of contraction In general, freshly oxygenated blood/hemolymph is In general, freshly oxygenated blood/hemolymph is

first circulated to the head.first circulated to the head. Vessel diameter and flowVessel diameter and flow

Paradox: diameter flow rate Problem: need Problem: need lowlow flow at capillaries (why?) flow at capillaries (why?) Solution: Solution: total total cross-sectional area at cross-sectional area at

capillaries capillaries flow rate! flow rate!

Bauplans: key features Circulation and gas exchange

Gas exchange and transport OO22 uptake from air or water over uptake from air or water over moistmoist membrane membrane

(body surface or specialized structures) (body surface or specialized structures) Why moist?

Often diffuses into a “circulatory body fluid”, then Often diffuses into a “circulatory body fluid”, then to cellsto cells

COCO22 moves in opposite direction moves in opposite direction

Bauplans: key features Circulation and gas exchange

Gas exchange and transport Body fluids have relatively low OBody fluids have relatively low O22-carrying capacity-carrying capacity

Respiratory pigments increase that capacity O2 binds to a metal, usually copper or iron

Bauplans: key features Circulation and gas exchange

Gas exchange and transport COCO2 2 primarily converted to carbonic acid and primarily converted to carbonic acid and

bicarbonatebicarbonate Requires carbonic anhydraseRequires carbonic anhydrase COCO22 + H + H22O HO H22COCO33 H H++ +HCO +HCO33

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