Invertebrate Zoology Lecture 3: Bauplans (cont.)

Lecture outline  Animal Bauplans  Key features of body plans (cont.)  Excretion and osmoregulation  Circulation and Gas Exchange

Bauplans: key features  Excretion and osmoregulation: overview  Excretion, defined: ridding body of metabolic wastes  Carbon dioxide  Water (if in excess)  Nitrogenous and other wastes (=many are toxic)  Excretion usually tied to osmoregulation  CO2 often excreted separately  Excretion ≠ removal of solid waste

Bauplans: key features  Excretion and osmoregulation  Nitrogenous wastes & water conservation  Protein digestion  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 changes?  Osmoconformers  Osmoregulators Estuary: fresh water  seawater

Bauplans: key features  Excretion and osmoregulation  Osmoregulation and habitat  What if osmolarity changes (cont.)?  Most osmoconformers can osmoregulate (a bit)  Most osmoregulators have limits to osmoregulation  Osmoregulation can occur at the cellular level  Example: Cell placed in hypotonic solution might initially swell, then respond by excreting salts. (Why would this help?)

Bauplans: key features  Excretion and osmoregulation  Specialized structures  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:  Tubules acquire water/and or ions at one end and excrete wastes through pores

Bauplans: key features  Excretion and osmoregulation  Specialized structures  Nephridia  Protonephridia: proximal end closed  Metanephridia: proximal end open

Bauplans: key features  Circulation and gas exchange  Overview  Nutrients, wastes, and gases move through the body  Transport systems allow for movement beyond diffusion  Origin 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 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 hemocoel  Associated with reduced coelom,  peritoneum  Less efficient than closed system?  Additional functions (i.e. hydrostatic)  Secondary systems have evolved to compensate

Bauplans: key features  Circulation and gas exchange  Hearts and other pumping mechanisms  Pump blood/hemolymph; maintain blood pressure  Several types  Contractile vessels (Annelida)  Ostiate hearts (Arthropoda)  Allows entry of hemolymph back into heart from the hemocoel  Chambered hearts (Mollusca)

Bauplans: key features  Circulation and gas exchange  Other key concepts (circulation)  Myogenic vs. neurogenic control of contraction  In general, freshly oxygenated blood/hemolymph is first circulated to the head.  Vessel diameter and flow  Paradox:  diameter  flow rate  Problem: need low flow at capillaries (why?)  Solution: total cross-sectional area at capillaries   flow rate!

Bauplans: key features  Circulation and gas exchange  Gas exchange and transport  O 2 uptake from air or water over moist membrane (body surface or specialized structures)  Why moist?  Often diffuses into a “circulatory body fluid”, then to cells  CO 2 moves in opposite direction

Bauplans: key features  Circulation and gas exchange  Gas exchange and transport  Body fluids have relatively low O 2 -carrying capacity  Respiratory pigments increase that capacity   O 2 binds to a metal, usually copper or iron

Bauplans: key features  Circulation and gas exchange  Gas exchange and transport  CO 2 primarily converted to carbonic acid and bicarbonate  Requires carbonic anhydrase  CO 2 + H 2 O H 2 CO 3 H + +HCO 3 -