Invertebrate Zoology Lecture 3 Bauplans cont Lecture outline

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 «CO 2 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 -