Estuaries fresh salt meet Tremendously Productive DETRITUS Origin

Estuaries fresh & salt meet Tremendously Productive DETRITUS

Origin and Types • • Drowned river valleys or coastal plain estuaries Bar-built estuary Tectonic estuary Fjords

Drowned or Coastal Plain • 18 K yr last ice age • Chesapeake Bay, Delware and St Lawrence, Thames

Bar-built Estuary • Sand bars and barrier islands • Barrier between ocean and river’s freshwater • Texas coast, N. Carolina coast, N. Sea coast

Tetonic Estuaries • Land subsided from crust’s movements • San Francisco Bay

Fjords • • • Cut by retreating glaciers Steep wall Alaska Norway Chile New Zealand

The body Diversity Adaptations

Classification by Developmental Pattern • Multicellular animals have been divided into two groups based on the # of germ layers – Germ layer • Diploblastic – Ectoderm – Endoderm • Triploblastic Most metazoans are triploblastic – Mesoderm 10 Invertebrate Classification & Relationships

Different Developmental Types Triploblastic Acoelomate Pseudocoelomate Protostomes 11 Coelomates Deutrostomes Invertebrate Classification & Relationships

Classification by Developmental Pattern • Triploblastic animals can be classified even further Pseudocoelomate Acoelomate Coelomate 12 Invertebrate Classification & Relationships

Body Plans Provide Diversity • A Question of Adaptation • Often – Consumer and Consumed Co-Evolve • Driver of Speciation – Exploitation of New Energy Resources • Topics on the diversity of higher organisms – Anatomy • Skin – keeps the body intact, etc. • Jaws –respiration and feeding • Appendages – locomotion and buoyancy – Cardiovascular system – Respiratory system

Energy Budgets Intake ( I = Income) • Macronutrients – Carbohydrates – Fats/Oils – Proteins • Micronutrients – Vitamins – Essential • Fatty Acids • Amino Acids • Sugars Energy Use (E = Expenditure) • Respiration • Osmoregulation • Movement • Feeding • Digestion • IF I=E I<E I>E Reproduction Growth = 0 Growth = +

Keystone System Circulatory system

Plausible Scenarios • Ancestor chordates evolved in an isotonic setting – All were marine since the start • • • No osmotic gradients No energy required for osmoregulation Body surface was highly permeable Some ion regulation Kidneys were exclusively for excretion When early vertebrates invaded freshwater – Osmotic disruption resulting in excess water • Absorption through thin epithelium • Water intake from feeding • Need to solve this problem along with ion balance

Osmosis is the tendency of water to move between two solutions of different osmolarity separated by a barrier permeable for water (e. g. membrane).

Living organisms • an aqueous solution with solutes contained within a series of membrane system • volume [solutes] maintained within a narrow limits for the optimal function • deviations from physiological composition: incompatible with life • maintain the proper concentrations of body fluid which invariably differ from the environment • unlike cell walls of plants, the animal cellular plasma membrane is not equipped to deal with high pressure differences or large volume changes

Osmoregulation: ability to hold constant total electrolyte and water content of the cells. Critical for survival and success

Concepts of osmorality • Osmotic concentration of a solution can be expressed as osmorality (osmoles per liter) • Concentration of a dissolved substance is expressed in units of molarity (number of moles per liter solution)

• Osmorality of a nonelectrolyte (sucrose) equals the molar concentration: 1 M = 1 Osm per liter • Osmorality of an electrolyte (Na. Cl) has a “higher” osmorality because of ionic dissociation and hence exerts a “higher” osmotic force – Not exactly because concentration and the interactions between ionic charges with water can influence the system – Along with the low osmotic coefficient of Na. Cl (Φ = 0. 91)

• Osmotic concentration determined by – measuring freezing point depression – vapor pressure of the solution – Seawater osmotic concentration: 1000 m. Osm • 470 mmol Na & 550 mmol Cl

Two categories of osmotic exchange Obligatory has little control such as trans-epithelial diffusion, ingestion, defecation, metabolic water production Regulated physiologically controlled and help maintain homeostasis (active transport)

Two Strategies to minimize this problem • Decrease the concentration gradient between animal to environment • Lower the permeability to the outside in areas that are compromised (gills, gut)

Even so • Always some diffusive leaks • For a counter-flow system to equal this leak – needs energy – Osmoregulators spend 5% to 30% of their metabolism in maintaining osmotic balance • Highly variable aquatic environment – – – Freshwater Brackish water Seawater Hypersaline water (Med ) Soft water runoffs

• • • Euryhaline: Stenohaline: isomotic: osmoconformer: osmoregulator:

Four groups of regulation dealing with water in fishes • • Hagfish Marine elasmobranchs Marine teleosts Freshwater teleosts and elasmobranchs

Five groups of regulation dealing with ions in fishes • • • Hagfish Marine elasmobranchs Marine teleosts and lampreys Freshwater teleosts Euryhaline and diadromous teleosts

Aganthans • Lampreys live in sea and freshwater but hagfish are strictly marine • Both employ different solution to life in the sea

Hagfish • Are the only true vertebrates whose body fluids have salt concentration similar to seawater • Have pronounced ionic regulation

Lamprey • • Egg & larvae develop in fresh water Some species stay, some migrate to sea Adults return to breed (anadromous fish) Osmotic concentration about 1/4 to 1/3 of the seawater • Face similar problems to that of the teleosts

Marine Elasmobranchs & Holocephalans • [Salt] at about 1/3 of seawater • Osmotic equilibrium achieved by the addition of large amount of organic compounds – primarily urea (0. 4 M) – various methylamine substances • 2 urea : 1 TMAO • trimethylamine (TMAO), sarcosine, betaine, etc.

• Blood osmotic concentration slightly greater than seawater • Water is taken up across the gills, which is used to remove excess urea via urine formation • Small osmotic load for the gills • Urea and TMAO are efficiently reabsorbed by the kidneys

But • Urea disrupts, denatured, cause conformational changes in proteins, collagen, hemoglobin, and many enzymes • Some elasmobranch proteins are resistance to urea • Yancey & Somero (1979): – Proteins are actually protected by the presence of TMAO – found to have a consistent ratio of 2 urea to 1 TMAO (also in Holocephalan and Latimeria)

Neat invention • Strategy of using waste products as an economical way for osmoregulation; unlike the invertebrates which invest on free amino acids to increase serum osmorality • ionic composition is different from seawater, hence still need to spend energy for ionic regulation • Need to have the ornithine-urea cycle

Freshwater elasmobranchs • sawfish, bull shark (C. leucas), stingrays are euryhaline – live in brackish and even freshwater for long time (Bull in Lake Nicaragua, Mississippi rivers) • Urea (25 -35%), sodium, and chloride are reduced as compared to sw counterparts • produce copious flow of dilute urine to deal with the water influx

• In freshwater rays, they abandoned urea retention, and reduced ionic content to cope with this problem • These freshwater rays are not able to make urea when presented in seawater

Coelacanth • Blood composition is similar to the marine elasmobranchs • Total osmorality is less than seawater • This maybe due to the habitats they live in: aquifers feeding into the caves and fissures that could presumably lower salinity: hence a localized hyperosmotic to the surrounding? ?

Teleost Fish • Maintain osmotic concentration at about 1/4 to 1/3 of seawater • Marine teleosts have a somewhat higher blood osmotic concentration • Some teleosts can tolerate wide range of salinities • Some move between fresh and salt water and are associated with life cycle (salmon, eel, lamprey, etc)

Marine teleosts • Hyposmotic, constant danger of losing water to surrounding via the gill surfaces • Compensate for water loss by drinking • Salts are ingested in the process of drinking • Gain water by excreting salt in higher concentration along the length of its convoluted tubules • Produce small amount but very concentrated urine – 2. 5 ml/kg body mass/day

• Kidney cannot produce urine that is more concentrated than the blood • Need special organ, the gills • Active transport requires energy • Water loss from gill membrane and urine • Fish drink to balance the water deficits • Na and Cl secreted via the gill’s chloride cells • Gut: for elimination of divalent salts