#Week 4 - Circulation - Gas Exchange - Defense: The immune system and defense mechanisms - Option 1. Exercise- and (or) hypoxia-induced anaerobic metabolism in a teleost fish. --- #9. Circulation - Overview: - Every organism must exchange materials and energy with its environment, and this exchange ultimately occurs at the cellular level. - Cells live in aqueous environments - The resources that they need, such as nutrients and oxygen, move across the plasma membrane to the cytoplasm - Metabolic wastes, such as carbon dioxide, move out of the cell - Most animals have organ systems specialized for exchanging materials with the environment, and many have an internal transport system that conveys fluid (blood or interstitial fluid) throughout the body - For aquatic organisms, structures such as gills present an expansive surface area to the outside environment. - Oxygen dissolved in the surrounding water diffuses across the thin epithelium covering the gills and into a network of tiny blood vessels (capillaries). At the same time, carbon dioxide diffuses out into the water- These two concepts will be addressed in the next lecture. - There is a tight connection between circulation (this lecture) and gas exchange (next lecture). - The circulatory system (Ch. 45, pp. 916-925) - Animals WITHOUT circulatory system (Ch. 45, pp 916) - Ways of maximizing the surface area available for diffusion of gases and other key solutes - The 1 mm rule: Diffusion is an effective means of transporting substances (e.g., gases) only when distances is <1 mm - Cnidarians, planarians, etc. have a large, highly folded gastrovascular cavity –Revise concepts from lecture 6 Nutrition: basic concepts and feeding invertebrates-” - For animals with many cell layers, gastrovascular cavities are insufficient for internal distances because the diffusion transports are too great - Animals WITH circulatory system - Open circulatory system (Ch. 45, pp 916-917) - Hemolymph (blood and interstidial fluid) empties into hemocoel and bathes tissue and organs directly - Lack of discrete continuous vessels: Heart-vessel-hemolymph-vessel-heart - Normally, low pressure and high volume (up to 40% of body mass) - Most of invertebrates - Close circulatory system (Ch. 45, pp 917-918) - Blood remains in vessels; capillaries allow close contact between blood and tissues - Important advantage: blood directed in a precise way in response to the tissues’ needs –at any given time, only 5-10% of the body’s capillaries have blood flowing through them - High pressure and low volume (5-10% of body mass) - All vertebrates and some invertebrates (e.g., annelids, and cephalopods-support intense muscular activity-) - Basic components of both close and open circulatory systems - Muscular bomb/s (heart) - Vessels - Circulatory fluid - Types of blood vessels: arteries, capillaries and veins (Ch 45, pp 917-918) - The capillary system, interstitial fluid and lymphatic system and their communication (Ch 45, pp 918-919) - Exchange of substance between the blood and the interstitial fluid that bathes the tissues. https://www.youtube.com/watch?v=ZJVUTkgYhhg - Mechanism: - Diffusion- Fick’s law (see Ch. 45 pp 905-906) - Bulk flow- Starling’s and concept of microcirculation law (see Ch 45, pp 919, Fig. 45.21) - Filtration (Hydrostatic pressure > Osmotic pressure) - Reabsorption (Hydrostatic pressure < Osmotic pressure) - Transcytosis (exocytosis and endocytosis) - Metabolic rate is an important factor in the evolution of cardiovascular systems. - In general, animals with high metabolic rates have more complex circulatory systems and more powerful hearts than animals with low metabolic rates. - Similarly, the complexity and number of blood vessels in a particular organ are correlated with that organ’s metabolic requirements. - Perhaps the most fundamental differences in cardiovascular adaptations are associated with gill breathing in aquatic vertebrates compared with lung breathing in terrestrial vertebrates. - The heart (Ch 45, pp 919-925) - Evolution of the circulatory system: Vertebrate phylogeny is reflected in adaptations of the cardiovascular system (Ch 45, pp 920, Fig. 45.22), see links of interest -surveying animal circulatory systems- - Single-loop circulation (e.g., fishes, see below) - Double-loop circulation (higher vertebrates) - Amphibians (oxygen-rich and oxygen-poor mix in the ventricle) - Non-bird reptiles (partial septum) - Crocodilians, birds and mammals (complete septum). Advantages. - Circulatory system in fishes: key concepts - A fish heart has two main chambers, one atrium and one ventricle - Blood is pumped from the ventricle to the gills (the gill circulation) where it picks up oxygen and disposes of carbon dioxide across the capillary walls - The gill capillaries converge into a vessel that carries oxygenated blood to capillary beds in the other organs (the systemic circulation) and back via veins to the atrium of the heart - In fish, blood must pass through two capillary beds, the gill capillaries and systemic capillaries - When blood flows through a capillary bed, blood pressure—the motive force for circulation—drops substantially - Therefore, oxygen-rich blood leaving the gills flows to the systemic circulation quite slowly (although the process is aided by body movements during swimming) - This constrains the delivery of oxygen to body tissues and, hence, the maximum aerobic metabolic rate of fishes - Blood (Ch 42, pp846-847 and Ch45 pp 912) - In invertebrates with open circulatory system: hemolymph is not different from interstitial fluid - In vertebrates: specialized connective tissue consisting of several kinds of cells suspended in a liquid matrix called plasma - Blood composition - Plasma (water, dissolved proteins, ions, waste products, respiratory gases, hormones, etc.) - Blood cells: - Platelets (thrombocytes) - White (leukocytes) - Red (erythrocytes)-Introduce next lecture Links of interest Surveying animal circulatory systems with emphasis in vertebrates (fish, amphibians and mammal/bird)-simple and short video https://www.youtube.com/watch?v=5XqEQr-KsW8 A little more advance reading: From hagfish to tuna: a perspective on cardiac function in fish http://www.jstor.org/stable/30156237?seq=1#page_scan_tab_contents Microcirculation https://www.youtube.com/watch?v=HhUiY_RLg_g #10. Gas exchange - Overview - To support continued production of ATP, cells have to obtain O2 and expel excess of CO2 continuously. Revise concepts from lecture 4 on “Bioenergetics” ![fig1](https://cloud.githubusercontent.com/assets/13633831/9481477/991aa59e-4b3f-11e5-94b8-25b3fca5619c.jpg) - Basic concepts - Gas exchange is the uptake of molecular O2 from the environment and the discharge of carbon dioxide CO2 to the environment. - In general gas exchange involves four steps (Ch 45, pp 903; Fig. 45.1, Ch 45, pp. 903) - Ventilation - Gas exchange in respiratory surface - Circulation (previous lecture) - Cellular respiration - Steps 1 and 2 are the respiratory system - Step 3 is the circulatory system- Revise key concepts from previous lecture - Revise concepts from previous lectures - How do O2 and CO2 behave in water? (Ch. 45, pp. 904). Effects of - Temperature - Salinity - Pressure - Availability of O2 in aquatic environments (students should be familiar with these concepts from Marine Biology 250) (Ch. 45, pp. 904-905) - Photosynthetic organisms, upwelling systems - Surface vs. deep water - Rapids, waterfalls, white waters, etc - Dissolved O2 in water is much less than an equivalent volume of air - Organs of gas exchange (Ch. 45, pp 905-912) - Movements of CO2 and O2 across the respiratory surface occur ENTIRELY BY DIFFUSION - The respiratory surface of terrestrial and aquatic animals must be moist to maintain the cell membranes - Fick’s law of diffusion (Ch. 45, pp 905-906). Rate of diffusion depends on 5 parameters: - Solubility of the gas in the aqueous film lining the gas exchange surface - Temperature - Surface area - Difference in partial pressure of the gas across the gas exchange surface - Thickness of the barrier - Therefore, respiratory surfaces tend to be thin and have large areas, maximizing the rate of gas exchange - Animals WITHOUT respiratory organs - Gas exchange occurs over the entire surface area of protists and other unicellular organisms - Similarly, for some relatively simple animals, such as sponges, cnidarians, and flatworms, the plasma membrane of every cell in the body is close enough - However, in most animals, the bulk of the body lacks direct access to the respiratory medium - Animals WITH dermal respiration - Earthworms and some amphibians, use the entire outer skin as a respiratory organ - Just below the moist skin is a dense net of capillaries - However, because the respiratory surface must be moist, the possible habitats of these animals are limited to water or damp places - Animals that use their moist skin as their only respiratory organ are usually small and are either long and thin or flat in shape, with a high ratio of surface area to volume - Animals WITH respiratory organs - For most other animals, the general body surface lacks sufficient area to exchange gases for the entire body. The solution is a respiratory organ that is extensively folded or branched, enlarging the surface area for gas exchange. The three most common respiratory organs: - Gills- found is most of aquatic animals, we’ll put more emphasis - Lungs- marine mammals - Tracheae-only in terrestrial insects - How do gills work? (Ch. 45, pp 906-907) - In invertebrates, gills are simple shape and distributed over much of the body (e.g., sea star) - Many segmented worms and nudibranchs have flap-like gills that extend from each body segment, or long feathery gills clustered at the head or tail - The gills of clams, crayfish, and many other animals are restricted to a local body region - The total surface area of gills is often much greater than that of the rest of the body - Water has both advantages and disadvantages as a respiratory medium - There is no problem keeping the cell membranes of the respiratory surface moist, since the gills are surrounded by the aqueous environment - However, O2 concentrations in water are low, especially in warmer and saltier environments - Thus, gills must be very effective to obtain enough oxygen - Ventilation, which increases the flow of the respiratory medium over the respiratory surface, ensures that there is a strong diffusion gradient between the gill surface and the environment - Crayfish and lobsters have paddle-like appendages that drive a current of water over their gills - Most fishes open and close their mouth and operculum. The pumping action of the mouth and operculum creates a pressure gradient that moves water over the gills - Unlike bony fish, they do not have gill covers. Water must continually flow across these slits in order for the shark to breathe. This can be accomplished by the shark's swimming, by it standing still in a current, or by it fanning water across the gills with its fins (this is done by the nurse shark) - Some sharks have spiracles, which are special gill slits located just behind the eyes. They supply oxygen directly to the eyes and brain of the shark - The fish gill is a countercurrent system: concurrent vs. countercurrent system (Ch. 45, pp 906-907, Fig. 45.5, and Fig. 45.6); also see in links of interest: Countercurrent circulation in fish gills - The countercurrent exchange mechanism is so efficient that the gills can remove more that 80% if the oxygen from water to blood - Critical thinking: Breathing air - Advantages - Air has a much higher concentration of oxygen Also, since O2 and CO2 diffuse much faster in air than in water, respiratory surfaces exposed to air do not have to be ventilated as thoroughly as gills - When a terrestrial animal does ventilate, less energy is needed because air is far lighter and much easier to pump than water and much less volume needs to be breathed to obtain an equal amount of O2 - Disadvantages - The respiratory surface, which must be large and moist, continuously loses water to the air by evaporation - This problem is greatly reduced by a respiratory surface folded into the body - How do lungs work? (Ch. 45, pp 909-912) - Basics concepts - How do insect tracheae work? (Ch. 45, pp 907-909) - Basics concepts - How are O2 and CO2 transport in blood? (Ch. 45, pp 912-916) - Oxygen transport - O2 is highly insoluble in water, most of the O2 is bound to respiratory pigments - A diversity of respiratory pigments has evolved in various animal taxa to support their normal energy metabolism: - Hemocyanin, found in the hemolymph of arthropods and many molluscs - Hemerythrin, found in in the marine invertebrate phyla of sipunculids, priapulids, brachiopods - Chlorocruorin, found in marine polychaeta - Hemoglobin, all vertebrates - Hemoglobin - Structure and function of hemoglobin (Ch. 45, pp. 912-913) - The respiratory pigment of almost all vertebrates - Contained within red blood cells - Hemoglobin consists of four subunits, each with a cofactor called a heme group that has an iron atom at its center - Because iron actually binds the O2, each hemoglobin molecule can carry four molecules of O2 - Like all respiratory pigments, hemoglobin must bind oxygen reversibly, loading oxygen at the lungs or gills and unloading it in other parts of the body - Loading and unloading depend on cooperation among the subunits of the hemoglobin molecule. - The binding of O2 to one subunit induces the remaining subunits to change their shape slightly such that their affinity for oxygen increases - When one subunit releases O2, the other three quickly follow suit as a conformational change lowers their affinity for oxygen. - Cooperative oxygen binding and dissociation curve for hemoglobin (Ch. 45, pp 912-914) - Effect of temperature and pH (Bohr Effect) on O2 unloading from hemoglobin (Ch. 45, pp 914) - CO2 transport (Ch. 45, pp 915-916, Fig. 45.18) - ~ 5% carried as free CO2 in solution - ~ 10% of carbon dioxide binds to hemoglobin (carbaminohemoglobin) - ~ 85% carried in blood as bicarbonate hydrogen carbonate - Carbon dioxide from respiring cells diffuses into the blood plasma and then into red blood cells - The CO2 first reacts with water, assisted by the enzyme carbonic anhydrase, to form H2CO3, which then dissociates into a hydrogen ion H+ and a bicarbonate ion (HCO3−). This reaction maintains the partial pressure gradient favoring the entry of CO2 into red blood cells - Most of the H+ attaches to hemoglobin and other proteins, minimizing the change in blood pH. - The HCO3− diffuses into the plasma - As blood flows through the lungs, the process is rapidly reversed as diffusion of CO2 out of the blood shifts the chemical equilibrium in favor of the conversion of HCO3− to CO2 - If there is some extra time we can include some information about the adaptation of air-breathing aquatic animals - When an air-breathing animal swims underwater, it lacks access to its normal respiratory medium. - Most humans can hold their breath for only 2 to 3 minutes and swim to depths of 20 m or so - However, a variety of seals, sea turtles, and whales can stay submerged for much longer times and reach much greater depths - The Weddell seal of Antarctica can plunge to depths of 200–500 m and remain there from 20 minutes to more than an hour - Elephant seals can dive to 1,500 m and stay submerged for up to 2 hours - One adaptation of these deep-divers, such as the Weddell seal, is an ability to store large amounts of O2 in the tissues - Compared to a human, a seal can store about twice as much O2 per kilogram of body weight, mostly in the blood and muscles. - About 36% of our total O2 is in our lungs, and 51% is in our blood - In contrast, the Weddell seal holds only about 5% of its O2 in its small lungs and stockpiles 70% in the blood. - Several adaptations create these physiological differences between the seal and other deep-divers in comparison to humans. - First, the seal has about twice the volume of blood per kilogram of body weight as a human - Second, the seal can store a large quantity of oxygenated blood in its huge spleen, releasing this blood after the dive begins. The spleen can store about 24 L of blood. - Third, diving mammals have a high concentration of an oxygen-storing protein called myoglobin in their muscles. This enables a Weddell seal to store about 25% of its O2 in muscle, compared to only 13% in humans. - Diving vertebrates not only start a dive with a relatively large O2 stockpile, but they also have adaptations that conserve O2. - They swim with little muscular effort and often use buoyancy changes to glide passively upward or downward - Their heart rate and O2 consumption rate decrease during the dive, and most blood is routed to the brain, spinal cord, eyes, adrenal glands, and placenta (in pregnant seals)-Characteristic of a close circulatory system! - Blood supply is restricted or even shut off to the muscles, and the muscles can continue to derive ATP from fermentation after their internal O2 stores are depleted. - During dives of more than 20 minutes, a Weddell seal’s muscles deplete the O2 stored in myoglobin and then derive ATP from fermentation instead of respiration Link of interest Countercurrent circulation in fish gills https://www.youtube.com/watch?v=rlC8fXRmVZ0 Respiratory pigments https://books.google.com/books?id=AljmCAAAQBAJ&pg=PR4&lpg=PR4&dq=respiratory+pigments+lab&source=bl&ots=oVN5KmdzG7&sig=ZwXigyNZLPUDvr8cXRaaeXVkAh8&hl=en&sa=X&ved=0CCoQ6AEwAmoVChMI95LR3bfMxwIVDgySCh27OgMN#v=onepage&q=respiratory%20pigments%20lab&f=false #11. Defense: The immune system and defense mechanisms - Overview: - Organisms live in a hostile environment - An animal must defend itself against unwelcome intruders—the many potentially dangerous viruses, bacteria, and other pathogens it encounters in the air, in food, and in water - It must also deal with abnormal body cells, which, in some cases, may develop into cancer - Two major kinds of immunity have evolved to counter these threats: - Innate / non-specific immune response: - First line of defense - Barriers - Second line of defense - Inflammatory response - Phagocytes (neutrophils, monocytes (and –derived macrophages), eosinophils, dendritic cells) - Natural killer - Adaptive immunity - Lymphocytes - B-lymphocytes (B cells, bursa of Fabricius or bone marrows) - Humoral response - T-lymphocytes (T cells, thymus) - Cell-mediated response - In the second part of this lecture, we will briefly analyze different strategies that animals have developed to protect themselves against predators: Anti-predator adaptations - Innate / non-specific immune response (Ch. 51, pp 1038-1041) - Innate defenses are largely nonspecific, provides broad defenses against infection - Barriers to entry (Ch. 51, pp 1038-1039). An invading microbe must penetrate the external barrier formed by the skin and mucous membranes, which cover the surface and line the openings of an animal’s body - First line of defense - Intact skin is a barrier that cannot normally be penetrated by bacteria or viruses - Likewise, the mucous membranes that line the digestive, respiratory, and genitourinary tracts bar the entry of potentially harmful microbes - Microbial colonization is also inhibited by the washing action of saliva, tears, and mucous secretions that continually bathe the exposed epithelium - Stomach acid - If microbes penetrate the body’s protective barrier, particular cells initiate the innate immune response (first response to pathogens, still non-specific, Ch. 51, pp1039-1041): - The leukocytes involved in innate immunity provide an important, generic response that is directed against the general type of pathogen encountered-The innate response is able to distinguish between fungi and bacteria but cannot identify a specific strain either group - The inflammatory response and phagocytes (Ch. 51, pp 1040-1041; Fig. 51.3, and table 51.2). See a good video by Khan Academy in links of interest - Adaptive immune response - While microorganisms are under assault by phagocytic cells, the inflammatory response, and antimicrobial proteins, they inevitably encounter lymphocytes, the key cells of acquired immunity, the body’s second major kind of defense - As macrophages and dendritic cells phagocytose microbes, they secrete certain cytokines that help activate lymphocytes and other cells of the immune system - Thus the innate and acquired defenses interact and cooperate with each other - Characteristics of the adaptive immune response - Specificty - Diversity - Memory - Self-nonself recognition -*Note: I believe that the Review of the immune system by Khan Academy (8 videos) is an excellent way to approach this lecture (see links of interest). - General characteristics of B- and T-cells (Ch. 51, pp1041-1047) - The vertebrate body is populated by two main types of lymphocytes: B lymphocytes (B cells) and T lymphocytes (T cells). - Lymphocytes that migrate from the bone marrow to the thymus develop into T cells. - Lymphocytes that remain in the bone marrow and continue their maturation there become B cells –sharks, skates and rays do not have bones, and therefore bone marrow, but they synthesize B cells (see notes at the end) - B and T cells recognize antigens by means of antigen-specific receptors embedded in their plasma membranes. - A single B or T cell bears about 100,000 identical antigen receptors - Because lymphocytes recognize and respond to particular microbes and foreign molecules, they are said to display specificity for a particular epitope on an antigen - However, while the receptors on B cells recognize intact antigens, the receptors on T cells recognize small fragments of antigens that are bound to normal cell-surface proteins called MHC molecules - MHC molecules are encoded by a family of genes called the major histocompatibility complex (MHC) - Activation of the adaptive immunity (Ch. 51, pp 1047-1051) - T cell activation (Ch. 51, pp 1049, Fig. 51.12) - Antigen is phagocytosed by an antigen presenting cells (mostly dendritic cells) - Antigen presentation (links the innate and adaptive arms of the immune system, Ch. 51 pp 1049, Fig. 51.11) - MHC proteins I interact with CD8+ T cells (develop into cytotoxic or killer) - MHC proteins II interact with CD4+ T cells (differentiate into helpers) - B cells activation (Ch. 51, pp 1051, Fig. 51.14) - BCR binds antigen - BCR-antigen complex is internalized (NO phagocytosed) - Digested fragments are loaded onto a MHC protein II (showing different epitopes on its surface) - CD4+ T cell (effector T helper) with complementary receptor binds to the MHC-peptide complex on the B cell - T helper releases cytokines and fully activate B cells - Fully activated B cells replicates and produce memory B cells and effector B cells (plasma cells, which produce antibodies) - Therefore, adaptive immune system can be subdivided in two types: - Humoral immunity involves B cell activation and clonal selection and results in the production of antibodies that circulate in the blood plasma and lymph. - Circulating antibodies defend mainly against free bacteria, toxins, and viruses in the body fluids. - Cell-mediated immunity involves activation and clonal selection of cytotoxic T lymphocytes allows these cells to directly destroy certain target cells, including “nonself” cancer and transplant cells. - The humoral and cell-mediated immune responses are linked by cell-signaling interactions, especially via helper T cells. - Memory of the adaptive immunity (CH. 51, pp 1051-1055) - Notes: B cells in sharks - Sharks, skates, and rays lack a bony skeleton, and so do not have bone marrow - In mammals, immune cells are produced and mature in the bone marrow and other sites, and, after a brief lag time, these cells are mobilized to the bloodstream to fight invading substances. - In sharks, the immune cells are produced in the spleen, thymus and unique tissues associated with the gonads (epigonal organ) and esophagus (Leydig organ) - Some maturation of these immune cells occurs at the sites of cell production, as with mammals. But studies have determined that a significant number of immune cells in these animals actually mature as they circulate in the bloodstream - Like the ever-present IgM molecule, immune cells already in the shark's blood may be available to respond without a lag period, resulting in a more efficient immune response ![sharkimmune](https://cloud.githubusercontent.com/assets/13633831/9535628/395be006-4cd8-11e5-9c2b-118cf65bf05f.JPG) - Notes: Immune system in marine invertebrates - Little is known about the immune system in invertebrates - Current evidence suggests that invertebrates lack cells analogous to lymphocytes, the white blood cells responsible for acquired, specific immunity in vertebrates. - The predominant mechanism of marine invertebrate’s internal defense involves phagocytosis by immune cells (innate immune system) - Even in animals such as the Cnidaria, which lack mobile phagocytes, hemolymph or an impermeable barrier to invading organisms active phagocytosis has been demonstrated, being carried out by ectodermal as well as endodermal epithelial cells - Immune cells, or phagocytes, are particularly abundant in haemolymph, - Anti-predator adaptations (we can use this last part to lighten up this lecture) - Evolutionary success is measured in offspring produced or genetic contribution to the next generation, but to reproduce it is necessary to survive long enough to do so - Mechanisms developed through evolution that assist prey organisms in their constant struggle against predators (some examples found in marine organisms) - Avoiding detection - Staying out of sight- e.g. Flatfishes - Camouflage- e.g. cephalopods - Warding off attack - Starling the predator- e.g. cephalopods - Defensive structures (spine, needle-like structures, etc.)- e.g. Sohal surgeonfish, cnidaria - Distraction- e.g. mollusks - Mimicry - e.g. cephalopods - Group living- e.g. cardumenes - Fighting back - Chemical defense- e.g. pufferfish, hagfish (see video) - Escaping - Swim away - Autotomy- e.g. certain sea slugs discard stinging papillae; arthropods such as crabs can sacrifice a claw, which can be regrown over several successive moults ![cephalop](https://cloud.githubusercontent.com/assets/13633831/9535632/48446e80-4cd8-11e5-8c12-4863d9f2de8b.JPG) Links of interest Podcast the immune system by Bozeman Science – simple and didactic https://www.youtube.com/watch?v=z3M0vU3Dv8E Review of the immune system by Khan Academy (8 videos)-very good and complete https://www.youtube.com/playlist?list=PL14EB6C745989FC22 Gill-clogging slime secretion in hagfishes: A defense mechanism against predation https://www.youtube.com/watch?v=Bta18FdkVcA Coagulation and innate immune responses: can we view them separately? - A little more advance reading but very interesting http://www.bloodjournal.org/content/bloodjournal/114/12/2367.full.pdf?sso-checked=true Immune system of cnidarians –very interesting reading http://worldoceanreview.com/en/wor-1/medical-knowledge/the-causes-of-disease/ Cnidarian-microbe interactions and the origin of the innate immunity in metazoans http://www.annualreviews.org/doi/pdf/10.1146/annurev-micro-092412-155626 Review article: Immunological function in marine invertebrates: responses to environmental perturbation http://www.sciencedirect.com/science/article/pii/S1050464811001215 Mimicry in cephalopods http://www.reed.edu/biology/professors/srenn/pages/teaching/web_2007/armmil_site/index.html #LAB WORK 4 - Two options: - Option 1. Exercise- and (or) hypoxia-induced anaerobic metabolism in a teleost fish. - We can adapt the protocol shown in http://advan.physiology.org/content/33/1/72.long - This links concepts of bioenergetics and gas exchange - Again we would need to work with a vertebrate (IACUC problems???) - Option 2. Dissect a rock anemone and view cnidocytes under the microscope - We can use this lab to review the concepts of circulation and gas exchange in invertebrates seen this week - We can also complete the last part of the third lecture week on anti-predator adaptations - For the activation of cnidocytes we can follow this protocol https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCIQFjAAahUKEwjpqb_jwMzHAhVXF5IKHc8rA1o&url=http%3A%2F%2Fwww.ableweb.org%2Fvolumes%2Fvol-29%2Fv29reprint.php%3Fch%3D20&ei=sbXgVamNL9euyATP14zQBQ&usg=AFQjCNHuNHYaB3vL-lXGHSdbHz2of07wYw&sig2=S5JOtBgj3LZBkp9_4A7c6Q&cad=rja