Muscle types • Fish have the same three basic types of muscles as other vertebrates: skeletal, smooth, and cardiac. • Skeletal: Voluntary, used for locomotion, comprises the majority of the fish’s muscle mass. • Smooth: Involuntary such as intestine, many organs, and the circulatory system. • Cardiac: Heart
Skeletal Fish Muscle: • Essentially three types of fish muscle: red, white, pink. • Red muscle (oxidative): Highly vascularized, myoglobin containing tissue used during sustained swimming. Small diameter and high blood volume = rich O2 supply! Presence leads to strong flavor in some fishes (tuna). • White muscle (glycolytic): Little vascularization. Used during “burst” swimming. Large diameter fibers. • Pink muscle: This one is sort of in between red and white. Serves in sustained swimming, but not to the extent that red muscle is used.
Red vs. White Muscle Fibers Red White Capilary beds Extensive Sparse Muscle fiber density Low High Myoglobin content High Low Glycogen content Low High Muscle mass Low High
Alimentary Canal • Essentially the gastrointestinal tract (GI). • Two parts: (Antierior) mouth, buccal cavity, pharynx (Posterior) esophagus, stomach, intestine, rectum. • Mouth to esophagus & rectum is comprised of voluntary muscle while the stomach to posterior is involuntary. • GI tract varying considerably from spp. to spp. group. • Nutrient absorption increased by folding and increase of surface area (typhlosole, sprial valve).
Alimentary Canal Oddities... • Esophagus (Peristalsis) -one-way trip for food! • Stomach (Killer pH!) -Some tilipia <2! Can actually break down plant cell walls in absence of appropriate gastric enzymes. • No stomach (lungfish)! If no stomach, then no HCl = no shell or • bone digestion.
Alimentary Canal Oddities... • Intestine -Pyloric caeca are fingerlike pouches that may aid in nutrient uptake.
GI (cont.) • Liver-fat storage, detox., oil source. Sharks—huge liver ~50% of gut space, but they don’t get cancer?? • Gallbladder—source of bile (fat emulsification). • Pancreas—source of digestive enzymes part of liver in some fish and crustaceans (hepatopancreas)
Buoyancy • Fish regulate buoyancy several ways: • (1) Low density tissue (liver in sharks)—increase fat • (2) “Lift” from fin movement or hydrodynamics • (3) Reduced heavy tissue (bones and muscle) • (4) Gas (swim) bladder
Gas Bladder • Used for buoyancy control. • Physostomas-gas bladder is connected to the stomach. • Buoyancy achieved by gulping air. • Physoclistous-not connected to stomach. Fish has • developed rete mirable and gas gland which serve • to promote gas exhange.
Circulatory System Mammals double circuit 1- heart to lungs 2- heart to body Fish single circuit heart gills body heart
Special conditions for fish circulation – Environment is oxygen poor – Heart is simplest of vertebrates – Fish have less blood volume than other vertebrates • Adaptations by fish– Composition of blood – Morphology of circulatory apparatus – Behavioral responses to oxygen availability
Functions of the Circulatory System • Delivers oxygen • Delivers nutrients • Removes metabolic waste • Fights pathogens
Components of the Circulatory System to Study • Blood– Erythrocytes – Leukocytes – Structure of Hemoglobin • Vascular system– Heart – Vessels
Blood Oxygen Affinity • pH– Decreasing pH decreases affinity – Often associated with carbon dioxide • Carbon dioxide– Increase in CO2 drives off O2 (Bohr effect) – Decrease in blood pH magnifies Bohr effect
Blood Oxygen Affinity • Temperature– Increase in temperature depresses oxygen affinity and capacity – Results in fish having narrow temperature tolerances • Organic phosphate– ATP depresses O2 affinity – Urea increases O2 affinity
Fish Circulatory System • Primary circulation– Closed system • Heart • Arteries • Capillaries • Veins • Secondary circulation – Collects blood that is outside the primary – Originally thought to be lymphatic • No lymph or lymph nodes
Divisions of Primary Circulation • Branchial circulation – Blood from heart through gills • Systemic circulation – Blood from gills to body to heart • Blood flow is continuous from heart, to lungs, to body, back to heart
Proximity of Heart & Gills • Exceptions to Normal Circulation • Hagfish have accessory inline hearts • Lungfish have pulmonary circulation • There are also many small adaptations in some species
Structure of the Fish Heart • Four chambered heart • All four chambers are in line • The heart pumps only venous blood • Except for a few air breathing fish, all blood is pumped to the gills
Chambers of the Fish Heart (1) Sinus venous– Collects blood from venous ducts (2) Atrium– Accelerates blood flow (3) Ventricle – Large muscled chamber – Provides propulsive flow for circulation (4) Bulbus arteriosus (bony) Conus arteriosus – Changes blood from a pulse to continuous flow
Conus Arteriosus vs. Bulbus Arteriosus • Conus Arteriosus– Contractile – Cardiac muscle – More than one valve • Bulbus Arteriosus– Elastic – Mostly connective tissue – One valve dividing it from ventricle
Regulation of the Fish Heart • Self-regulating • Timing can be modified by brain (influence on the autonomic nervous system) • Pace is set by pacemaker cells • Many areas show pacemaker activity
The Hagfish Heart • Most primitive • Sinus venous well developed– Divided into two parts to receive different veins • Bulbus arteriosus • Have 3 additional hearts– Cardinal heart in head – Caudal heart near end of tail – Portal heart – pumps blood through liver
Lamprey Heart • Largest of fish hearts • Atrium overlies ventricle • Bulbus arteriosus
Elasmobranch Heart • Conus arteriosus • Sinus venosus with almost no cardiac muscle • Ventricle has two muscle layers – Compacta = compact outer layer – Spongiosa = inner layer
Teleost Heart • Variation exists across the group • Sinus venosus is thick-walled • Most have bulbus arteriosus • Some have conus arteriosus (usually more primitive)
Lungfish Heart • Atrium is divided into two parts by an incomplete septum – Functional 3 chamber heart – Like amphibians – Right atrium larger than left – Right = deoxygenated from sinus venosus – Left = oxygenated from pulmonary vein
Blood and Freezing Temp. • Osmolality • fp = delta freezing point • -0.06 FW • -0.75 SW • Ice fishes – Nototheniidae • glycoproteins • Winter Flounder -- Pleuronectes
Circulatory Systems of Fishes: Functions • Delivery of needed substances for metalolism to tissues where needed: • oxygen • nutrients (sugars, lipids, proteins) • minerals • hormones
Functions of Circulatory System • Delivery of waste products away from tissues: • carbon dioxide • nitrogenous wastes (NH3, NH4+, urea) • excess minerals • invading organisms (pathogens)
Functions of Circulatory System • Maintenance of stable pH via buffer system: • H20 + CO2 = H2CO3 = HCO3- + H+ = 2H+ + CO3= • Last step only at pH > 10, so not in fish blood
Components of Fish Circulatory Systems • Blood: • aqueous solution • solutes (proteins, sugars, minerals) • blood cells • erythrocytes (red blood cells) • leucocytes (white blood cells) • lymphocytes • thrombocytes • monocytes • granulocytes
Components of Fish Circulatory Systems • Plumbing: • heart • sinus venosus • atrium • ventricle • bulbus (conus) arteriosus • Blood vessels • arteries • veins • capillaries
Nervous Systems of Fishes Sensory, Motor and Integrative Functions
Organization of the brain(anterior to posterior) • Telencephalon (forebrain): • olfactory sensation • coordination of smell-driven activities • receives visual and mechanical information, too • Diencephalon: • homeostasis • pineal organ (gland) • light sensitive • endocrine functions (hypothalamus)
Brain Organization (anterior to posterior) • Mesencephalon (mid-brain): • Optic tectum (dorsal portion of mesencephalon): • receives visual input (optic nerve) • central processing center • coordinates visual input with other sensory inputs • sends out motor signals to musculature, e.g. escape response from sight of predator
Brain (cont.) • Metencephalon (cerebellum): • coordinates swimming activity • coordinates: • balance input with motor response • electrical sense input with motor response