Exam 1

Question 1

What is a fish?

Answer 1

Describe in terms of shared characteristics
of all members of the group: has a
backbone, breathes water, completes its
life cycle in water, body shape, muscles
organized in longitudinal segments,
appendages (when present) are fins.

Question 2

Why are there so many fishes?

Answer 2

-The common ancestor of all vertebrates was
a “fish like” vertebrate, probably much like
modern jawless organisms
– representatives in the fossil record that look
like hagfishes (a jawless vertebrate) are 500
million years old.
– Genetic revolutions in early vertebrates –
genome duplication

Question 3

How can fish survive in so many different water environments?

Answer 3

• water is dense(800 X air) provides structural support
  • Fishes neutrally buoyant, energy directed toward
  swimming
  • Water resists motion because of density and
  near incompressibility
  • Fishes usually streamlined to reduce resistance

Question 4

Other useful properties of water

Answer 4

Nearly incompressible
• used by fishes in lateral line system; can
detect turbulence from displacement
• suction feeding and respiration; create
negative pressure to force water into
buccal cavity, over gills
-Universal solvent: dissolved oxygen, though in a much lower concentration
-Low light penetration (photic zone is 1000m)

Question 5

Skeletal system

Answer 5

-chordates and vertebrates
Cranium
• Vertebral column
– Articulation with the skull
– Articulation with the tail (caudal region)
• Appendicular skeleton
– Pectoral girdle
– Pelvic girdle

Question 6

Skull

Answer 6

Chondrocranium and Dermatocranium
– Derived from embryonic cartilage
– Derived from dermal bone

Question 7

Shape of skull is reflective of function

Answer 7

Reflects multiple functions:
• Protection
• Ventilation
• Sensory systems
• Feeding

Question 8

5 groups of Cranial region bones to

remember (in bony fishes)

Answer 8

• Neurocranium
– Ethmoid
– Optic
– Otic
– Basiocciptal
• Hyoid arch (aka Suspensorium)
• Jaws (upper and lower)
• Opercular Bones
• Branchohyoid (supports gills, etc)

Question 9

Teeth

Answer 9

• Canine – snappers (Lutjanidae)
• Villiform – small fine teeth (Centrarchidae)
• Molariform – crushing teeth
• Cardiform – pharyngeal teeth in Escocidae
• Incisor – nipping teeth
• Beak-like teeth
• Triangular teeth – sharks, piranhas
• Pharyngeal teeth - Cyprinidae

Question 10

Vertebral column

Answer 10

• Development of the vertebral column ranges from cartilaginous sheath to
solid bone.
• Vertebrae at anterior end allow articulation with the skull, at the posterior
end articulate with rays of the caudal fin
• Dorsal process of vertebrate modified into a neural arch that accommodates
the spinal cord, also serves as attachment for dorsal musculature. Hemal
canal on the ventral side carries major blood vessels
• Usually one vertebra per body segment, ventral and dorsal ribs associated
with each vertebra
• Lateral processes – parapophyses (rib attachment); zygapophyses
• Ribs and intramuscular bones

Question 11

Caudal fin types

Answer 11

• Protocercal – hagfish and lampreys
• Heterocercal – Chondrichthyes
• Homocercal – Most teleosts
• Leptocercal (or diphycercal) -
Sarcopterygians

Question 12

Fins

Answer 12

• Paired versus unpaired fins
• Position and shape closely related to fish activity
patterns
• Caudal fin shape – homocercal or heterocercal
• Pectoral fin shape & height
• Pelvic fin position (abdominal, jugular, thoracic)
• Dorsal and anal fin length, modifications for
rover-predators, e.g. tunas
• Adipose fin
• Lepidotrichia, Ceratotrichia

Question 13

Fish Skin

Answer 13

• Epidermis
– Stratum germinativum – cell generation
– Stratum corneum – keratin layer
– Mucus glands, venom glands, photophores,
chromatophores
• Dermis
– Nerves, blood cells, sense organs,
– Stratum laxum
– Stratum compactum

Question 14

Scales

Answer 14

• Placoid: found in cartilaginous fishes – arose independently of scales
in bony fishes, more like tiny teeth

• Cosmoid: Known only from the fossil record – may have arisen from the
fusion of placoid scales

• Ganoid: ancestral condition for bony fishes—found in gars; Bone covered by enamel
• Cycloid: in pikes, herrings, minnows, and trouts
• Ctenoid: found in “hollow-spined” fishes (Acanthopterygii)

Question 15

Soft parts of fishes

Answer 15

• Muscles
• Cardiovascular system
• Digestive tract – Alimentary canal
• Swim (Gas) Bladder
• Kidneys and Gonads
• Nervous system

Question 16

Musculature

Answer 16

• Striated (voluntary), smooth, cardiac
– Antagonistic pairs (i.e., protractors, retractors)
– Peristaltic
• W-shaped bundles in each body segment;
myomeres – organized laterally on the
body, originate and insert on vertebral
elements and body wall, respectively

Question 17

Muscle fibers

Answer 17

– Red muscle (slow) highly vascularized – aerobic;
myoglobin present: sustained swimming
– White muscle (fast) poor blood supply; anaerobic
metabolism – conversion of lactate to glycogen and
glucose can fatigue easily: speed bursts
– Pink – used when activity is to high for red but too low for white

Question 18

Cardiovascular system

Answer 18

-distribute nutrients
• Blood – production in hemopoietic tissues
• RBC – contain hemoglobin and cell nuclei
• WBC – antigen presenting cells; phagocytes;
lymphocytes
• Plasma – contains dissolved ions and gases, etc.

Question 19

Hemopoietic Tissues in Fishes

Answer 19

– hagfishes – mesodermal tissues surrounding gut
– lampreys – fatty tissue dorsal to nerve cord
– Elasmobranchs – Leydig’s organ; spleen
– Chondrostei – lymphomyeloid tissue in head and
around heart
– Neopterygii – kidney and spleen

Question 20

circulatory system

Answer 20

Capillaries, Vessels, Heart – closed circulatory system
• Veins: oxygen depleted blood
• Arteries: oxygen enriched blood (except afferent arteries)
Heart – four chambers – all surrounded by pericardium
• Sinus venosus – reservoir
• Atrium
• Ventricle– thick walled, myocardial muscle
• conus (Elasmobranchs) or bulbous (Teleosts) arteriosus

Question 21

Digestive Tract (Alimentary Canal)

Answer 21

Mouth, buccal cavity, pharynx, esophagus, stomach,

pyloric caeca, small intestine, cloaca

Question 22

Gas bladder types

Answer 22

Physostomous

Physoclistous

Question 23

Physostomous

Answer 23

– connection b/w gut and swim bladder
• Ancestral Teleosts, salmonids, ostariophysans
• pneumatic duct between esophagus and swim bladder
• restricted to shallow-water dwellers, gas volume reduced by
pressure
• can reduce buoyancy by gas-spitting reflex

Question 24

Physoclistous

Answer 24

– closed: gases derived from blood
• Derived Teleosts – Perciformes
• inflation via rete mirabile (counter-current exchange system)
• swim bladder surrounded by connective tissue and interspersed
guanine crystals ; prevents diffusion of gas from swim bladder

Question 25

Rete Mirable (“wonderful net”)

Answer 25

``` • found in gas gland of swim bladder, behind retina of eye: interlocking system of afferent and efferent capillaries • Chemistry and counter-current exchange of carbonate, lactate favor oxygen dumping to tissues with high metabolic need. ```

Question 26

Kidney and Reproductive Organs

Answer 26

• Discussed together because they often share ducts in common • Kidneys are located on the dorsal wall of the visceral cavity • Reproductive organs contained within the visceral cavity

Question 27

Central Nervous System | CNS

Answer 27

* Tripartite brain * Spinal cord * Cranial nerves

Question 28

problem with being large

Answer 28

Body mass increases as a cube function, surface | area as a square

Question 29

Overcoming metabolic challenges

Answer 29

– Efficient gas exchange mechanism (respiration) – Efficient distribution mechanism – circulation system – Tripartite brain and sensory capability – Efficient feeding mechanism

Question 30

Diffusion

Answer 30

- the process whereby particles in dissolved substances move from a region of higher to one of lower concentration (water included!)

Question 31

osmosis

Answer 31

movement of a solvent (i.e., water) through a semipermeable membrane (as of a living cell) into a solution of higher solute concentration that tends to equalize the concentrations of solute on the two sides of the membrane

Question 32

aquaporins

Answer 32

specialized protein channels that facilitate/inhibit movement of water and small, uncharged solutes across cell membranes (Nobel Prize to Peter Agre in 2003)

Question 33

How do fishes extract and distribute enough oxygen to meet metabolic demands?

Answer 33

• Incompressibility, sound and pressure wave propagation, but…………… • Very low concentration of dissolved oxygen in water (30 X less than air) • Metabolism proportional to body size (to the ¾ power), levels of activity in fishes, environmental temperature, food intake

Question 34

Oxygen Requirements

Answer 34

``` Depend on: • Body mass • Activity level • Environmental Temperature • Feeding ```

Question 35

Gills - structure and function

Answer 35

• Gas exchange occurs across lamellae; thin walled, highly vascularized structures that look like pages of a book, or a radiator – Lamellae are made up of thin epithelial cells outside, and a thin basement membrane inside – lamellae are supported by bone and cartilage on gill filaments. – Counter-current exchanger • Amount of blood carried by lamellae depends on metabolic oxygen needs – Trout experiment -- hypoxia, epinephrin injections increase the number of lamellae perfused with blood

Question 36

Ventilation

Answer 36

In order to maintain the oxygen concentration | gradient, water must be flowing across the gills

Question 37

Ram ventilation

Answer 37

• swimming with mouth open, which forces water | across the gills

Question 38

Buccal and opercular pumping

Answer 38

• Creation of negative and positive pressure by actively lowering and raising the buccal floor, and expanding and contracting the opercles • Under hypoxic conditions fishes increase the stroke number and volume

Question 39

air breathing in fishes

Answer 39

Modified gills •Clarias batrachus (Clariidae) “respiratory trees” •Trichogaster (Belontiidae) “labyrinth organ” Cutaneous respiration •Anguilla anguilla (Anguillidae) body must remain moist; skin highly vascularized •Buccal respiration highly vascularized mouth, reduced gills, air gulping –Electrophorus electricus (Electrophoridae) –Gillichthys mirabilis (Gobiidae)

Question 40

Swim bladders as lungs

Answer 40

obligate and faculatative

Question 41

Obligate air-breathers

Answer 41

``` African lungfish (Protopterus) • South American lungish (Lepidosiren) • possess true lungs for oxygen uptake, release CO2 via vestigial gills ```

Question 42

Facultative air-breathers

Answer 42

* Australian lungfish (Neoceratodus) * bichirs (Polypterus sp. – Polypteridae), * bowfins (Amia calva – Amiidae) * gars (Lepisosteus sp. – Lepisosteideae)

Question 43

gas transport

Answer 43

Erythrocytes (RBCs): • contain hemoglobin (pigment with oxygen affinity) and cell nuclei • active fishes have more but smaller RBCs • hematocrit, and concentration of RBCs changes seasonally Oxygen -- binding and dissassociation • vast majority of oxygen is reversibly bound to hemoglobin (monomer and tetramer-- more than one form; Catostomus example) • smaller proportion is dissolved directly in the plasma • relative proportions depend on temperature; Channichthyidae example

Question 44

Bohr and Root Effects

Answer 44

``` •Affinity for oxygen in hemoglobin differs under different chemical conditions – low PO2: high PCO2 in tissues – low pH from CO2 accumulation in tissues conversion to bicarbonate (HCO3-) and H+ ions; lactic acid – “salting out” – temperature ```

Question 45

Hemoglobin

Answer 45

* Hemoglobin is monomeric in hagfish and lampreys * Tetrameric in gnathostomes (with exceptions) * Affinity and capacity altered by physical environment (pH especially

Question 46

Sensory Perception of Fishes

Answer 46

1. Chemoreception-Smell and Taste 2. Auditory- hearing 3. Pressure sensitivity in muscles, skin-Touch 4. Vision ____________________________________ 5. Lateralis system – water displacement 6. Electroreception – electrical fields

Question 47

Acoustico-lateralis system

Answer 47

Functions: • Auditory • Maintenance of balance • Near-field water pressure differentials Nature of sound in water: • Sound propagation 4.8 X faster in water than air – Near-field – water particle displacement – Far-field – pressure waves

Question 48

Hearing in Fishes

Answer 48

pars superior pars inferior hair cells

Question 49

pars superior

Answer 49

labyrinth organ, maintains positional | equilibrium (detects yaw, pitch, and roll)

Question 50

pars inferior

Answer 50

sacculi and lagunae, each with otoliths sound detection • most fish tissues are transparent to sound, similar • density as water. Otoliths (ear bones) are more dense, displacement by sound wave lags

Question 51

hair cells

Answer 51

mechanical deformation stimulates action potential • present in labyrinth, sacculus and neuromast cells

Question 52

Accessory sound amplification | structures

Answer 52

• extensions of swim bladder ending close to ear – EX: squirrelfishes (Holocentridae), tarpons (Megalopidae), deepsea cods, sea bream (Sparidae) • Weberian ossicles – otophysans – Characiformes, Cypriniformes, Siluriformes • Macula neglecta connects inner ear to – “tympanum” on some Elasmobranchs – sensitive only to low frequency sounds, but – show evidence of locating objects in far-field (250 m)

Question 53

Lateral line (Lateralis) system

Answer 53

• Canals on head – supra-, infra-orbital, preopercular • Line down the lateral surface of fish • Particularly well developed in stream fishes • Receptor cells, neuromasts (hair cells with cupula) can be in canal or on the surface. • Disruption of waves produced by swimming detected by lateral line system

Question 54

G-protein coupled receptors

Answer 54

• Transmembrane receptors that sense molecules outside the cell and activate inside signal transduction pathways and, ultimately, cellular responses. – Vision – Rhodopsin – Olfaction – Olfactory epithelium cells – Taste: sweet, bitter, savory (not salt or sour)

Question 55

examples of g proteins

Answer 55

• Opsins use a photoisomerization reaction to translate electromagnetic radiation into cellular signals. • Receptors of the olfactory epithelium bind odorants (olfactory receptors) and pheromones (vomeronasal receptors) • regulation of immune system activity and inflammation: chemokine receptors bind ligands that mediate intercellular communication between cells of the immune system; receptors such as histamine receptors bind inflammatory mediators and engage target cell types in the inflammatory response • autonomic nervous system transmission: both the sympathetic and parasympathetic nervous systems are regulated by GCPR pathways, responsible for control of many automatic functions of the body such as blood pressure, heart rate, and digestive processes

Question 56

Vision in Fishes

Answer 56

* thin cornea * iris – elasmobranchs can change pupil diameter, teleosts can not * lens – spherical in teleosts, focus by moving lens relative to retina * retina: 5-layers, pigment epithelium, photoreceptor layer, bipolar layer and ganglion layer, nerve fiber layer * choriod may contain tapetum lucidum; photomechanical movement * choriod gland – rete mirable

Question 57

Photoreceptors

Answer 57

``` • Rods-sensitive to low light levels, motion detection • Cones- bright light, color and detail discrimination vary in sensitivity to different wavelengths – some can see UV! • Relative numbers of rods and cones correlate well to light environment • Spectral tuning of pigments through mutation of Rhodopsin ```

Question 58

olfaction

Answer 58

• homing in salmonids depends on imprinting smells to identify natal spawning grounds – perhaps smell of conspecifics • deep sea angler-fishes: – males: highly developed olfaction; – females: poorly developed olfaction

Question 59

Taste

Answer 59

• Taste buds – Bulbous epithelial structures that protrude through epidermis • sensory neurons synapse with receptor cells, activation results from binding of receptor sites to stimulus molecules • Taste buds located in and on : – mouth, gill rakers, pharynx (most Teleosts) – barbels, and other body parts (catfishes), – pelvic fins: cod (Gadidae) gouramis (Belontiidae) – not elaborated in Elasmobranchs – enlarged vagal lobe in brain usually indicates reliance on taste

Question 60

Electroreception

Answer 60

Receptor Cells – probably phylogenetically related to neuromast cells; but lack cilia. Ca+ ion cascade in response to changes in electrical field induce neurotransmitters • Ampullary receptors – ampullae of Lorinzini (elasmobranchs) detectweak electric fields of prey: Skin conductivity low, tissues high, differences between freshwater and saltwater fishes • Tuberous receptors – found in fishes that generate electric fields, not • sensitive to weak fields

Question 61

endocrine control

Answer 61

* Osmoregulation * Growth * Color changes * Reproduction * Metabolism * Development and Metamorphosis * Stress response

Question 62

Autonomic Nervous Control

Answer 62

* Heart rate * Blood pressure * Blood flow to gills * Smooth muscle contraction

Question 63

Regulation of Homeostasis | Neuroendocrine System

Answer 63

``` • Regulates physical functions and permits communication among organs • Endocrine Glands – Pituitary – Hypothalamus – Thyroid – Interrenal tissues ```

Question 64

Hormones

Answer 64

• Vasotocin and isotocin – protect from water loss in high-salt environments (pituitary) * Prolactin – osmoregulation (pituitary) * Growth Hormone – growth & anadromy (pituitary) * Thyroxin (thyroid gland) – growth & development • Insulin – Glucogon – glucose uptake/fat metabolism (islet cells – pancreas) • Epinephrin & norepinephrin – fight or flight (interrenal tissue) • Melatonin – (pineal gland) behavioral influence ``` • Urotensin I interrenal glands & II digestive tract uptake of ions (caudal neuroendocrine system) ```

Question 65

Temperature Regulation

Answer 65

``` • Fishes are (mostly) ectotherms • Regional endothermy – Counter-current heat exchangers – Heater cells • Heat-shock proteins (HSPs) • Prevention of ice-crystal formation ```

Question 66

Osmoconformers (use minimal energy | for water balance)

Answer 66

Hagfish • Stenohaline (vs. Euryhaline) • Maintain body concentration at approximately the same concentration as seawater • Regulate divalent ions through kidneys (Ca++, Mg++) • Mucous coat may prevent water loss

Question 67

Hyposmotic Osmoregulators | invest energy in water balance

Answer 67

• Chondrichthyes – High levels of Urea, TMAO – Rectal gland and chloride cells on gills – Actively pump monovalent (Na+, K+) ions through membranes • Osteichthyes – “Mitochondria-rich” cells pump out extra ions – Drink constantly; excrete concentrated urine

Question 68

Hyperosmotic osmoregulators

Answer 68

• Chondrichthyes – Rectal gland and mitochondria-rich cells pump in reverse • Osteichthyes – Mitochondria-rich cells pump ions in from water – Drink seldomly, excrete dilute urine

Question 69

Euryhaline Fishes

Answer 69

• diadromous: juvenile fresh, adult marine • anadromous: adult fresh, juvenile marine – ontogenetic hormonal changes -- cortisol injections can increase densities of mitochondria-rich cells, photoperiod may also cue changes • Estuarine - intertidal fishes--cortisol, high Ca++ conc.

Question 70

Nitrogenous waste excretion

Answer 70

• Enzymatic reduction of nitrogen to ammonia a by-product of protein synthesis • Aquatic vertebrates can diffuse ammonia directly into the water across the gills • Chondrichthyes convert ammonia to urea through enzyme action

Question 71

Fish Immune Systems

Answer 71

``` • Innate (Non-specific) immunity – Anti-microbial, anti-fungal peptides • Specific (Adaptive) immunity – T-cells (killer and helper) – B-cells (immunoglobulins) – MHC class I and MHC class II ```

Question 72

Gila trout - threats to persistence

Answer 72

* Floods and Fires * Hybridization * Land and Water Use * Infectious disease

Question 73

Nucleotide and AA variation - | MHC

Answer 73

• 32 variable nucleotide sites out of 268 total sites • 22 variable amino acid sites out of 89 total residues • Four distinct MHC alleles identified through genomic sequencing • Cloning revealed a fifth distinct allele, detected only in two heterozygotes

Question 74

Genetic status of Gila trout

Answer 74

• Genetic drift appears to be most influential in shaping genetic diversity in contemporary populations; even at MHC – few alleles • Trans-species polymorphism and high levels of allelic divergence suggest action of balancing selection in the past • Fish repatriated from hatcheries tend to have even fewer alleles at MHC – mate choice? • Lost diversity due to fire