Exam 1 Flashcards
What is a fish?
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.
Why are there so many fishes?
-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
How can fish survive in so many different water environments?
- 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
Other useful properties of water
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)
Skeletal system
-chordates and vertebrates Cranium • Vertebral column – Articulation with the skull – Articulation with the tail (caudal region) • Appendicular skeleton – Pectoral girdle – Pelvic girdle
Skull
Chondrocranium and Dermatocranium
– Derived from embryonic cartilage
– Derived from dermal bone
Shape of skull is reflective of function
Reflects multiple functions: • Protection • Ventilation • Sensory systems • Feeding
5 groups of Cranial region bones to
remember (in bony fishes)
• Neurocranium – Ethmoid – Optic – Otic – Basiocciptal • Hyoid arch (aka Suspensorium) • Jaws (upper and lower) • Opercular Bones • Branchohyoid (supports gills, etc)
Teeth
- 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
Vertebral column
• 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
Caudal fin types
• Protocercal – hagfish and lampreys • Heterocercal – Chondrichthyes • Homocercal – Most teleosts • Leptocercal (or diphycercal) - Sarcopterygians
Fins
• 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
Fish Skin
• 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
Scales
• 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)
Soft parts of fishes
- Muscles
- Cardiovascular system
- Digestive tract – Alimentary canal
- Swim (Gas) Bladder
- Kidneys and Gonads
- Nervous system
Musculature
• 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
Muscle fibers
– 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
Cardiovascular system
-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.
Hemopoietic Tissues in Fishes
– 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
circulatory system
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
Digestive Tract (Alimentary Canal)
Mouth, buccal cavity, pharynx, esophagus, stomach,
pyloric caeca, small intestine, cloaca
Gas bladder types
Physostomous
Physoclistous
Physostomous
– 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
Physoclistous
– 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
Rete Mirable (“wonderful net”)
• 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.
Kidney and Reproductive Organs
• 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
Central Nervous System
CNS
- Tripartite brain
- Spinal cord
- Cranial nerves
problem with being large
Body mass increases as a cube function, surface
area as a square
Overcoming metabolic challenges
– Efficient gas exchange mechanism (respiration)
– Efficient distribution mechanism – circulation system
– Tripartite brain and sensory capability
– Efficient feeding mechanism
