Vertebrates (subphylum vertebrata)
• Possess a backbone (aka vertebral column,
spine)
• Vertebrae=Dorsal row of hollow skeletal
elements (usually bone)
• Nerve cord=spinal cord, protected by
vertebrae, (part of nervous system), ends in
brain
• Bilateral symmetry, endoskeleton
Fish Form & Function
Goals for this lab
• Learn about fish: Topics
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Skin/scales
Coloration
Locomotion
Fins
Muscles
• Discuss 3 classes of fish
• Dissect different fish- up to 3 different
forms
• Write paper comparing different fish
forms
– Due next Monday/Tuesday
– Details to follow
Global Habitats
41.2%
58.2%
39.9%
Fish importance
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Appeared > 500 mya
Comprise half of vertebrate species
Feed on all types of marine organisms
some organisms previously discussed use fish as their
home (bacteria to crustaceans)
Some animals eat fish
Most economically important marine organism
Vital source of protein to millions of humans
Ground up for chicken feed, fertilizer, leather, glue,
vitamins obtained from them
Some kept as pets
Fish Morphology
Skin
Color
Bioluminescence
Swimming Locomotion
Fins
Muscles
Skin
Organ of the body
Consists of connective tissue
Muscles pull against skin tissue & skeleton
Key component of the muscle-tendon-tail fin system
Layers
Epidermis
Typically 250 m thick  10-30 cell layers
Range 20 m – 3 mm
Dermis
Fish Skin
Function:
Hold fish together
Serves as barrier against abrasive agents
Osmoregulation (what does this mean?)
Permeable  respiratory function
Biomechanical properties in sharks
Fish Skin
Derivatives:
Mucous formed in epidermis cells
Protect against infection
Constantly shed to remove bacteria and fungus
Ex. Clingfish lack scales, protect their bodies by
a thick layer of mucous
Bone is also skin derivative
scales, most important
Fish Scales
First appear as dermal bone
Found in fossil of Cambrian period (570 mya)
Layered bone, solid armor-constrained movement
Evolved smaller and reduced into scales
5 types of scales (examples with images to follow)
Placoid
Cosmoid
Ganoid
Cycloid
Ctenoid
Fish Scales: Placoid
Found in elasmobranchs (sharks
& rays)
“teeth like”, same composition
As fish grows, do not increase in
size, instead new scales are added
Fish Scales: Cosmoid
In the Sarcopterygii (fish with fleshy
lobe fins), primitive fish
Less evolved than Elasmobranchs
and Actinopterygii (fish with rayed fins)
Scales found in fossil record but not
in any living fish,
Except in simplified version
of coelocanth and lungfish
Fish Scales: Ganoid
In primitive Actinopterygii
Found in reedfish, polypterus, gar,
bowfin, and sturgeons
Were thick heavy scales when first
appeared
Rhomboid-shaped
Developed into teleost scales
Fish Scales: Teleost scales
Two types:
Ctenoid-higher fish
Cycloid-soft-rayed, anchovies, sardine
Mineralized surface layer & inner
collagenous layer
Ctenoid scales
Scales surrounded by dermis, in dermal
pockets
Grow from top, bottom, and insides; overlap
lower part
Scales grow with fish
Characterized by concentric ridges (growth
increments)
Cycloid scales
Coloration
Coloration
Fish display a multitude of patterns involving
2 or more colors,
in many tints and shades,
arranged in spots, stripes, patches, and blotches
3 Types of coloration predominant in oceans
Silver – pelagic, upper zone
Red – deeper zone (~ 500 m)
Black or violet – deep sea
Countershaded near shore and colorful in coral reefs
Coloration
Chromatophores
Colored cells from which light is reflected off
Located in the skin (dermis), eyes
Various colors/hues-combination of different chromatophores
Functional Roles of Colors in Fishes-examples of each to follow
Social Roles
Advertisement
Mimicry
Hiding
Protection from sun (especially larvae)
Coloration: Social roles
Cleaner Fish:
distinctive markings
recognized by larger fish
Coloration:
Advertisement:
Bright, bold and showy males indicate:
Reproductive availability, either
permanently or seasonally, e.g. cichlids,
wrasses, minnows, sunfish
Unpalatable or venomous, e.g. lionfishes
Mimicry – Disguise:
Disguises: look like something in habitat,
e.g. leaffish, sargasso fish
Mimicry: mimic distasteful species
Coloration: Concealment
General color resemblance –
resemble background
Variable color resemblance – change
with background, e.g. flatfish
Obliterative shading –
countershading, dark above, light
below (invisible fish)
Disruptive coloration – disruptive
contours that breakup outline; bold
stripes, bars, false eye spots
Coincident disruptive coloration –
joining together of unrelated parts of
the body to reduce recognition; e.g. sea
dragon
Bioluminescence
Most luminous fish found 300-1000 m depths, few shallow
3 Types of light producing methods:
Self-luminous (on/off)
Symbiotic bacteria nurtured in special glands
Acquire from other bioluminescent organisms- diet contains
light-emitting compounds
Function:
Concealment by counter-illumination - ventral placement
matches background from above, against attack from below
Dorsal photophores safeguard against predators from above
Advertisement for courting, maintaining territory, to startle and
confuse predators, and feeding
Fish Locomotion
Means of Locomotion:
Simplest form: Passive drifting of larval fish
Some can:
Burrow
Walk, hop, or crawl
Glide
Fly
Most can:
Swim in a variety of ways
Types of fins:
Fins
Paired fins: pectoral and pelvic
Median fins: dorsal, caudal, anal, & adipose
Fins
Main functions:
Swimming – increase surface area w/o increasing mass
Stabilizers – yaw, stability-dorsal and anal fins
- brake, pitch, roll, reverse -pectoral/pelvic
thrust with caudal fin
Modifications in fins:
Defense – spines, enlarge fish
Locomotion – modified for crawling, flying, gliding
Hunting – lures, sensory organs
Respiratory organ – lungfish, supply oxygen to eggs
Fins
Soft rays vs. Spines
Soft rays:
Spines:
Usually soft and not pointed
Usually hard and pointed
Segmented
Unsegmented
Usually branched
Unbranched
Bilateral, w/left and right halves
Solid
Fish Muscles
Muscles provide power for swimming
Myomers=bands of muscle, run along sides of body, attached to
backbone
Constitute up to 80% of the fish itself
Much hardly used except during emergencies
Don’t have to contend with same effect of gravity
Fish muscle arrangement not suitable on land
Cow: 30% muscle/wt
Tuna: 60% muscle/wt
Contraction causes oscillation of body and tail
Body bends as one side contracts b/c of an incompressible
notochord or vertebral column
Caused by bands of muscle = myomeres
Fish Muscles
Major fibers (see handout):
Red, pink, and white
Pink intermediate between red
and white
Muscle types do not intermingle
Different motor systems used for
different swimming conditions
Red – cruising
White – short duration, burst
swimming
Pink – sustained swimming,
used after red and before white
Fish Locomotion
Swimming classified into 2 generic categories:
Periodic (or steady or sustained)- e.g. running marathons,
for covering large distance at constant speed
Transient (or unsteady) – e.g. like running sprints, used
for catching prey or avoiding predators
pectoral
Rajiform - pectoral
anal
Diodontiform - pectoral Labriform -pectoral oscillate
Gymnotiform -anal
dorsal
Isolate and
move only
fin(s)
Amiiform -dorsal
Tetraodontiform – anal+dorsal
Balistiform – anal+dorsal
Ostraciform-rigid
body, caudal main
propulsion
Flex caudal
portion, fast
swimmers
Carangiform
Undulate
the body:
eels,
elongate
fish
Thunniform-rigid
body, caudal main
propulsion
Subcarangiform
Anguilliform
(Wavelike)
(fanlike)
http://www.oceanfootage.com/stockfootage/Titan_Tr
igger_Fish//?DVfSESSCKIE=7305db92882366fd26
c463edc209393f8e25bdc9
Tuna: Ultimate Living Swimming Machine
Swim continuously – feeding, courtship, rest, reproduction
Tuna: Ultimate Living Swimming Machine
hydrodynamic adaptations
Big size-high performance engine
Streamlining-spindle shaped & rigid body
Small structures at various parts of the body to improve swimming
efficiency and reduce drag, e.g.
Eyes flush with body – don’t protrude
Adipose eyelid - smooth, reduce drag
Depression grooves for dorsal, pelvic, & pectoral fins at high speed
Keeled peduncle - cutting through water
Finlets for cross-flow - delayed separation
Tuna: Ultimate Living Swimming Machine
Must swim to survive:
No gas bladder, rigid body, ram ventilation
High blood volume, large heart, maintain warm core
(25oC)
School to utilize vortices generated by other fish (~like
race car driver who “slipstreams” and then slingshots past
Slipstream: The area of reduced
leading car)
pressure or forward suction
Adopt swim-glide for energy savings (like birds)
produced by and immediately
behind a fast-moving object as it
moves through air or water.
High narrow tails – propulsion with least effort, used to
design efficient propulsion systems for ships
Fish-mouth types (some)
• Large mouth with teeth (e.g. barracuda)
• Long snout/small mouth (e.g. butterfly fish)
• Protrusible mouth (e.g. slipmouth)
• Beak-like mouth (e.g. parrotfish)
• Large mouth (e.g. herrings)
Fish
Three Classes:
Agnatha
Chondrithyes
Osteicthyes
Class Agnatha
Jawless fishes
Ex. Hagfish, lampreys
No paired fins
Gill holes, no slits or operculum
Large sucking mouth with teeth
Scavengers
As a defense mechanism, secrete slime then tie itself in
knots to escape predators
Also tie in knots for pulling food off carcasses, and
cleaning slime from body
Class Agnatha
Hagfish’s
mouth
http://www.soest.hawaii.edu/oceanography/faculty/csmith/index.html
Class Chondricthyes
Sharks and rays
Skeleton = cartilage, not bone
Paired fins-efficient
swimming
Gill slits exposed,
no operculum
Large oil-filled liver
Heterocercal tail (upper
longer than lower lobe)
Placoid scales-skin like
sandpaper
Class Osteichthyes
Bony fish
Largest group of living vertebrates
Bones for skeletons
Gill covering (operculum)
Swim bladder (balloon-like)
Homocercal tails (even)
Cycloid & Ctenoid scales
Dissection Worksheet
•Working in groups of 2 or 3 people,
• dissect 1 fish following the worksheet and writing the answers to
the questions in your notebook as you go.
• Need to draw 3 external illustrations in your notebooks
• 1 of the fish you are dissecting, before you dissect it
• 2 others that have specialized mouths and caudal fins
• label the type of mouth and caudal fin each has
• Label the following structures on each illustration:
• gill cover, pectoral fins, pelvic fins, dorsal fin,
• anal fin, adipose fin (if present), lateral line
• give the head length, total length, and the fork length (of the
dissected one ONLY, see handout)
• look at a scale under a microscope and draw it.
Dissection Worksheet continued
• Cut through body cavity
– Find the following
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Heart
Liver
Stomach/intestines
Swim bladder (if applicable)
Spine
• Cut cross section, 2/3 down the body
– Red muscle
– White muscle
Scales- use slides
• Draw
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Placoid
Ganoid
Cycloid
Ctenoid