Fish Classification, Structure

7/31/2019 Fish Classification, Structure

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Vertebrates (subphylum vertebrata)

Possess a backbone (aka vertebral column,spine)

Vertebrae=Dorsal row of hollow skeletalelements (usually bone)

Nerve cord=spinal cord, protected by

vertebrae, (part of nervous system), ends inbrain

Bilateral symmetry, endoskeleton


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Fish Form & Function

Goals for this lab Learn about fish: Topics

Skin/scales

Coloration

Locomotion

Fins

Muscles

Discuss 3 classes of fish

Dissect different fish- up to 3 differentforms

Write paper comparing different fishforms

Due next Monday/Tuesday

Details to follow


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Global Habitats

58.2%

41.2%

39.9%


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Fish importance

Appeared > 500 mya

Comprise half of vertebrate species

Feed on all types of marine organisms

some organisms previously discussed use fish as theirhome (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


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Fish Morphology

Skin

Color

Bioluminescence

Swimming Locomotion

Fins

Muscles


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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 layersRange 20 m3 mm

Dermis


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Fish Skin

Function:

Hold fish together

Serves as barrier against abrasive agents

Osmoregulation (what does this mean?)

Permeable respiratory function

Biomechanical properties in sharks


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Fish Skin

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

Derivatives:


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Fish ScalesFirst 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


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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


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Fish Scales: Cosmoid

In the Sarcopterygii (fish with fleshylobe 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


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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


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Fish Scales: Teleost scales

Ctenoid scales

Cycloid scales

Two types:

Ctenoid-higher fish

Cycloid-soft-rayed, anchovies, sardine

Mineralized surface layer & inner

collagenous layer

Scales surrounded by dermis, in dermal

pockets

Grow from top, bottom, and insides; overlaplower part

Scales grow with fish

Characterized by concentric ridges (growth

increments)


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Coloration


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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

Silverpelagic, upper zoneReddeeper zone (~ 500 m)

Black or violetdeep sea

Countershaded near shore and colorful in coral reefs


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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)


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Coloration: Social roles

Cleaner Fish:

distinctive markingsrecognized by larger fish


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Coloration:Advertisement:

Bright, bold and showy males indicate:

Reproductive availability, either

permanently or seasonally, e.g. cichlids,

wrasses, minnows, sunfishUnpalatable or venomous, e.g. lionfishes

MimicryDisguise:

Disguises: look like something in habitat,

e.g. leaffish, sargasso fish

Mimicry: mimic distasteful species


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Coloration: ConcealmentGeneral color resemblance

resemble backgroundVariable color resemblancechange

with background, e.g. flatfish

Obliterative shading

countershading, dark above, light

below (invisible fish)

Disruptive colorationdisruptive

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


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Coloration


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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 placementmatches 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


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Fish LocomotionMeans of Locomotion:

Simplest form: Passive drifting of larval fish

Many can:

Burrow

Walk, hop, or crawl

Glide

Fly

Most can:

Swim in a variety of ways

i


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FinsTypes of fins:

Paired fins: pectoral and pelvic

Median fins:dorsal, caudal, anal, & adipose


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Fins

Main functions:

Swimmingincrease surface area w/o increasing mass

Stabilizersyaw, stability-dorsal and anal fins

- brake, pitch, roll, reverse -pectoral/pelvic

thrust with caudal fin

Modifications in fins:

Defensespines, enlarge fish

Locomotionmodified for crawling, flying, gliding

Huntinglures, sensory organs

Respiratory organlungfish, supply oxygen to eggs


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FinsSoft rays vs. Spines

Soft rays:

Usually soft and not pointed

Segmented

Usually branched

Bilateral, w/left and right halves

Spines:

Usually hard and pointed

Unsegmented

Unbranched

Solid

Fi h M l


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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 emergenciesDont 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

Fi h M l


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Fish MusclesMajor fibers (see handout):

Red, pink, and white

Pinkintermediate between red

and white

Muscle types do not intermingle

Different motor systems used for

different swimming conditions

Redcruising

Whiteshort duration, burstswimming

Pinksustained swimming,

used after red and before white


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Fish-Body shapes-see textbook for images

(Figure 8.9)

Fusiform-spindle shaped, e.g. tuna

Compressiform-laterally compressed,angelfish, butterfly fish

Anguilliform-eel-like

Filiform-even smaller anguilliform, e.g. snipeeel


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Body shapes continued

Depressiform-flatfish,rays, flounder

Taeniform-gunnel

Sagittiform-e.g. pike

Globiform-e.g.lumpsucker


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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


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Undulate

the body:

eels,

elongate

fish

Flex caudalportion, fast

swimmers

Isolate and

move only

fin(s)

Anguilliform

Carangiform

Subcarangiform

Ostraciform-rigid

body, caudal mai

propulsion

Thunniform-rigid

body, caudal main

propulsion

Labriform -pectoral oscillateDiodontiform - pectoral

Rajiform - pectoral

Amiiform -dorsalBalistiformanal+dorsal

(Wavelike) (fanlike)

Gymnotiform -anal

Tetraodontiformanal+dorsal

pectoral

anal

dorsal


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Tuna: Ultimate Living Swimming MachineSwim continuouslyfeeding, courtship, rest, reproduction

T Ul i Li i S i i M hi


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Tuna: Ultimate Living Swimming Machine

hydrodynamic adaptationsBig 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 bodydont 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

T Ulti t Li i S i i M hi


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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 pastleading car)

Adopt swim-glide for energy savings (like birds)

High narrow tailspropulsion with least effort, used todesign efficient propulsion systems for ships

Slipstream: The area of reduced

pressure or forward suction

produced by and immediately

behind a fast-moving object as it

moves through air or water.


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Fish-mouth types (some)

Large mouth with teeth (e.g. barracuda)

Long snout/small mouth (e.g. butterfly fish)

Protrusible mouth (e.g. slipmouth)

Large mouth (e.g. herrings)

Beak-like mouth (e.g. parrotfish)


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Fish

Three Classes:

Agnatha

Chondrithyes

Osteicthyes

Cl A h


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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


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Class Agnatha

Hagfishs

mouth

http://www.soest.hawaii.edu/oceanography/faculty/csmith/index.html

Cl Ch d i th
http://www.soest.hawaii.edu/oceanography/faculty/csmith/index.htmlhttp://www.soest.hawaii.edu/oceanography/faculty/csmith/index.html


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Class ChondricthyesSharks and rays

Skeleton = cartilage, not bone

Paired fins-efficient

swimming

Gill slits exposed,

no operculum

Large oil-filled liver

Heterocercal tail (upperlonger than lower lobe)

Placoid scales-skin like

sandpaper

Class Osteichthyes


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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

Fish Classification, Structure

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