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– 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

58.2%

41.2%

39.9%

Fish importance

• 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

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:

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

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; overlap lower part

Scales grow with fish

Characterized by concentric ridges (growth increments)

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 rolesCleaner 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: ConcealmentGeneral 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 LocomotionMeans 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

FinsTypes of fins:

Paired fins: pectoral and pelvic

Median fins: dorsal, caudal, anal, & adipose

FinsMain 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

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

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/wtTuna: 60% muscle/wt

Contraction causes oscillation of body and tailBody bends as one side contracts b/c of an incompressiblenotochord or vertebral columnCaused by bands of muscle = myomeres

Fish MusclesMajor 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

Undulate the body:

eels, elongate

fish

Flex caudal portion, fast swimmers

Isolate and move only

fin(s)

Anguilliform

Carangiform

Subcarangiform

Ostraciform-rigid body, caudal main propulsion

Thunniform-rigid body, caudal main propulsion

Labriform -pectoral oscillateDiodontiform - pectoralRajiform - pectoral

Amiiform -dorsalBalistiform – anal+dorsal

(Wavelike) (fanlike)

Gymnotiform -anal

Tetraodontiform – anal+dorsal pe

ctor

alan

aldo

rsal

http://www.oceanfootage.com/stockfootage/Titan_Trigger_Fish//?DVfSESSCKIE=7305db92882366fd26c463edc209393f8e25bdc9

Tuna: Ultimate Living Swimming MachineSwim continuously – feeding, courtship, rest, reproduction

Tuna: Ultimate Living Swimming Machinehydrodynamic 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 leading car)

Adopt swim-glide for energy savings (like birds)

High narrow tails – propulsion with least effort, used to design 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.

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)

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

• 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– Placoid– Ganoid– Cycloid– Ctenoid