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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
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