Lab III: Biology and Adaptations of Fishes

Question 1

Feeding Adaptations - Jaws

Answer 1

• In acanthodians, placoderms, sharks
• First actively predaceous vertebrates
• Protrusible jaws in bony fishes - upper and lower jaw margins move forward together with balanced symmetrical action
  
  • Creates suction and allows mouths to close faster than non-protrusible jaws

Question 2

Feeding Adaptations - Mouth Types

What are the different types of mouths?

Answer 2

• Superior (directed upwards): Feed near surface (e.g., guppy)
• Terminal (directed anteriorally): Most teleosts (e.g., perch)
• Inferior (directed ventrally): Bottom-feeders (e.g., skates/rays)

Question 3

Feeding Adaptations - Food eaten, feeding habits, and dentition

Answer 3

• Predaceous: Sharply pointed teeth; grasp, puncture, and hold prey
• Plankton feeders: Feed on encrusting **periphyton **(attached microflora); toothless jaws and weak mouths; filtering system of branched gill rakers
• **Herbivorous **and coral-eaters: Crushing teeth. Grinding mill of flattened plates or teeth on floor of pharynx

Question 4

Feeding Adaptations - Teeth types

What are the five types of teeth?

Answer 4

• Molariform = Numerous, lateral teeth with flattened surfaces for grinding
• Caniniform = Dog-like or fang-like. Elongated and sub-conical, straight or curved. Adapted for piercing and holding prey (e.g., barracuda)
• Villiform = Numerous, fine, pointed teeth. Usually elongated. Used for gripping (e.g., pike)
• Coalesced = Teeth are fused for biting and sheering (e.g., puffer)
• Pharyngeal = Found on floor of pharynx. No teeth on jaw margins. Teeth bite against horny pad on roof of mouth (e.g., cyprinids - goldfish etc.)

Question 5

Adaptations for Swimming

What are the three types of swimming?

Answer 5

• Anguilliform - Muscle contractions move animal’s body from side-to-side. Contractions propagate down animal from head to toe
  
  • Thrust produced through additive motions
  • Magnitude of force of thrust depends upon:
    
    • Area of surface of body/fins
    • Speed and extend of body/fin movement
    • Angle of attack
• Carangiform - Powerful swimmers, high speeds for long periods of time. Propel by oscillations of tail region
  
  • Large caudal fins, longer body length relative to depth, less flexibility
• Ostraciiform/tunaform - Inflexible body, moves by undulations of tail
  
  • Balistiform - Move by undulations of median fins
  • Labriform - Move by rowing pectoral fins

Question 6

How do fish overcome gravity and drag?

Answer 6

• Overcome gravity with production of lift
  
  • Body at angle to flow of water produces lift
  • Extend pectoral fins at positive angle of attack to water produces lift
  • Swim bladder can cause neutral buoyancy
    
    • Physostomous = duct to pharynx
    • Physoclistous = no attachment to pharynx
  • Deep sea fish/sharks have oil deposits that produce static lift
• Overcome drag with production of thrust
  
  • Two types of drag:
    
    • Viscous = From friction between fish’s body and water
    • Inertial = Pressure difference from displacement of water

Question 7

What is the function of a swim bladder?

What are the two types?

Answer 7

• Swim bladder can create neutral buoyancy
• Physostomous = duct to pharynx
• Physoclistous = no attachment to pharynx

Question 8

Adaptations for Swimming - Fins

How do fins control roll, pitch, and yaw?

Answer 8

• Fins resist roll (rotation around body axis) by pressing against water in direction of roll
• Fins counteract pitch (tilting up and down) by projecting horizontally near anterior end of body
• Fins control **yaw **(swinging left to right) through vertical fins

Question 9

What are six general adaptations in primary swimmers?

Answer 9

• All fish are primary swimmers
• Sharks swim by passage of waves along metamerically arranged muscles
• In specialized teleosts, pectorals are higher up on body and used as brakes
• Anterior pelvic fins control rising and diving in specialized teleosts. Dorsal and caudal fins control stability in transverse plane
• In higher forms, caudal fin is homocercal (increases turning efficiency)
• Streamlined bodies increase speed

Question 10

Protective Mechanisms of Bony Fishes

Scales and Surface Armour

Answer 10

• Protective armour of Palaeozic fishes - thick, overlapping bony plates
• Cycloid and ctenoid scales for covering of thin, overlapping bony plates

Question 11

Protective Mechanisms of Bony Fishes

Spines and poison glands

Answer 11

• Scales with upstanding spines with pulp cavity attached, opening to poison gland
• Spines can be in opercular/dorsal area
• Angler fishes with modified spines for angling prey

Question 12

Protective Mechanisms of Bony Fishes

Luminescent Organs

Answer 12

• Organs can have luminous bacteria
• Modified mucous glands with guanine crystals
• Startles attackers/hides fish’s silhouette

Question 13

Protective Mechanisms of Bony Fishes

Electric Organs

Answer 13

• Emit electric discharge
• Also used for navigation, communication, and offense

Question 14

Protective Mechanisms of Bony Fishes

Two types of fish colours

Answer 14

• Pigments - located in chromatophores
• Structural - light-reflecting crystals in chromatophores

Question 15

Protective Mechanisms of Bony Fishes

Groupings of protective use of colour

Answer 15

• Concealment/cryptic colouration:
  
  • ​Red colouration - usually in nocturnal/deep sea fish
  • Obliterative/countershading - Dark top, light bottom (e.g., trout, shark)
  • Disruptive colouration - Eye lines, lateral or vertical stripes
  • Cryptic/camouflage colouring - Bottom dwellers, effective with decreased movement
• **Warning colouration **- Bright colours to advertise noxious attribute. Mimicry is prevalent
• Social colouration - Sexual and courtship behaviours. Maintenance of group

Question 16

Protective Mechanisms of Bony Fishes

Fear Scents

Answer 16

• Lets of noxious chemical when skin is broken
• Predator avoidance
• Warning sign to fish of same species to adopt predator avoidance techniques