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16.7: Adaptations to the Marine Environment

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    Adaptations to the Marine Environment

    • Ability to float (Zooplankton – some produce fats or oils to stay afloat)
    • Ability to swim (Nekton – larger fish and marine mammals)

    Propulsion and movement of fish - the body plan of fish reflect adaptations to feeding on prey and fleeing predators.

    Width/Length Ratio

    Tuna - .28
    Dolphin - .25
    Swordfish - .24
    Whale - .21

    Most efficient is about.25, but there is a size-scale factor.
    Ratio produced from natural selection “the fittest survive and produce offspring”

    Figure 16.42. Swordfish

    Compare with Surfboard Design!

    Type Width Length Ratio Comments
    Short Board 19 ¼" 6’4” 0.25 Small – medium waves
    PT (Ebenizer Townsend, 1798) 19 ¼" 6'7" 0.24 Large waves
    Average Long Board 22" 9'0" 0.20 Like a whale – scale factor
    Average Surf Board 18 ¼" 6’2” 0.25 rapid turns, harder to control

    Kinds of Zooplankton

    Includes organisms described as floaters and drifters. All forms are invertebrates.
    Microscopic Zooplankton
    Radiolarians, Foraminifers, Copepods

    Macroscopic Zooplankton:
    • Krill ( resemble mini shrimp or large copepods, critical in Antarctic food chains)

    Copepods krill
    Figure 16.43. Copepods Figure 16.44. Krill

    Floating Macroscopic Zooplankton include:

    Portuguese man-of-war (have gas-filled float)
    Jellyfish (have soft, low-density bodies; there are hundreds of species)

    Many species of portuguese man-of-war and jellyfish can sting or produce potent toxins.

    Portugese man-of-war Jellyfish floating
    Figure 16.45. Portuguese man-of-war Figure 16.46. Jellyfish

    Swimming (Nekton) Organisms

    Includes all fish, squids, sea turtles and sea snakes, and marine mammals.

    • Swim by trapping water and expelling it (squid, octopus)
    • Swim by curving body from front to back (fish, etc.)

    Figure 16.47. Squid

    Adaptations for Finding Prey

    Lungers wait for prey and pounce (grouper).
    Cruisers actively seek prey (tuna).

    Grouper Bluefin tuna
    Figure 16.48. Groupers are lungers Figure 16.49. Tuna are cruisers

    Adaptations to Avoid Predation
    Hiding: includes Transparency, Camouflage and Countershading
    Poison (to touch or eat: examples: sea snakes, blowfish, lion fish)
    Schooling (safety in numbers, appear as a larger unit, maneuvers confuse predators)

    Figure 16.50. Lionfish are highly poisonous.
    Video: Schooling anchovies at Scripps Pier (Scripps Institute of Oceanography)

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