14.2 What adaptations do pelagic organisms possess for seeking prey?

adaptations include:

• mobility (lunging vs cruising)

• swimming speed

• body temperature

• unique circulatory systems

Mobility: Lungers vs Cruisers

some fish wait patiently for prey and exert themselves only in short bursts as they lung at their prey. others cruise relentlessly through the water, seeking prey.

**there’s a huge difference in the musculature of fish between these different styles

Lungers

sit and wait for prey to come close by

• truncate caudal fins for speed and maneuverability

• almost all muscle tissue is white

Cruisers

actively seek prey, <1/2 cruiser’s muscle tissue is white - most is red

Significance between red vs white muscle tissue

red muscle tissue contains fibers that are 25-50microns in diameter

white muscle tissue contains fibers 135microns in diameter w/ much lower concentrations of myoglobin

• myoglobin = red pigment w/ affinity for oxygen

red muscle tissue supplies a much greater amount of oxygen and supports a much higher metabolic rate than white tissue

• this is why cruisers have so much red muscle tissue: it allows them to have the endurance needed to support their active lifestyle

lungers need very little red tissue bc they don’t move continually

• instead, they need white tissue which fatigues more rapidly than red tissue for quick bursts of speed to capture prey. cruisers use white tissue to, for short period of acceleration while on the attack

Swimming Speed

although rapid swimming consumes a lot of energy, it also helps organisms capture prey. fish swim slowly when cruising, fast when hunting for prey, and fastest of all when trying to escape predators

generally when comparing fish of similar shapes, the larger the fish, the faster it can swim

• Ex. tuna: well adapted for sustained cruising and short, high-speed bursts, cruising speed avgs 3 body lengths per second

  • they can maintain a max speed of 10 body lengths per second but only for one second

• Ex. yellowfish tuna been clocked at 74.6 km/hr but only for fraction of a second

Swimming Speed in Cold-Blooded vs Warm-Blooded Fish

temp of a fish relative to its environment affects the speed at which a fish swims. most marine fish = cold-blooded or poikilothermic —> body temps are nearly same as environment —> usualy not fast swimmers

however, mackerel, yellowtail, and bonito are fast swimmers w/ body temps 1.3, 1.3, and 1.8 ^oC higher than the surrounding seawater

warm-blooded / homeothermic can swim faster

• maintain higher temp using a heat exchange system surrounding the active swimming muscles along the midsection

why do fish exert so much energy to maintain their high body temps, which is a costly adaptation that is hard to maintain in the ocean, while other fish do quite well with lower body temperatures?

• high body temp in fish associated w/ higher metabolic rates —> increases power output of muscle tissue, allowing them to more effectively seek and capture prey

• higher temp speeds up physiological process w/in the body, resulting in muscles that contract faster and neurological transmissions that occur more quickly, leading to faster swimming speeds, better vision, and enhanced response times = great predatorial advantages

Adaptations of Deep-Water Nekton

deep-water nekton food source = detritus

lack of abundant food limits # of organisms (total biomass) and size of these organisms —> RESULT = small pops of these organisms, and most are <30cm long, also many have low metabolic rates to conserve energy

• deep-sea fish have special adaptations to efficiently find and collect food: good sensory devices i.e. long antennae or sensitive lateral lines that can detect movement of other organisms w/in the water column

• bioluminescence = produce light biologically and “glow in the dark”

  • 90% of deep-sea marine life is bioluminescent

  • most bioluminescent organisms use light-producing organs = photophores, which can be simple luminous spots or may be quite complex and equipped w/ lenses, shutters, color filters, and reflectors

bioluminescent light is produced from:

• compounds during digestion of prey

• specialized cells in organism

• associated w/ symbiotic bacteria that’s culture and lives inside the organism

light is produced when molecules of biological pigment luciferin are excited and emit photons o flight in the presence of oxygen

• light production process is very efficient, only 1% loss of energy required to produce the light

bioluminescence is useful for a variety of purposes including:

• searching for food items in dark

• attracting prey

• staking out territory by constantly patrolling an area

• communicating or seeking a mate by sending signals

• escaping from predators by using a flash of light to temporarily blind or distract them

• avoiding predators by use of a “burgalr alarm’ by attracting unwanted attention with brilliant displays of bioluminescence

• counterillumination = camouflaging by using belly lights to match color and intensity of dim filetered sunlight from above and obliterate a telltale shadow to become effectively invisible

to take advantage of bioluminescent light, deep-sea species have large and sensitive eyes, about 100x more sensitive to light than human eyes —> enabling them to see potential prey

• to avoid becoming prey, many species are dark in color so they blend w/ environment

• other species are blind and rely on senses such as smell to track down prey

other adaptations include:

• large sharp teeth

• expandable bodies to accommodate large food items

• hinged jaws that can unlock to open widely

• mouths that are huge in proportion to their bodies

these allow deep-sea fish to ingest species that are larger than they are and to process food efficiently whenever it’s captured

RECAP

adaptations of pelagic organisms for seeking prey include mobility (lunging vs. cruising), high swimming speed, and high body temp. deep-water nekton exhibit a host of unusual adaptations including bioluminescence that allow them to survive in deeper waters

CONCEPT CHECK 14.2

(1) Are most fast-swimming fish cold-blooded or warm-blooded? What advantage does this provide?

• most are warm-blooded —> advantage = they can move faster to get prey

(2) What are the two food sources of deep-water nekton? List several adaptations of deep-water nekton that allow them to survive in their environment.

• detritus

• each other

• adaptations:

  • bioluminescence

  • dark body colors

  • large teeth

  • expandable bodies

  • contractable jaws

(3) Describe the mechanism by which bioluminescence is accomplished in deep-sea organisms. What is bioluminescence useful for in the marine environment?

• light produced from compoiunds during digestion of prey, specialized cells in the organism, or associated w. symbiotic bacteria that’s cultured and lives inside the organism

• light is produced when molecules of bio pigment luciferin are excited and emit photons of light when in contact with oxygen

• only 1% loss of energy required for this

bioluminescence is useful for:

• searching for food in dark

• camouflaging w/ upper sunlit waters and darker waters

• attracting prey

• establishing a territory

• escaping from predators

• communicating with mates