8 the water column nekton
Download
Skip this Video
Download Presentation
8 The Water Column: Nekton

Loading in 2 Seconds...

play fullscreen
1 / 49

8 The Water Column: Nekton - PowerPoint PPT Presentation


  • 147 Views
  • Uploaded on

8 The Water Column: Nekton. Notes for Marine Biology: Function, Biodiversity, Ecology By Jeffrey S. Levinton. ©Jeffrey S. Levinton 2001. Nekton: Definitions. Nekton: organisms living in the water column that can swim strongly enough to move counter to modest water currents.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about '8 The Water Column: Nekton' - verdi


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
8 the water column nekton

8 The Water Column: Nekton

Notes for Marine Biology: Function, Biodiversity, Ecology

By Jeffrey S. Levinton

©Jeffrey S. Levinton 2001

nekton definitions
Nekton: Definitions
  • Nekton: organisms living in the water column that can swim strongly enough to move counter to modest water currents
nekton constraints
Nekton: Constraints
  • Nekton: live under high Reynolds number, meaning that inertial forces dominate over viscous forces
  • Boundary layer on fast moving forms is thin
  • Minimizing pressure drag is important for fast and continual motion
nekton principal members
Nekton - Principal Members
  • Cephalopods
  • Fish
  • Mammals (cetaceans, otters)
  • Birds (divers)
cephalopods
Cephalopods
  • Phylum Mollusca
  • Mouth - powerful beak
  • Mantle + siphon = rapid movement
  • Squids and octopus have an ink gland; ink expulsion confuses predators
cephalopod buoyancy
Cephalopod Buoyancy
  • Gas production
  • Nautilus - chambers
  • Cuttlefish - cuttlebone + osmotic pump
slide9
Fish
  • Chondrichthyes - cartilaginous fishes including sharks, skates, rays - cartilaginous skeleton, replacable tooth rows
  • Osteichthyes - bony fishes, true bony skeleton - much more diverse than Chondrichthyes, teeth fixed in jaws
form and function
Form and Function
  • Form of fishes strongly related to their locomotion type and feeding ecology
form and function 2
Form and Function 2
  • Rover predatorslong and torpedo-shaped, with fins spaced - maneuverability

Tuna

form and function 3
Form and Function 3
  • Surface-oriented fishes (e.g. flying fishes) mouth oriented upward to capture prey at surface

Flying fish

form and function 4
Form and Function 4
  • Bottom fish - variable, but often flattened to be close to bottom

Flounder

form and function 5
Form and Function 5
  • Deep-bodied fish - flattened laterally, excellent at maneuvering, not prolonged swimmers

Butterfly fish

form and function 6
Form and Function 6
  • Eel-like fish - well adapted to moving in crevices, such as moray eels
form and swimming
Form and Swimming
  • Form is a combination of three modes:
  • Acceleration
  • Cruising
  • Maneuvering
swimming
Swimming
  • Swimming usually involves undulation of entire body

Components of force during swimming

swimming1
Swimming
  • Swimming usually undulation of body
  • Bony fishes use vertebral column as a skeleton to oppose muscular action
  • Sharks - helical external meshwork of collagen against which muscular action works
oxygen use
Oxygen Use
  • Water over gills
  • Water flows over gill lamellae and oxygen diffuses into gills
  • Blood flow (hb) is in opposite direction of water flow - countercurrent exchange - same principle as for heat conservation in dolphins (ch. 4)
buoyancy
Buoyancy
  • Fish can regulate bulk chemistry
  • Sharks have high lipid content - reduces bulk density
  • Bony fish have lower salt content than sea water - reduces bulk density
  • Swim Bladder - most fish
buoyancy1
Buoyancy
  • Most bony fish have a swim bladder; fish can acquire air at surface and esophagus is connected to swim bladder
  • Gas gland facilitates gas uptake and release
  • Rete mirabile - intertwined capillaries and veins that use countercurrent exchange to retain oxygen near the gas gland
buoyancy swim bladder
Buoyancy: Swim Bladder

Rete mirabile: countercurrent

exchange to retain oxygen

fish feeding
Fish Feeding
  • Two mechanisms in water column: suction and ram feeding
  • Many fish chew prey by means of teeth; some have specialized crushing teeth (puffer fish, some sculpins)
  • Some species suspension feed, trap zooplankton, phytoplankton, or particulate organic matter on gill rakers
slide26

Snail shell with

punctures

Vulmer, the crushing

mouthpart

X ray of bivalves in fish gut

A shell-crushing fish, sculpin Asemichthys taylori

Pacific Northwest U. S. A.

sensory perception
Sensory Perception
  • Lateral line system - mechanoreceptors used in spatial location, perception of approaching stimuli (e.g., predators)
  • Eyes - fish often have excellent vision
  • Otoliths - suspended and in contact with hairlike fibers, gives information on spatial orientation
schooling
Schooling
  • Behaviorally based aggregation of fish
  • Most tightly schooling species have silvery sides
  • Schools sometimes in the form of “fish balls”
  • Behavior related to predation; fish leaving school are attacked successfully
  • Schooling may also reduce drag, save on energetic cost of swimming
body temperature
Body temperature
  • Most fishes - temperature conformers
  • Tunas and relatives, some sharks, use countercurrent heat exchange to reduce heat loss - have elevated body temperature
  • Elevated body temperature allows higher metabolic rate, localized heating of nervous system in some species (e.g., swordfish)
mesopelagic fishes 3
Mesopelagic Fishes3
  • Fish living 150-2000 m
  • Fish have well developed eyes, often large mouths for feeding on large prey
  • Many have ventral photophores, serves purpose of counterillumination - camouflage to blend in with low light from above
slide32

Chauliodus has specialized backbone to accommodate

Opening of large mouth to consume prey

mammals
Mammals

Cetaceans: whales and porpoises

Pinnipeds: seals, sea lions, walruses

Mustelids: sea otters

Sirenians: sea cows, dugongs

whales and porpoises
Whales and Porpoises
  • All belong to the Cetacea
  • Odontoceti include toothed whales (e.g., sperm whale, porpoises)
  • Mysticeti include baleen whales - feed by means of baleen, which strains macrozooplankton, megazooplankton
whales and porpoises1
Whales and Porpoises
  • All homeothermic
  • Reproduce much the same as terrestrial mammals
  • Posterior strongly muscular - propulsion by means of flukes
odontoceti
Odontoceti
  • Toothed, usually good hunters, feed on squid, fish, small mammals
  • Good divers
  • Oral communication common
  • Many species have bulbous melon, filled with oil - function could be sound reception
  • Usually social, killer whales live in pods, maternally dominated
mysticeti
Mysticeti
  • Adults have horny baleen plates, which strain zooplankton
  • Right whales are continuous ram feeders
  • Rorqual whales (e.g. Blue) are intermittent ram feeders, periodically squeeze water out of large mouth chamber
slide40

Continuous

ram

feeding

Ventral furrows

Intermittent

ram

feeding

other marine mammals
Other Marine Mammals
  • Pinnipeds include seals, sea lions, walruses - have hair but lack thick blubber of cetaceans
  • Sea otters belong to the otherwise terrestrial family Mustelidae
slide42

Seal

Sea

Lion

sirenians
Sirenians
  • Includes manatee, dugong, extinct Stellar Sea Cow
  • Sluggish, herbivorous
  • Live in inshore waters, estuaries
diving by marine mammals
Diving by Marine Mammals
  • Must breathe at surface
  • Problem of having enough oxygen for long dives
  • Most have increased volume of arteries and veins
  • Have increased blood cell concentration
  • Can decrease heart beat rate and O2 consumption
  • Can restrict peripheral circulation and circulation to abdominal organs
gas bubble problems 3
Gas Bubble Problems 3
  • Upon ascent, gas bubbles may be released in blood stream as pressure decreases - The Bends
  • Not as bad a problem as you might think, because marine mammals don’t breathe air under pressure at depth, like human divers
  • Seals and whales can restrict circulation between lungs and rest of circulatory system and have small lung capacity
ad