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Animals of the Pelagic Environment Making a living--Adaptations Staying Above the Seafloor

Gas Containers Floaters Swimmers (nekton)

Eating Mobility Speed Temperature

Group Behavior Reproduction Schooling Migrations

Adaptations To make a living organisms must meet

the following challenges: 1) where to live 2) what food to eat and how to obtain it 3) how to avoid predators 4) where, how, when to reproduce

They are strongly influenced by theusual factors: temperature, density, etc.

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Planktonic forms: Zooplankton Zooplankton are the animals of the

plankton. They cannot swim againstthe currents.

Every major phylum of the animalkingdom is represented

Their size ranges from micrometers(protists) to tens of meters ("Jellies")

Zooplankton Continued... Zooplankton typically grow fast, and

this is very dependent on the foodsupply

Distribution - Zooplankton typicallyoccur in patches with a high density oforganisms, but they may accumulatealong a particular depth e.g., thepycnocline, DSL

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Common Zooplankton Copepods and euphausids (krill) Foraminifera and radiolarians Transparent forms or "Jellies". There

are the so-called true Jellies (Cnidaria)and the Ctenophores, or comb-jellies

Salps and tunicates

True Nekton This group can regulate both their

horizontal and vertical position, andinclude: Fish Molluscs (squid, cuttlefish, nautilus) Reptiles Marine Birds Marine Mammals (>50% of time at sea)

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Buoyancy 4 groups, based on vertical positioning:

Size-Independent This includes the smallest organisms

Primarily the smaller zooplankton So small they don’t sink very rapidly

Adaptations are size- and shape-related Gas Containers Floaters (no hard parts)-neutrally buoyant Swimmers

Buoyancy: Gas Containers Use a gas chamber to regulate depth

(buoyancy)--similar to a diver’s BCD Limited to about 500 m depth (the

crush depth) for nautilus

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Buoyancy: Fish Bladders A special case of gas containers, as

most fish swim instead NOT found in fish that swim all the time

such as tuna

Below about 7000m, the gas isreplaced by fat

Can be rapidly orslowly adjusted

Buoyancy: Floaters Contain very little hard tissue Includes:

Coelenterates Siphonophores Scyphazoans

Tunicates Ctenophores Chaetognaths (usually placed in

zooplankton group)

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Coelenterates-->Siphonophores

Bodies are more than 95% water Use a pneumatophore for buoyancy

Colonial organism,with specializedindividuals

Includesnematocysts(stingers)

Coelenterates-->Scyphazoans

True jellyfish Don’t contain a float-bag Uses muscular

contraction of the bell toprovide movement

Capable of explosivegrowth by asexualbudding

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Tunicates Also called sea

squirts, salps Are chordates, but

don’t have a spine Use jet propulsion Can grow up to 40%

per day in size! Can be important for

export of organicmaterial to depth

Ctenophores Also called “comb jellies”, sea

gooseberries Always pelagic, marine Carnivorous

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Also called arrowworms

very importantcarnivores,intermediate stepbetween smallzooplankton andfish

Chaetognaths

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Nekton (true swimmers) Squid

Fishes Marine Mammals All of these groups expend more

energy to maintain buoyancy

Adaptations for Feeding Mobility and Speed are largely

dependent on 3 factors: Length:Width (barracuda vs. sunfish) Caudal Fin morphology Red vs. white muscle mass

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Body Temperature Tuna are an example of countercurrent

heat exchange systems

Body Temperature The opposite extreme are cold-water

fishes that use antifreeze These glycoproteins bind to small ice

crystals in the cell, keeping them fromforming bigger crystals

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Marine Mammal Adaptations Marine Mammals: spend more than

50% of the time at sea Cetaceans (obviously) Pinnipeds Sea Otters Sirenians (manatees, dugongs, Stellar

sea cow [extinct]) Polar Bears

Breathing Deep diving mammals have evolved to

reduce oxygen consumption by: Increasing blood volume, capacity “gliding” as they dive Shutting off unnecessary organs during

dives Developing flexible ribs No nitrogen narcosis

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Behavioral Adaptations Schooling: found in over 2000 species

of fishes Reduce the predator-prey encounter rate Less likely to eat any given individual May appear as a “single” organism Confusing to predators

Can be reproducedusing simple rules ona computer

Behavior: Migration

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Behavior: Abduction Some organisms “borrow” another one

to enhance survival