Chapter 14 Animals of the Pelagic

Environment

Essentials of Oceanography

7th Edition

Pelagic organisms

Organisms that live in the pelagic environment:

Live suspended within the water column

Can float or swim

Have adaptations that allow them to stay above the ocean floor

Staying above the ocean floor

Adaptations for staying above the ocean floor:

Rigid gas containersSwim bladderAbility to float

Figure 14-1

Figure 14-2

Gas containers in cephalopods

Swim bladder

Microscopic floating organisms: Radiolarians

Radiolarians produce a hard test composed of silica

Tests have projections to increase surface area

Figure 14-3

Microscopic floating organisms: Foraminifers

Foraminifers produce a hard test composed of calcium carbonateTest is segmented or chambered

Figure 14-4

Microscopic floating organisms: Copepods

Copepods have a hard exoskeleton and a segmented body with jointed legsRelatives of shrimp, crabs, and lobsters

Figure 14-5

Macroscopic floating organisms: Krill

Krill are related to copepods but are larger in size

Abundant in Antarctic waters, where they are a favorite food of the largest whales Figure 14-6

Macroscopic floating organisms: Coelenterates

Coelenterates are soft-bodied organisms including:

Siphonophores (Portuguese man-of war)Scyphozoans (jellyfish) Figure 14-7a

Swimming organisms (nekton)

Larger pelagic organisms can swim against currents and often migrate long distances

Nektonic organisms include:Squid

Fish

Marine mammals

Squid

Squid are invertebrates that swim by taking water into their body cavity and forcing it out through their siphon

Figure 14-8

Fish: Swimming motions and fins

Figure 14-9

Fish: Adaptations

Feeding styles: Lungers versus cruisersLungers sit and wait for prey to come close by

Cruisers actively seek prey

Cold-blooded versus warm-bloodedMost fish are cold-blooded

A few active fish are warm-blooded

Many fish school to avoid predators

Fish: Deep-water nekton

Adaptations of deep-sea fish:

Good sensory devicesBioluminescenceLarge, sharp teethLarge mouths and expandable bodiesHinged jaws

Figure 14-11

Marine mammals

Characteristics of marine mammals:Warm-blooded

Breathe air

Have hair (or fur)

Bear live young

Females have mammary glands that produce milk for their young

Marine mammals: Order Carnivora

All members of order Carnivora have prominent canine teeth

Includes:Sea otters

Polar bears

Pinnipeds (flipper-footed)Walrus

Seals

Sea lions/fur seals

California sea lions

Figure 14-17c

Differences between seals and sea lions/fur seals

Seals:Lack ear flaps

Have small front flippers

Have claws

Cannot rotate hind flippers beneath themselves

Figure 14-18

Marine mammals: Order Sirenia

Sirenian characteristics:Large body sizeSparse hair all over bodyVegetariansToenails (on manatees only)

Includes:ManateesDugongs

Marine mammals: Order Cetacea

Cetacean characteristics:Blowholes on top of skull

Skull telescoped (streamlined shape)

Very few hairs

Includes:Whales, dolphins, and porpoises

Marine mammals: Order Cetacea

Figure 14-20

Two suborders of order Cetacea

Suborder Odontoceti (toothed whales)Echolocate (send sound through water)

Includes killer whale, sperm whale, dolphins, porpoises, and many others

Suborder Mysticeti (baleen whales)Have rows of baleen plates instead of teeth

Includes blue whale, finback whale, humpback whale, gray whale, and many others

Differences between dolphins and porpoises

Dolphins have:An elongated snout (rostrum)

A sickle-shaped (falcate) dorsal fin

Teeth that end in points

Figure 14-22

Killer whale jawbone

Generation of Odontoceti echolocation clicks

Figure 14-23

Odontoceti echolocation

Sound is bounced off objects to determine:

SizeShapeDistanceInternal structure

Figure 14-24

Mysticeti: The baleen whales

Mysticeti whales have baleen instead of teeth

Baleen plates:Hang as parallel rows from the upper jaw

Are made of keratin

Are used as a strainer to capture zooplankton

Allows baleen whales to eat krill and small fish by the ton

Baleen

Figure 14-25

Types of baleen whales

Baleen whales include three families:Gray whale (a bottom-feeder with short baleen)Rorqual whales (medium-sized baleen)

Balaenopterids (blue whales, finback whales, and other large whales )Megapterids (humpback whales)

Right whales (surface skimmers with long baleen)

An example of migration: Gray whales

Gray whales undertake the longest annual migration of any mammal:

Spend wintertime in birthing and breeding lagoons in MexicoSpend summertime feeding in highly productive Arctic waters

Figure 14-27

End of Chapter 14

Essentials of Oceanography

7th Edition