The Nekton 1

What are Nektonic Animals?

Organisms that have developed powers of locomotion

Feeding Biology Practically all members of the nekton are

carnivorous Planktivorous Piscivorous

The Nekton 2

The Epipelagic Environment

This is a challenging environment to live in Extreme 3

dimensionality No solid substrate No landmarks to use

for navigation

The Nekton 3

Adaptations of the Nekton To be successful,

nektonic animals must develop: Faster swimming speeds Adaptations to float Refined defensive

mechanisms Complex nervous

systems to navigate and capture food

The Nekton 4

Staying Afloat Like plankton, nekton also incorporate lipids into their tissue Sharks concentrate high oil levels in a large liver

The Nekton 5

• Fishes use stiff fin elements with movable spines• These fins are used as wings to generate lift• Heterocercal tails are used in sharks to generate lifts

Staying Afloat

The Nekton 6

Staying Afloat

The Nekton 7

Faster Swimming Speeds Adaptations are directed towards

decreasing drag and increasing forward propulsion Elimination of protuberances and a

streamlined body shape helps Fast swimmers tuck fins into grooves

The caudal fin provides the major component of thrust

The Nekton 8

A Swimming Machine

The Nekton 9

Defense Mechanisms There is no cover to hide in the

epipelagic This is a very intense selective pressure,

everyone is evolving mechanisms of defense

Sense Organs Sight Lateral line Otoliths Echolocation Ampullae of Lorenzini

The Nekton 10

The Nekton 11

The Nekton 12

Defense Mechanisms Color and Camouflage

Countershading - dark dorsal side, light ventrally

The Nekton 13

Defense Mechanisms Behavior

Schooling behavior is a method of protection for small fish

Flying Fish Use modified pectoral fins for

gliding above the surface

The Nekton 14

Migrations Why are migrations made?

Many animals undergo extensive migrations usually for feeding or reproduction

Salmon Sea Turtles

Tuna undergo extensive migrations to fully exploit food resources

Marine mammals (baleen whales) make migrations in a north and south fashion for feeding and calf rearing

The Nekton 15

Tuna Migrations

The Nekton 16

Baleen Whale Migrations

The Nekton 17

Migrations How do marine animals

make migrations? Use variations in water

temperature Walker et al. (1984) found

tuna use the earth’s weak geomagnetic field

Magnetite (Fe3O4) crystals transduce the geomagnetic field to the nervous system