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 (Fe 3 O 4 ) crystals transduce the geomagnetic field to the nervous system