Pelagic Life and Nektonic Adaptations

Flashcards covering the physiological, morphological, and behavioral adaptations of pelagic life, including buoyancy, swimming mechanics, and marine mammal classifications.

Nektonic Animals

Organisms that are not small or transparent and have evolved to move horizontally through the water column.

Fusiform

A streamlined body shape that allows nektonic animals to move more easily through water.

Swim bladder

An internal gas container used by fish to increase buoyancy and avoid sinking.

Myomeres

Muscles whose alternate contraction and relaxation sends a wave of body curvature along the animal to produce forward thrust.

Midline fins

Fins such as the dorsal and anal fins that act as stabilizers and assist with balance.

Lateral fins

Always paired fins, including pectoral and pelvic fins, used primarily for steering and sometimes balance.

Caudal fin

The tail fin specifically used to provide thrust for the animal.

Rounded caudal fins

Flexible tail fins that allow for maneuverability at slow speeds.

Lunate fins

Rigid tail fins that provide significant thrust for fast-swimming animals.

Heterocercal fins

Asymmetrical fins, such as those found on sharks, that provide lift for buoyancy.

Aspect ratio (formula)

$AR = h^2 / SA$, where $h$ is the greatest vertical height of the fin and $SA$ is the surface area of the fin.

Aspect ratio (effect)

An increase in this ratio results in faster speed but less maneuverability.

Lungers

Predators like the grouper that wait for prey and pounce, characterized by mainly white muscle tissue.

Cruisers

Predators like the tuna that actively seek prey, characterized by mostly red muscle tissue.

Homeothermic

An adaptation where body temperature is maintained above the surrounding sea water temperature.

Bioluminescence

A common adaptation of deep-water nekton to produce light in the dark ocean depths.

Schooling

A pelagic antipredator adaptation providing protection in groups, hydrodynamic advantages, and social benefits.

Pinnipeds

A group of marine mammals within the order Carnivora that includes seals, sea lions, fur seals, and walruses.

Sirenians

Herbivorous marine mammals with land-dwelling ancestors, including manatees and dugongs.

Cetacea

An order of marine mammals with streamlined bodies for fast swimming, including whales, dolphins, and porpoises.

Oxygen absorption in Cetacea

Deep-diving adaptation where animals are able to absorb $90\%$ of oxygen inhaled.

Odontoceti

A suborder of Cetacea consisting of toothed whales, such as dolphins and killer whales, that use echolocation.

Mysticeti

A suborder of Cetacea consisting of baleen whales that use fibrous plates to sieve prey items.

Echolocation

A sensory system used by Odontoceti to determine the distance, direction, shape, and size of objects.

Baleen

Fibrous plates, reaching up to $2.8\,m$ in Northern Right Whales, used to strain copepods and krill from water.