marine ecology - nekton pt 1

nekton pt 1 marine ecology - nc/wcpss standards (generic)

Nekton

organisms that move against the water motion. nekton includes fish, mammals, reptiles, and birds

holopelagic

spend their entire life in the epipelagic (blue sharks, marlins, tunas)

meroepipelagic

spend only parts of their life in the epipelagic; usually spawn in coastal waters (herrings, whale sharks, salmon)

upward force of a fluid

buoyant force

buoyant force on an object is equal to the weight of the fluid absorbed by the object

archimedes priniciple

most significant adaptations of nektonic animals

the adaptation to stay suspended (relating to buoyancy)

physostome systems

swim bladders are filled via fish gulping air through a direct duct to the esophagus

physoclist systems

swim bladders are filled through a network. ofblood vessels called the rete mirabile

adaptations: locomotion

the adaptations of nekton relating to locomotion fall into how many categories? 

2 (creation of propulsive force, reduction of frictional resistance and drag)

fast-swimming fish…

typically have a fusiform body with a lunate (deeply forked) tail and a small caudal peduncle. speed is generated by muscle contractions; waves pass down the body.

slow-swimming fish…

typically have a deep and laterally compressed body with a broad tail and a large caudal peduncle

camouflage is…

the most common defense mechanism in nekton

cryptic coloration

involves a blending of colors to match the background of the organsim

countershading

involves lighter colors on the bottom side and darker colors on the top side

top side

dorsal side

bottom side

ventral side

Sensory infomration by nekton are similar to…

land animals with some additional senses

Lateral lines

possessed by all fish, sensitive to pressure changes in water

ampullae of lorenzini

present in sharks and rays, jelly-filled pores that detect/are sensitive to small/minute electric currents

most pelagic bony fish are…

broadcast spawners

broadcast spawners

producing immense amount of eggs that float and are subject to huge losses

sharks and rays have…

internal fertilization.

how many paths are there after internal fertilization?

3 - ovoviparous, oviparous, viviparous

ovoviparous

eggs hatch within the mother (ex: nurse sharks)

oviparous

laying eggs in the water (ex: hornshark)

viviparous

with a placental link, akin to mammals (ex: hammerhead sharks)

trophic structure of the pelagic zone: polar waters

in cold polar waters, the top carnivores are marine mammals

trophic structure of the pelagic zone: tropical waters

in warm tropical waters, the top carnivores are various fishes

trophic structure of the pelagic zone: temperate zones

in temperate waters, the top carnivores are sharks and marine birds and mammals

major nekton phyla: phylum

chordata

major nekotn phyal: superclass

pisces

actinopterygii (class)

ray-finned fishes

elasmobranchii (class)

sharks, rays, and skates

holocephali (class)

chimaeras

sarcopterygii (class)

lobe-finned fishes