Fishs & Adaptations Flashcards
What is Nekton?
Organisms capable of sustained locomotion against the motion of water
Opposite of plankton
Can be divided into 2 main groups (holo epipelagic, and mero epipelagic)
Holo Epipelagic
Organisms spend their entire lives in the epipelagic (upper part of the ocean)
EX. Whale shark, marlins, tuna, etc.
Mero Epipelagic
Organisms spend only part of their lives in the epipelagic
They usually come up to the upper parts of the ocean to spawn and feed
EX. Lanternfish, barreleye fish, sabertooth fish, etc.
Fish Adaptations : Buoyancy
The most significant adaptation of fish is that which keeps the organisms suspended or buoyant in the water column
Bony Fish Buoyancy
Most have swim (gas) bladders, in which they can regulate the amount of gas to help regulate their position in the water column
Shark Buoyancy
Do not have swim bladders, instead store oil from the fish they consume as well as using a constant swimming motion to stay afloat
Fish Adaptations : Locomotion
The adaptations of fish related to moving through the water fall into 2 main categories
- Creation of propulsive force (tail shape)
- Reduction of frictional resistance and drag (body and fin shape)
Fast Swimming Fish
Typically have a fusiform body with a lunate tail
The speed is generated by muscle contraction waves that pass down the body
Slow Swimming Fish
Typically have a deep and laterally compressed body with a broad paintbrush tail
Fusiform Body
Thin, long, hydrodynamic body
Lunate Tail
Deeply forked tail
Fish Adaptations : Defense & Camouflage
Camouflage is the most common defense mechanism in fish
There are 2 main ways in which fish use camouflage
- Cryptic coloration
- Countershading
Cryptic Coloration
Often involves a blending of colors to match the background of the organism
Typically prey
Countershading
Often involves lighter colors on the ventral side and darker shading on the dorsal side
Typically predator
Fish Adaptations : Sensory Systems
Most sensory systems that fish have evolved are similar to those seen in land animals
Lateral Lines
All fish have this
Sensitive to pressure changes in the water
Allows fish to school
Ampullae of Lorenzini
Sharks and rays have this
Sensitive to minute electrical currents in the hearts of other organisms
Fish Adaptations : Reproduction
There are 5 reproductive strategies used by fish:
* Ovuliparity
* Oviparity
* Ovoviviparity
* Viviparity
* Hermaphroditism
Ovuliparity
Also known as “broadcast spawning”
Female and male fish release gametes in to the water at the same time
Oviparity
Fertilization occurs internally and then the female releases the recently fertilized eggs into the water
Est. about 97% of fish reproduce this way
Ovoviviparity
Fertilized eggs develop internally using yolk sacs within the female fish
Live young are then expelled
Viviparity
Embryos develop internally and nutrients are received via tissues or blood from the female
Hermaphroditism
Occurs when a species of fish contains both male and female reproductive organs, or can alternate possession one and then the other
Marine Reptiles
All marine reptiles evolved on land and have since returned to the sea
Only one species of crocodile (giant saltwater crocodile) and one species of lizard (marine iguana)
There are many species of sea snakes and sea turtles
Sea Turtles
There are 7 species of sea turtle, ALL of which are classified as endangered or threatened
Sea turtles use a geomagnetic sensory system (use the magnetic poles of Earth to migrate)
Female sea turtles lay their eggs at the same location they were born, year after year
Sea turtle eggs hatch as either male or female depending on the temperature of the sand
Cooler sand —-> Male
Warmer sand —-> Female
Threats to Sea Turtles
Entanglement in fishing gear (bycatch)
Poaching, illegal trade of eggs, meat, and shells
Coastal development
Plastic and other marine debris
Global warming
Ocean pollution
Pinnipeds
Include seals, sea lions, and walruses
They are divided into 3 groups:
* Odobenidae
* Otariidae
* Phocidae
Typically prefer cold waters
Almost all have fur coats
Odobenidae
Walrus
Otariidae
“Eared seals”
Sea lions
Fur seals
Phocidae
“Earless seals”
True seals
