Marine Fishes Flashcards
Why are marine fishes important?
- Feed on nearly all types of marine organisms
- The most economically important organisms
- Vital source of protein for millions of people
- Sportfishing
- Pets
What are characteristics of vertebrates/chordates?
Have a backbone (vertebral column or spine)
Dorsal Hollow Nerve Cord (spinal cord)
Notochord
Post-anal tail
Bilateral symmetry
Presence of an endoskeleton
What are the 3 groups of fishes?
- Jawless fish
- Cartilaginous fishes
- Bony fishes
What class are jawless fishes?
Class Agnatha
What are the types of jawless fish?
- Hagfish
- Slime eels
- Lampreys
What class are cartilaginous fishes?
Class Chondrichthyes
What are the types of cartilaginous fishes?
Sharks, skates, rays, and ratfishes
What are characteristics of jawless fish?
- Lack jaws
- Feed by suction with the aid of a round, muscular mouth and rows of teeth
- Body is cylindrical and elongated
- Lack paired fins and scales
What are characteristics of cartilaginous fishes?
- Ancient group
- Skeleton made of cartilage
- Movable jaws
- Well developed teeth
- Mouth is almost always ventral
- Paired lateral fins for efficient swimming
- Rough, sandpaper like skin because of the presence of tiny placoid scales
What invertebrate did fishes evolve from?
Chordate
What are characteristics of sharks?
- Fusiform body shape (spindle-shaped)
- Caudal fin or tail is well developed and powerful
- Heterocercal tail ~ upper lobe is longer than the lower lobe
- Usually two dorsal fins ~ first larger and triangular
- Paired pectoral fins are large and pointed
- 5 to 7 gill slits
- Powerful jaws have rows of numerous teeth
- Lost teeth are replaced by new teeth like a conveyor belt
- Found throughout the oceans depth, but most common in tropical coastal waters
What are benefits of sharks?
- Shark meat is eaten around the world
- Subject to disastrous fishing
- Fished for their oil
- Skin is turned into leather
- Skin is also used as sandpaper
- Fins are used for soup in the Orient
What are characteristics of rays and skates?
- Dorsoventrally flattened bodies
- Live on the bottom ~ demersal
- 5 paired gill slits on the underside of the body
- Pectoral fins are like wings
- Eyes are on the top of the head
What are characteristics of ratfishes or chimaeras
- 30 species
- Deepwater
- One pair of gill slits covered by a flap of skin
- Feed on bottom dwelling crustaceans and mollusks
What class are bony fishes?
Class Osteichthyes
What are characteristics of bony fishes?
- Skeleton made of bone
- Scales are made of bone and are covered by a thin layer of skin
- Operculum or gill cover ~ flap of bony plates and tissue that protects the gills
- Upper and lower lobes of the tail are the same size or homocercal
- Fins consist of thin membranes that are supported by bony spines or fin rays
- Mouth is terminal and located at the anterior end
- Jaws are protrusible because they can be projected outward from the mouth
- Teeth attached to the jaw bones
- Swim bladder ~ gas-filled sac just above the stomach
- Small intestines ~ allows the fish to adjust its buoyancy to keep from sinking or rising
What is Ichthyology
The study of fishes
What can colors tell us about fishes?
Mood, reproductive condition, whether they are dangerous, poisonous or taste bare
What is disruptive coloration?
The presence of color stripes, bars or spots that help break up the outline of a fish
Describe swimming in sharks
- Tend to sink because they lack a swim bladder
- Large stiff pectorals that provide lift
- Upper lobe of tail also provides lift
- Large amount of oil in the liver provides buoyancy
Describe swimming in bony fishes
- Have a swim bladder
- Pectoral fins can serve other purposes (hover, swim backwards) - maneuverability
Describe feeding in sharks
- Carnivorous
- Feed by taking bites from prey larger than themselves
- Have formidable jaws and shake their heads
- Eat almost anything
Describe filter feeding in sharks
- Whale shark, basking shark, manta, devil rays, and the megamouth shark
- Filter the water with their gill rakers, slender projections on the inner surface of the gill arches
Describe feeding in bony fishes
- Very diverse in the way they feed
- Protrusible jaws allow them much more flexibility in feeding habits
- Bony fish have well-developed teeth for catching, grasping, and holding their prey
- Roof of mouth, gill rakers, and pharynx may also have teeth to help hold the prey
What are the steps of digestion?
1) After being swallowed, food goes into the pharynx
2) Then the esophagus
3) Then into the stomach, where the process of digestion begins
4) From the stomach food enters the intestine
5) Anterior portion of the intestine may contain (pyloric caeca) (secrete digestive enzymes)
6) Pancreas also secretes digestive enzymes
7) Liver produces bile which breaks down fat
Distinguish between intestines
- Carnivorous fish have short, straight intestines
- Grazers have coiled intestines because the plant matter is harder to break down
- The intestine (primary digestive organ) is responsible for
absorbing the nutrients
Describe circulatory system
- All fish have a two chambered heart located below the gills
- Deoxygenated blood comes into the first chamber of the heart from the body
- Blood is then pumped into the second chamber
- Blood is then pumped to the gills where gas exchange takes place
- Oxygenated blood (red) then travels through arteries - capillaries (gas exchange occurs) and then enters the veins (blue) which return it to the heart
Describe respiratory system
- Fishes obtain oxygen dissolved in water and release carbon dioxide from their blood through paired gills
- Gills lie in the pharynx
- Fishes get the oxygen they need by extracting it from the water
- Water must flow over the gills ~ must irrigate or ventilate the gills
- Bony fish have an operculum, sharks do not
- Kidneys excrete the salt and little water
- Chloride cells in the gills also remove salts
What is the function of the lateral line?
Allows a fish to detect vibrations in the water
Describe reproductive system
- Sexes are usually separate
- Both sexes have paired gonads located in the body cavity
- Urogenital opening ~ behind anus for gametes and urine
Distinguish between external and internal fertilization
Internal Fertilization
- Sperm is directly transferred from males to females through the act of copulation
- Male sharks, skates, and rays have paired copulatory organs called claspers located along the inner edge of the pelvic fins
External Fertilization
- Release of gametes into the water (broadcast spawning)
- More common in bony fish
- Fertilization occurs in the water
