Fishes Flashcards
1
Q
Basics to the Protochordata, Craniata and Gnathostomata
A
- All are within Phylum Chordata
- Protochordata (do not have a true brain, skull, or vertebral column)
- Craniata
Have a skull (cranium) and/or vertebral column
Agnatha (Hagfish and Lampreys) only have a skull (no vertebrae) - Gnathostomata
Craniates with jaws
Includes all of Craniata except for Agnatha
2
Q
Fish or Fishes?
A
- The study of fish (Ichthyology)
- Use fish as the plural form when you are talking about multiple individuals of the same species
- Use fishes as the plural form when you are talking about more than one species
3
Q
What is a fish?
A
- Historically
Mixed assortment of water dwelling animals
In 16th century seals, whales, amphibians, crocodiles, and even hippopotamuses were called fish - Today
Aquatic vertebrate
Gills
Appendages, if present, in the form of fins
Skin with scales
4
Q
Why are fish interesting?
A
- Move in three dimensions
- Unique adaptations
Fish gills are the most effective respiratory devices in the animal kingdom
Extract oxygen from a medium that contains less than 1/20 as much oxygen as air - Incredible diversity and life history
5
Q
Introduction to fish
A
- Not a monophyletic group
All vertebrates that are not tetrapods - Diverse: Approx 28,000 identified species
More than all other species of vertebrates combined
6
Q
What is their Phylogeny?
A
- Agnatha
Class Myxini (hagfishes)
Class Petromyzontida (lampreys)
- Chondrichthyes
Sharks, rays and chimaeras
- Osteichthyes (Bony Fishes)
Class Actinopterygii (ray-finned fishes). Includes teleosts which represent 96% of all living fishes, and nearly half of all vertebrates
Class Sarcopterygii (lobe-finned fishes). Represented today by coelacanths and lungfishes
7
Q
How are they today?
A
- Phylogenetic relationships within Phylum Chordata
- General characteristics
Form
Locomotion in water
Neutral buoyancy and the swim bladder
Respiration
Osmotic regulation
8
Q
What are their types of scales?
A
- Placoid scales
Small, conical, toothlike structures
Typical of Chondrichthyes
Modified to teeth in sharks
- Ganoid scales
Diamond shaped
Early bony fishes and living gars
- Cycloid and Ctenoid scales
Arranged in overlapping rows
Typical of teleost fish
9
Q
What is their locomotion in water?
A
- Propulsive mechanism: trunk and tail musculature
- Movement achieved through undulation of the posterior end
- Generates thrust (forward motion) and lateral force (sideways motion)
- The lateral force causes fish head to “yaw”, or deviate in the same direction as the tail
- The “yaw” occurs more in more flexible fish
- A less flexible body plan is conducive to speed
10
Q
How is their buoyancy?
A
- Fishes are slightly heavier than water
- Various adaptations to deal with buoyancy
- Swim bladder = gas filled organ
Volume adjusted for neutral buoyancy
Remain suspended indefinitely at any depth with no muscular foot
Volume of gas can be adjusted as fish moves up and down water column (some fish do this more quickly than others) - Swim bladder present in most pelagic (open sea) bony fishes
- Swim bladder absent from tuna, most abyssal (very deep) fish, and most bottom dwellers
Deep fishes don’t have as much need to maintain neutral buoyancy
Tuna never stop moving (fast swimming) - Chondrichthyes have no swim bladder
Asymmetrical tail provides lift
Large livers with squalene (particularly buoyant lipid)
11
Q
How is their respiration?
A
- Most fishes use gills
Breathe dissolved oxygen (oxygen that is in the water) - Gills are located in the pharyngeal cavity
Remember that one of the hallmarks of chordates is pharyngeal slits - Gills are covered with an operculum in bony fishes
Increases efficiency of respiration
Not preset in sharks and rays - Some fish also have lungs
Capable of breathing air - Gill composed of thin filaments covered with an epidermal membrane
- The membrane is folded repeatedly into plate like lamellae
Enormous surface area
Lamellae contain main blood capillaries - Water is pumped continuously in the mouth, over the gills and out through the gill slits
Some very active fish need to continuously swim forward to meet their high oxygen demands - Gas exchange occurs across thin walls of blood capillaries
12
Q
What is osmotic regulation?
A
- Maintenance of balance of fluids
- Freshwater and Marine fish have opposite challenges
- Freshwater fish are hyperosmotic regulators
- Marine fish are hypoosmotic regulators
13
Q
Explain hyperosmotic regulators
A
- Greater salt concentration in fish than in surrounding water
- Scales and mucous protect the fish, but water can enter across membranes
- Water pumped out by kidneys
- Salt absorbing cells in the gill move salt from water to blood
14
Q
Explain hypoosmotic regulators
A
- Contain a smaller concentration of salt than surrounding water
- Salt secretory cells in the gill move salt out the body
- Salt is voided with feces or excreted by the kidney
15
Q
What are the major groups of fishes?
A
- You should know the three major groups (Agnatha, Chondrichthyes, Osteichthyes)
- You should know the class names Actinopterygii (ray-finned fishes) and Sarcopterygii (lobe-finned fishes)
- You are not responsible for the class names fir hagfishes and lampreys or for the subclasses
- You should know the following common names/groups, how they are related to each other, and which major groups they belong to: hagfishes, lampreys, sharks, rays, chimaeras, bony fish, ray fined fish, lobe finned fish, teleost, coelacanths, lungfish for all the groups discussed
16
Q
What are the Agnatha (hagfishes)?
A
- Jawless
- Entirely marine groups
- Feed on annelids, molluscs, crustaceans, and dead or dying fishes
- Scavengers and predators (not parasitic)
- Poorly developed eyes
- Keenly developed sense of smell and touch
- Produce slime as a defence mechanism
- Hagfish rasps bits of flesh from its prey
- Keratinized plates on tongue
- Can itself into knot
Passes the knot forward along its body until it is pressed securely abasing the side of its prey (for leverage)
17
Q
What are the Agnatha (lamprey)?
A
- Class Petromyzontida
- 20 species in North America
- Invasive species in the Great Lakes
- Half are parasitic
- They use tooth like plates of keratin for rasping a hole through which fluids and tissues are sucked
18
Q
What are the Chondrichthyes?
A
- Cartilaginous fishes (sharks, rays, chimaeras)
- Distinct features
Cartilaginous skeleton (Bone entirely absent. Derived feature-descended from ancestors with well-developed bone) - Placoid scales: made of material similar to teeth
- No swim bladder
Heterocercal tail: asymmetrical, provides lift
Large livers with squalene (particularly buoyant lipid) - Rays: skates, stingrays, electric rays and manta rays (dorsoventrally flattened bodies)
- Chimaeras (also called ratfishes)
Closest living relatives are sharks
Instead of teeth their jaws bear large flat plates - Sharks
Apex predators-most feed at the top of the marine food chain
Some exceptions: e.g. whale shark-largest extant fish species-is slow moving and feeds on plankton
Spined pigmy shark feeds on small fishes
19
Q
Sharks
A
- Asymmetrical heterocercal tail
- Vertebral column turns upward and extends into the dorsal lobe of the tale
- Provides lift as the shark swims
- Must constantly move to avoid sinking (even while sleeping)
20
Q
What are the Osteichthyes?
A
- Bony fish (bone replaces cartilage)
- 2 groups (ray-finned fish and lobe-finned fish)
- Gas filled pouch branches from esophagus
In fish that use these pouches primarily for gas exchange, they are called lungs
In fishes that use these pouches primarily for buoyancy, they are called swim bladders
21
Q
Gills vs Lungs
A
- Gills probably evolved first, but lungs also evolved early
- Ancestor of ray finned and lobe finned fishes had gills and lungs
In lobe finned fishes (and tetrapods) lungs were preserved (modern lobe finned fish also retained gills)
In ray finned fishes, gills were preserved and lungs were adapted into swim bladder
22
Q
Explain the ray-finned fishes
A
- Symmetrical homocercal tail allows for greater speed
- Permitted by the swim bladder and improved control of buoyancy (the heterocercal tail in sharks keeps them from sinking)
- Gills and swim bladder
23
Q
Explain the lobe-finned fishes
A
- Small group
6 species of lungfishes
2 species of coelacanths - Ancestor of tetrapods is found within an extinct lineage of this group
- Lobe fins with a single bone that articulates with rest of body
- Diphycercal tails
- Lungs and gills
24
Q
Explain the lungfishes
A
- Can live out of water for extended periods of time
25
Q
What is stasis?
A
Some lineages don’t change much, even over millions of years
