Chapter 26 - Fishes

Notes for Chapter 26: Aquatic Vertebrates ("Fishes")

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or back to Chapter 25
or ahead to Chapter 27

Chapter 26 Assignment: 507-528; RQ-26: 3, 5-7, 13, 15-17
Next: Ch. 27: 538-548, 556-557; RQ-27: 1-3, 8-9, 12
Next: Ch. 28: 559-571, 576-579; RQ-28: 2-5, 7, 10, 16-17
Then: Ch. 30: 609-621, 624-626, 634-639;
RQ-30: 1-2, 6-8, 11, 15-16 (last two lectures)

Introduction: What Is a Fish?

Source of Image

Featured Animal: Hammerhead shark
More Links: 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10

The following outline of lecture notes does not follow Ch. 26 headings.

Also note, the text cladogram figures have some problems. Here are more details.

Review: What are synapomorphies for:
Chordata? Craniata? Vertebrata?

Fig. 26-2 revisions (compare with handout):
  Delete Agnatha
  Craniata Vertebrata (Craniata = hagfishes + vertebrates)
  Osteichthyes should also include tetrapods
  Sarcopterygii ("lobe-finned" fishes) should also include tetrapods

Gnathostomes have what synapomorphy?

How did jaws evolve?

What sensory equipment do sharks have?

If sharks are members of Chondrichthyes, what are Osteichthyes?

What are two major subgroups of Osteichthyes? How are they different?
What specific group of Osteichthyes has the most species?

How do fish stay bouyant? How do fish osmoregulate?

Classification of "bony fishes"
(including the terrestrial members of this clade):

Osteichthyes (bony fishes)
   ray-fins
   lobe-fins (or fleshy-fins; muscles in lateral fins)
      coelacanths
      Choanata (have choana)
         lungfishes
         Tetrapoda (have 4 limbs)
            Amphibia (or Lissamphibia)
               caecillians
               Batrachia
                  salamanders
                  frogs and toads
           Amniota (have amniotic egg)
               Reptilia (or Sauropsida)
               Mammalia

Bony fishes - ray-fin and lobe-fin clades

key terms: slime glands, fusiform body, heterocercal caudal fin, claspers, cartilaginous endoskeleton, urea, squalene, placoid vs. ganoid vs. cycloid vs. ctenoid scales, endochondral bone, operculum, swim bladder, homocercal tail, double circulation, gas gland, rete mirabile, hyper- vs. hypoosmotic regulators, anadromous life history

Ray-fins include teleosts (most vertebrates, 96% of fishes)
Lobe-fins include coelacanths, lungfishes, and tetrapods

Rayfins have swim bladder to maintain bouyancy (p. 526)

Two methods:
   simple (trout):
       pneumatic duct connection to esophagus
   elaborate (diverse teleosts):
       gas in from blood: gas gland
          network of blood capillaries ("rete mirabile")
       gas removed from bladder: resorptive area

Gas gland is highly efficient:
    Example: fish living at depth of 2400 m
       tremendous oxygen pressure differential:
       blood must be kept at sea surface pressure (0.2 atmosphere)
       swim bladder must be kept inflated (> 240 atmospheres)

How does gas gland work?
    secretes lactic acid into blood
    forces localized release of oxygen from hemoglobin
    oxygen diffuses into swim bladder
    deep-sea fish have longer rete capillaries

More on how a fish works
    Respiration:
       gills use countercurrent exchange
       blood flows opposite direction to water pumped in from mouth
       active fishes use ram ventilation
       continuous swimming forces water in diverse fish can gulp air

Osmoregulation:
    Freshwater fishes
       blood is about 0.25 M
       freshwater is 0.003 M
       they are hyperosmotic regulators
       use kidney to pump out excess water
       kidney has large "glomerulus"
       also absorb salt with special gill cells
    Saltwater fishes
       blood is about 0.35 M
       seawater is 1 M
       they are hypoosmotic regulators
       kidney excretes salts
       intestine excrete salty feces
       secrete salt with special gill cells

Click link to return to Lecture Schedule
or back to Chapter 25
or ahead to Chapter 27