Chapter 8 - Fishes, Sharks, and Kin

Notes for Chapter 8:
The Marine Vertebrates I: Fishes, Sharks, and Kin

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Case History: The Most Famous Living Fossil
of the Twentieth Century

RQ 8.1: What is the common name of Latimeria
        and why was it heralded as such an important
        discovery? Why is the geographic range described
        in the text somewhat outdated? More links: 1 - 2
    Get a cool $5 Latimeria keychain here

I. The Rise of Vertebrates - More Links
terms: agnathan (jawless)

         Featured organisms:
     Pikaia (530 mya ancient chordate, Fig. 8.1a)
     Early jawless fish (400 mya, Fig. 8.1b)
            Huge placoderm, an early fish with jaws
                (380 mya, Fig. 8.1c, click here and scroll down to
         Dunkleosteus)

RQ 8.2: Describe some important changes in the appearance,
        abundance, and feeding of chordates that started with an
        ancient ancestor, perhaps like Pikaia, and led to early
        fishes with jaws, including the gigantic placoderm,
     Dunkleosteus.

II. The "Jawless Fishes" (no longer recognized as formal Class)
Skip the following mini-essay on phylogeny if you wish:

        Why does this matter? Grouping fishes such as hagfishes and lampreys
        together in taxon, Agnatha, implies that these are closely related. In fact,
        as strange as it seems, we humans are more closely related to a lamprey,
        and vice versa, than either of us is to a hagfish. Lampreys and humans
        are members of Vertebrata, descendants of a common ancestor that had
        vertebrae in its backbone. Hagfishes do not have vertebrae, and they are
        not members of Vertebrata, but along with vertebrates they are members
        of the more ancient larger group, the craniates. Members of Craniata have
        a cranium (brain case) that is not found in more distant chordate relatives,
        such as Pikaia or sea squirts. Pikaia (an ancient kind of lancelet) and sea
        squirts are not craniates but they are chordates, because they share chordate
        features including a notochord (see end of Chapter 7). The point is that formal
        taxa (e.g., Vertebrata, Craniata, Chordata) should be based on the evidence of
        shared features, such as the vertebrae, cranium, and notochord, respectively,
        not based on which features they do not have (e.g., those fishes without jaws).
        Incidently, the taxon Gnathostomata includes the first fish with jaws, and
        all its descendants, including us. Thus, a species such as humans can always
        be grouped into groups (technically called clades) whose last common ancestor
        is relatively more ancient: Primates (with fingerprints, etc.), Mammalia (with
        fur and mammary glands), Amniota (with an amniotic egg), Tetrapoda (with
        four limbs), Osteichthyes (with internal bony skeleton), Gnathostomata (with
        jaws), Vertebrata, Craniata, Chordata, etc. Click on these links to see more
        detailed evolutionary trees called cladograms showing these relationships or
     here for a simplified version.

III. The Cartilaginous Fishes (Chondrichthyes)
terms: elasmobranchs (sharks, rays, skates, sawfishes)
and chimaerid (ratfishes)

RQ 8.3: Rank the following groups in descending order
        according to number of species in marine habitats:
        a) "bony fishes" ("fish"); b) condricthyans; c) jawless
        fishes; c) amphibians (frogs and salamanders);
        d) "reptiles" (turtles, sea snakes, iguanas and
        crocodiles); e) birds; f) mammals. Which of these
        groups is has the most species in land plus freshwater
        habitats?

    a) Shapes, Anatomies, and Life Cycles of Sharks and
            Their Relatives
        terms: two pairs of dorsal fins: pectoral fins (behind
            gills) and pelvic fins (to the rear), single anal fin,
            tail or caudal fin, heterocercal vs. homocercal
            tail (Fig. 8.4), males sharks have claspers, females
            can be ovoviviparous, viviparous, or oviparous

RQ 8.4: Contrast the habitat and feeding of a shark such as
a great white shark with that of a skate or ray. What
do the largest species of sharks and rays feed on?

RQ 8.5: Characterize the distinction between ovoviviparous,
viviparous, and oviparous life history modes in sharks
(you will not be required to memorize which is which).

b) Attacks by Sharks on Human Beings

RQ 8.6: Name three ways that sharks might be provoked to
attack a human, and three ways to avoid such provocation
while snorkling, scuba diving, or surfing.

c) Attacks by Human Beings on Sharks

RQ 8.7: Characterize at least two arguments of those who are
        currently arguing that it is actually sharks that are endangered
        by us, rather than the other way around. For help beyond
        the brief mention presented in the text, see these links:
     1 - 2 - 3 - 4 - 5 - 6

IV. The Bony Fishes (Osteichthyes, traditionally only included
            "fishes" but currently also includes the "tetrapod"
            descendants on land, including humans)
        terms: bony fishes

a) The Forms and Functions of Fishes

RQ 8.8 (Fig. 8.6): Briefly characterize at least three examples
of how fins have become specialized in modern bony fishes.

    b) Reproduction and Life Cycles
        terms: diadromous vs. anadromous vs. catadromous
            life histories, eye migration in flatfishes (Fig. 8.9),
            leptocephalus larvae (Fig. 8.10)

   RQ 8.9 (Fig. 8.7): Briefly contrast the parental care strategies
        in a true cod, a lingcod, and a surfperch. Do not memorize
        the chart. Instead, be able to write a couple of sentences that
        characterizes the general pattern of differences.

   RQ 8.10 (Fig. 8.8): Contrast anadromous and catadromous
        life histories in fishes, and characterize where each is
        most common.

   RQ 8.11 (Fig. 8.9): How and why do flatfish end up with
     eyes on the same side of their head, and how do starry
     flounders and Black Sea turbots do this differently?

c) Commercial Fishes

        1) Herrings and their relatives dominate the harvests of
            world fisheries.
        terms: clupeiform fishes (small plankton-eating fishes)

   RQ 8.12: Characterize the commercial fishing history of
        anchovetas off Peru and Chile since the late 1950s.
        What other impacts have the decline in anchoveta
        populations had? (For a parallel situations in Monterey
        Bay, southern California, and elsewhere, see these websites:
     1 - 2 - 3 - 4 - 5 - 6 - 7)

         Featured organisms (Fig. 8.11):
       herrings
       anchovies
            Movie of Monterey Bay anchovies here
       sardines

        2) Cods and their relatives are second only to herrings
            in their commercial importance (recently collapsed
            in the northern Atlantic)
        terms: gadiform fishes (cods, pollocks, haddocks, hakes)

3) Salmons are commercially small-scale, politically
colossal.

RQ 8.13: Why are salmon so important politically even though
their catch is relatively minor compared with other fisheries?

4) Tunas have low tonnage, a high profile.

RQ 8.14: How are dolphin populations affected by tuna fisheries
and what can be done to lessen this impact?

d) Sport Fishes

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