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CLASS AGNATHA

Critter of the Day Common Name: Sun fish Scientific Name: Mola mola Phylum Chordata, Class Osteichthyes. CLASS AGNATHA. Basic Internal & External Anatomy. External Anatomy:  -jawless -generally small in length

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CLASS AGNATHA

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  1. Critter of the DayCommon Name: Sun fishScientific Name: Mola molaPhylum Chordata, Class Osteichthyes

  2. CLASS AGNATHA

  3. Basic Internal & External Anatomy External Anatomy:  -jawless -generally small in length -most generally lack fins, and instead wriggle/slither across the sea floor/bed. (generally move like snakes) - agnatha that do have fins are very active -mouths are circular or slit-like openings -some have a 3rd eye on top of head or bottom (for hagfish, it functions more as a pineal gland) Internal anatomy: - some such as lampreys feed on body fluids of host as a parasite ( attach to host fish, cut hole with teetch and feed on blood and tissues using tongue) (suspension feeding) -others are scavengers -close circulatory sytem w/ 3 types of blood vessels (arteries, veins, capillaries) -some primitive features: -simple skeleton -notochord during adulthood -skull is cartilage -multiple gill slits -not much of an identifiable stomach  -some live in freshwater streams and reach maturity when they reach salt water - some skip larval stage and live in saltwater their whole life

  4. Lampreys Lampreys  Has toothed, funnel-like sucking mouths Mostly coastal & fresh waters No scales Large eyes 1 nostril on top of head 7 gills on each side Cartilaginous (cartilage) skeleton  Unique immune system – unrelated antibodies found in mammals; very high tolerance to iron overload w/ biochemical defenses to detoxify itself Freshwater larvae (toothless, rudimentary eyes, feeding on microorganisms ; 5~7 years) -> metamorphosis involves rearranging of organs, development of eyes & mud-dwelling filter feeding to a swimming parasite / predator – adult attaches to prey w/ mouth secreting anticoagulants, eating on fresh & blood of host (most species last 18 months in this stage) Some lampreys stay in freshwater & some stop feeding after larvae stage Lampreys return to freshwater to reproduce, build a nest, spawn, and die

  5. Hagfish They live in the sediment of the continental shelf. Round mouths, with no jaws, that have many sensory appendages surrounding the mouth. They prey on animals with soft inner skin and also the organs of other prey they find decomposing. They abrade flesh with their soft rasping tongue. In order to separate flesh from large prey, the hagfish typically will knot its snake-like body to get a better grip and more pressure to pull the piece of flesh away. To defend its self against danger, the hagfish has slime glands that produce a mucus with a terrible odor and covers its body in it because it deters most other animals from attacking. In order to remove the mucus after danger has passed the hagfish also will knot its body and passes it from the head to the tail, squeezing the mucus off its skin. Because they have no fins they undulate their flattening tail at the end of their body to move forward.

  6. http://youtube.com/watch?v=EWltIBYuv3M&feature=related (fear factor hagfish) http://youtube.com/watch?v=letqkpG3b5Q&feature=related (Blue Planet hagfish Eating) http://youtube.com/watch?v=Bb2EOP3ohnE (hagfish sliming)

  7. Class Agnatha • Lamprey • Eel-like in appearance • Cartilaginous skeleton • Lack paired fins • Well developed dorsal/ventral finfolds • Mouth is longitudinal slit when closed, elliptical disk when open • Hooked teeth, 11-12 rows, innermost are the largest • Seven open gill slits on each side

  8. Hagfish • Share many characteristics with lampreys • 18 inches long • Also eel-like • Have a cartilaginous skeleton • Have six barbels, or whiskers, around the mouth, and a single nostril. • Hagfish can tie themselves into knots. This is useful for escaping prey, cleaning slime off their bodies, and for tugging meat off carcasses. • Blind

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