Vertebrate Zoo L4: Lamprey

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  • The Lamprey
    • General features
      • Mostly freshwater; some marine
      • Some parasitic, mostly scavenger
      • Funnel mouth with concentric rings
      • Several inches to a metre long
      • Scale-less skin
      • Jaw-less; bone-less; no-paired fins' 2 dorsal fins
        • Fin number/ position
      • Blood and flesh feeders
        • Morphology of the mouth and arrangement of teeth related to feeding strategy
      • Adaptive immune system as in jawed vertebrates
      • Highest chromosome number among vertebrates in the Northern lamprey
      • Some species tolerant of free iron
    • Other characteristics of lamprey
      • Larval stage + metamorphosis
      • Slightly elaborate skulls
        • Brain
          • Poorly developed cerebellum
          • Large optic lobes
          • NO intrinsic eye muscles
      • Single small dorsal nostril
      • Nasal duct ends in blind pouch
      • Protrusible tooth-covered tongue
      • Vertebrae consisting of simple dorsal elements
      • Buccal funnel armed with teeth
      • 7 pairs of external gill slits arranged along a slanting line
      • Atrium and ventricle closely set
      • Adult heart with nervous regulation
      • Neuromasts of lateral line system
      • Left and right gonads are fused up
      • Gill-based blood osmoregulation
      • Subdivided pharynx
    • Key points
      • Opening of nostril
      • Extent of hypophyseal complex
      • Position of olfactory sac
        • Near nostril opening (round mass, small)
      • Location/shape of tongue
        • Protrusible tooth-covered tongue
        • Buccal funnel armed with teeth
      • Cartilages/ muscles of tongue
        • Protractor then retractor behind it along the lamprey length
      • Gill openings (external and internal)
        • 7 pairs of external gill slits arranged along a slanting line
      • Mouth shape
        • Funnel mouth with concentric rings
      • Fin number/ position
    • Skeleton key points
      • Mostly situated in the head, and trunk region
      • Mostly slender cartilaginous elements (arches like dorsal vertebrae)
      • Cartilages support oral cone,, nasohypoyseal, tongue and heart
      • Brachial basket
      • Slightly elaborate braincase contributing to nasal and auditory capsules, with interposed cartilages between capsules
      • Slender rays in the caudal fin (ALSO FOUND IN HAGFISH!)
    • Feeding mechanism
      • Attaches to prey using buccal funnel (oral cone)- suction created
        • Suction: constriction of annular musculature = narrowing of funnel
          • Aided by passive elastic recoiling of brachial basket
          • Activates protractor musculature = lingual cartilage pulled forward (moved outward and downward like a conveyor belt)
        • Salivary glands secrete anticoagulant
        • Retractor muscle (mretr) fibres pull the tongue inward and upward while the piston-like cartilage (pistc) is pulled back
          • Ensures scraping action of tongue (chunks of flesh ripped off and ingested via suction of fluids (suction via inhaled H2O current moving through gills)
          • Velum ensures H2O currents carrying food particles are conveyed towards the oesphagus.
            • Lamprey can breathe while feeding

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