JEB desktop wallpaper calendar 2016

JEB desktop wallpaper calendar 2016

The functional morphology of hooding in cobras
Bruce A. Young, Kenneth V. Kardong

SUMMARY

Many snakes, particularly cobras, form as part of a defensive display, a hood, an active lateral expansion of their neck skin and underlying musculature and ribs. We identified muscle groups possibly involved in hooding based on their attachments on the specialized ribs of the neck. We then used a combination of morphology, kinematic analysis, morphometrics, electromyography and muscle stimulation to test hypotheses about the functional basis of hooding. We confirmed that hood protraction and erection is an active process that begins cranially and extends caudally, often in stages, through the combined action of several sets of muscles. One set of axial muscles (levator costae and supracostalis lateralis superior) coursing along a line of action to rib displacement are the prime erectors acting to lift the hood. However, a second set of muscles connecting ribs to skin primarily keep the skin taut, rather than to displace the ribs relative to the vertebrae. A third set of muscles coursing between ribs function primarily to transmit forces between adjacent ribs rather than to move ribs. The maintenance of the erect hood requires continued muscle activity. Hood relaxation is due to both active muscle contraction of a fourth set of axial muscles and to passive recoil events in the costovertebral ligaments. The shape of the fully erect hood is reflective of the morphometrics of the underlying ribs, while the duration and kinematics of hood erection and relaxation are related to the behavioral context of the display.

  • LIST OF ABBREVIATIONS

    ci
    costocutaneous inferior
    co
    costovertebrocostalis
    cs
    costocutaneous superior
    CT
    computed tomography
    EMG
    electromyography
    ie
    intercostalis externus
    il
    iliocostalis
    iq
    intercostalis quadrangularis
    lc
    levator costae
    oai
    obliquus abdominus internus
    oid
    obliquus internus pars dorsalis
    oiv
    obliquus internus pars ventralis
    sli
    supracostalis lateralis inferior
    sls
    supracostalis lateralis superior
    ta
    transversus abdominus
    tu
    tuberculocostalis
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