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  • 1
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Electromyography and cinematography were used to determine the activity of epaxial muscles of colubrid snakes during terrestrial and aquatic lateral undulatory locomotion. In both types of lateral undulation, at a given longitudinal position, segments of three muscles (Mm. semispinalis-spinalis, longissimus dorsi, and iliocostalis) usually show synchronous activity. Muscle activity propagates posteriorly and generally is unilateral. With each muscle, large numbers of adjacent segments (30 to 100) show simultaneous activity. Terrestrial and aquatic undulation differ in two major respects. (1) During terrestrial undulation, muscle activity in a particular region begins when that portion of the body has reached maximal convex flexion and ends when it is maximally concave; this phase relation is uniform along the entire snake. During swimming, however, muscle activity passes posteriorly faster than the wave of vertebral flexion, causing the relation of muscle activity to flexion to change along the length of the snake. (2) In the terrestrial mode, the block of active muscle segments remains approximately constant in size as it passes down the snake, whereas during swimming the number of adjacent active muscle segments increases posteriorly. Despite the fact that Elaphe obsoleta has nearly twice as many body vertebrate as Nerodia fasciata (240 vs. 125), the only difference observed in the swimming of these two species is that a larger number of adjacent muscle segments is simultaneously active in comparable regions of Elaphe obsoleta than in Nerodia fasciata.
    Additional Material: 19 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 172 (1982), S. 83-96 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Segments of the spinalis portion of the M. semispinalis-spinalis (SSP) were examined in 107 snakes representing 94 species, 85 genera, and 11 families. Allowing for slight variation within individuals and species, the following generalizations can be made. (1) Three major types of segments of the SSP were found in Typhlops, booids, and colubroids. (2) Within each type, differences in the segmental length of the spinalis result primarily from different lengths of the anterior tendons. (3) Specializations in habitat and locomotor modes usually account for variations in the segmental lengths of the spinalis. (4) Constrictors seem to have undergone selection for increased flexibility which is gained by having relatively more vertebrae and, in some cases, shorter muscle segments.
    Additional Material: 2 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 220 (1994), S. 185-205 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We used X-rays and dissection of myotomes to quantify the axial morphology of four species of centrarchid fishes (Micropterus salmoides, Ambloplites rupestris, Pomoxis nigromaculatus, and Lepomis macrochirus). Proceeding from dorsal to ventral, we designated the two epaxial and two hypaxial protions of the myomeres AB, BC, CD, and DE, respectively. For each of 11 myomeres, spaced at 10% increments along the length of the fish, a total of 14 variables described the length and orientation of each portion, the dorsalventral symmetry, and the overall height and longitudinal span of the entire myomere. Nine variables described the lengths, orientation, and symmetry of the vertebral centra, neural and hemal spines, and ribs. Analysis of variance revealed that, with one exception, all 23 morphological variables varied significantly both among species and among longitudinal locations within a species. However, the extent of longitudinal and interspecific variance differed considerably among different variables. Maximal myomeric height ranged from about 45% of the standard length (SL) in Lepomis to 27% SL in Micropterus. Longitudinal and interspecific increases in overall height of the trunk myomeres resulted primarily from greater lengths of CD. Compared to other portions of the myomere, the length of BC was most conservative both longitudinally and interspecifically. Dorsal-ventral symmetry of the myomeres and axial skeleton was greater in the caudal region than in the trunk in all species, and the myomeric morphology diverged least among species in the posterior caudal region. The overall longitudinal span of superficial myomeric landmarks varied from 6% to 18% SL, and, including the deep portions of the myomeres, the longitudinal span varied from about 7 to 10 vertebrae. Within each of the species, myomeric and skeletal variables were often not significantly correlated, but for the pooled data of all species there were usually highly significant correlations between myomeric and skeletal morphology. For example, strong correlations existed between BC and the underlying neural spines, and between CD and the underlying ribs and hemal spines. In contrast, the longitudinal spans of entire myomeres and underlying axial skeletal segments were only weakly associated. © 1994 Wiley-Liss, Inc.
    Additional Material: 14 Ill.
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