. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. LOCOMOTION IN MHLAMl'US 313 to determine which portions of the sole are experiencing upward or downward (weight-bearing) forces during each stage in the crawl-step cycle. The forces exerted during locomotion were measured as snails crawled across a moveable bar positioned in a slit in a plexiglass platform. Five to six step cycles were required for snails to crawl across the bar and therefore at each successive step the transducer measured forces from a more posterior region of the foot. The pattern of upward and downward de
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. LOCOMOTION IN MHLAMl'US 313 to determine which portions of the sole are experiencing upward or downward (weight-bearing) forces during each stage in the crawl-step cycle. The forces exerted during locomotion were measured as snails crawled across a moveable bar positioned in a slit in a plexiglass platform. Five to six step cycles were required for snails to crawl across the bar and therefore at each successive step the transducer measured forces from a more posterior region of the foot. The pattern of upward and downward deflections recorded in this manner was fairly constant from crossing to crossing and animal to animal. Figure 6A is typical of the recordings that were produced. These data were interpreted as described in the methods. Postures characteristic of Stages I-III for each step were identified with particular points on the force recording as illustrated in Figure 6A. Upward * * Downward 1 III 211 B. AAA n VV7 87654 32 Stage I 765432 Stage II 765 4321 Stage III FIGURE 6. A is the force transducer recording of upward and downward forces exerted on a bar as a snail crawled across it. A portion of the snail's foot was in contact with the bar for six complete steps and the end and beginning of two other steps, for a total of 24 sec. Each point at which the simultaneously-recorded motion picture film indicated that the snail assumed one of the postures characteristic of Stage I, II or III of the crawl step cycle was marked on the transducer recording. The dotted line represents a baseline adjustment that was inserted to compensate for the overwhelming effect of passage of the shell mass onto the bar. In B the information obtained from the force recording is represented as a pattern of upward and downward-pointing triangles showing the distribution of vertical forces exerted by the foot on the substratum at Stages I, II and III of the step cycle. Regions exerting no vertical force are indica
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
