. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ocular, groove Podophthalmus vigil ?. normal nighttime position of distal segment FIGURE 4. The Hawaiian crab, Podophthalmus rif/il, maintains the vertically of the distal segment of each eyestalk while moving about with the proximal segments raised by day or partly lowered at night, and while moving sidewise over an inclined surface, (Data from Sather, 1962.) 65 degrees. Often this suffices to keep its compound eyes in clear water above the silt, where vision is possible. Both at night and when the proximal segments are ele
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ocular, groove Podophthalmus vigil ?. normal nighttime position of distal segment FIGURE 4. The Hawaiian crab, Podophthalmus rif/il, maintains the vertically of the distal segment of each eyestalk while moving about with the proximal segments raised by day or partly lowered at night, and while moving sidewise over an inclined surface, (Data from Sather, 1962.) 65 degrees. Often this suffices to keep its compound eyes in clear water above the silt, where vision is possible. Both at night and when the proximal segments are elevated into daytime position, the distal segments are kept vertical. Only when the crab is lifted out of the water or its eyestalks are molested is the distal segment lowered into the protective groove across the anterior edge of the broad carapace. Thus, the elongated proximal segments serve to raise the eyes high above the body of this silt-dwelling crab, while muscular adjustments of the short distal segment stabilize the visual field. Sand grains, serving as statoliths in the antennular statocysts of crayfishes and lobsters, appear necessary in the sensory system that permits these animals to right themselves and make compensatory adjustments of their eyestalks to. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clarence, 1890-1983. Woods Hole, Mass. : Marine Biological Laboratory
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
