. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. BODY VERSUS SHELL GROWTH IN BALANUS 229 Shell growth. In contrast to the body, which may grow only at the time of molting, the calcareous plates of the shell grow continuously. Figure 3 compares the growth rates of shell and maxillae for one barnacle. As indicated previously, there were periods up to three molts when no increase in maxillae size occurred. During this same interval of time the shell continued to grow. Costlow and Bookhout (1953), comparing shell growth of B. improvisus in the laboratory with that found in the
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. BODY VERSUS SHELL GROWTH IN BALANUS 229 Shell growth. In contrast to the body, which may grow only at the time of molting, the calcareous plates of the shell grow continuously. Figure 3 compares the growth rates of shell and maxillae for one barnacle. As indicated previously, there were periods up to three molts when no increase in maxillae size occurred. During this same interval of time the shell continued to grow. Costlow and Bookhout (1953), comparing shell growth of B. improvisus in the laboratory with that found in the natural environment of the harbor, found that while the two rates followed the same general curve, growth in the laboratory was approximately one- .0. BODY GROWTH 10 15 20 25 30 DAYS 35 40 45 50 55 FIGURE 4. Comparison of average shell growth and average body growth, as indicated by measurements of the maxillae, for 20 Balanus improvisus over a period of 20 molts. Maxillae size X 10-1. third that found in nature. Thus, while not optimal, laboratory conditions will support growth of the shell and the absence of body growth cannot be attributed to starvation. Figure 4 shows the average increase in size of maxillae and shell for 20 barnacles. It will be noted that the initial ratio between maxillae and shell sizes is not main- tained over any great length of time. As the body can grow only by molting, it might be expected to show an increase in size which would correspond with shell growth for that particular intermolt period. As shown in Figure 5, however, the per cent growth of the maxillae rarely equals the per cent accumulated shell growth during that intermolt period. With the exception of the third molt, the total per. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these ill
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