. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. COPEPOD TOOTH FORMATION 357. FIGURE 3. Mandibular gnathobase from adult female Acartia tnnsa reared at silicic acid (experiment Ki). The central tooth shows severe reduction (3 on the reduction rating scale). The black bar represents 5 /urn. The ventral tooth is at left. SEM by Alfred H. Soeldner () using ISI Mini-SEM. DISCUSSION Acartia tonsa successfully extracted silicic acid from concentrations in seawater as low as /xM and formed it into teeth. On the other hand those teeth were not normal. Formation of n
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. COPEPOD TOOTH FORMATION 357. FIGURE 3. Mandibular gnathobase from adult female Acartia tnnsa reared at silicic acid (experiment Ki). The central tooth shows severe reduction (3 on the reduction rating scale). The black bar represents 5 /urn. The ventral tooth is at left. SEM by Alfred H. Soeldner () using ISI Mini-SEM. DISCUSSION Acartia tonsa successfully extracted silicic acid from concentrations in seawater as low as /xM and formed it into teeth. On the other hand those teeth were not normal. Formation of normal teeth required concentration of /xM or above. Thus we must consider both 1 ) the ability of copepods to draw silicon for tooth formation from lower concentrations and 2) the possible ecologic significance of low silicic acid availability. Before we conclude that Acartia tonsa can draw enough silicon for tooth forma- tion from media with low concentrations of silicic acid, several other possibilities must be considered. It could be that moderate amounts of silicon are present in seawater and LSM which do not react in the acid-molybdate analysis. Silicic acid can form polymers that do not produce the molybdate complex (Alexander, 1953), but which could possibly be used by copepods for tooth formation. How- ever, Burton ct al. (1970) have done a careful study of this problem. They found "no detectable amount of unreactive silicon in any of the natural water samples analyzed. Polymeric silicon added to the [ sea j water samples was unstable and depolymerized completely within a few ; It seems unlikely, therefore, that copepods have any source of silicon in our experiments beside the low levels of reactive silicate which we measure. The result itself argues against another source. Normality of teeth improved with increasing reactive Please note that these images are extracted from scanned page images that may have been digitally enhanced for reada
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