. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. AMMONIA INDUCES OYSTER SETTLEMENT 299 o z K m x o LJ > UJ 100 ^- 80-- fi Li_ O UJ O < z LU O LU Q_ CD 60--. 40-- 20-- Concentrotion of NH4CI [NH-j] • • [] mM A A [] mM A A [] mM D D [] mM V V [] mM T V Contra 10 15 20 TIME (min) 25 30 Figure 1. Percentages of O90% within 5 min of exposure to an NH4C1 solution of mA/at pH = Responses to higher concentrations of NH4C1 are not shown because larvae in these solutions exhibited re- duced activity levels after short exposures.
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. AMMONIA INDUCES OYSTER SETTLEMENT 299 o z K m x o LJ > UJ 100 ^- 80-- fi Li_ O UJ O < z LU O LU Q_ CD 60--. 40-- 20-- Concentrotion of NH4CI [NH-j] • • [] mM A A [] mM A A [] mM D D [] mM V V [] mM T V Contra 10 15 20 TIME (min) 25 30 Figure 1. Percentages of O90% within 5 min of exposure to an NH4C1 solution of mA/at pH = Responses to higher concentrations of NH4C1 are not shown because larvae in these solutions exhibited re- duced activity levels after short exposures. Between and mM (pH = ), the larval response to NH4C1 was concentration dependent. As the NH4C1 concentra- tion increased, the percentage of larvae exhibiting settle- ment behavior increased, and the length of time required for the maximum percentage of larvae to respond de- creased. Following the maximum larval response, the percentage of larvae continuing to exhibit settlement be- havior rapidly declined so that 30 min after the initial exposure, almost all the larvae had "habituated" to the NH4C1 solutions and had resumed normal swimming. No subsequent metamorphosis was observed after 24 to 48 h. Larvae also exhibited high levels of settlement behavior in response to (NH4)iSO4, indicating that either NH, or NH4+ was the active chemical species. This was corrob- orated by the observation that larval settlement behavior was not induced by Cl — as NaCl or KC1 — at concentra- tions comparable to inductive NH4C1 solutions (data not shown). Methylamine and trimethylamine, which are weak bases like NH3, induced high levels of oyster settle- ment behavior (Table I). The active species is AT/,- rather than AT// Ammonia has a pKas of in seawater and its cal- culated speciation as a function of pH is shown in Figure 2 A. As the pH of the NH4C1 solution decreases from to , which is within the physiological tolerance range for oyster larvae, the N
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
