Induction of Larval Settlement by KCl in Three Species of Bugula (Bryozoa)
NOTE: At the time of publication, the author Dean E. Wendt was not yet affiliated with Cal Poly.
Elevation of the K+ concentration in seawater (added as KCl) induces larval settlement and metamorphosis in Bugula simplex, B. stolonifera, and B. turrita. All three of these bryozoan species have similar bell-shaped dose-response curves: 5 mM excess K+ is sufficient to increase settlement and metamorphosis significantly over seawater controls in all the species and optimal responses to excess K concentrations occur ations at 10-25 mM, 5-10 mM, and 10-15 mM for B. simplex, B. stolonifera, and B. turrita, respectively. Percent settlement in all three species is decreased at levels greater than 25 mniM excess KCl. Similar bell-shaped curves have been observed for KCl-induced settlement of larvae from other, but not all, invertebrate groups. Larvae of B. turrita do not settle at a significantly higher level than seawater controls when exposed to excess K+ concentrations >25 mM even in the presence of a second favorable artificial inducer, filmed chicken eggshell membrane, indicating that K+ at high concentrations interferes with the normal settlement process. Furthermore, pulse exposures for 5 min, 15 min, and 30 min to 10 mM excess K+ are ineffective at inducing settlement over levels in seawater controls. When larvae of B. turrita were induced to settle by 10 mM excess K+, completion of metamorphosis was not significantly different from that of controls lacking excess KCl (86% and 91%, respectively). However, if larvae induced by 10 mM excess K+ are not removed from the 10 mM excess K+ after settlement, the success ratio of metamorphosis is significantly lower than in controls (72% and 91%, respectively). Our results confirm previous studies demonstrating that settlement of bryozoan larvae can be induced by excess K+. Bryozoan larvae examined to date become responsive around 5-10 mM excess K+. These data suggest that shared under- lying features exist in the mechanism triggering settlement and metamorphosis in bryozoans and that excess K+ is a useful experimental tool for inducing settlement of bryozoan larvae.
Dean E. Wendt and Robert M. Woollacott. "Induction of Larval Settlement by KCl in Three Species of Bugula (Bryozoa)" Invertebrate Biology 114.4 (1995): 345-351.
Available at: http://works.bepress.com/dwendt/18