. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CA2+ DEPENDENCE OF HYDROID SETTLEMENT 49 O CD § cc B 40 120 160. 40 80 120 time (sec) 160 Figure 4. |Ca2*], transients during atrichous isorhiza discharge in (A) Ca^-free artificial seawater (ASW), (B) Mg-+-supplemented ASW (200 mM Mg2+), (C) 20 pM Gd' + -ASW. and (D) regular ASW. this is the first demonstration of Ca2 +-dependent nemato- cyst discharge in larvae. We also confirmed and quantified the Ca2+-dependence of actinular settlement in Tubitlaria mesembryanthemum. Reduced-Ca2 + seawater also inhibits m
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CA2+ DEPENDENCE OF HYDROID SETTLEMENT 49 O CD § cc B 40 120 160. 40 80 120 time (sec) 160 Figure 4. |Ca2*], transients during atrichous isorhiza discharge in (A) Ca^-free artificial seawater (ASW), (B) Mg-+-supplemented ASW (200 mM Mg2+), (C) 20 pM Gd' + -ASW. and (D) regular ASW. this is the first demonstration of Ca2 +-dependent nemato- cyst discharge in larvae. We also confirmed and quantified the Ca2+-dependence of actinular settlement in Tubitlaria mesembryanthemum. Reduced-Ca2 + seawater also inhibits metamorphosis of Hydractinia cchintita plunula larvae (Berking, 1988; Muller, 1985). The EC50 of external Ca2 + was 3 mM for T. mesembryanthemum actinular settlement, comparable to that of both H. echimita settlement and actinular AI discharge (Kawaii et ui, 1997). Since actinulae immersed in Ca2+-free ASW tended to disintegrate, settle- ment assays were not performed in Ca2 + -free ASW. The action of K+-ASW was strongly inhibited by in- creasing the Mg2 + concentration of the bathing solution, and the inhibitory effects of the Mg2+ ion increased when the external Ca2+ concentrations were lowered. Similarly, Muller (1985) found that TPA-induced metamorphosis of H. echimita was promoted in Mg2 +-reduced seawater. Mg2+ and Ca2 + ions compete with each other in many biological processes; consequently, we expected that an increase of Mg2+ concentration in the bathing solution would reduce the Ca2+ influx, thus inhibiting actinular settlement and AI discharge. However, the rise of R340/38o values measured in Mg2+-supplemented ASW was equiva- lent to that observed in Ca2+-free ASW, and there was no influx of Ca2+ ions from the Mg2 +-supplemented ASW to nematocytes. These observations indicate that inhibition of AI discharge by Mg2+ did not result from the lowering of nematocyte [Ca2 + ], level by competitive influx of Mg2 + and Ca2+ ions. The enhancement of AI discharge and larval se
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
