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Elemental imaging by X-ray microanalysis of fully frozen-hydrated samples shows that when Malpighian tubules of the black field cricket (Teleogryllus oceanicus L.) are incubated in saline in which Rb+ has been substituted for K+, Rb+ replaces much of the cellular K+ in the main segment of control Malpighian tubules and this is prevented by incubation in saline containing Ba2+, a non- selective K+ channel blocker. Similarly the amount of cellular K+ is greatly reduced when tubules incubated in normal, i.e. K+ containing, saline are exposed to Ba2+. By considering the amounts of cellular K and Rb remaining in the main segments of tubules incubated in either K+ containing saline or Rb+ containing saline after Ba+ treatment, it is suggested that: (a) a major part (56%) of cellular K+ enters by Ba2+ sensitive K+ channels and that Rb+ can also enter by this route; (b) a smaller fraction (26%) of cellular K+ enters by a previously proposed Na+/K+/2CI- co-transporter, which can also transport Rb+ (a) a previously proposed Na+/K+-ATPase is responsible for maintaining a K+ pool (18%) in the tubule cells that is not exchangeable by Rb+ and (d) entry by this Na+/K+-ATPase is not available to Rb+. [ABSTRACT FROM AUTHOR]

The surface concentration dynamics of Ca2+ and O2 in the scleractinian coral Galaxea fascicularis were investigated by means of 2 mm-sized sensors (mini-electrodes). Mini-electrodes were used to measure the light-regulated uptake of Ca2+ for calcification, and the secretion of O2, produced by photosynthesising zooxanthellae, at the surface of the oral ectoderm of Galaxea polyps. The concentration of Ca2+ measured in the boundary layer of seawater adjacent to the polyp surface was variable but always higher than in bulk seawater in the dark and fell to levels closer to the value in bulk seawater on illumination. The fall in concentration, representing an influx of Ca2+ into the ectoderm, increased with increasing photosynthetic photon flux density of illumination. The decrease in Ca2+ concentration on illumination was insensitive to ruthenium red but sensitive to verapamil and acetazolamide. Oxygen secretion at the ectoderm, manifested by an increase in O2 concentration in the boundary layer, increased on illumination but was not sensitive to any of the inhibitors used in the calcium experiments. The results suggest that Ca2+ uptake involves calcium channels and is coupled in someway to the uptake of inorganic carbon for calcification. Uptake is also strongly coupled to photosynthesis. [Copyright &y& Elsevier]

Reports on the low temperature X-ray microanalysis of calcium in a scleractinian coral. Nature of samples; X-ray microanalysis of sewater compartments; X-ray microanalysis of mucocytes.

Investigates the effect of increased calcium concentration in sea water on calcification and photosynthesis in the scleractinian coral, Galaxea fascicularis. Bisphosphonate; Photosynthesis; Change in respiration rate.