Ionic Composition Of Haemolymph Research Articles

Hemolymph composition, gene expressions in the gills, and thus the survival of euryhaline crabs are controlled by ambient minor cations according to osmotic condition-dependent manner.

Na+ and Cl− are the most abundant dissolved ions in seawater, constituting ~ 85% of total ions. They significantly affect the osmolality of body fluids of marine invertebrates. Seawater also contains minor ions such as Mg2+, Ca2+, K+, and SO4 2‐ , but their effects on marine organisms are unclear. This study analyzed the effects of Mg2+, Ca2+, and K+ (ambient minor cations) on survival, hemolymph ionic composition, and gene expression in the gills of three euryhaline crabs: Helice tridens, Macrophthalmus japonicus, and Chiromantes dehaani. Ambient minor cations were required for survival of H. tridens and M. japonicus under isosmotic conditions with seawater. The ambient minor cations also affected the osmolality and ionic composition of hemolymph by regulating expressions of specific genes in the gills required for Na+ uptake, such as Na+/K+ ATPase, cytoplasmic carbonic anhydrase, and Na+/H+ exchanger. Administration of carbonic anhydrase and Na+/H+ exchanger inhibitors increased the survival rate even if ambient minor cations did not exist. In contrast, under hypo‐osmotic conditions, ambient minor cations had different effects on crabs, a lethal effect on M. japonicus, and an increase of the hemolymph K+ concentration in H. tridens and M. japonicus. It is thus concluded that the effects of ambient minor cations are osmolality‐dependent. In contrast, in C. dehaani, the hemolymph ionic composition and survival rate were hardly affected by ambient minor cations, probably reflecting the habitat of this species. These results strongly indicated that C. dehaani is less susceptive to ambient minor cations compared to H. tridens and M. japonicus.

Ionic composition of haemolymph and myoplasm in lepidoptera in relation to their membrane potentials.

Abstract1. The results of haemolymph and myoplasm ionic analysis show that lepidopteran muscle has a low transmembrane potassium gradient, and a sodium gradient such that Na0/Nai is less than unity2. The theoretical potassium electrode potential is much smaller than the observed resting potential, and the sodium electrode potential is totally unrelated to the observed « undershoot » in lepidopteran muscle. The chloride electrode potential gives a much closer fit to the resting potential, but the transmembrane potassium and chloride gradients are not reciprocal.3. The possible existence of a peripheral diffusion barrier is discussed and rejected. On the evidence available, it seems likely that active transport of ions is responsible, at least in part, for membrane potential maintenance in the Lepidoptera, and possibly in some other insects.