The chemical composition of haemolymph in insects and some other arthropods, in relation to their phylogeny

Summary Many species of tardigrades are known to tolerate extreme environmental stress, yet detailed knowledge of the mechanisms underlying the remarkable adaptations of tardigrades is still lacking, as are answers to many questions regarding their basic biology. Here, we present data on the inorganic ion composition and total osmotic concentration of five different species of tardigrades (Echiniscus testudo, Milnesium tardigradum, Richtersius coronifer, Macrobiotus cf. hufelandi and Halobiotus crispae) using high-performance liquid chromatography and nanoliter osmometry. Quantification of the ionic content indicates that Na+ and Cl- are the principle inorganic ions in tardigrade fluids, albeit other ions, i.e. K+, NH4+, Ca2+, Mg2+, F-, SO42- and PO43- were also detected. In limno-terrestrial tardigrades, the respective ions are concentrated by a large factor compared to that of the external medium (Na+, ×70-800; K+, ×20-90; Ca2+ and Mg2+, ×30-200; F-, ×160-1040, Cl-, ×20-50; PO43-, ×700-2800; SO42-, ×30-150). In contrast, in the marine species H. crispae Na+, Cl- and SO42- are almost in ionic equilibrium with (brackish) salt water, while K+, Ca2+, Mg2+ and F- are only slightly concentrated (×2-10). An anion deficit of ~120 mEq 1-1 in M. tardigradum and H. crispae indicates the presence of unidentified ionic components in these species. Body fluid osmolality ranges from 361±49 mOsm kg-1 in R. coronifer to 961±43 mOsm kg-1 in H. crispae. Concentrations of most inorganic ions are largely identical between active and dehydrated groups of R. coronifer, suggesting that this tardigrade does not lose large quantities of inorganic ions during dehydration. The large osmotic and ionic gradients maintained by both limno-terrestrial and marine species are indicative of a powerful ion-retentive mechanism in Tardigrada. Moreover, our data indicate that cryptobiotic tardigrades contain a large fraction of unidentified organic osmolytes, the identification of which is expected to provide increased insight into the phenomenon of cryptobiosis.

Section: Ionic Composition In Tardigradessupporting

confidence: 71%

“…high Na + and Cl -concentrations). Sutcliffe argued that definitive types of hemolymph in insects are related to the systematic position within Insecta (Sutcliffe, 1962;Sutcliffe, 1963 ). Moreover, the ionic contributions to the total osmotic concentrations are remarkably similar (Table5).…”

Section: Ionic Composition In Tardigradesmentioning

confidence: 99%

Inorganic ion composition in Tardigrada: cryptobionts contain large fraction of unidentified organic solutes

Halberg

Larsen

Jørgensen

et al. 2012

“…Sodium is the major inorganic ion in the hemolymph of drosophilids (Sutcliffe, 1963). A consequence of the voluminous hemolymph pool in hydrated D flies is a significant increase in hemolymph Na + content (Folk and Bradley, 2003).…”

Section: Restoration Of Sodium Contentmentioning

confidence: 99%

The evolution of recovery from desiccation stress in laboratory-selected populations ofDrosophila melanogaster

Folk

Bradley

2004

We examined the capacity for physiological recovery from the effects of desiccation in five replicate populations of Drosophila melanogaster that have been selected for enhanced desiccation resistance (D populations) and in five replicate control populations (C populations). The capacity to recover was signified by the ability to restore three somatic components, namely whole-body water, dry mass and sodium content, all of which are reduced during desiccation. Throughout a period of recovery following a bout of desiccation, the flies were offered one of three fluids: distilled water, saline solution, or saline+sucrose solution. Our findings indicate that, when allowed to recover on saline+sucrose solution, D populations have the capacity to restore water at a greater rate than C populations and are able to fully restore dry mass and sodium content to the levels observed in non-desiccated, hydrated D flies. When provided with this same solution during recovery, C flies are unable to restore dry mass and are faced with an elevated sodium load. Desiccation resistance of the flies subsequent to recovery was also examined. We provide evidence that the greatest desiccation resistance in the D populations is associated with the restoration of all three somatic components, suggesting that not only water content, but also dry mass and sodium, may contribute to the enhanced desiccation resistance that has evolved in these populations.

“…We propose that the increased hemolymph volume of the D flies plays a role in buffering water loss from the tissues. One consequence of this large pool (Sutcliffe, 1963). The loss of water during desiccation without a concomitant loss of Na + would lead to an increase in the Na + concentration of the hemolymph.…”

mentioning

confidence: 99%

“…Potassium is the principal intracellular cation and is found only in very low concentrations within the hemolymph of dipterans (Sutcliffe, 1963). We anticipated that because of the increased capacity of the desiccation-resistant populations to prevent cell shrinkage during desiccation, the maintenance of cellular ion composition would also be enhanced.…”

mentioning

confidence: 99%

Evolved patterns and rates of water loss and ion regulation in laboratory-selected populations ofDrosophila melanogaster

Folk

Bradley

2003

hemolymph pool is that the hydrated D flies contained approximately seven times more sodium within the hemolymph than did the hydrated C flies. Despite a continual loss of hemolymph volume in the D flies during lengthy periods of desiccation, the sodium content of the hemolymph was significantly reduced only during a single event. We provide evidence that the regulation of extracellular sodium, as well as chloride, occurred via excretory processes during desiccation. In addition, wholebody potassium was not significantly decreased in the D flies during desiccation but was reduced (i.e. excreted) in the C flies; hence, we suggest that the potassium content paralleled tissue water level.