title: Accumulation of free amino acids during exposure to drought in three springtail species.
abstract: Springtails are closely related to insects, but they differ from these with respect to water balance, in particular because springtails are small and have high integumental permeability to water. Here we report a series of experiments addressing the dynamics of osmoregulation, water content and accumulation of free amino acids (FAAs) in three springtail species during exposure to a gradually increasing environmental desiccation simulating conditions in drought exposed soil. Folsomia candida and Protaphorura fimata (both living in the deeper soil layers; euedaphic species) were active throughout the 3week exposure, with the developing drought regime ending at -3.56MPa (the soil water activity at the permanent wilting point of plants is -1.5MPa) and remained hyperosmotic (having an body fluid osmolality higher than the corresponding environment) to their surrounding air. Sinella curviseta (living in upper soil/litter layers; hemiedaphic species) also survived this exposure, but remained hypoosmotic throughout (i.e. with lower osmolality than the environment). The body content of most FAAs increased in response to drought in all three species. Alanine, proline and arginine were the most significantly upregulated FAAs. By combining our results with data in the literature, we could account for 82% of the observed osmolality at -3.56MPa in F. candida and 92% in P. fimata. The osmolality of S. curviseta was only slightly increased under drought, but here FAAs were considerably more important as osmolytes than in the two other species. We propose that FAAs probably have general importance in drought tolerance of springtails.
authors.affiliation: Aarhus University, Department of Bioscience, Vejlsøvej 25, PO Box 314, 8600 Silkeborg, Denmark. Electronic address: martin.holmstrup@bios.au.dk.
authors.forename: Martin
authors.initials: M
authors.lastname: Holmstrup
authors.affiliation: Aarhus University, Department of Bioscience, Vejlsøvej 25, PO Box 314, 8600 Silkeborg, Denmark.
authors.forename: Stine
authors.initials: S
authors.lastname: Slotsbo
authors.affiliation: Institute of Entomology, Biology Centre of The Czech Academy of Sciences, Branišovská, 370 05 České Budějovice, Czech Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Rozsypal
authors.affiliation: Aarhus University, Department of Bioscience, C.F. Møllers Allé, Universitetsparken, 8000 Aarhus C, Denmark.
authors.forename: Per G
authors.initials: PG
authors.lastname: Henriksen
authors.affiliation: Aarhus University, Department of Bioscience, C.F. Møllers Allé, Universitetsparken, 8000 Aarhus C, Denmark.
authors.forename: Mark
authors.initials: M
authors.lastname: Bayley
mesh_terms: D000220:Adaptation, Biological / Q000502:physiology; D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001181:Arthropods / Q000502:physiology*; D055864:Droughts; D064587:Osmoregulation; D012987:Soil / Q000737:chemistry; D014867:Water
chemical_list: D000596:Amino Acids; D012987:Soil; D014867:Water
keywords: Collembola; Desiccation; Osmoregulation; Soil fauna; Soil water content